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BB,
Don't bother with anymore replies. Doug knows he FU and is trying to get a reply that he can bebunk. The example of the plank supported at both ends is good for the Topping lift at the end of the boom. It doesn't hold for the Solid vang. With a solid vang one of the horses would have to be done away with. Doug knows that. Its just to much for him to admit, as stated originally, that a rigid vang cannot give the same lifting power as a topping reinforced main at the end Ole Thom. |
If you change to a rigid vang, you still have the
topping lift for all these things--unless you take it off. "Thom Stewart" wrote Bart, I know that topping lift can be a PITA but it still has a lot of advantages over the rigid vang. Just to mention a few; A spare and ready back stay A man overboard hoist An end reinforcement of the boom when you want to use it as a crane (Dingy recovery) |
Thom Stewart wrote:
BB, Don't bother with anymore replies. Yes. Please. ... Doug knows he FU and is trying to get a reply that he can bebunk. ??? So far I haven't "debunked" anything. I have tried to explain some basic engineering. The example of the plank supported at both ends is good for the Topping lift at the end of the boom. It doesn't hold for the Solid vang. With a solid vang one of the horses would have to be done away with. ??? A better analogy would be a plank locked in place at one end, and supported somewhere along it's length. Doug knows that. Its just to much for him to admit, as stated originally, that a rigid vang cannot give the same lifting power as a topping reinforced main at the end Yes it can, and many of them do. DSK |
| Why not? If the boom can take the torsion in one direction, then unless | it is a very weird asymmetric structure, then it will take the same in | the opposite direction. Capt. Mooron wrote: This is where you stray from engineering principal... that is not the case at all nor is it the rule. Oh? Are you saying that a symmetric structural member is stronger one way than the other? If you nail a board into a frame, you have to be careful to put it label side up or something? | Sure it is. It's exactly the same in both directions. No Doug... it is most assuredly not the same in both directions if only by the points of compression Well, go explain that to Newton. He had a little to say on the subject. .... forget the boom or assume it indestrutructable and unbendable. OK | The max forces are limited by the righting moment of the boat. On a 30 | footer, it doesn't need to be that massive. On bigger boats... take a | look at the vangs on IACC racers... Nobody is discussing righting moment here Doug... Well, if we're not discussing the strength of the boom, nor the limit of force on the whole system, then the only thing to complain about it the compressive strength of the vang itself (which with a proper one, should not be an issue) or the strength of the connections between vang, mast, & boom. If you break the gooseneck, then it probably wasn't strong enough anyway. The vang connections take greater strain than the gooseneck (due to the greater leverage) and thus they have to be stronger yet. So that rules them out. Now all you're left with is the strength of the vang itself. How about a hydraulic cylinder? Some are. How about a very thick solid SS turnbuckle with machine threads? Some are. That leaves the little fiberglass rod ones (which I agree are not going to hold up much load) and the spring loaded locking kind. I suggest you take a look at the specs on several and see if you can't find one or two that look strong enough to hold up a substantial load. They're there. ... we are discussing the ability of basic mathematics in regards to the placement of the vang and the loads you expect it to encounter. Not really. You were trying to obfuscate the basic point that a vang needs to be strong enough to stand up to hard sailing, and if it will do that, it is almost certainly strong enough the other way too (unless it's one of those wimpy hen-pecked little fiberglass rod ones). | For using the boom as a lifting device.... you will stress the vang unduly | with a set-up located that far back on the load arm. | | ??? Well come on now Doug.... it's basic common sense engineering principal! It can't be that basic, I have no clue what you're talking about. Doesn't seem to pertain to vangs, though. | ... It's not designed for | that. | | It should be. Anything less would not be safe for sailing IMHO. No it's not... it's designed as a VANG! I guess a tackle employed as a vang would not be strong enough to use for anything else? I do one thing... you can't push a rope. DSK |
Bart,
That is what started this discussion. I believe it was you that said,"That with a Rigel Vang you could get rid of the topping lift." I mentioned that although TL is a PITA it does have other function. You should weigh them all before doing away with it. |
On Wed, 18 Aug 2004 07:33:02 -0400, DSK wrote:
Thom Stewart wrote: If you use the solid vange to hold up the boom when using it for a crane, it will soon be like Neals Boom, with a pipe in it. The topping lift bears the load. The boom only position the lifting location. Not if it was built properly in the first place. I must be more spoiled than I realize, having sailed boats with strong spars and decent rigging. Oh well. If your boom will not lift a dinghy then it will not stand up to hard sailing either. A topping lift might "bear the load" but it also puts the boom under more compression than the weight of the load. The usual failure point (in my experience) is the gooseneck. Fresh Breezes- Doug King I am no engineer, but my boat does have a well built boom (Hall) and a solid vang (Offshore Spars) and a topping lift. I am not worried about any of the three under any conditions. My vang does have a means to "lock" it with a quick release pin and a number of holes into which it can be placed. Last year I was sailing when the water levels were VERY low and we managed to find a shallow sandy spot and run aground. Hey, not the first time or the last, I am sure. We were able to swing the boom out over the side and my friend climbed out on the end of it to give us some heel as we had very little wind to work with. We managed to sail off and enjoy the day. No big deal. I keep the topping lift because it is quick and easy to lift the boom for extra clearance above the bimini when the sail is down, rather than screwing with the vang. Just my preference, but it works well for me. If my main had more roach to it that was creating a chaffe issue, I would probably get rid of it as I don't really *need* it, but I like it, so the) |
Doug,
I mentioned early in this discussion that with a topping lift hoisting boom, the boom only positions the location of hoist. There is very, very little force on the boom. The hoist is on the topping lift. Mooran re-stated this. You are the one insisting the force is the same on the end of the boom supported on the other end by a Vang and a gooseneck. We say BS and sign off. Ole Thom |
No they don
DSK wrote: Maybe if you sailed anything other than a cheap old beater, maybe if you had some experience with other than obsolete gear, maybe if you hung around sailors who know how to sail and how to rig their boats properly, you'd know that solid vangs have locks. Since you are always right, I can only surmise that my locks were lost at the factory. Cheers |
Hi Thom
Actually the force is revealed as compression on the boom in the topping lift case and bending in the vang lifgt case. I wonder how many booms Dog has bent lifting loads that way??? In our case, the solid vang only serves to hold the boom up is the sail is dropped (and no topping lift used). Just another thought, do you suppose Doug thinks that compressive and tensile strengths are the same in symmetrical structures??? Cheers Thom Stewart wrote: Doug, I mentioned early in this discussion that with a topping lift hoisting boom, the boom only positions the location of hoist. There is very, very little force on the boom. The hoist is on the topping lift. Mooran re-stated this. You are the one insisting the force is the same on the end of the boom supported on the other end by a Vang and a gooseneck. We say BS and sign off. Ole Thom |
DSK wrote: Think about this, Thom... the force on the end of the boom is going to be very great when sailing hard... enough to lean the boat over a lot. Good lord! I wonder why I can pull the end of the boom to windward by hand on the traveller but not lift the side of the boat up???? superman!!! Cheers |
DSK wrote: Thom Stewart wrote: If you use the solid vange to hold up the boom when using it for a crane, it will soon be like Neals Boom, with a pipe in it. The topping lift bears the load. The boom only position the lifting location. Not if it was built properly in the first place. I must be more spoiled than I realize, having sailed boats with strong spars and decent rigging. Oh well. If your boom will not lift a dinghy then it will not stand up to hard sailing either. A topping lift might "bear the load" but it also puts the boom under more compression than the weight of the load. Compression is not the same as bending from a point load on a hollow spar. Shessh. Look, my boom may support 10 tons in conpression but would fold instantly if that weight was palced at the end of the boom with it being held up at the vang attachment. Think about it or try an experiment with a toothpick. It's really engineering 101! Cheers |
Yes, we have a solid vang and topping lift for good reason.
Cheers Thom Stewart wrote: Bart, That is what started this discussion. I believe it was you that said,"That with a Rigel Vang you could get rid of the topping lift." I mentioned that although TL is a PITA it does have other function. You should weigh them all before doing away with it. |
Please contact Garhauer, who is a major player, if not the biggest in this
field and ask how many of their vangs have locks. You might want to check your facts. Hall Spar's Quick Vang is probably the #1 selling solid vang. Garhaur's units which are very well made are seen mostly as supplied equipment on new Catalinas. S/V Express 30 "Ringmaster" "Trains are a winter sport" |
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Lots of these rigid vangs break, compared to rope vangs
which are more reliable, obviously. As OZ stated booms often break right at the vang attachment point. This is a weak point because of the leverage, as CM stated. Nevertheless, a rigid vang could be used to support a boom for hauling a person out of the water. I would not call a man overboard, a heavy load. Many vangs feature a lock, as Doug stated, to bypass the internal spring. From what I've read, this is one of the failure points, along with the mast and boom attachments flanges. If a sail is hoisted, so that some or all boom lifting is provided by the sail, the load at the end of the boom could be increased, probably to the point where the vang could be disabled completely. The sail would serve to carry the load normally carried by the topping lift. For any kind of heavy load a sail, halyard, or topping lift is the way to go. On larger boats with beefier systems, a rigid vang should be robust enough to lift some substantial loads. However, would you want to risk breaking it, if a wire topping lift was available? "DSK" wrote wrote: Apparently you think the term "rigid vang" means essentially a solid, steel pipe. It doesn't mean that at all. A Rigid vang "telescopes" and has springs inside it. All the ones I've seen also have locks. ...(stupid BS snipped) ... I'm not surprised you don't know this. Maybe if you were other than an armchair wannabe sailor... Maybe if you sailed anything other than a cheap old beater, maybe if you had some experience with other than obsolete gear, maybe if you hung around sailors who know how to sail and how to rig their boats properly, you'd know that solid vangs have locks. DSK |
I'll bet that Garhauer outsells Hall 10 to 1. Garhauer is amazingly
inexpensive compared to everyone else. I have had my vang, made by Offshore Spars, for some years now. They no longer make them, probably because they couldn't compete from a pricing perspective. Looking at it, there is really no reason it should have cost anywhere near as much as it did. It is nothing more than an anodized, low tech shock absorber with some beefy fittings. Certainly nothing that should have cost close to $600, if my failing memory serves. Garhauer is about a third of that. Agree about the cost of most units. What's even more insulting is the price of the boom and mast attachment fittings. As far as Garhauer outselling others 10-1 afraid I don't see it. Yes the Garhauer seems to be a value and appears to be bullitt proof but walking the docks at any marina I hardly ever see them compared to Quick Vangs. S/V Express 30 "Ringmaster" "Trains are a winter sport" |
Lots of these rigid vangs break, compared to rope vangs
which are more reliable, obviously. As OZ stated booms often break right at the vang attachment point. This is a weak point because of the leverage, as CM stated. Not if installed correctly. I had my Quick Vang boom bracket break loose from the boom once as we crossed the starting line of a race. The reason for the failure ..... the nitwit who installed the boom fitting attached it to the thin walled boom with machine screws and no backing plate. I would be all of 2 threads had been holding that fitting on. I drilled and tapped proper sized holes in a 5' long piece of 1/2" x 1/2" aluminum bar stock and placed it inside the boom. Now those machine screws have much more meat to get a grip on and the 5' length really spreads the load. We've done a couple of auto jibes in big winds on downwind legs with nothing breaking since then. S/V Express 30 "Ringmaster" "Trains are a winter sport" |
BB,
Based on his posts, I'd say Doug is probably the best sailor in this whole group, and he is certainly the most outstanding topic contributor. Spinlock rigid vangs lock. Also hydraulic vangs don't have a lock per se, but can be locked hydraulically. I've also seen beefy mechanical screw type rigid vangs that can be locked in any position. I've seen such mechanical devices used for backstay adjusters where they are probably better suited. Rigid vangs that lock in position are not uncommon. The Spinlock is the rigid vang I've been considering, and the reason I started this thread. Here is evidence that rigid vangs do lock, as Doug stated. http://us.binnacle.com/online/produc...&dept_id=15110 *****************************************8 I'm wondering about boats with floating goosenecks. My Ericson's gooseneck can slide on a track, in lieu of a Cunningham, to flatten the sail. In such a case, a rigid vang may not have the play I need to function properly. Also of concern is the fact that a rigid vang would work against my boom downhaul. Anyone have any experience with this? wrote On Wed, 18 Aug 2004 19:38:18 -0400, DSK wrote: All the ones I've seen also have locks. ...(stupid BS snipped) ... I'm not surprised you don't know this. Maybe if you were other than an armchair wannabe sailor... Maybe if you sailed anything other than a cheap old beater, maybe if you had some experience with other than obsolete gear, maybe if you hung around sailors who know how to sail and how to rig their boats properly, you'd know that solid vangs have locks. DSK Just more proof that DSK is no sailor and simply parrots what he "thinks" he read in a magazine. Please contact Garhauer, who is a major player, if not the biggest in this field and ask how many of their vangs have locks. Doug is an idiot of Jax proportions. BB |
Why don't you put one of those downward pushing
vangs on your boat like the one on Ocean Planet? http://www.blumhorst.com/potterpages...0015/h0010.htm "Thom Stewart" wrote I'm not knocking the Rigid Vang. I wish I could fit one on my boat but the Pilothouse makes that impossible. I'm thinking I might be able to use a KICKER. I'm pointing out that PITA top lift still is a worthwhile addition. |
In such a case the force of the mainsail on the boom would
be partially offset by the mainsheet and vang, reducing and spreading the load on the boom..... "DSK" wrote Think about this, Thom... the force on the end of the boom is going to be very great when sailing hard... enough to lean the boat over a lot. If the boom end can take that force, then it should take that same force in the form of a weight heavy enough to heel the boat over. |
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A fine idea.
"SAIL LOCO" wrote ... I drilled and tapped proper sized holes in a 5' long piece of 1/2" x 1/2" aluminum bar stock and placed it inside the boom. Now those machine screws have much more meat to get a grip on and the 5' length really spreads the load. We've done a couple of auto jibes in big winds on downwind legs with nothing breaking since then. |
So how do you like the Offshore Spares solid vang? Could you live
without it, or is it a major plus having it? "felton" wrote I am no engineer, but my boat does have a well built boom (Hall) and a solid vang (Offshore Spars) and a topping lift. I am not worried about any of the three under any conditions. My vang does have a means to "lock" it with a quick release pin and a number of holes into which it can be placed. |
A fine idea, my ass!!
Any rigger worth his Salt would have drill thru the boom (2 holes) Through bolted with the proper size bolt, lock washers and nut in place. Ole Thom |
Thom Stewart wrote:
A fine idea, my ass!! Any rigger worth his Salt would have drill thru the boom (2 holes) Through bolted with the proper size bolt, lock washers and nut in place. With a compression fitting on the inside, of course. DSK |
Thom Stewart wrote:
Doug, I mentioned early in this discussion that with a topping lift hoisting boom, the boom only positions the location of hoist. There is very, very little force on the boom. The hoist is on the topping lift. Mooran re-stated this. You are the one insisting the force is the same on the end of the boom supported on the other end by a Vang and a gooseneck. We say BS and sign off. In other words, you're saying that 100# on the end of the boom supported by a topping lift is not the same as 100# on the end of the boom supported by a solid vang? OK but I'm a little confused... how does the weight know the difference? DSK |
You have 'way too much common sense. WTF are you trying to do, stop an
argument? BTW is your Hall boom a box section? DSK felton wrote: I am no engineer, but my boat does have a well built boom (Hall) and a solid vang (Offshore Spars) and a topping lift. I am not worried about any of the three under any conditions. My vang does have a means to "lock" it with a quick release pin and a number of holes into which it can be placed. Last year I was sailing when the water levels were VERY low and we managed to find a shallow sandy spot and run aground. Hey, not the first time or the last, I am sure. We were able to swing the boom out over the side and my friend climbed out on the end of it to give us some heel as we had very little wind to work with. We managed to sail off and enjoy the day. No big deal. I keep the topping lift because it is quick and easy to lift the boom for extra clearance above the bimini when the sail is down, rather than screwing with the vang. Just my preference, but it works well for me. If my main had more roach to it that was creating a chaffe issue, I would probably get rid of it as I don't really *need* it, but I like it, so the) |
I don't consider the power release an advantage since you add another
manual operation to using the vang. Increase the mech advantage of the tackle if the spring or piston resistance is too much. On my boat, as originally rigged with a soft vang, the lazy jacks performed the topping lift function On Thu, 19 Aug 2004 06:05:02 GMT, "Bart Senior" wrote: BB, Based on his posts, I'd say Doug is probably the best sailor in this whole group, and he is certainly the most outstanding topic contributor. Spinlock rigid vangs lock. Also hydraulic vangs don't have a lock per se, but can be locked hydraulically. I've also seen beefy mechanical screw type rigid vangs that can be locked in any position. I've seen such mechanical devices used for backstay adjusters where they are probably better suited. Rigid vangs that lock in position are not uncommon. The Spinlock is the rigid vang I've been considering, and the reason I started this thread. Here is evidence that rigid vangs do lock, as Doug stated. http://us.binnacle.com/online/produc...&dept_id=15110 *****************************************8 I'm wondering about boats with floating goosenecks. My Ericson's gooseneck can slide on a track, in lieu of a Cunningham, to flatten the sail. In such a case, a rigid vang may not have the play I need to function properly. Also of concern is the fact that a rigid vang would work against my boom downhaul. Anyone have any experience with this? wrote On Wed, 18 Aug 2004 19:38:18 -0400, DSK wrote: All the ones I've seen also have locks. ...(stupid BS snipped) ... I'm not surprised you don't know this. Maybe if you were other than an armchair wannabe sailor... Maybe if you sailed anything other than a cheap old beater, maybe if you had some experience with other than obsolete gear, maybe if you hung around sailors who know how to sail and how to rig their boats properly, you'd know that solid vangs have locks. DSK Just more proof that DSK is no sailor and simply parrots what he "thinks" he read in a magazine. Please contact Garhauer, who is a major player, if not the biggest in this field and ask how many of their vangs have locks. Doug is an idiot of Jax proportions. BB |
You could have stuck a piece of pipe in your boom. I have heard of
that being done:). The 1/2" square piece of aluminum bar stock was easier to cut than cast iron. S/V Express 30 "Ringmaster" "Trains are a winter sport" |
Any rigger worth his Salt would have drill thru the boom (2 holes)
Through bolted with the proper size bolt, lock washers and nut in place. LOL.................. That might work if your boom was only 2 feet long or if you had 6 foot arms. S/V Express 30 "Ringmaster" "Trains are a winter sport" |
On Thu, 19 Aug 2004 06:23:51 GMT, "Bart Senior"
wrote: So how do you like the Offshore Spares solid vang? Could you live without it, or is it a major plus having it? I like it, but if I were buying another one I would get the Garhauer. Mine is strongly built but that spring does have a somewhat awful sound, like a rusty spring in a car suspension. Probably the most annoying thing about it is the series of holes for the quick release pin, which is much like the Spinlock. While this is not an issue for most (all) of the rest of you, down here we have these annoying mud wasps that love nothing better than holes like that. They must think of them as birdhouses. In two weeks time they could completely fill my vang tube with mud, which is not easily removed and really screws up the ability of the vang to be adjusted. I'll bet you didn't expect that in my report, did you?:) I have to keep the holes covered with rigging tape. It is a nice thing to have and it is very strongly made. I would definitely want to have a solid vang, but I would be just as happy with a Garhauer, which, while inexpensive, *might* be on the heavy side for serious racers. "felton" wrote I am no engineer, but my boat does have a well built boom (Hall) and a solid vang (Offshore Spars) and a topping lift. I am not worried about any of the three under any conditions. My vang does have a means to "lock" it with a quick release pin and a number of holes into which it can be placed. |
On Thu, 19 Aug 2004 06:28:38 -0400, DSK wrote:
You have 'way too much common sense. WTF are you trying to do, stop an argument? Who, me? Nope, I love an argument but I was getting lost in the engineering jargon:) BTW is your Hall boom a box section? No, but it does seem to be strongly constructed. My spar is quite bendy but my boom can handle anything my vang or my mainsheet tackle can generate. Even my friend out on the end was no cause for concern. It could be because my boat wasn't built as a weight saving racer. It seems much more solidly built than the C&C it replaced, which was obviously built with a greater emphasis on performance/weight saving construction. DSK felton wrote: I am no engineer, but my boat does have a well built boom (Hall) and a solid vang (Offshore Spars) and a topping lift. I am not worried about any of the three under any conditions. My vang does have a means to "lock" it with a quick release pin and a number of holes into which it can be placed. Last year I was sailing when the water levels were VERY low and we managed to find a shallow sandy spot and run aground. Hey, not the first time or the last, I am sure. We were able to swing the boom out over the side and my friend climbed out on the end of it to give us some heel as we had very little wind to work with. We managed to sail off and enjoy the day. No big deal. I keep the topping lift because it is quick and easy to lift the boom for extra clearance above the bimini when the sail is down, rather than screwing with the vang. Just my preference, but it works well for me. If my main had more roach to it that was creating a chaffe issue, I would probably get rid of it as I don't really *need* it, but I like it, so the) |
Backing plates are used everywhere on boats--it is a good method and
excellent solution to Loco's problem. You don't specify how the thru-bolts are drilled horizontally, or vertically. Most booms have holes drilled horizontally with a bale attached. That would not work with a rigid vang. You would need to make a custom wrap-around bracket to thru-bolt horizontally. You could use a piece of solder shaped around the mast and boom to transfer the shape to template such a part--Garhauer method. Machine screws into tapped hole into a backing plate inside the boom strike me as an excellent method of reinforcement to spread the load along the axis of the boom. I've also seen sections of snug fitting tubing sleeved as reinforcement at places prone to failures like the vang attachment, and sometimes the gooseneck to increase boom strength. The method is commonly used to built taller masts in sections. My Ericson mast is the original, was constructed in three pieces and has not failed in over 30 years of use. This would be the best solution. Thru-bolting adds extra holes and can weaken both sides of the boom, particularly if over tightened, by crushing or dimpling the shape of the boom, thus creating a weak spot. This is more common on smaller and lighter booms, and vang related failure occur where? Right at the thru-bolts! Reinforcement is common for boom repairs. Loco's method is a good one to spread the load and secure the vang to the boom. If your boat has a reputation for failing at a certain place like the vang attachment at the boom, consider reinforcing it before the boom brakes. "Thom Stewart" wrote A fine idea, my ass!! Any rigger worth his Salt would have drill thru the boom (2 holes) Through bolted with the proper size bolt, lock washers and nut in place. Ole Thom |
Ah Balls Bart,
Count up the number of holes drilled and tapped with the backing stock and connection of the vang and then compare it to a full bale. Ole Thom |
"DSK" wrote in message | In other words, you're saying that 100# on the end of the boom supported | by a topping lift is not the same as 100# on the end of the boom | supported by a solid vang? | | OK but I'm a little confused... how does the weight know the difference? Doug.... the weight remains the same that's not the point. The load bearing forces between those delivered to the topping lift and the boom acts as a "spreader"... while with the vang all the load is delivered to the boom and the vang is subjected to the magnified loads.... in other words the load is delivered to the vang and the leverage is delivered by the boom. That's why I mentioned the fulcrum earlier. When the boom is the spreader the force is compressive and much less than the forces applied to the vang in such a situation. The topping lift bears the entire load. The vang supports the boom distal to the load point so as to magnify the bearing force. Can you see the point of my argument now?? CM |
Capt. Mooron wrote:
Doug.... the weight remains the same that's not the point. Oh. ... The load bearing forces between those delivered to the topping lift and the boom acts as a "spreader"... You mean the boom takes the load as compression... guess what, so does the mast, and all the rigging, which transfers it to the hull. The load is the same, the total amount of stress is the same, except that much of the rigging is pre-loaded. And the compression on the mast is likely to be a multiple of the weight involved. ...while with the vang all the load is delivered to the boom and the vang is subjected to the magnified loads.... in other words the load is delivered to the vang and the leverage is delivered by the boom. That's why I mentioned the fulcrum earlier. OK. It's still not a good explanation and tends to muddy the engineering points. The weight is the same... check. With a topping lift, you seem to think that the boom has very little stress on it. That is not the case. Imagine this... replace the boom with your arms. Hang a 100# weight from a long rope, and then try to push it 12' away from hanging straight down. Depending on the angle to the point of hoist, you could end up with more than 100 pounds of force. When the boom is the spreader the force is compressive and much less than the forces applied to the vang in such a situation. The topping lift bears the entire load. No it does not. Do you think the force magically goes away because there is a topping lift? Can you see the point of my argument now?? Yes, can you see the error you're making? You should make a diagram of the forces involved. It will help you visualize the situation properly. With a solid vang, that the force on the boom vang is greater than the weight is not (or should not be) a problem, no more than the compression on an old-timey noodley boom is. They're designed for that. If the gear is designed & built properly for it's use, then it is fine. Ever notice how on modern boats, the boom is not just s shorter section of the same type extrusion as the mast? There are engineering reasons for that (plus it looks cool). Fresh Breezes- Doug King CM |
Count up the number of holes drilled and tapped with the backing stock
and connection of the vang and then compare it to a full bale. The 4 - 3/16" socket head screws that hold the Quick Vang bracket to the boom are of no consequence when compared to the 3/8" or larger holes that would have to be drilled for a bail. Plus a bail wouldn't work with a Quick Vang bracket. And with a 1/2" piece of aluminum bar stock installed inside the boom it's like da holes ain't even there. S/V Express 30 "Ringmaster" "Trains are a winter sport" |
"DSK" wrote in message | You mean the boom takes the load as compression... guess what, so does | the mast, and all the rigging, which transfers it to the hull. The load | is the same, the total amount of stress is the same, except that much of | the rigging is pre-loaded. And the compression on the mast is likely to | be a multiple of the weight involved. No Doug.... I believe that assumption to be incorrect... you fail to incorporate the dispersion of the load from the mast head to compression of the mast and delivery of portions of the load to the shrouds. When you transfer the load to the vang alone [ via the boom].. the mast is only subject to a side load from the vang fitting and all the force is supported by the boom/vang. None of the load is distributed to the entire mast or the shrouds. In other words any portion of the mast above the boom is not utilized in the dispersion of the forces generated by the bearing loads. | | | ...while with the vang all the load is delivered to the boom and | the vang is subjected to the magnified loads.... in other words the load is | delivered to the vang and the leverage is delivered by the boom. That's why | I mentioned the fulcrum earlier. | | OK. It's still not a good explanation and tends to muddy the engineering | points. The only thing muddy here is your refusal to approach this with an open mind.. | | The weight is the same... check. | | With a topping lift, you seem to think that the boom has very little | stress on it. That is not the case. I never stated very little stress.. I stated much less stress by a greater margin than with the vang based option. | | Imagine this... replace the boom with your arms. Hang a 100# weight from | a long rope, and then try to push it 12' away from hanging straight | down. Depending on the angle to the point of hoist, you could end up | with more than 100 pounds of force. Ridiculous... the force required to push it away would be far less than the force required to keep the arm level while applying force to a point just aft of my elbow! | | | | When the boom is the spreader the force is compressive and much less than | the forces applied to the vang in such a situation. The topping lift bears | the entire load. | | No it does not. Do you think the force magically goes away because there | is a topping lift? It does not go away nor did I say it did... I said the load is more evenly distributed over a greater span.. Mast, Boom, Topping lift, Shrouds... etc. This of course increases the ability of the rig to undertake the bearing forces. Gawd forbid you would ever be required to calc break-out forces generated by excavators. | | | Can you see the point of my argument now?? | | Yes, can you see the error you're making? You should make a diagram of | the forces involved. It will help you visualize the situation properly. I am most definitely not in error here Doug... you are... swallow your pride and look at this problem with an eye to structural engineering. I am visualizing the situation and after much thought and further toying with the idea I came to the conclusion that you are not correct in your theory regarding forces delivered to the vang. You have yet to present a viable defense for your position on this while I have offered several sound, reasoned, and logical counterpoints to your pretense. | | With a solid vang, that the force on the boom vang is greater than the | weight is not (or should not be) a problem, no more than the compression | on an old-timey noodley boom is. They're designed for that. If the gear | is designed & built properly for it's use, then it is fine. No Doug... it's not the case at all.... the vang is badly situated to handle the loads you intend to place to it. The topping lift offers a much better and more efficient distribution of the load ... thus increasing it's ability to handle much greater loads. | | Ever notice how on modern boats, the boom is not just so shorter section | of the same type extrusion as the mast? There are engineering reasons | for that (plus it looks cool). Quit toying with the damn boom.... look think of it this way... how many lifting devices utilize a support located under the boom at less than 25% of the boom length? NONE! Now how many utilize a cable [topping lift] to the end of the boom?? MOST! You are dead wrong on this Doug... really! CM |
"SAIL LOCO" wrote in message ... | There are engineering reasons | for that (plus it looks cool). | | No, what looks cool are big boat booms with holes in them. Loco ... Please! Either join this discussion and add to it or stay on the side lines and refrain from inane comments. I'm not being mean here.... but I am requesting a modicum of intellectual input on an interesting discussion. Now allow me to ask you if you believe a vang as suited to load bearing ability as a topping lift. Let's refine this by placing the caveat that the strength of the vang is equal to the strength of the topping lift in maximum load bearing abilities. In other words if you beef up the vang you can as well beef up the topping lift. Assume the loads are well within the stress capacities acceptable to both the boom and the mast/shrouds. CM CM |
Loco ... Please! Either join this discussion and add to it or stay on the
side lines and refrain from inane comments. I'm not being mean here.... but I am requesting a modicum of intellectual input on an interesting discussion.? LOL........... As always your too full of yourself. S/V Express 30 "Ringmaster" "Trains are a winter sport" |
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