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I had a 97 38 top gun Kevlar half cabin that porpoised a lot also had 380 k planes put five blade hydromotive p5 porpoise went away
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Anyone ever try lengthening the inner strakes by a foot or two ?
looked at a few other conventiontional bottom vee hulls and some have the inner strakes running quite a bit further aft than the Cigs. Watched some cigs while they were doing their hop, and looked like they were bouncing on and off the inside strakes . Almost as if the drives are trying to lift the bow without the help of the strakes, but just cant hold it there , and it falls back on to them, then lifts off them again.. |
Not sure if my input will matter running 70 ish top speed at this point, but my 87 does not barely at all, I use no tabs, and run drives neutral most times, like Justin I have yet to really see a speed gain with anymore trim, it is a NO NOTCH and SSMIII boat, my buddy has a 93 with TRS and a notch, also another buddy with 89 and notch also TRS, both porpoise... all of us are 70-75 mph
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Originally Posted by frickstyle
(Post 4635601)
MOSES - same running gear I assume? Engines, trans, drive, prop, etc?
Mine porpoises, not ashamed to admit it. Hammer down on the throttles, everything settles around 75, and it actually starts to ride better up on top of the water. Noticed it's pretty sensitive to drive and tab position. Any amount of tab below even KILLS speed big time. Drive trim position will influence it a lot around neutral and above, not a big speed gain by trimming drives up. drive ratio both 1.5 both bravo xr’s power 500efi vs. 540 hawks props both 26 bravo 4 blade agreed on the tab past nuetral. Our speed plummets. |
Tim,
not sure how fast you were going in the video above, 45-50mph? The porpoise effect seems to happen around 60-70mph. You may not be "experiencing" porpoise because you are not cruising at that speed? For instance, I can "cruise" at 70 and not see the porpoise, but if I back down or decelerate, it bounces around and I have to correct it. MILD - interesting comment on longer strakes, didn't ICDED do that mod? |
Originally Posted by frickstyle
(Post 4635648)
Tim,
not sure how fast you were going in the video above, 45-50mph? The porpoise effect seems to happen around 60-70mph. You may not be "experiencing" porpoise because you are not cruising at that speed? For instance, I can "cruise" at 70 and not see the porpoise, but if I back down or decelerate, it bounces around and I have to correct it. MILD - interesting comment on longer strakes, didn't ICDED do that mod? |
Originally Posted by frickstyle
(Post 4635648)
Tim,
not sure how fast you were going in the video above, 45-50mph? The porpoise effect seems to happen around 60-70mph. You may not be "experiencing" porpoise because you are not cruising at that speed? For instance, I can "cruise" at 70 and not see the porpoise, but if I back down or decelerate, it bounces around and I have to correct it. MILD - interesting comment on longer strakes, didn't ICDED do that mod? |
Originally Posted by frickstyle
(Post 4635571)
So the mod is done just outside of the inner strakes? Nothing is done to the "keel" portion of the V towards the center?
Originally Posted by 47 lightning
(Post 4635623)
I had a 97 38 top gun Kevlar half cabin that porpoised a lot also had 380 k planes put five blade hydromotive p5 porpoise went away
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Originally Posted by thisistank
(Post 3790116)
Straight bottom cigs do not like flat water. There's a sweet spot in most every straight bottom cig I've been in while in flat water. Each boats slightly different but its somewhere with the drives kicked out a bit and tabs down a bit right before you feel the "drag" and slowing. Sone will also drop one tab a little more than the other to get the boat to roll over slightly off the vee.
Just play with it. You'll figure it out. But get it in any type of swell or chop, not only will the porpoise go away, you'll actually see the speed climb! (Less drag the better). |
Originally Posted by 47 lightning
(Post 4635623)
I had a 97 38 top gun Kevlar half cabin that porpoised a lot also had 380 k planes put five blade hydromotive p5 porpoise went away
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