Whip 20 Help me break 70mph

[kevinpratt823]

I am confused. You were running the strut too deep yet you lowered the strut even more to go faster??


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Before today, I had been running the strut at around 7/8" to 1", and trying to get what I wanted with changing the angle. I had the idea in my head that this was already pretty shallow, and the boat seemed wet, but actually I think it just seemed wet because the prop was running too deep and throwing water.
I started today off by going rather far in the other direction as an experiment for myself, and I set the strut at about 5/8" the first run. At 5/8" I saw an improvement in the ride, and got 66.4mph, but felt the prop wasn't quite as loaded as it could be and the transom wasn't far enough out of the water. I lowered the strut a bit to about 3/4", which is still 1/8" higher than I had been running it previously, does that make more sense now?

I will add that it was a combination of input about unloading props from you(Fluid), higher revs(Kris Flynn), and shallower strut(Detox) that provoked me to continue in this direction, so thank you guys again for your input!

EDIT: I just re-read my previous post, I said "I learned that I have been running the strut too deep, and 1/8" lower made a big difference all around for me", I meant to say "1/8" HIGHER", I will go back and edit that............sorry for the confusion.

[Fluid]

I am confused. You were running the strut too deep yet you lowered the strut even more to go faster??


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[Heaving Earth]

well i think even a tiny change on the strut will make a big difference in the angle of attack in which the sponsons hit the water. find the sweet spot and you're golden

[kevinpratt823]

Nice job Kevin!

Thanks man. I should abb that the first set of packs ran 66.4mph with the 1650, and strut was at 5/8", I dropped it down an 1/8" for the run that got the 71mph.

[Heaving Earth]

Nice job Kevin!

[kevinpratt823]

Sent from my SCH-I535 using Tapatalk 2

Drilled the turnfin again and got it up to 1-7/8" down from ride pad, with a bit less downward angle, also raised the strut up to 3/4", completely flat. Made one pass with the back-cut, slightly cupped 1650 that looked very promising, then lost the prop when the nut came loose, as the hub is kind of long on that prop and the setup didn't allow much threads(I will be changing that), retrieved the boat, left it taped, tried a heavily back-cut 2047 and a 1745/3 just because I had them, but both props need a lot of angle on the strut so they didn't go all that well as is, then put on the H-10 and ran great for the last few minutes. GPS came back with 71mph! It was definitely either the H-10 or the 1650, looking forward to trying to back it up when I can get back out! I am very pleased with the trial and error/learning process, and above all I learned that I have been running the strut too deep, and 1/8" higher made a big difference all around for me, as I did not blow over once during the 2 sets of packs, also got a better feel for turn fin adjustments. It helps that the water was nice today also.

Thank you everybody who contributed and gave me food for thought, and keep it coming!

[kevinpratt823]

My whip went 93mph and change in 2007 with a 1521/1D, 4S1P 25C 5300's, V947. No turnfin, knife blade rudder and some minor sponson mods.

Unfortunately, it didn't survive the crash at 100+.

Thanks for chiming in! It looks like your ride pads are similar to what I have, but I don't have the corners cut. Do you think it's reasonable for me to get over 70 with some minor adjustments and maybe the right prop? Your setup was turning 10,000 rpm's more than mine, so obviously that's a big difference. I like the way she runs for the most part as is, just looking to get her over 70 for a personal best, without making it a SAW boat. Anny suggestions are welcome.

[Heaving Earth]

If I were doing ride pads, I would use thin carbon fiber plate. seems like it would be a good flat solid material

[detox]

[QUOTE=kevinpratt823;526937]Your ride pads do look nice, what type of wood did you use, and how did you seal and attach them? I did something similar on my UL-1 before with cedar shingles, but it's prob not the best material. [QUOTE]

I made those from maple, but softer woods will work also. First i cut square a short piece of 2" x 4" wall stud in the miter saw. Then i superglued a piece of maple to the end of stud and cut all pieces 1 degree. You will need a sharp blade to get good cut on hard maple. I sealed wood with good low viscosity epoxy then painted.

A less deep strut setting and maybe a little weight added to stern may help your stern hop problem.

[detox]

My whip went 93mph and change in 2007 with a 1521/1D, 4S1P 25C 5300's, V947. No turnfin, knife blade rudder and some minor sponson mods.

Unfortunately, it didn't survive the crash at 100+.

Thanks for showing those pictures. You have a good memory. I bet trimming the inside bottom of tips reduces lift.

[raptor347]

My whip went 93mph and change in 2007 with a 1521/1D, 4S1P 25C 5300's, V947. No turnfin, knife blade rudder and some minor sponson mods.

Unfortunately, it didn't survive the crash at 100+.

[Heaving Earth]

Also, what affect does moving the fin further away from the sponson have?

[Heaving Earth]

How about a straight turn fin Kevin

[kevinpratt823]

I have heard of water lines bursting during high speed saw passes. You may need stronger hose...i forget what type to use. Maybe two stroke fuel line.

I would not run strut too deep. This will lift stern and cause sponsons to run wet. 1/2" or shallower from bottom of stern to bottom of strut may be a good start with that large prop.

1 degree more AOA on sponsons would help also. I have cut the 1 degree ride pads using miter saw. Then glue on and finish.
4s2p is pretty heavy for the standerd width ride pads, i would also widen them 1/8"
4s1p would work for two saw passes, but be easy on the throttle during start.

Actually water line just pulled off a barb, I put some Great Planes clips on them now. It could have worked free a bit when installing, as my SK180 sits just under the front cowl on top of the packs.
Strut is right about 7/8", I will try lower, but the problem is more keeping the sponsons on the water, and not blowing over, I'm trying to control that with the strut angle also, but if I go too flat it gets the wa-wa's/prop hop.
Your ride pads do look nice, what type of wood did you use, and how did you seal and attach them? I did something similar on my UL-1 before with cedar shingles, but it's prob not the best material.
I bought the hull from Ray Shwaren, I know he did some modding to the ride pads, but I'm pretty sure he just raised them 1/8", looks like they were just filled in from the step all the way back, as I have no initial step at the front, possibly catering to a lower power setup.
Thanks for the input Detox.
Another area I have for improvement is the turn fin. I could take it off, as Kris mentioned, but I'm not too keen on running without it where I go, I don't have a huge area to slow down and make wide turns without going into the choppier water or losing visibility. It had a Virginia Craftsman fin, which was rather large with a flat bottom/curved. I drilled a new pair of holes to bring it up some, but it still hangs down about 2-3/16"(not sure if I can grind the top down more and drill another set to raise it up again), I also took the front corner off and rounded/sharpened it. I am still running it with a lot of down angle, which is surely causing some drag, but I'm having trouble keeping it on the water if I don't.

Perhaps the modded ride pads are holding me back by catching too much air or something, would some type of air dam be worth looking into....?
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[kevinpratt823]

Turn fin off
Sharpen up all ride surfaces
Shorten rudder
More revs, 50mm is a big prop for a small boat to handle 'nicely'

Any reccomendations? I still haven't run the H-6.....or do you think I should go back to the H-7/H-10, or 1716 and tune it in?
Ride surface are reasonable, but considering the hull has broken 90mph on 4s, I don't think it's unreasonable(for me) to break 70 and still turn and handle OK without going the full SAW setup route with no fin and short rudder, I would prefer not to, and I will learn more if I try to get there without doing so, but it will be a last resort to reach my goal if I am not there before it gets too cold out.
Thanks for your input!