Cut and Fold Aluminum
I hesitate to suggest this in relation to boat building except that you
might be able to make some difficult shapes with this technique. (and create hard points) Braking aluminum can be a real challenge. Especially if you want to make a sharp corner in a long piece of sheet. A brake that will handle an 8' piece of .125 is gonna cost some serious bucks. More than the average backyard boat builder is going to want to spend. (never mind the wealthy tool whores or that I would have one if I could afford it) I have used this technique for making some support angle in other than 90 deg applications. I've only done this with .125 5052. The longest bend I have made this way so far is about 3 feet. Cut the sheet half thickness along a line. I used my table saw to do this. Clamp the sheet to a rigid surface. I used a cast iron table saw and a piece of 3/8 angle iron. I also clamped 1/4 aluminum plate to the free side to help keep it rigid and straight. Bend in a moderately fast single motion to the desired angle. Depending on what angle you are trying to reach and the size piece you are working with this can be easier than you think. At this point I hade a piece with a very nice small radius outside bend, and the angle I desired. I made several pieces like this for one project that had an inside angle of about 70 degrees. Of course the piece is very weak at this point (thickness) and very hard (work hardening) along the bend. Its almost impossible to bend it again if you didn't get it right the first time. Instead you wind up distorting the legs of your angle. Lets assume the piece would be at the correct angle at this point. Then I took a good stainless brush and polished the inside of the angled and then welded a bead right down the inside. No worries about air contamination since there is no opening to the other side. No back chipping necessary. If you get your rig setup just right you will see you can get almost perfect penetration by looking at the other side. It welds very fast, and each piece is trapped to the other piece by the remaining portion of the cut groove. I experimented a little with different pieces at this point. Some I lock stitched and back filled and others I just welded as fast as I could go (once I got dialed in for the heat and the thickness) from one end to the other. Eyeballing with a good straight edge both pieces came out pretty square and straight. I would probably still stay with the lock stitch and backfill technique because there might be hidden stresses in the metal you just can't see without some more involve testing. Ok, you might ask. "You used this technique to make some non critical support brackets. What is the big deal?" The temptation. Think about a blue printed fiberglass racing pad... like on a modern bass boat. Oh! Yeah. Now you see the point. You could make a really sharp square racing pad this way out of aluminum. Sharp edges on a pad means fast. Some of the guys who race boats like this have the edges of the pad so sharp they will almost cut you. That sharp a corner would not be possible even with this technique, but it would be a thousand times sharper than you could do on a sheet metal brake. Now comes the part that makes me scared to try this technique. By making a sharp corner like that you are creating a hard point. Is the weld on the inside going to account for that. I don't know, and I don't know how to find out. It is certainly a very critical location on the boat. Its taking all the force of running and pounding and flexing of the entire boat. The only thing under more stress is the transom which at speed is carrying the entire weight of the boat suspended in the air. I suppose you could use a v-groove cutter on a router to get a better cut with thicker aluminum. Obviously the technique would need to be adjusted and modified based on material thickness, angle, desired size of weld bead etc... You might argue you could just corner weld two pieces of sheet together and for some shapes you would have no choice. (curve along a line) There are some things about corner welding two pieces. To do a perfect job you need to weld it twice for one thing. Weld the inside. Back chip the outside, and then weld the outside. You are going to get some distortion of your associated planes. You are going to get a lumpy weld (by comparison) not a nice clean sharp corner. Although I suppose you could over weld and build up your bead and then grind back to square. I have done a couple pieces this way also just to see what I would get. For small stuff you could not tell, but with my level of skill as a welder I could see some distortion in the sheets only as long as 2 or 3 feet when I threw my straight edge on them. I have had this process floating around in my head for a year. Now its time for you to tear it apart. |
Cut and Fold Aluminum
On Thu, 10 Dec 2009 09:17:37 -0700, "Bob La Londe"
wrote: I hesitate to suggest this in relation to boat building except that you might be able to make some difficult shapes with this technique. (and create hard points) Braking aluminum can be a real challenge. Especially if you want to make a sharp corner in a long piece of sheet. A brake that will handle an 8' piece of .125 is gonna cost some serious bucks. More than the average backyard boat builder is going to want to spend. (never mind the wealthy tool whores or that I would have one if I could afford it) I have used this technique for making some support angle in other than 90 deg applications. I've only done this with .125 5052. The longest bend I have made this way so far is about 3 feet. Cut the sheet half thickness along a line. I used my table saw to do this. Clamp the sheet to a rigid surface. I used a cast iron table saw and a piece of 3/8 angle iron. I also clamped 1/4 aluminum plate to the free side to help keep it rigid and straight. Bend in a moderately fast single motion to the desired angle. Depending on what angle you are trying to reach and the size piece you are working with this can be easier than you think. At this point I hade a piece with a very nice small radius outside bend, and the angle I desired. I made several pieces like this for one project that had an inside angle of about 70 degrees. Of course the piece is very weak at this point (thickness) and very hard (work hardening) along the bend. Its almost impossible to bend it again if you didn't get it right the first time. Instead you wind up distorting the legs of your angle. Lets assume the piece would be at the correct angle at this point. Then I took a good stainless brush and polished the inside of the angled and then welded a bead right down the inside. No worries about air contamination since there is no opening to the other side. No back chipping necessary. If you get your rig setup just right you will see you can get almost perfect penetration by looking at the other side. It welds very fast, and each piece is trapped to the other piece by the remaining portion of the cut groove. I experimented a little with different pieces at this point. Some I lock stitched and back filled and others I just welded as fast as I could go (once I got dialed in for the heat and the thickness) from one end to the other. Eyeballing with a good straight edge both pieces came out pretty square and straight. I would probably still stay with the lock stitch and backfill technique because there might be hidden stresses in the metal you just can't see without some more involve testing. Ok, you might ask. "You used this technique to make some non critical support brackets. What is the big deal?" The temptation. Think about a blue printed fiberglass racing pad... like on a modern bass boat. Oh! Yeah. Now you see the point. You could make a really sharp square racing pad this way out of aluminum. Sharp edges on a pad means fast. Some of the guys who race boats like this have the edges of the pad so sharp they will almost cut you. That sharp a corner would not be possible even with this technique, but it would be a thousand times sharper than you could do on a sheet metal brake. Now comes the part that makes me scared to try this technique. By making a sharp corner like that you are creating a hard point. Is the weld on the inside going to account for that. I don't know, and I don't know how to find out. It is certainly a very critical location on the boat. Its taking all the force of running and pounding and flexing of the entire boat. The only thing under more stress is the transom which at speed is carrying the entire weight of the boat suspended in the air. I suppose you could use a v-groove cutter on a router to get a better cut with thicker aluminum. Obviously the technique would need to be adjusted and modified based on material thickness, angle, desired size of weld bead etc... You might argue you could just corner weld two pieces of sheet together and for some shapes you would have no choice. (curve along a line) There are some things about corner welding two pieces. To do a perfect job you need to weld it twice for one thing. Weld the inside. Back chip the outside, and then weld the outside. You are going to get some distortion of your associated planes. You are going to get a lumpy weld (by comparison) not a nice clean sharp corner. Although I suppose you could over weld and build up your bead and then grind back to square. I have done a couple pieces this way also just to see what I would get. For small stuff you could not tell, but with my level of skill as a welder I could see some distortion in the sheets only as long as 2 or 3 feet when I threw my straight edge on them. I have had this process floating around in my head for a year. Now its time for you to tear it apart. I suppose the most logical question is "why". Yes, you can bend aluminum at a sharper angle and have a less radiused bend by thinning the aluminum at the fold line but what is the necessity for this fabrication? I'm not sure what you mean by a "racing pad" but I can't see any correlation between sharp and speed. Unless you mean that the hard chines have a sharp edge whereby they are more effective in combating lateral forces? I agree, that if one is determined to use this sort of bend that one can probably design something that necessitates it but it is doubtful that it is really necessary. In addition, I do not believe that, providing you are talking about lengths usually found in boat building, say chine logs, that run the length of the boat that warping will not be a problem. You say you can see some warping in a 3 ft. piece... What about 45 ft. chines on a sail boat? My assessment, for whatever it is worth, is that "your" system is certainly viable and, depending on the size of the weld bead, may even be stronger then a simple bend, however... It takes more time to make and will be more costly as well as offering more chances of error in manufacture then alternate methods. Cheers, Bruce (bruceinbangkokatgmaildotcom) |
Cut and Fold Aluminum
"Bruce In Bangkok" wrote in message
I suppose the most logical question is "why". Yes, you can bend aluminum at a sharper angle and have a less radiused bend by thinning the aluminum at the fold line but what is the necessity for this fabrication? I'm not sure what you mean by a "racing pad" but I can't see any correlation between sharp and speed. Unless you mean that the hard chines have a sharp edge whereby they are more effective in combating lateral forces? On certain types of boats there is a narrow "pad" along the keel about a foot wide. This will vary based on design, weight, and over all size of the boat. At high speeds the boat is running mostly on this pad. Far be it from me to explain the dynamics of it, (I'm just parroting what the speed junkies say here) but there are a couple things that can improve speed. I certainly do not know all the design characteristics that contribute to optimum design, but one of them is supposed to be the sharpness of the edge of this pad. Perhaps it has something to due with the way it sheds water or breaks the surface tension of the water. Another is a rough rather than smooth finish to the bottom of the pad. That most definitely has to do with breaking the surface tension of the water. Like a shark skin bathing suit or the finish on certain high tech racing sail boats. I agree, that if one is determined to use this sort of bend that one can probably design something that necessitates it but it is doubtful that it is really necessary. Well, obviously if the goal does not involve eeking 1 more MPH out of your hull's top speed there's no point. LOL. Pun intended. In addition, I do not believe that, providing you are talking about lengths usually found in boat building, say chine logs, that run the length of the boat that warping will not be a problem. I think it would be much less of a problem than with two separate pieces joined to make the same edge. You say you can see some warping in a 3 ft. piece... What about 45 ft. chines on a sail boat? Ah, see. Now I know you didn't understand what I wrote. I saw that kind of warping in pieces that long that were welded together to form the edge. Not in a single piece thinned and folded. Big difference. My apologies for not being clear. When you start with one piece that is bent to form an angle its going to be much more rigid than two pieces stuck together. The remaining metal that holds the two legs of the angle together will not allow them to expand and contract at different rates due to vagaries in welding technique. I was mostly trying to point out that after I had completed my initial work pieces I experimented some to see what else worked and how it worked. My assessment, for whatever it is worth, Its worth a lot. If I do not look at ideas from a different point of view I can't see what's wrong with them or how to make them better. It forces me to engage my brain. is that "your" system is certainly viable and, depending on the size of the weld bead, may even be stronger then a simple bend, however... It takes more time to make and will be more costly as well as offering more chances of error in manufacture then alternate methods. Like? Roller bending? Edge welding two pieces? Braking? Well, I don't know what you can do with roller bending, but they use it to put longitudinal creases in sheet for strength. Not sure how it would apply in this case anyway. I guess it might be an alternative way to make my thinned and folded edge instead of the brute force method I used before. It might make doing this more practical on longer pieces. Edge welding. No way. To do an ideal corner weld you have to weld it twice. I covered that. Most commercial mass production builders don't, but a lot of their boats crack too. Weld, back chip, weld. Braking? Well see this one is arguable. A brake is a tried and true method. It works and its fast. If you can afford one big enough to do the job. At this time I can't. It will definitely not make a bend as sharp as the process I describe. I can setup a built rig to bend "thinned" metal. I am sure the weld will be better than two pieces edge welded in less time. IN GENERAL... There is some grey area about the actual deep corner of the inside of the bend. I guess to resolve that I would need to weld up some more pieces and then slice it up to see if I get those corner voids I fear. If it gets a void in it then there is a very thin bit of aluminum on the outside which could break through easily. Not an issue for one outing or even a dozen, but it could create a pocket that could trap water. We know about trapped water and aluminum over time. Big potential problem. The ability to perform the process is not in question. The reason is in question depending on your goals. My reason for considering the idea is building an aluminum boat that will out run a glass boat in the same size class. ie to take advantage of the weight savings with out throwing them away on hull shape. My biggest concern would be the stresses on this very sharp hard point. A hard point (as I am sure you already know) is a corner, turn, or bend in the design of a boat or other structure that may concentrate the stress from external forces due to a fast or abrupt change in shape. That's why we often see stress cracks in the gel coat of glass boats in the corners of the top cap. Its also why we see cracks at the weld in the back corner of a lot of older Trackers and some other boats or at the front corners of square jon boats. (HAZ and alloy selection not withstanding.) |
P.S. Cut and Fold Aluminum
P.S. Thank you. A different point of view is appreciated.
|
Cut and Fold Aluminum
Bob La Londe wrote:
/snip/ I took a good stainless brush and polished the inside of the angled and then welded a bead right down the inside. No worries about air contamination since there is no opening to the other side. No back chipping necessary. Wire-feed? Mig? Tig? Bronze weld stick?? Brian W |
Cut and Fold Aluminum
On Thu, 10 Dec 2009 19:02:23 -0700, "Bob La Londe"
wrote: "Bruce In Bangkok" wrote in message I suppose the most logical question is "why". Yes, you can bend aluminum at a sharper angle and have a less radiused bend by thinning the aluminum at the fold line but what is the necessity for this fabrication? I'm not sure what you mean by a "racing pad" but I can't see any correlation between sharp and speed. Unless you mean that the hard chines have a sharp edge whereby they are more effective in combating lateral forces? On certain types of boats there is a narrow "pad" along the keel about a foot wide. This will vary based on design, weight, and over all size of the boat. At high speeds the boat is running mostly on this pad. Far be it from me to explain the dynamics of it, (I'm just parroting what the speed junkies say here) but there are a couple things that can improve speed. I certainly do not know all the design characteristics that contribute to optimum design, but one of them is supposed to be the sharpness of the edge of this pad. Perhaps it has something to due with the way it sheds water or breaks the surface tension of the water. Another is a rough rather than smooth finish to the bottom of the pad. That most definitely has to do with breaking the surface tension of the water. Like a shark skin bathing suit or the finish on certain high tech racing sail boats. I agree, that if one is determined to use this sort of bend that one can probably design something that necessitates it but it is doubtful that it is really necessary. Well, obviously if the goal does not involve eeking 1 more MPH out of your hull's top speed there's no point. LOL. Pun intended. In addition, I do not believe that, providing you are talking about lengths usually found in boat building, say chine logs, that run the length of the boat that warping will not be a problem. I think it would be much less of a problem than with two separate pieces joined to make the same edge. You say you can see some warping in a 3 ft. piece... What about 45 ft. chines on a sail boat? Ah, see. Now I know you didn't understand what I wrote. I saw that kind of warping in pieces that long that were welded together to form the edge. Not in a single piece thinned and folded. Big difference. My apologies for not being clear. When you start with one piece that is bent to form an angle its going to be much more rigid than two pieces stuck together. The remaining metal that holds the two legs of the angle together will not allow them to expand and contract at different rates due to vagaries in welding technique. I was mostly trying to point out that after I had completed my initial work pieces I experimented some to see what else worked and how it worked. My assessment, for whatever it is worth, Its worth a lot. If I do not look at ideas from a different point of view I can't see what's wrong with them or how to make them better. It forces me to engage my brain. is that "your" system is certainly viable and, depending on the size of the weld bead, may even be stronger then a simple bend, however... It takes more time to make and will be more costly as well as offering more chances of error in manufacture then alternate methods. Like? Roller bending? Edge welding two pieces? Braking? Well, I don't know what you can do with roller bending, but they use it to put longitudinal creases in sheet for strength. Not sure how it would apply in this case anyway. I guess it might be an alternative way to make my thinned and folded edge instead of the brute force method I used before. It might make doing this more practical on longer pieces. Edge welding. No way. To do an ideal corner weld you have to weld it twice. I covered that. Most commercial mass production builders don't, but a lot of their boats crack too. Weld, back chip, weld. Braking? Well see this one is arguable. A brake is a tried and true method. It works and its fast. If you can afford one big enough to do the job. At this time I can't. It will definitely not make a bend as sharp as the process I describe. I can setup a built rig to bend "thinned" metal. I am sure the weld will be better than two pieces edge welded in less time. IN GENERAL... There is some grey area about the actual deep corner of the inside of the bend. I guess to resolve that I would need to weld up some more pieces and then slice it up to see if I get those corner voids I fear. If it gets a void in it then there is a very thin bit of aluminum on the outside which could break through easily. Not an issue for one outing or even a dozen, but it could create a pocket that could trap water. We know about trapped water and aluminum over time. Big potential problem. The ability to perform the process is not in question. The reason is in question depending on your goals. My reason for considering the idea is building an aluminum boat that will out run a glass boat in the same size class. ie to take advantage of the weight savings with out throwing them away on hull shape. My biggest concern would be the stresses on this very sharp hard point. A hard point (as I am sure you already know) is a corner, turn, or bend in the design of a boat or other structure that may concentrate the stress from external forces due to a fast or abrupt change in shape. That's why we often see stress cracks in the gel coat of glass boats in the corners of the top cap. Its also why we see cracks at the weld in the back corner of a lot of older Trackers and some other boats or at the front corners of square jon boats. (HAZ and alloy selection not withstanding.) I wish that you could point me at a url showing this "speed pad" as I can't seem to visualize it, nor can I find more then the words, i.e., has a speed pad. I am somewhat familiar with the hulls of both three point hulls (the old speed boat hulls with the sponsons) and more modern open ocean racing stuff, but the speed pad defeats me True that corners can be stress risers, or hard points, but simply having a sharp corner does not cause cracking, it simply provides a location where, assuming that the item is incorrectly designed, stresses will concentrate. So, if you have an item that is not designed to resist the forces applied to it a sharp corner will be the likely location for deformation to occur. Again, as I previously wrote, if you want to use a bent/welded structure then you will certainly be able to design a need for it :-) Cheers, Bruce (bruceinbangkokatgmaildotcom) |
Cut and Fold Aluminum
"brian whatcott" wrote in message
... Bob La Londe wrote: /snip/ I took a good stainless brush and polished the inside of the angled and then welded a bead right down the inside. No worries about air contamination since there is no opening to the other side. No back chipping necessary. Wire-feed? Mig? Tig? Bronze weld stick?? My work pieces and experimental pieces were MIG welded with a big blue 212 is 5000 series wire (I can never remember without looking it up) on 5052 ..125 sheet. |
Cut and Fold Aluminum
"Bruce In Bangkok" wrote in message
... I wish that you could point me at a url showing this "speed pad" as I can't seem to visualize it, nor can I find more then the words, i.e., has a speed pad. I am somewhat familiar with the hulls of both three point hulls (the old speed boat hulls with the sponsons) and more modern open ocean racing stuff, but the speed pad defeats me Most modern high performance fiberglass bass boats made today have a pad style bottom atleast to some degree. Fast Cat (tunnel) and a few shallow V and pocket tunnel flats boats being the exceptions. http://www.bwbmag.com/output.cfm?id=1122481 "When we think of a bass boat, we typically envision a modified V hull, with a pad bottom, and more often than not, an extended transom/built-in jackplate. Pretty cool stuff, right? " Kinda goes to the argument that it's a pretty common thing if that's what "we typically envision." Here is an aluminum one, but I do not like their design. Most are flatter, although a lot of Rangers have a semi V pad like that. I mostly do not like the sandwiched or layer construction for aluminum as it can trap water. Their V pad might be the most efficient design for some setups, or possibley the best compromise: http://www.freepatentsonline.com/6666162.html Here is a picture of the inside the hull for one under construction. The outside view would be much more defined. http://media.photobucket.com/image/b...lassonhull.jpg I am finding that there is an amazing dearth of pictures online of the bottom of bass boats. I am finding myself headed out to the shop to take pictures of the bottom of my Basscat. Here is a view from the transom: http://www.yumabassman.com/pictures/shelf-001.gif And here is another from underneath. I played with the colors and the contrast so that you could see it's a fairly long structure on the bottom of the boat. About half the length of the boat. http://www.yumabassman.com/pictures/shelf-002.gif The boat in the last two pictures is not particularly fast as bass boats in this size class go. Its being pushed by a factory stock Mercury 250 Pro XS that dynos out at about 260-270 prop shaft horsepower depending on elevation, temperature, humidity, etc. It's a 20 foot 4 inch fiberglass boat and it weighs about 3000 lbs give or take depending on fuel, livewells, gear, driver, and passengers, etc. I have GPSed it at 74+ MPH (statute miles) with a pretty good load. With this particular boat I have been able to average 60+ in 3 foot chop for a 30+ mile run in a tournament. There are guys running a slightly different prop getting 78-79 out of this same hull with what we call a "full tournament load." I picked the prop that gave me the better hole shot. I also have a sloppy hydraulic jack plate on this boat which I need to replace. I imagine it complicates my high speed driving a bit. Similar lighter boats the same size will run high 80s and there are a few pushing the century mark. I'm talking production 20 foot class fiberglass "modified V" pad bottom boats with a factory configuration 250 Pro XS motor. Not a hot rodded motor or a blue printed hull. Allison I am sure has several semi custom 20' glass composite pad Vs that will break 100 MPH in his stable running similar horsepower. He holds enough world records. He doesn't like the new 3 liter motors much though. Too heavy for his favorite boats. I am most definitely not grasping at some obscure concept as you seem to imply. Skeeter, Ranger, Triton, Champion, Procraft, Nitro, Allison, Bullet, Gambler, Blazer, Bass Cat, Hydrasports, etc all use a modified V pad bottom design in some form. It is not a new concept. Its been around for atleast 25 years that I know of first hand. Our first pad bottom boat was a 20' Hydrasport back in the mid 1980s. We ran an Evirnrude 235 race motor on it, we never had the nerve to find out how fast it would go. It was fast enough. To my knowledge none of the manufacturers make a production boat with super sharp edges on the pad because they would wear off quickly in typical use, and the edges would break easily compared to a rounded corner. The only thing that might be in question is my belief from the hearsay of professional boat builders and speed junkies that a sharp edge on the pad can somehow improve top speed. I've certainly seen the hulls that have been flipped over and trued up and the pads with the razor sharp corners. A single sheet stamped and formed might be able to achieve all that wonderfulness. The only stamp formed aluminum boat I am aware of the is the Tracker Avalanche and it is discontinued. I also think it as not a pad bottom, and it was welded right down the keel to join two piece. LOL. So much for wonderfulness. Yeah, I threw of non supporting side information in there, but I think it makes for a more interesting read. |
Cut and Fold Aluminum
"Bob La Londe" wrote in message
... I was looking at something else entirely when I ran across this. http://www.allisonboats.com/skid_planer.php He's hawking his lifting plate, but you can clearly see the pad on the rear of the boat in the pictures. |
Cut and Fold Aluminum
On Fri, 11 Dec 2009 20:44:31 -0700, "Bob La Londe"
wrote: "Bruce In Bangkok" wrote in message .. . I wish that you could point me at a url showing this "speed pad" as I can't seem to visualize it, nor can I find more then the words, i.e., has a speed pad. I am somewhat familiar with the hulls of both three point hulls (the old speed boat hulls with the sponsons) and more modern open ocean racing stuff, but the speed pad defeats me Most modern high performance fiberglass bass boats made today have a pad style bottom atleast to some degree. Fast Cat (tunnel) and a few shallow V and pocket tunnel flats boats being the exceptions. http://www.bwbmag.com/output.cfm?id=1122481 "When we think of a bass boat, we typically envision a modified V hull, with a pad bottom, and more often than not, an extended transom/built-in jackplate. Pretty cool stuff, right? " Kinda goes to the argument that it's a pretty common thing if that's what "we typically envision." Here is an aluminum one, but I do not like their design. Most are flatter, although a lot of Rangers have a semi V pad like that. I mostly do not like the sandwiched or layer construction for aluminum as it can trap water. Their V pad might be the most efficient design for some setups, or possibley the best compromise: http://www.freepatentsonline.com/6666162.html Here is a picture of the inside the hull for one under construction. The outside view would be much more defined. http://media.photobucket.com/image/b...lassonhull.jpg I am finding that there is an amazing dearth of pictures online of the bottom of bass boats. I am finding myself headed out to the shop to take pictures of the bottom of my Basscat. Here is a view from the transom: http://www.yumabassman.com/pictures/shelf-001.gif O.K. I see what you are talking about now. Essentially a flat bottomed boat once you reach the optimum speed. Cheers, Bruce (bruceinbangkokatgmaildotcom) |
Cut and Fold Aluminum
"Bruce In Bangkok" wrote in message
... On Fri, 11 Dec 2009 20:44:31 -0700, "Bob La Londe" wrote: "Bruce In Bangkok" wrote in message . .. I wish that you could point me at a url showing this "speed pad" as I can't seem to visualize it, nor can I find more then the words, i.e., has a speed pad. I am somewhat familiar with the hulls of both three point hulls (the old speed boat hulls with the sponsons) and more modern open ocean racing stuff, but the speed pad defeats me Most modern high performance fiberglass bass boats made today have a pad style bottom atleast to some degree. Fast Cat (tunnel) and a few shallow V and pocket tunnel flats boats being the exceptions. http://www.bwbmag.com/output.cfm?id=1122481 "When we think of a bass boat, we typically envision a modified V hull, with a pad bottom, and more often than not, an extended transom/built-in jackplate. Pretty cool stuff, right? " Kinda goes to the argument that it's a pretty common thing if that's what "we typically envision." Here is an aluminum one, but I do not like their design. Most are flatter, although a lot of Rangers have a semi V pad like that. I mostly do not like the sandwiched or layer construction for aluminum as it can trap water. Their V pad might be the most efficient design for some setups, or possibley the best compromise: http://www.freepatentsonline.com/6666162.html Here is a picture of the inside the hull for one under construction. The outside view would be much more defined. http://media.photobucket.com/image/b...lassonhull.jpg I am finding that there is an amazing dearth of pictures online of the bottom of bass boats. I am finding myself headed out to the shop to take pictures of the bottom of my Basscat. Here is a view from the transom: http://www.yumabassman.com/pictures/shelf-001.gif O.K. I see what you are talking about now. Essentially a flat bottomed boat once you reach the optimum speed. Essentially. Yes. A narrow flat bottom boat. Low resistance and tends to put motive force towards going forward rather than up. Speed and power available being major factors of course. I do not have the math skills or the engineering background to explain it all, but I think it works like this. The narrow pad creates less resistance than a V of similar surface area within the displacement envelope primarily, but not exclusively because of the surface tension of the water. There are other other forces such as angle of pressure, total pressure against forward movement etc. The idea is the boat comes up and then flattens out. The edge of the pad will break the surface tension of the water and shed the water much more quickly than than a straight V will, and it will have less surface area touching the water than a shallower V design or than a flat bottom boat. More of the extra power is used to push the boat forward rather than to lift the boat out of the water. I discovered this first hand when I went from a 225 (around 215-220 HP) to a 250 Pro XS (260-270 HP) on the boat I pictured. At 70+ I need less trim angle than I did at 68 (WOT) with the old motor. This has been bouncing around in my head as well since you forced me to think a little more. The reason I think a sharp edge is more efficient is basically the same as why a pad is more efficient at optimum speeds. The sharper edge will break the surface tension and shed water weight and reduce resistance much sooner than a rounded edge. The average boater will never notice the difference, but guys who are always running on the ragged edge (oxymoron not intended) and looking for the best performing prop to run right at redline will notice the extra 1 or 2 miles per hour. The difference is certainly much less than the simple large gains from a pad style bottom vs a V bottom. There are a lot of dynamics involved. Some can be engineered away, but since I am not an engineer I have to visualize and maybe experiment. ** Thought I better throw this in: ** Chine walk can be deadly scary in such a boat if not properly setup or if driven by somebody who hasn't taken the time to learn to drive their rig. The biggest safety move for anybody else reading this is to SLOW DOWN gradually. A sudden loss of throttle can be almost as dangerous. Especially in traffic in a busy system. Increase power (like I did) and Bob La Londe www.YumaBassMan.com |
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"Bob La Londe" wrote in message ... ** Thought I better throw this in: ** Chine walk can be deadly scary in such a boat if not properly setup or if driven by somebody who hasn't taken the time to learn to drive their rig. The biggest safety move for anybody else reading this is to SLOW DOWN gradually. A sudden loss of throttle can be almost as dangerous. Especially in traffic in a busy system. Increase power (like I did) and ... .... and it's a whole new rig to learn how to drive. Bob La Londe www.YumaBassMan.com |
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On Sat, 12 Dec 2009 14:01:13 -0700, "Bob La Londe"
wrote: "Bruce In Bangkok" wrote in message .. . On Fri, 11 Dec 2009 20:44:31 -0700, "Bob La Londe" wrote: "Bruce In Bangkok" wrote in message ... I wish that you could point me at a url showing this "speed pad" as I can't seem to visualize it, nor can I find more then the words, i.e., has a speed pad. I am somewhat familiar with the hulls of both three point hulls (the old speed boat hulls with the sponsons) and more modern open ocean racing stuff, but the speed pad defeats me Most modern high performance fiberglass bass boats made today have a pad style bottom atleast to some degree. Fast Cat (tunnel) and a few shallow V and pocket tunnel flats boats being the exceptions. http://www.bwbmag.com/output.cfm?id=1122481 "When we think of a bass boat, we typically envision a modified V hull, with a pad bottom, and more often than not, an extended transom/built-in jackplate. Pretty cool stuff, right? " Kinda goes to the argument that it's a pretty common thing if that's what "we typically envision." Here is an aluminum one, but I do not like their design. Most are flatter, although a lot of Rangers have a semi V pad like that. I mostly do not like the sandwiched or layer construction for aluminum as it can trap water. Their V pad might be the most efficient design for some setups, or possibley the best compromise: http://www.freepatentsonline.com/6666162.html Here is a picture of the inside the hull for one under construction. The outside view would be much more defined. http://media.photobucket.com/image/b...lassonhull.jpg I am finding that there is an amazing dearth of pictures online of the bottom of bass boats. I am finding myself headed out to the shop to take pictures of the bottom of my Basscat. Here is a view from the transom: http://www.yumabassman.com/pictures/shelf-001.gif O.K. I see what you are talking about now. Essentially a flat bottomed boat once you reach the optimum speed. Essentially. Yes. A narrow flat bottom boat. Low resistance and tends to put motive force towards going forward rather than up. Speed and power available being major factors of course. I do not have the math skills or the engineering background to explain it all, but I think it works like this. The narrow pad creates less resistance than a V of similar surface area within the displacement envelope primarily, but not exclusively because of the surface tension of the water. There are other other forces such as angle of pressure, total pressure against forward movement etc. The idea is the boat comes up and then flattens out. The edge of the pad will break the surface tension of the water and shed the water much more quickly than than a straight V will, and it will have less surface area touching the water than a shallower V design or than a flat bottom boat. More of the extra power is used to push the boat forward rather than to lift the boat out of the water. I discovered this first hand when I went from a 225 (around 215-220 HP) to a 250 Pro XS (260-270 HP) on the boat I pictured. At 70+ I need less trim angle than I did at 68 (WOT) with the old motor. As speed increases water pressure against the bottom of the boat increases and increases lift (if that is what you want to term the force acting against the bottom of the boat). If "X" lifting force is applied to a flat surface, at 90 degrees to the force, the entire force is applied to the surface at 90 degrees to the surface. If the same force is applied to a surface at other then 90 degrees only a part of the force will be applied at 90 degrees to the surface. Thus the same lift, derived from forward speed,applied to a vee hull will result in less force being applied to raise the boat "up" then if the same lifting force applied to a flat surface. This has been bouncing around in my head as well since you forced me to think a little more. The reason I think a sharp edge is more efficient is basically the same as why a pad is more efficient at optimum speeds. The sharper edge will break the surface tension and shed water weight and reduce resistance much sooner than a rounded edge. The average boater will never notice the difference, but guys who are always running on the ragged edge (oxymoron not intended) and looking for the best performing prop to run right at redline will notice the extra 1 or 2 miles per hour. Rather then "surface tension" I suspect (if the effect is not large) that it is simply a matter of surface area. Exactly the same reason that the small flat bottom is faster then a vee. At any speed it would take more "lift" to raise an inclined (vee) surface then one at right angles to the force, thus any rounded corner would act much the same as the vee, for that portion of the pad, and reduce total lifting force, by some percentage. However.... I have read that the multiple, sharp edged, chine designs actually increase speed because the sharp edged chines increase the amount of air that is trapped and forced to flow under the boat but whether that works to decrease drag by reducing the viscosity of the water or by reducing the wetted area I don't know. The difference is certainly much less than the simple large gains from a pad style bottom vs a V bottom. That is a simple to demonstrate. Hold your hand out of the window of a moving auto. If you hold your hand flat there is a large force applied to the hand. Turn your hand on edge and there is little force applied. There are a lot of dynamics involved. Some can be engineered away, but since I am not an engineer I have to visualize and maybe experiment. ** Thought I better throw this in: ** Chine walk can be deadly scary in such a boat if not properly setup or if driven by somebody who hasn't taken the time to learn to drive their rig. The biggest safety move for anybody else reading this is to SLOW DOWN gradually. A sudden loss of throttle can be almost as dangerous. Especially in traffic in a busy system. Increase power (like I did) and Bob La Londe www.YumaBassMan.com Cheers, Bruce (bruceinbangkokatgmaildotcom) |
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"Bruce In Bangkok" wrote in message
... On Sat, 12 Dec 2009 14:01:13 -0700, "Bob La Londe" wrote: "Bruce In Bangkok" wrote in message . .. On Fri, 11 Dec 2009 20:44:31 -0700, "Bob La Londe" wrote: "Bruce In Bangkok" wrote in message m... I wish that you could point me at a url showing this "speed pad" as I can't seem to visualize it, nor can I find more then the words, i.e., has a speed pad. I am somewhat familiar with the hulls of both three point hulls (the old speed boat hulls with the sponsons) and more modern open ocean racing stuff, but the speed pad defeats me Most modern high performance fiberglass bass boats made today have a pad style bottom atleast to some degree. Fast Cat (tunnel) and a few shallow V and pocket tunnel flats boats being the exceptions. http://www.bwbmag.com/output.cfm?id=1122481 "When we think of a bass boat, we typically envision a modified V hull, with a pad bottom, and more often than not, an extended transom/built-in jackplate. Pretty cool stuff, right? " Kinda goes to the argument that it's a pretty common thing if that's what "we typically envision." Here is an aluminum one, but I do not like their design. Most are flatter, although a lot of Rangers have a semi V pad like that. I mostly do not like the sandwiched or layer construction for aluminum as it can trap water. Their V pad might be the most efficient design for some setups, or possibley the best compromise: http://www.freepatentsonline.com/6666162.html Here is a picture of the inside the hull for one under construction. The outside view would be much more defined. http://media.photobucket.com/image/b...lassonhull.jpg I am finding that there is an amazing dearth of pictures online of the bottom of bass boats. I am finding myself headed out to the shop to take pictures of the bottom of my Basscat. Here is a view from the transom: http://www.yumabassman.com/pictures/shelf-001.gif O.K. I see what you are talking about now. Essentially a flat bottomed boat once you reach the optimum speed. Essentially. Yes. A narrow flat bottom boat. Low resistance and tends to put motive force towards going forward rather than up. Speed and power available being major factors of course. I do not have the math skills or the engineering background to explain it all, but I think it works like this. The narrow pad creates less resistance than a V of similar surface area within the displacement envelope primarily, but not exclusively because of the surface tension of the water. There are other other forces such as angle of pressure, total pressure against forward movement etc. The idea is the boat comes up and then flattens out. The edge of the pad will break the surface tension of the water and shed the water much more quickly than than a straight V will, and it will have less surface area touching the water than a shallower V design or than a flat bottom boat. More of the extra power is used to push the boat forward rather than to lift the boat out of the water. I discovered this first hand when I went from a 225 (around 215-220 HP) to a 250 Pro XS (260-270 HP) on the boat I pictured. At 70+ I need less trim angle than I did at 68 (WOT) with the old motor. As speed increases water pressure against the bottom of the boat increases and increases lift (if that is what you want to term the force acting against the bottom of the boat). If "X" lifting force is applied to a flat surface, at 90 degrees to the force, the entire force is applied to the surface at 90 degrees to the surface. If the same force is applied to a surface at other then 90 degrees only a part of the force will be applied at 90 degrees to the surface. Thus the same lift, derived from forward speed,applied to a vee hull will result in less force being applied to raise the boat "up" then if the same lifting force applied to a flat surface. This has been bouncing around in my head as well since you forced me to think a little more. The reason I think a sharp edge is more efficient is basically the same as why a pad is more efficient at optimum speeds. The sharper edge will break the surface tension and shed water weight and reduce resistance much sooner than a rounded edge. The average boater will never notice the difference, but guys who are always running on the ragged edge (oxymoron not intended) and looking for the best performing prop to run right at redline will notice the extra 1 or 2 miles per hour. Rather then "surface tension" I suspect (if the effect is not large) that it is simply a matter of surface area. Exactly the same reason that the small flat bottom is faster then a vee. At any speed it would take more "lift" to raise an inclined (vee) surface then one at right angles to the force, thus any rounded corner would act much the same as the vee, for that portion of the pad, and reduce total lifting force, by some percentage. However.... I have read that the multiple, sharp edged, chine designs actually increase speed because the sharp edged chines increase the amount of air that is trapped and forced to flow under the boat but whether that works to decrease drag by reducing the viscosity of the water or by reducing the wetted area I don't know. Several designs do trap air by a number of methods. One you see that is fairly common is that they make the front portion of the boat in a big rounded M if you were to cut it in cross section about 1/3 back. My Bass cat kinda has that look also. Lots of boats do. It certainly works well towards eliminating spray over the bow. The guys at Basscat have even warned me that excessive trim can cause the boat to kite with a net effect similar to chine walk. This is caused by air though rather than the falling off due to balance or prop torque like regular chine walk. I am sure multiple chines do something as lots of designers use them. I always thought it was for stability and steering control at various speeds. Also to increase lift at a particular speed from the flat bottom of the individual chines. I suppose they could trap some air also, but I don't think that is the primary reason for them. There are some tunnel hull designs that do a much better job of providing air cushion. One I had the chance to play with for a couple years was a Baker twin tunnel made by Baker Custom Boats. It was another 20 footer but only had an EFI 200 on it. It would consistently run right at 65 GPS **regardless of the load (within reason)**. The basic setup was about 500 pounds heavier than my Basscat. Since the Basscat was originally powered with a much more modern 225 and only ran 3-5 MPH faster that is saying something. Can't really compare since I put the bigger motor on the kitten now. The big problem with tunnels is the extra weight and lost flotation for similar durability of construction. No big deal when you are running flat out, but makes a difference when sitting still and fishing or running water to rough to run flat out. None of the boats I have direct experience with are paper thin, shave every ounce, race boats. I wish I still had the Baker for the sake of this conversation, because if I recall correctly the center hull/deflector also was kind of a pad design. It was the best handling boat I have ever driven at speed. It steered like a car at any speed above idle. As a side note. The tunnel hull took light chop a lot smoother at speed than any of the pad bottom modified Vs, but when it gets rough the pad-V can slow down a little and run like a V hull. The tunnel has to stay on the high end of its speed range and run wave top to wave top hoping not to spear one, or find safe harbor. Everything is a compromise. Anyway... I guess its time to start doing some basic math and figuring out the weight of my theoretical sharp pad aluminum pad-v. LOL. Who knows. I might build it someday. Its late. I know I'm gonna look at this post tommorrow and wonder... what was I thinking. LOL. Bob La Londe www.YumaBassMan.com |
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"Bruce In Bangkok" wrote in message
... On Sat, 12 Dec 2009 14:01:13 -0700, "Bob La Londe" wrote: This has been bouncing around in my head as well since you forced me to think a little more. The reason I think a sharp edge is more efficient is basically the same as why a pad is more efficient at optimum speeds. The sharper edge will break the surface tension and shed water weight and reduce resistance much sooner than a rounded edge. The average boater will never notice the difference, but guys who are always running on the ragged edge (oxymoron not intended) and looking for the best performing prop to run right at redline will notice the extra 1 or 2 miles per hour. Rather then "surface tension" I suspect (if the effect is not large) that it is simply a matter of surface area. Exactly the same reason that the small flat bottom is faster then a vee. At any speed it would take more "lift" to raise an inclined (vee) surface then one at right angles to the force, thus any rounded corner would act much the same as the vee, for that portion of the pad, and reduce total lifting force, by some percentage. That is certainly part of the equation now that I think about it. Surface tension has an affect as well. I'm sure the answer is not one dimensional. However.... I have read that the multiple, sharp edged, chine designs actually increase speed because the sharp edged chines increase the amount of air that is trapped and forced to flow under the boat but whether that works to decrease drag by reducing the viscosity of the water or by reducing the wetted area I don't know. That could be both. Air cushion is definitely a factor in many designs but I am not sure that it's the primary factor in multiple chines. Seems I read somewhere that multiple chines was to increase lift at various speeds until the boat is at optimum cruising speed. Basically the multiple chines help it come out of the hole faster. I seem to recall and I think you mentioned it in passing earlier in this thread that it also helps with stability and steering control. If you have ever run a flat bottom boat that is adequately powered I'm sure you know that it planes out almost immediately. The way it was explained to me is that multiple chines are a compromise. Gives you more lift like a flat bottom, but as they come out of the water they cease to create drag. Now I'm tempted to start a whole new thread on air cushion designs. Tunnels. Twin tunnels. The big M shape of the front 1/3 to 1/2 of many of those modified V-Pad bottom boats. We could talk about lift, cavitation, kiting, Miss Budweiser doing end over end flips, LOL. My experience with tunnels is more limited, but I did have a Baker Custom Boats twin tunnel for a few years. Awesome ride in light chop. I think we can both agree that the less boat you have in the water (in general) the faster it will go. ** Thought I better throw this in: ** Chine walk can be deadly scary in such a boat if not properly setup or if driven by somebody who hasn't taken the time to learn to drive their rig. The biggest safety move for anybody else reading this is to SLOW DOWN gradually. A sudden loss of throttle can be almost as dangerous. Especially in traffic in a busy system. Increase power (like I did) and it's a whole new rig to learn to drive. Left that last bit in because it bears repeating. Bob La Londe www.YumaBassMan.com |
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"I am Tosk" wrote in message
... The article I read years ago studied the air that runs along the dozens of chines on the old Viking ships. The theory was that as the boat moved through the water, air bubbles would get trapped along the angles formed by the lap strake type construction. I suppose that could have an affect at displacement speeds. ie: Viking long boat/galley. |
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On Sat, 19 Dec 2009 11:28:16 -0500, I am Tosk
wrote: In article , says... "I am Tosk" wrote in message ... The article I read years ago studied the air that runs along the dozens of chines on the old Viking ships. The theory was that as the boat moved through the water, air bubbles would get trapped along the angles formed by the lap strake type construction. I suppose that could have an affect at displacement speeds. ie: Viking long boat/galley. Well, I think that was the theory. The author suggested it gave the boat lift and less surface contact, water to wood... IIRC, it was a long time ago when I read it. I think I read the same article - from one of the Norse museums as I remember, but the story really didn't sound quite right. A rowing and sailing boat that moved so fat that air was trapped at the plank edges and gave the boat more speed??? Funny that modern lapstrake boats don't seem to have the same reputation except for the fast ones, the ones with 50 - 60 horsepower, or more. The old lapstrake fishing boats with the 5 H.P. fishing motor don't seem to go a bit faster, plank edges or not. Cheers, Bruce (bruceinbangkokatgmaildotcom) |
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"Bruce In Bangkok" wrote:
reputation except for the fast ones, the ones with 50 - 60 horsepower, or more. Really fast? How fast is really fast? Do they meet USCG guidelines for power for their size? |
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"Bob La Londe" wrote in message
... "Bruce In Bangkok" wrote: reputation except for the fast ones, the ones with 50 - 60 horsepower, or more. Really fast? How fast is really fast? Do they meet USCG guidelines for power for their size? Merry Christmas Bruce. The reason I ask is that while I know there are some stupidly fast 50-60 HP rigs out there the average USCG approved 50 HP rig is not going to top 40 MPH, Well not by much. After much tweaking I have 42-44 GPS on my 16' flat bottom with a stainless prop, light chop, cool dry air, with two guys in the boat so it balances pretty good. If in our other discussions you are thinking that's pretty fast then I can understand some of our disagreement. That's real fast for that boat, and I have had some folks express surprise when it goes by, but in the genre of small fishing and bass boats its not fast at all. |
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On Thu, 24 Dec 2009 10:51:11 -0700, "Bob La Londe"
wrote: "Bob La Londe" wrote in message ... "Bruce In Bangkok" wrote: reputation except for the fast ones, the ones with 50 - 60 horsepower, or more. Really fast? How fast is really fast? Do they meet USCG guidelines for power for their size? Merry Christmas Bruce. The reason I ask is that while I know there are some stupidly fast 50-60 HP rigs out there the average USCG approved 50 HP rig is not going to top 40 MPH, Well not by much. After much tweaking I have 42-44 GPS on my 16' flat bottom with a stainless prop, light chop, cool dry air, with two guys in the boat so it balances pretty good. If in our other discussions you are thinking that's pretty fast then I can understand some of our disagreement. That's real fast for that boat, and I have had some folks express surprise when it goes by, but in the genre of small fishing and bass boats its not fast at all. I think that you misread what I wrote - "50 - 60 horsepower, or more.." I didn't restrict my comments to only 50 - 60 H.P. I have no idea about Coastguard restrictions but can walk down the dock here and see boats with two 200 H.P. outboards bolted on the back and they are in the 20 ft. range in length. Tenders for some of the larger yachts... Cheers, Bruce (bruceinbangkokatgmaildotcom) |
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"Bruce In Bangkok" wrote in message
... On Thu, 24 Dec 2009 10:51:11 -0700, "Bob La Londe" wrote: "Bob La Londe" wrote in message ... "Bruce In Bangkok" wrote: reputation except for the fast ones, the ones with 50 - 60 horsepower, or more. Really fast? How fast is really fast? Do they meet USCG guidelines for power for their size? Merry Christmas Bruce. The reason I ask is that while I know there are some stupidly fast 50-60 HP rigs out there the average USCG approved 50 HP rig is not going to top 40 MPH, Well not by much. After much tweaking I have 42-44 GPS on my 16' flat bottom with a stainless prop, light chop, cool dry air, with two guys in the boat so it balances pretty good. If in our other discussions you are thinking that's pretty fast then I can understand some of our disagreement. That's real fast for that boat, and I have had some folks express surprise when it goes by, but in the genre of small fishing and bass boats its not fast at all. I think that you misread what I wrote - "50 - 60 horsepower, or more.." I didn't restrict my comments to only 50 - 60 H.P. I have no idea about Coastguard restrictions but can walk down the dock here and see boats with two 200 H.P. outboards bolted on the back and they are in the 20 ft. range in length. Tenders for some of the larger yachts... Actually in the 20' class there are plenty of boats than can handle that much HP and MORE. USCG's HP rating guideline booklet does not rate boats over 20'. Plenty are manufactured with "HP: UNLIMITED" on the data plate. My Baker Custom said unlimited on its data plate. My dad is running a pair of 150's on his 22' cuddy cabin, but it's a different class of boat. I was just wondering if we were thinking about the same speed ranges when conversing. Most of my thoughts were in regards to 20' class shallow draft 70-90 MPH boats. Usually in the 200 to 250 race tune power range. There are 20 footers in this class that will break 90 (some pushing the 100 mark) with a 200 and others with a 250XS that struggle to break 80. I actually have a spare 225 that I have been playing with the idea of building a fast hull for. What I will probably wind up with in the end is a compromise. Probably a shallow V (15 deg or less deadrise (just enough to shed air bubbles)) pocket tunnel (specifically for jets) with an extension plate to mate to the jet shoe, and swap the lower unit for a jet pump for river running. In the mean time of course I have wrapped my mind and visualization skills around a number of designs from super stable pretty fast twin tunnels to super fast pad bottoms. Since any boat I run is going to have internal configuration like a bass boat I pretty much dismissed CLASS As and pickle forks. |
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On Thu, 24 Dec 2009 22:46:53 -0700, "Bob La Londe"
wrote: "Bruce In Bangkok" wrote in message .. . On Thu, 24 Dec 2009 10:51:11 -0700, "Bob La Londe" wrote: "Bob La Londe" wrote in message ... "Bruce In Bangkok" wrote: reputation except for the fast ones, the ones with 50 - 60 horsepower, or more. Really fast? How fast is really fast? Do they meet USCG guidelines for power for their size? Merry Christmas Bruce. The reason I ask is that while I know there are some stupidly fast 50-60 HP rigs out there the average USCG approved 50 HP rig is not going to top 40 MPH, Well not by much. After much tweaking I have 42-44 GPS on my 16' flat bottom with a stainless prop, light chop, cool dry air, with two guys in the boat so it balances pretty good. If in our other discussions you are thinking that's pretty fast then I can understand some of our disagreement. That's real fast for that boat, and I have had some folks express surprise when it goes by, but in the genre of small fishing and bass boats its not fast at all. I think that you misread what I wrote - "50 - 60 horsepower, or more.." I didn't restrict my comments to only 50 - 60 H.P. I have no idea about Coastguard restrictions but can walk down the dock here and see boats with two 200 H.P. outboards bolted on the back and they are in the 20 ft. range in length. Tenders for some of the larger yachts... Actually in the 20' class there are plenty of boats than can handle that much HP and MORE. USCG's HP rating guideline booklet does not rate boats over 20'. Plenty are manufactured with "HP: UNLIMITED" on the data plate. My Baker Custom said unlimited on its data plate. My dad is running a pair of 150's on his 22' cuddy cabin, but it's a different class of boat. I was just wondering if we were thinking about the same speed ranges when conversing. Most of my thoughts were in regards to 20' class shallow draft 70-90 MPH boats. Usually in the 200 to 250 race tune power range. There are 20 footers in this class that will break 90 (some pushing the 100 mark) with a 200 and others with a 250XS that struggle to break 80. I actually have a spare 225 that I have been playing with the idea of building a fast hull for. What I will probably wind up with in the end is a compromise. Probably a shallow V (15 deg or less deadrise (just enough to shed air bubbles)) pocket tunnel (specifically for jets) with an extension plate to mate to the jet shoe, and swap the lower unit for a jet pump for river running. In the mean time of course I have wrapped my mind and visualization skills around a number of designs from super stable pretty fast twin tunnels to super fast pad bottoms. Since any boat I run is going to have internal configuration like a bass boat I pretty much dismissed CLASS As and pickle forks. Walking down the other dock the other day I came across an open boat with two 150 HP outboards. I measured the length and it was 20 ft. LOD. An essentially open boat. I think you'd call it a front loader or some such name as it had seats forward of the helm which was just a small panel located amidships with the wheel and instrument panel - with a little canopy over the seat and instrument panel. I wonder about whoever owns it... an open boat in a country where it is either pouring down rain or the sun is blazing down. Perhaps that is why it just sits there at the dock? Cheers, Bruce (bruceinbangkokatgmaildotcom) |
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"Bruce In Bangkok" wrote in message
... Walking down the other dock the other day I came across an open boat with two 150 HP outboards. I measured the length and it was 20 ft. LOD. An essentially open boat. I think you'd call it a front loader or some such name as it had seats forward of the helm which was just a small panel located amidships with the wheel and instrument panel - with a little canopy over the seat and instrument panel. Some guys favor a boat like that for some types of fishing as it allows them to fight a fish all the way around the boat. Some people just buy a boat because they think it looks cool. Some just want to be able to tell their friends they have a boat. |
I worked for many years on brake presses. The biggest one I worked on was a 600ton Cincinatti, which could bent a 20 ft length of half inch steel plate 90 degrees. Boy, I miss those toys.
Some types of aluminium bend a sharp 90 degrees with no risk of breaking, some have to be heated to make even a radiused 90 degree bend.On that stuff even a slight scratch on the back side of it will cause a crack. I build all my hatches by notching out the corners of a piece of 1/8th inch aluminium and after having slight kinks put in corner to corner for stiffness, I have the four sides bent up 90 degrees. This leaves one four 3 inch welds on the corners, to finish a fine aluminium hatch cover. As a former brake operator I know it's only about 20 minutes work, so it doesn't cost much to have a sheet metal shop do it. |
asp tree grid ejasjueuekfa
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