first run with scratch cat... a rocket! need some help tho

[dana]

so the boat is 27" x 9" from tip to transom. balsa and fiberglass, and light. im using the ul-1 power system 2030 kv motor, inline strut rudder, 2 x 2s lipo in series for 4s, and octura x440 2 blade prop. she comes completely outta the water when i hit it...i have to ease into the throttle then at full throttle she's a little unstable, not too bad but shes def riding on all prop. question is is what to do now... add weight? bring strut up/down? change prop? any help would be great. heres a pic on placement of everything

[blackcat26]

I'd say make sure your COG is about right then adj. your strut angle. Too much positive and your bow will rise too much. Try the angle at neutral (level with the bottom of the sponsons)and see what she does.

[dana]

ok, but should the bottom of the strut be level with the bottom of the sponsons? or should i bury it deeper? bring it up? any suggestions?

[blackcat26]

I'd try it like this first....bottom of strut same height as bottom of the sponsons. This should be a good starting point.

[dana]

sounds good. what about turn fins on a cat? i noticed some have em some dont... any thoughts?

[blackcat26]

Cats don't need em. The blackjack has em but that's because for the most part it's a poor handling hull. Can you post a picture of the transom so he can take a gander at that baby? I love the color by the way and your hull shape is killer man!

[dana]

heres a couple, thanks for the kind words =) the paint is some i made up at work, altho the pics do it no justice. its about the color of a tennis ball lol

[crabstick]

well done man, that's an awesomely finished scratch build, looks like a mini Avenger

[dana]

thanks man, im very happy with it i must say, still needs some finish work on the decals and what not...but its there. took months of working at it here and there

[Rumdog]

Raise the strut.Start maybe 1/8" up from the sponson bottoms. You need to get more hull in the water if it's riding on just prop. Keep the strut level for starters. If it's still too light on the water, raise it more. I'd say start with CG around 30 percent.

[Jesse J]

looks very cool! yes raise strut, Fluid often says to have it as high as 3/16" above base sponsons. Is your strut backwards or is it a weird camera angle.. looks like taper is in back?

very sweet build! Mine would do the same thing when I first strapped her down and got her wet, flip over on her back even. Now she rides smooth and flat.

[dana]

ok so i tried raising the strut 1/8 above sponson bottoms, putting it flush, and putting it below with a neutral strut angle. in all cases is rides perfect at half throttle, starts to hop in the front at 3/4 throttle, and turns into an airplane when i nail it!!! the only thing i can think of is there just isnt enough weight. the best i got out of it was putting the strut below the sponsons and strut angeld so the prop was directed toward the ground, but still an airplane..... any thoughts? im thinking putting some fishing weights in balloons and dropping them into the hull up front more. because of all the balsa framework im pretty much at my limit as far as moving batteries forward.

[dana]

naw jesse its all in there right... weird camera angle. so how did you solve this? your strut is that far up?

[dana]

from what ive been reading what i have is what as known as porpoising. what i have gathered is that i need to put the prop deeper or add negative camber the the strut. ill give it a shot. still think the hull just needs weight plain and simple. ill try to shoot some vids soon

[Simon.O.]

I'll be following this one with interest as I have a 18 cat that performs that way too. At wot it rides the prop and is very fast but a bit unstable. I raised the strut so that the centre line of the prop is 6.25mm 1/4" above the sponson line and this is with a 427 prop.
It is still nuts even with a bit of neg angle on the strut. Lead is my next addidtion.

Nice hull you have there too.