What determines which way to mount trim tabs ( straight or angled )
#31
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with the boat being short what they mean is. if your running them even and your bouncing around in 3 footers they could dig in and force the bow to stuff causing possible death to you or hurting you and the boat. the small cats that I have been in run great without and just using the trim, boats were a trip ob 30 spectra and a twin skater 24. we ran the 30 in 4 to 5s off block island in a pokerrun at 90 it was hairy at times and only lasted ten minutes then back to the bay where it was only 2 footers and wakes. you should be fine without them even the 24 ran good in the bay running in 2 to 3s and jumping wakes from big yachts. so save your money. art
#32
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I dont know if this will help, but here are some pics of transoms from my last two boats.
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with the boat being short what they mean is. if your running them even and your bouncing around in 3 footers they could dig in and force the bow to stuff causing possible death to you or hurting you and the boat. the small cats that I have been in run great without and just using the trim, boats were a trip ob 30 spectra and a twin skater 24. we ran the 30 in 4 to 5s off block island in a pokerrun at 90 it was hairy at times and only lasted ten minutes then back to the bay where it was only 2 footers and wakes. you should be fine without them even the 24 ran good in the bay running in 2 to 3s and jumping wakes from big yachts. so save your money. art
#34
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#35
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I guess some clarification is needed.
Trim tabs mounted at an angle simply extend the running surface when set level or slightly above the bottom. Chine walking is a very subtle problem when it starts, and gets progressively worse with each rebounding cycle. Therefore you want to stop it with a slight subtle "nudge". To do this you insert a small outer corner of two opposing trim tabs into the water flowing off the bottom which creates a stabilizing (centering) affect on the hull without increasing drag beyond the bare minimum. You can't do this with angled tabs since they are an "all or nothing" proposition. You either put the entire tab surface in the water...or take it out. The Bennett style tabs shown in most of the pictures above are used more to help in planing and holding the bow down than to reduce chine walking, and they are a medium duty unit rather than a high performance tab. In addition when you mount tabs at an angle you are creating a "hook" at the transom which will create more bow steer and scrub speed. The only reason I can see where this might improve a hull is if the builder or rigger put too much rocker into the hull, or the C/G is too far aft, and you need artificial means to correct what is basically a flaw in construction, rigging, or design.
The hull that started this thread has an extremely deep vee and certainly could benefit from properly fitted and mounted tabs IMHO.
I hope this helps.
T2x
Trim tabs mounted at an angle simply extend the running surface when set level or slightly above the bottom. Chine walking is a very subtle problem when it starts, and gets progressively worse with each rebounding cycle. Therefore you want to stop it with a slight subtle "nudge". To do this you insert a small outer corner of two opposing trim tabs into the water flowing off the bottom which creates a stabilizing (centering) affect on the hull without increasing drag beyond the bare minimum. You can't do this with angled tabs since they are an "all or nothing" proposition. You either put the entire tab surface in the water...or take it out. The Bennett style tabs shown in most of the pictures above are used more to help in planing and holding the bow down than to reduce chine walking, and they are a medium duty unit rather than a high performance tab. In addition when you mount tabs at an angle you are creating a "hook" at the transom which will create more bow steer and scrub speed. The only reason I can see where this might improve a hull is if the builder or rigger put too much rocker into the hull, or the C/G is too far aft, and you need artificial means to correct what is basically a flaw in construction, rigging, or design.
The hull that started this thread has an extremely deep vee and certainly could benefit from properly fitted and mounted tabs IMHO.
I hope this helps.
T2x
Last edited by T2x; 12-06-2010 at 02:37 PM.
#37
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Thank you all for your input, I will try mounting them straight and see how I like,
since i dont have any tabs right now i think I will like it..
[email protected]
since i dont have any tabs right now i think I will like it..
[email protected]
#38
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Also remember that where you mount the tabs on the transom - whether it be angled or straight across - makes a difference too.
Most folks mount tabs all the way out towards the chines. I talked to a number of folks and looked at lots of pictures of Progression 22's before electing to mount mine a bit further in - over the lifting strakes. Why? Take a look at the picture below and note where the tabs are a just under 80 MPH. If I mounted them at the chines, no matter how low I dropped them, not much would happen at speed.
Most folks mount tabs all the way out towards the chines. I talked to a number of folks and looked at lots of pictures of Progression 22's before electing to mount mine a bit further in - over the lifting strakes. Why? Take a look at the picture below and note where the tabs are a just under 80 MPH. If I mounted them at the chines, no matter how low I dropped them, not much would happen at speed.
#39
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Flat mounted tabs on my Donzi. Rarely need to use them except in quartering seas.
With my Kryptonite, the angled tabs gave me more length and I ran them even with the bottom and a touch down in following seas.
As T2X said, different set ups depending on how they are being used.
With my Kryptonite, the angled tabs gave me more length and I ran them even with the bottom and a touch down in following seas.
As T2X said, different set ups depending on how they are being used.
#40
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generally for top end, flat. but general use (i.e., all around use) level with the hull.
Flat tabs really won't do much to help you with a list from weight, etc. while cruising. So if you want to use them for the all purpose tab use, angled is best. if you really want to fly top out, generally flat is best.
Flat tabs really won't do much to help you with a list from weight, etc. while cruising. So if you want to use them for the all purpose tab use, angled is best. if you really want to fly top out, generally flat is best.