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3 or 4 blade props?
Hi
I have just purchased a 2950 Proline with twin 225 OceanRunners. I am trying to get the best economical cruise speed I can. I was wonderig what would be the advantages to a 4 blade prop as apposed to a three blade prop... Thanks Rick |
3 or 4 blade props?
For this application, good performance SS 4 blade props would be the best
choice. They will give you better acceleration, planing speed, and low speed cruising ability. You will loose a few mph on top end but chances are your not trying for top end speed anyway. You will definetly like the way the boat behaves. Prop for right at max rpms on the engines at wide open. Don't waist your money on aluminum 4 blade or composite 4 blade as you have too much torque for these props to hold their shape over time. -- Tony my boats and autos - http://t.thomas.home.mchsi.com "Diver1055" wrote in message ... Hi I have just purchased a 2950 Proline with twin 225 OceanRunners. I am trying to get the best economical cruise speed I can. I was wonderig what would be the advantages to a 4 blade prop as apposed to a three blade prop... Thanks Rick |
3 or 4 blade props?
For this application, good performance SS 4 blade props would be the best
choice. They will give you better acceleration, planing speed, and low speed cruising ability. You will loose a few mph on top end but chances are your not trying for top end speed anyway. You will definetly like the way the boat behaves. Prop for right at max rpms on the engines at wide open. Don't waist your money on aluminum 4 blade or composite 4 blade as you have too much torque for these props to hold their shape over time. -- Tony my boats and autos - http://t.thomas.home.mchsi.com "Diver1055" wrote in message ... Hi I have just purchased a 2950 Proline with twin 225 OceanRunners. I am trying to get the best economical cruise speed I can. I was wonderig what would be the advantages to a 4 blade prop as apposed to a three blade prop... Thanks Rick Tony, I don't disagree with the response as far as the qualities of 4 blades but he was asking for the most economical cruise. I can't imagine a 4 blade being more economical than a 3. Common sense tells me there would be less drag with one less blade. Barry |
3 or 4 blade props?
The most economical cruise is going to be at the lowest rpms and maintaining
plane. A 4 blade will allow for a lower rpm than the 3 blade at minimal plane speed. It will also give you better throttle response and quicker planing. -- Tony My boats and autos - http://t.thomas.home.mchsi.com "F330 GT" wrote in message ... For this application, good performance SS 4 blade props would be the best choice. They will give you better acceleration, planing speed, and low speed cruising ability. You will loose a few mph on top end but chances are your not trying for top end speed anyway. You will definetly like the way the boat behaves. Prop for right at max rpms on the engines at wide open. Don't waist your money on aluminum 4 blade or composite 4 blade as you have too much torque for these props to hold their shape over time. -- Tony my boats and autos - http://t.thomas.home.mchsi.com "Diver1055" wrote in message ... Hi I have just purchased a 2950 Proline with twin 225 OceanRunners. I am trying to get the best economical cruise speed I can. I was wonderig what would be the advantages to a 4 blade prop as apposed to a three blade prop... Thanks Rick Tony, I don't disagree with the response as far as the qualities of 4 blades but he was asking for the most economical cruise. I can't imagine a 4 blade being more economical than a 3. Common sense tells me there would be less drag with one less blade. Barry |
3 or 4 blade props?
"Tony Thomas" wrote in message news:eJDob.72698$HS4.632907@attbi_s01... The most economical cruise is going to be at the lowest rpms and maintaining plane. A 4 blade will allow for a lower rpm than the 3 blade at minimal plane speed. It will also give you better throttle response and quicker planing. Nope! Not 100% correct. The most economical cruise is going to be near the most effective RPM of the motor. It is going to be a bit higher than the max torque RPM, but still a bit under max HP RPM. To find what RPM gives the most economical cruise, you just have to do som testing. As speed increases, the drag increases. This will offset the economy RPM. A 4 blade prop has more drag due to one more blade to push through the water, so the 3 blade may be better for economy. This again depends on propeller design. A good 3 blade SS prop is probably best for economy. A good 4 blade prop gives better accelration and less vibration, but lower top speed. Trond |
3 or 4 blade props?
In the lower rpm range, while traveling in displacement mode, (I do a
lot of that) will a 4 blade "push" more water at a lower rpm? That is to say will a 4 blade 21"x18" stainless perform as well as a 3 blade 21"x21" or would I simply be overloading the motor? Capt. Frank Trond Solem wrote: "Tony Thomas" wrote in message news:eJDob.72698$HS4.632907@attbi_s01... The most economical cruise is going to be at the lowest rpms and maintaining plane. A 4 blade will allow for a lower rpm than the 3 blade at minimal plane speed. It will also give you better throttle response and quicker planing. Nope! Not 100% correct. The most economical cruise is going to be near the most effective RPM of the motor. It is going to be a bit higher than the max torque RPM, but still a bit under max HP RPM. To find what RPM gives the most economical cruise, you just have to do som testing. As speed increases, the drag increases. This will offset the economy RPM. A 4 blade prop has more drag due to one more blade to push through the water, so the 3 blade may be better for economy. This again depends on propeller design. A good 3 blade SS prop is probably best for economy. A good 4 blade prop gives better accelration and less vibration, but lower top speed. Trond |
3 or 4 blade props?
First of all, normally a 4 blade prop will have a smaller diameter than the
3 blade to compensate for the extra blade surface. You want to go with the same pitch prop. The 18 will be way too small a prop and will travel less and be less efficient than the 21. Stay with same pitch which is inches of travel forward per revolution (in theory not compensating for slip). A 4 blade will have less slip at lower rpms than a 3 blade which is why it will be more efficient at cruise. -- Tony my boats and autos - http://t.thomas.home.mchsi.com "Capt. Frank Hopkins" wrote in message .net... In the lower rpm range, while traveling in displacement mode, (I do a lot of that) will a 4 blade "push" more water at a lower rpm? That is to say will a 4 blade 21"x18" stainless perform as well as a 3 blade 21"x21" or would I simply be overloading the motor? Capt. Frank Trond Solem wrote: "Tony Thomas" wrote in message news:eJDob.72698$HS4.632907@attbi_s01... The most economical cruise is going to be at the lowest rpms and maintaining plane. A 4 blade will allow for a lower rpm than the 3 blade at minimal plane speed. It will also give you better throttle response and quicker planing. Nope! Not 100% correct. The most economical cruise is going to be near the most effective RPM of the motor. It is going to be a bit higher than the max torque RPM, but still a bit under max HP RPM. To find what RPM gives the most economical cruise, you just have to do som testing. As speed increases, the drag increases. This will offset the economy RPM. A 4 blade prop has more drag due to one more blade to push through the water, so the 3 blade may be better for economy. This again depends on propeller design. A good 3 blade SS prop is probably best for economy. A good 4 blade prop gives better accelration and less vibration, but lower top speed. Trond |
3 or 4 blade props?
Ok, Tony,
That makes sense. Is there a formula for calculating a prop's thrust? rpm vs hp? Given 21" pitch and the current 3 blade a 21" diameter (stainless steel) 21?RČ(0.66)=19.0250?RČ(0.80) it doesn't work out exactly. If the formula doesn't display in the newsgroup, I will try a different venue. Thanks, Capt Frank Tony Thomas wrote: First of all, normally a 4 blade prop will have a smaller diameter than the 3 blade to compensate for the extra blade surface. You want to go with the same pitch prop. The 18 will be way too small a prop and will travel less and be less efficient than the 21. Stay with same pitch which is inches of travel forward per revolution (in theory not compensating for slip). A 4 blade will have less slip at lower rpms than a 3 blade which is why it will be more efficient at cruise. |
3 or 4 blade props?
Only formula I am aware of is the speed formula.
rpm x pitch ------------------ = theoritical speed x efficiency = actual speed 1056 x gear ratio 1056 is a conversion factor to get from inches of pitch and rev per minute into miles per hour. gear ratio will be 1.5 or 1.86 or 2.0 depending on your motor usually. -- Tony my boats and autos - http://t.thomas.home.mchsi.com "Capt. Frank Hopkins" wrote in message nk.net... Ok, Tony, That makes sense. Is there a formula for calculating a prop's thrust? rpm vs hp? Given 21" pitch and the current 3 blade a 21" diameter (stainless steel) 21?RČ(0.66)=19.0250?RČ(0.80) it doesn't work out exactly. If the formula doesn't display in the newsgroup, I will try a different venue. Thanks, Capt Frank Tony Thomas wrote: First of all, normally a 4 blade prop will have a smaller diameter than the 3 blade to compensate for the extra blade surface. You want to go with the same pitch prop. The 18 will be way too small a prop and will travel less and be less efficient than the 21. Stay with same pitch which is inches of travel forward per revolution (in theory not compensating for slip). A 4 blade will have less slip at lower rpms than a 3 blade which is why it will be more efficient at cruise. |
3 or 4 blade props?
Thanks a lot Tony.
I will see what else I can find on the subject and post it. CF Tony Thomas wrote: Only formula I am aware of is the speed formula. rpm x pitch ------------------ = theoritical speed x efficiency = actual speed 1056 x gear ratio 1056 is a conversion factor to get from inches of pitch and rev per minute into miles per hour. gear ratio will be 1.5 or 1.86 or 2.0 depending on your motor usually. |
3 or 4 blade props?
On Sun, 02 Nov 2003 05:16:31 GMT, "Capt. Frank Hopkins"
wrote: Ok, Tony, That makes sense. Is there a formula for calculating a prop's thrust? rpm vs hp? Given 21" pitch and the current 3 blade a 21" diameter (stainless steel) 21?RČ(0.66)=19.0250?RČ(0.80) it doesn't work out exactly. If the formula doesn't display in the newsgroup, I will try a different venue. ======================================== Capt Frank, Recommend that you get a copy of Dave Gerr's excellent book: "Propeller Handbook" http://tinyurl.com/te13 I bought a copy earlier this year after pondering many of the same questions and issues. Excellent reading and very thorough coverage of a complex subject. To make a long story short, Gerr says that prop slip is basically a function of blade area. Three blades are more efficient if you can swing a big enough prop to get the required area. Many boats however have insufficient prop aperature space for a large prop without compromising blade tip clearance between prop and hull. It turns out that insufficient tip clearance leads to vibration because of asymetric blade loading. For those boats with insufficient clearance, a 4 bladed prop offers a way to increase blade area without increasing the prop diameter (and decerasing clearance). Hope that helps but I still recommend the book for the complete story, and many, many, design equations and charts. |
3 or 4 blade props?
Thanks Wayne,
I will seek out the book. Capt. Frank Wayne.B wrote: On Sun, 02 Nov 2003 05:16:31 GMT, "Capt. Frank Hopkins" wrote: Ok, Tony, That makes sense. Is there a formula for calculating a prop's thrust? rpm vs hp? Given 21" pitch and the current 3 blade a 21" diameter (stainless steel) 21?RČ(0.66)=19.0250?RČ(0.80) it doesn't work out exactly. If the formula doesn't display in the newsgroup, I will try a different venue. ======================================== Capt Frank, Recommend that you get a copy of Dave Gerr's excellent book: "Propeller Handbook" http://tinyurl.com/te13 I bought a copy earlier this year after pondering many of the same questions and issues. Excellent reading and very thorough coverage of a complex subject. To make a long story short, Gerr says that prop slip is basically a function of blade area. Three blades are more efficient if you can swing a big enough prop to get the required area. Many boats however have insufficient prop aperature space for a large prop without compromising blade tip clearance between prop and hull. It turns out that insufficient tip clearance leads to vibration because of asymetric blade loading. For those boats with insufficient clearance, a 4 bladed prop offers a way to increase blade area without increasing the prop diameter (and decerasing clearance). Hope that helps but I still recommend the book for the complete story, and many, many, design equations and charts. |
Winterizing your safety equipment saves $$$
I have updated my web page about safety equipment & abandon ship info. I
would appreciate any comments. http://www.home.earthlink.net/~aartworks/solas.html Capt. Frank |
Winterizing your safety equipment saves $$$
Is there really an effective shark repellent these days? I remember reading
that none of them were worth a flip. Also, the inflatable life jackets are now approved by the USCG, but have to be worn to count. "Capt. Frank Hopkins" wrote in message ink.net... I have updated my web page about safety equipment & abandon ship info. I would appreciate any comments. http://www.home.earthlink.net/~aartworks/solas.html Capt. Frank |
Winterizing your safety equipment saves $$$
I remember Batman had shark repellant on his utility belt, it seemed to work
pretty good. "Keith" wrote in message ... Is there really an effective shark repellent these days? I remember reading that none of them were worth a flip. Also, the inflatable life jackets are now approved by the USCG, but have to be worn to count. "Capt. Frank Hopkins" wrote in message ink.net... I have updated my web page about safety equipment & abandon ship info. I would appreciate any comments. http://www.home.earthlink.net/~aartworks/solas.html Capt. Frank |
3 or 4 blade props?
Tony,
I don't disagree with the response as far as the qualities of 4 blades but he was asking for the most economical cruise. I can't imagine a 4 blade being more economical than a 3. Common sense tells me there would be less drag with one less blade. Barry Hey Barry I am basically am looking to be able to plain at a slower speed than I am currently achieving. My boat doesnt like to hold a plain at under 25mph, and when it gets rough, I'd like to go slower than bouncing from one wave to another. And yes I am also looking to maximize my range. Thank you all, I appreciate your inputs... Rick |
Winterizing your safety equipment saves $$$
Yeah, but Batman's shark was stuffed.
:) CF Paul wrote: I remember Batman had shark repellant on his utility belt, it seemed to work pretty good. "Keith" wrote in message ... Is there really an effective shark repellent these days? I remember reading that none of them were worth a flip. Also, the inflatable life jackets are now approved by the USCG, but have to be worn to count. "Capt. Frank Hopkins" wrote in message hlink.net... I have updated my web page about safety equipment & abandon ship info. I would appreciate any comments. http://www.home.earthlink.net/~aartworks/solas.html Capt. Frank |
3 or 4 blade props?
Hey Barry I am basically am looking to be able to plain at a slower speed than I am currently achieving. My boat doesnt like to hold a plain at under 25mph, and when it gets rough, I'd like to go slower than bouncing from one wave to another. And yes I am also looking to maximize my range. Thank you all, I appreciate your inputs... Rick You need trim tabs, not a prop change. http://www.bennetttrimtabs.com/ |
3 or 4 blade props?
Hey Barry
I am basically am looking to be able to plain at a slower speed than I am currently achieving. My boat doesnt like to hold a plain at under 25mph, and when it gets rough, I'd like to go slower than bouncing from one wave to another. And yes I am also looking to maximize my range. Thank you all, I appreciate your inputs... Rick Rick, Sounds like trim tabs would do more for you than changing props. Their is probably no better way to achieve slower planing speed than good trim tabs. Of course, that certainly won't be the most economical speed. Most new outboards are most economical in the 3500 to 4000 rpm range. At certain rpm ranges, I imagine a 4 blade could be more economical than a 3 blade but I'd still be real surprised if you took an outboard motor on a typical v-hull boat and tried just to maximize the most mileage per gallon possible that could be gotten out of that engine, a 3 blade prop would be the winner. What do you think, Tony? Barry |
3 or 4 blade props?
In article , F330 GT
writes Rick, Sounds like trim tabs would do more for you than changing props. Their is probably no better way to achieve slower planing speed than good trim tabs. Of course, that certainly won't be the most economical speed. Most new outboards are most economical in the 3500 to 4000 rpm range. Surely you mean most efficient, not most economical. There is no way an outboard running at 3500rpm gets less gph than one running at 1000rpm. Equally, there is no way it gets better mpg than one running at 1000rpm. Only, m/g/h would it be more economical. I can run all day on a river at 1000rpm (6mph) and only use half a tank. Run on a lake at 25-30mph and 3500rpm and I get through a whole tank in a few hours! -- Nick |
3 or 4 blade props?
All depends. A 3 blade prop will almost always be faster at top end than a
4 blade prop due to the decrease in blade surface. However, a 4 blade prop will almost always plane faster and give better acceleration (assuming we are talking about similar props in terms of design and similar pitch). Having said that, in theory they will both be about the same economy wise at say 3000 rpms since they are both the same pitch and about the same efficiency wise in the mid rpm area. Each person has to decide if they want better low end or better top end. There is no perfect combination. Even the shift props will be less efficient on top end than a regular prop of the same pitch. Again, you compromise absolute top speed for acceleration. Just like gearing in a car. Now for trim tabs. Great for slow planing but will kill fuel economy doing so. They create a lot of drag to force the bow down at slower speeds. Of course you can raise them and get the efficiency back. Dolfins work the same way by forcing the bow down (not as much as a trim tab but it does help). You just have to trim the motor out to stop the bow push. Of course you always get some push since it is in the water unless you have the engine raised to the point that it is out of the water at higher speeds. -- Tony My boats and autos - http://t.thomas.home.mchsi.com "F330 GT" wrote in message ... Hey Barry I am basically am looking to be able to plain at a slower speed than I am currently achieving. My boat doesnt like to hold a plain at under 25mph, and when it gets rough, I'd like to go slower than bouncing from one wave to another. And yes I am also looking to maximize my range. Thank you all, I appreciate your inputs... Rick Rick, Sounds like trim tabs would do more for you than changing props. Their is probably no better way to achieve slower planing speed than good trim tabs. Of course, that certainly won't be the most economical speed. Most new outboards are most economical in the 3500 to 4000 rpm range. At certain rpm ranges, I imagine a 4 blade could be more economical than a 3 blade but I'd still be real surprised if you took an outboard motor on a typical v-hull boat and tried just to maximize the most mileage per gallon possible that could be gotten out of that engine, a 3 blade prop would be the winner. What do you think, Tony? Barry |
3 or 4 blade props?
writes
Rick, Sounds like trim tabs would do more for you than changing props. Their is probably no better way to achieve slower planing speed than good trim tabs. Of course, that certainly won't be the most economical speed. Most new outboards are most economical in the 3500 to 4000 rpm range. Surely you mean most efficient, not most economical. There is no way an outboard running at 3500rpm gets less gph than one running at 1000rpm. Equally, there is no way it gets better mpg than one running at 1000rpm. Only, m/g/h would it be more economical. I can run all day on a river at 1000rpm (6mph) and only use half a tank. Run on a lake at 25-30mph and 3500rpm and I get through a whole tank in a few hours! -- Nick I mean the highest miles per gallon. I'd consider that the most efficient and most economical if I'm trying to to get from point a to point b. The most economical from your perspective would be to leave it in the garage on a trailer. Barry |
3 or 4 blade props?
Now for trim tabs. Great for slow planing but will kill fuel economy doing so. They create a lot of drag to force the bow down at slower speeds. Of course you can raise them and get the efficiency back. I've found the opposite to be true. |
3 or 4 blade props?
"Joe" wrote in message ...
Now for trim tabs. Great for slow planing but will kill fuel economy doing so. They create a lot of drag to force the bow down at slower speeds. Of course you can raise them and get the efficiency back. I've found the opposite to be true. Really, JoeTechnician? Please do tell how you think that trim tabs don't create drag when they are deployed? And, if they are creating drag, unfortunately, they are also hurting fuel economy. |
3 or 4 blade props?
"basskisser" wrote in message om... "Joe" wrote in message ... Now for trim tabs. Great for slow planing but will kill fuel economy doing so. They create a lot of drag to force the bow down at slower speeds. Of course you can raise them and get the efficiency back. I've found the opposite to be true. Really, JoeTechnician? Please do tell how you think that trim tabs don't create drag when they are deployed? and in And, if they are creating drag, unfortunately, they are also hurting fuel economy. Who said they didn't create drag? But, if the drag they do create is less than the drag they reduce (stern dive, pushing a wall of water against the bottom of the hull), and inefficient prop angle (wasted energy pushing the bow up instead of the boat forward) then the overall decrease in drag will result in increased fuel efficiency. |
3 or 4 blade props?
In article , F330 GT
writes writes Rick, Sounds like trim tabs would do more for you than changing props. Their is probably no better way to achieve slower planing speed than good trim tabs. Of course, that certainly won't be the most economical speed. Most new outboards are most economical in the 3500 to 4000 rpm range. Surely you mean most efficient, not most economical. There is no way an outboard running at 3500rpm gets less gph than one running at 1000rpm. Equally, there is no way it gets better mpg than one running at 1000rpm. Only, m/g/h would it be more economical. I can run all day on a river at 1000rpm (6mph) and only use half a tank. Run on a lake at 25-30mph and 3500rpm and I get through a whole tank in a few hours! -- Nick I mean the highest miles per gallon. I'd consider that the most efficient and most economical if I'm trying to to get from point a to point b. The most economical from your perspective would be to leave it in the garage on a trailer. Well fuel is so expensive here in the UK that your suggestion is about the best way to save money... :) -- Nick |
3 or 4 blade props?
I know my boat gets on plain using them if I don't use them and have allot
of people onboard I never get on plain and it would be very inefficient to keep trying I would think, but then again I don't have a flow scan and a gps so I can't tell u for sure, but I know if I'm not on plain I'm not going anywhere fast. Just sitting back relaxing, taking a cruise. Happy boating "Joe" wrote in message ... "basskisser" wrote in message om... "Joe" wrote in message ... Now for trim tabs. Great for slow planing but will kill fuel economy doing so. They create a lot of drag to force the bow down at slower speeds. Of course you can raise them and get the efficiency back. I've found the opposite to be true. Really, JoeTechnician? Please do tell how you think that trim tabs don't create drag when they are deployed? and in And, if they are creating drag, unfortunately, they are also hurting fuel economy. Who said they didn't create drag? But, if the drag they do create is less than the drag they reduce (stern dive, pushing a wall of water against the bottom of the hull), and inefficient prop angle (wasted energy pushing the bow up instead of the boat forward) then the overall decrease in drag will result in increased fuel efficiency. |
3 or 4 blade props?
"Wildest Dream" wrote in message I know my boat gets on plain using them if I don't use them and have allot of people onboard I never get on plain and it would be very inefficient to keep trying I would think, but then again I don't have a flow scan and a gps so I can't tell u for sure, but I know if I'm not on plain I'm not going anywhere fast. Just sitting back relaxing, taking a cruise. Happy boating If you can't plane at full throttle without tabs, but can plane with them, there is no doubt that using the tabs on your boat is improving your fuel consumption. |
3 or 4 blade props?
"Joe" wrote in message ...
"basskisser" wrote in message om... "Joe" wrote in message ... Now for trim tabs. Great for slow planing but will kill fuel economy doing so. They create a lot of drag to force the bow down at slower speeds. Of course you can raise them and get the efficiency back. I've found the opposite to be true. Really, JoeTechnician? Please do tell how you think that trim tabs don't create drag when they are deployed? and in And, if they are creating drag, unfortunately, they are also hurting fuel economy. Who said they didn't create drag? But, if the drag they do create is less than the drag they reduce (stern dive, pushing a wall of water against the bottom of the hull), and inefficient prop angle (wasted energy pushing the bow up instead of the boat forward) then the overall decrease in drag will result in increased fuel efficiency. ****, here we go again, JoeTechnician, I even have to explain what to hell YOU responded to. Read the second sentence of the original post: They create a lot of drag to force the bow down at slower speeds. Of course you can raise them and get the efficiency back. At slower speeds, they definately DO create more drag. AT SLOWER SPEEDS, get it? You are plunging a planar piece of material, at an angle, into the water. Do you think that is creating drag, yes or no please. Now, that in turn, pushes the bow down, again, we are AT SLOWER SPEEDS. So, you are essentially putting more of the hull in contact with the water. Do you not think this, AT SLOWER SPEEDS, creates drag? Yes or no, please. |
3 or 4 blade props?
****, here we go again, JoeTechnician, I even have to explain what to
hell YOU responded to. Read the second sentence of the original post: They create a lot of drag to force the bow down at slower speeds. Of course you can raise them and get the efficiency back. I know exactly what I responded to and stand by my statement. At slower speeds, they definately DO create more drag. AT SLOWER SPEEDS, get it? You are plunging a planar piece of material, at an angle, into the water. Do you think that is creating drag, yes or no please. If not correctly adjusted they might (extended too far). Here's a shocker for you, they usually work better at slower speeds and rougher seas than they do at higher speeds and calmer seas. I'm not talking about idle speeds when I say "slower speeds" but they will begin to be efficient approximately at the point that you can plane with the tabs adjusted down. Here's real world scenario for you- On my boat (21.5' CC 200hp), at 3000rpm the boat will ride with a bow high attitude with stern dive. As I actuate the trim tabs the stern rises, the bow lowers and the boat planes. Once planed the rpm's will immediately climb (without touching the throttle) and my speed increases. I then can reduce throttle back to 3000rpm and continue along on a plane. Now, tell me, do you think my boat is more, or less efficient at 3000rpm's with my tabs down or tabs up? Now, that in turn, pushes the bow down, again, we are AT SLOWER SPEEDS. So, you are essentially putting more of the hull in contact with the water. Do you not think this, AT SLOWER SPEEDS, creates drag? Yes or no, please. Trim tabs, when activated, will *always* add some drag, and as I said- "But, if the drag they do create is less than the drag they reduce (stern dive, pushing a wall of water against the bottom of the hull), and inefficient prop angle (wasted energy pushing the bow up instead of the boat forward) then the overall decrease in drag will result in increased fuel efficiency." Here's some reading for you. http://www.bennetttrimtabs.com/whatdo.htm http://www.trimmaster.net/id114.htm http://www.boatus.com/boattech/trimtabs.htm http://www.powerandmotoryacht.com/fe...abs/index.html http://www.h-ri.com/Product/Duraplane/Duraplane_01.html |
3 or 4 blade props?
I see you have decided not to argue against the facts for a change. There may be hope for you yet. |
3 or 4 blade props?
"Joe" wrote in message ...
I see you have decided not to argue against the facts for a change. There may be hope for you yet. Idiot boy, do you not think that a PROPERLY TRIMMED boat, ie: weight distribution, would out perform the exact same boat that was not trimmed properly, but instead used trim tabs? You can do the exact same thing with an aircraft, you can either trim it out by distributing the weight properly, which then you don't need to use tabs to trim it, or you can stick trim tabs out in the air. Now, which would YOU think more fuel efficient?? |
3 or 4 blade props?
"Joe" wrote in message news:4hwqb.4312
Here's some reading for you. http://www.bennetttrimtabs.com/whatdo.htm http://www.trimmaster.net/id114.htm http://www.boatus.com/boattech/trimtabs.htm http://www.powerandmotoryacht.com/fe...abs/index.html http://www.h-ri.com/Product/Duraplane/Duraplane_01.html Uh, yeah, sure. All of the above are trying to sell a product, you idiot. McDonalds claims the Big Mac is the best burger in the world. Do you swear by that, too, JoeTechnician? Dol-fin claims that there product will increase fuel mileage, too. You are stupid if you think that by creating MORE DRAG, that you are increasing fuel economy. |
3 or 4 blade props?
"basskisser" wrote in message om... "Joe" wrote in message ... I see you have decided not to argue against the facts for a change. There may be hope for you yet. Idiot boy, do you not think that a PROPERLY TRIMMED boat, ie: weight distribution, would out perform the exact same boat that was not trimmed properly, but instead used trim tabs? No, it would not. Equalization of weight would not outweigh the advantages of the lift provided by trim tabs. Let me ask you a question, if a boat with trim tabs is able to plane at 20 knots with the tabs adjust correctly, but must achieve 30 knots to plane without tabs, will adjusting the weight distribution in the boat allow the boat to plane at 20 knots as it could with the tabs? You can do the exact same thing with an aircraft, you can either trim it out by distributing the weight properly, which then you don't need to use tabs to trim it, or you can stick trim tabs out in the air. Now, which would YOU think more fuel efficient?? Do you really think the dynamics of an aircraft flying through air is the same as a planing hull on water? |
3 or 4 blade props?
"basskisser" wrote in message om... "Joe" wrote in message news:4hwqb.4312 Here's some reading for you. http://www.bennetttrimtabs.com/whatdo.htm http://www.trimmaster.net/id114.htm http://www.boatus.com/boattech/trimtabs.htm http://www.powerandmotoryacht.com/fe...abs/index.html http://www.h-ri.com/Product/Duraplane/Duraplane_01.html Uh, yeah, sure. All of the above are trying to sell a product, you idiot. McDonalds claims the Big Mac is the best burger in the world. Do you swear by that, too, So, you're saying that they're all wrong and you're right? Who woulda thunk. JoeTechnician? Dol-fin claims that there product will increase fuel mileage, too. Don't know, never used them, never have heard anything good about them though. You are stupid if you think that by creating MORE DRAG, that you are increasing fuel economy. Open your eyes kevin, your only looking at one part of the equation. |
3 or 4 blade props?
You forgot to answer my question-
Here's real world scenario for you- On my boat (21.5' CC 200hp), at 3000rpm the boat will ride with a bow high attitude with stern dive. As I actuate the trim tabs the stern rises, the bow lowers and the boat planes. Once planed the rpm's will immediately climb (without touching the throttle) and my speed increases. I then can reduce throttle back to 3000rpm and continue along on a plane. Now, tell me, do you think my boat is more, or less efficient at 3000rpm's with my tabs down or tabs up? |
3 or 4 blade props?
"Joe" wrote in message .. .
You forgot to answer my question- Here's real world scenario for you- On my boat (21.5' CC 200hp), at 3000rpm the boat will ride with a bow high attitude with stern dive. As I actuate the trim tabs the stern rises, the bow lowers and the boat planes. Once planed the rpm's will immediately climb (without touching the throttle) and my speed increases. I then can reduce throttle back to 3000rpm and continue along on a plane. Now, tell me, do you think my boat is more, or less efficient at 3000rpm's with my tabs down or tabs up? Uh, you are changing the subject here. You previously said more FUEL efficient, now you are simply saying efficient. As far as fuel efficiency goes, 3000rpm is 3000rpm, whether the boat is running flat in the water, or straight up, so no, your fuel effeciency hasn't increased. Your ride may be better, at the SAME fuel rate, but your fuel effeciency hasn't changed. Do you not understand that? Do you also not understand that when you use a tab, you are sticking a metal plate out to drag in the water? Now, again, answer me....do you think it is more fuel efficient to create drag by using trim tabs, or to distribute weight to achieve the same ride characteristics? |
3 or 4 blade props?
"basskisser" wrote in message m... "Joe" wrote in message .. . You forgot to answer my question- Here's real world scenario for you- On my boat (21.5' CC 200hp), at 3000rpm the boat will ride with a bow high attitude with stern dive. As I actuate the trim tabs the stern rises, the bow lowers and the boat planes. Once planed the rpm's will immediately climb (without touching the throttle) and my speed increases. I then can reduce throttle back to 3000rpm and continue along on a plane. Now, tell me, do you think my boat is more, or less efficient at 3000rpm's with my tabs down or tabs up? Uh, you are changing the subject here. You previously said more FUEL efficient, now you are simply saying efficient. They're directly related. So I am saying both As far as fuel efficiency goes, 3000rpm is 3000rpm, whether the boat is running flat in the water, or straight up, so no, your fuel effeciency hasn't increased. Your ride may be better, at the SAME fuel rate, but your fuel effeciency hasn't changed. You're wrong again. Here's a hint- manifold vacuum. Observe the fuel efficiency of one boat towing another boat running at 3000 rpm's and then compare it to the same boat while not towing another boat running at 3000 rpm's. Do you think it's the same? According to your theory it is. On my boat I have to REDUCE the throttle to maintain 3000 rpm's after actuating the trim tabs. Tell me how I could possibly. be running at the same efficiency. Do you not understand that? Do you also not understand that when you use a tab, you are sticking a metal plate out to drag in the water? With a tab you are actuating a plate angularly to deflect water, when used correctly the deflection will decrease the wetted area of the hull by raising the stern, and lowering the bow. Other benefits are reducing the surface area of the lower unit exposed to water, and more efficient prop angle. Now, again, answer me....do you think it is more fuel efficient to create drag by using trim tabs, or to distribute weight to achieve the same ride characteristics? Yes, it is more efficient to properly engage the tabs than to distribute weight. |
3 or 4 blade props?
"Joe" wrote in message ...
"basskisser" wrote in message om... "Joe" wrote in message ... I see you have decided not to argue against the facts for a change. There may be hope for you yet. Idiot boy, do you not think that a PROPERLY TRIMMED boat, ie: weight distribution, would out perform the exact same boat that was not trimmed properly, but instead used trim tabs? No, it would not. Equalization of weight would not outweigh the advantages of the lift provided by trim tabs. Let me ask you a question, if a boat with trim tabs is able to plane at 20 knots with the tabs adjust correctly, but must achieve 30 knots to plane without tabs, will adjusting the weight distribution in the boat allow the boat to plane at 20 knots as it could with the tabs? Again,dumb JoeTechnician, you were speaking of EFFICIENCY. I don't give a damn about the speed at which the boat planes. I'm telling you that if you stick a couple of plates in the ****ing water, and drag them THROUGH the water, you are creating drag. You will use more power to plane at 20 knots because you have to drag those plates through the water. Does pulling a skier make your boat more efficient, too???? You can do the exact same thing with an aircraft, you can either trim it out by distributing the weight properly, which then you don't need to use tabs to trim it, or you can stick trim tabs out in the air. Now, which would YOU think more fuel efficient?? Do you really think the dynamics of an aircraft flying through air is the same as a planing hull on water? Never said they were the same thing, but, there is a direct correlation between tabs on an aircraft, and tabs on a boat. Thusly: they both create drag. They both create lift. BUT again, at a cost. Same thing with an airplane, you generally use some tabs for takeoff, because the lift is so much better. But, when you get up to altitude, you certainly don't use the tabs because the efficiency of dragging them through the air makes fuel consumption rates rise. |
3 or 4 blade props?
"basskisser" wrote in message om... "Joe" wrote in message ... "basskisser" wrote in message om... "Joe" wrote in message ... I see you have decided not to argue against the facts for a change. There may be hope for you yet. Idiot boy, do you not think that a PROPERLY TRIMMED boat, ie: weight distribution, would out perform the exact same boat that was not trimmed properly, but instead used trim tabs? No, it would not. Equalization of weight would not outweigh the advantages of the lift provided by trim tabs. Let me ask you a question, if a boat with trim tabs is able to plane at 20 knots with the tabs adjust correctly, but must achieve 30 knots to plane without tabs, will adjusting the weight distribution in the boat allow the boat to plane at 20 knots as it could with the tabs? Again,dumb JoeTechnician, you were speaking of EFFICIENCY. I don't give a damn about the speed at which the boat planes. I'm telling you that if you stick a couple of plates in the ****ing water, and drag them THROUGH the water, you are creating drag. You will use more power to plane at 20 knots because you have to drag those plates through the water. Does pulling a skier make your boat more efficient, too???? You can do the exact same thing with an aircraft, you can either trim it out by distributing the weight properly, which then you don't need to use tabs to trim it, or you can stick trim tabs out in the air. Now, which would YOU think more fuel efficient?? Do you really think the dynamics of an aircraft flying through air is the same as a planing hull on water? Never said they were the same thing, but, there is a direct correlation between tabs on an aircraft, and tabs on a boat. Thusly: they both create drag. They both create lift. BUT again, at a cost. Same thing with an airplane, you generally use some tabs for takeoff, because the lift is so much better. But, when you get up to altitude, you certainly don't use the tabs because the efficiency of dragging them through the air makes fuel consumption rates rise. You're forgetting something, when tabs are deployed on an aircraft, and produce lift, efficiency does not increase because the density of the air is equal on all sides of the aircraft. On a boat it is much different, water is approximately 800 times more dense than air and any reduction in wetted surface will always result in increased efficiency. Properly activated tabs reduce the wetted area by providing lift at the stern, planing the boat, and lowering the bow reducing the hill of water the boat must overcome. Add to this the more efficient prop angle which reduces prop slippage and energy wasted pushing up instead of forward and the overall efficiency of the boat is greatly increased. It's obvious that you have never owned a boat with trim tabs. I suggest you go along for a ride with someone who does have them and observe them in action. |
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