Fightercat Cheetah Twin Build Question

[kfxguy]

This was my first thought for using the two part foam. I see there are pros and cons to both. I think I will try the two part foam. Fingers crossed. I will post updates and pictures. Thanks everyone.

I guess the way I look at it is, hulls are cheap. Motors, esc's and batteries aren't. I'd rather destroy a hull and have to build the whole boat over but still get my electronics back rather than worry if I can make a repair to it. I'm so picky that a repair would nor be ok with me anyway. I'd rather just start over. But that's just me...and I'll have my electronics....just my .02

[keithbradley]

Several of us have found out the hard way that at least some popular two-part foams are not 100 percent stable. I know that one boat in which I poured foam sold by a popular FE on-line store almost had the deck collapse after sitting in the sun on several days. The foam shrunk and sucked the deck down. Fortunately I was able to slip a hacksaw blade between the foam and deck and cut them apart. The deck eventually rose back to it's original shape - almost. Now when I use foam I use a release agent on the underside of the deck. I can't always keep my boats out of the sun.

Read this post carefully. There's absolutely no reason NOT to follow this advice.

For the record, I thought mine shrunk from the cold here in Michigan. It's possible that any temperature too far on one end of the spectrum could cause issues.

[Fella1340]

Just throwing in pool noodles isn the best solution either. Run two bulkheads on the tunnel floor all the way to the tips then cut closed cell foam to fit the forward area precisely and cap with a header will give you similar flotation qualities to foam. The other benefit being an extremely strong rigid hull that isn't relying on foam for all its strength. It's a lot more work but is also quite satisfying once it's done.
It all depends on your goals, if the hull is a means to achieve 100 plus mph and is considered sacrificial in meeting that goal then foam may be the way to go. If it's something you want to keep for years with no intention of selling then spending the extra time and effort is well worth it.

[tlandauer]

Several of us have found out the hard way that at least some popular two-part foams are not 100 percent stable. I know that one boat in which I poured foam sold by a popular FE on-line store almost had the deck collapse after sitting in the sun on several days. The foam shrunk and sucked the deck down. Fortunately I was able to slip a hacksaw blade between the foam and deck and cut them apart. The deck eventually rose back to it's original shape - almost. Now when I use foam I use a release agent on the underside of the deck. I can't always keep my boats out of the sun.

Read this post carefully. There's absolutely no reason NOT to follow this advice.

For the record, I thought mine shrunk from the cold here in Michigan. It's possible that any temperature too far on one end of the spectrum could cause issues.

I agree, been there, seen it and wished the previous builder/owner didn't do it.

[ray schrauwen]

A full sized boat has a far thicker hull than our models and can deal with some expansion and contraction than our toy boats.
Doby has used hardware store spray foam consisently in all of his boats BUT, he is very slow, patient and cautious when using it a little bit at a time. I used 2 part foam in a Titan 33 and the deck sucked in really badly. Sometimes the problem is the product, sometimes it's the user. Personally I don't like it

I've talked to the manufacturer, distributor (Composites Canada) as well as the builder of my custom ski boat who has used it for over a decade to meet Coast Guard regulations. I've done as much due diligence as possible before I let the bow of my ski boat to be foamed.

I obviously can't speak to all 2 part foams, but I did the research on this:

http://www.compositescanada.com/prod...yurethane-foam

[Finest Racing]

Sounds like a release agent is needed to use a two part foam. Thanks for all the hands on info.

[ls1fst98]

I much rather two part foam. If you.crash and break the hull apart bad enough, your pool noodles or pink foam is all your gonna see floating...so what's the point? Two part foam is going to strengthen the hull and it also sticks to it. Break apart, good chance you'll still be able to get some stuff back besides pool noodles. To each their own tho....

id love to see a boat with 2 part wreck as bad as you state above and you be able to use your electronics after. in that kind of wreck, 2 part of pink foam is not going to save it.

[Finest Racing]

I have been trying different motors. I have tried the Castle 1515 2200KV, 1517 2650KV and now TP 4070 2200KV. When trying the Castle 1515 I was only able to hit 55mph. When I tried the 1517 I was able to go 57mph. Both motors where propped to there limit using a temp gun after making 4 minute runs. When I tried the TP last week, I hit 62mph and then the flex went swimming. I think I have more in it. I was using a three blade X446 with the TP. With the Castle motors, I was using two blade X props. I will try X448 two blade prop when I have my parts.

[kfxguy]

I have been trying different motors. I have tried the Castle 1515 2200KV, 1517 2650KV and now TP 4070 2200KV. When trying the Castle 1515 I was only able to hit 55mph. When I tried the 1517 I was able to go 57mph. Both motors where propped to there limit using a temp gun after making 4 minute runs. When I tried the TP last week, I hit 62mph and then the flex went swimming. I think I have more in it. I was using a three blade X446 with the TP. With the Castle motors, I was using two blade X props. I will try X448 two blade prop when I have my parts.

I'm currently tuning one myself. It's a single but still. The props like to be high up and have some positive in the prop angle. I got 63.1 out of it but it's got more. Just gotta figure out what it wants. It seems to be hard to get the nose up some.

[Finest Racing]

I'm currently tuning one myself. It's a single but still. The props like to be high up and have some positive in the prop angle. I got 63.1 out of it but it's got more. Just gotta figure out what it wants. It seems to be hard to get the nose up some.

I read your write up about the KBB Mono build. I race in NAMBA and I am searching for another P Mono boat. I see how you have been able to hit high mph but how does it turn? There are about three or four mono's I am looking at. The Cheetah can run a full oval (NAMBA race) at full throttle. Amazing how it handles.

I wish the flex did not let loose on me. I was hoping to try different props to see what the limits are. The old motors I had flex/cable savers. New motors have 8mm shafts. The new couplers reduced the space for the flex savers. I will trim the flex tube for them to fit so I am not going through this again.

[kfxguy]

I read your write up about the KBB Mono build. I race in NAMBA and I am searching for another P Mono boat. I see how you have been able to hit high mph but how does it turn? There are about three or four mono's I am looking at. The Cheetah can run a full oval (NAMBA race) at full throttle. Amazing how it handles.

I wish the flex did not let loose on me. I was hoping to try different props to see what the limits are. The old motors I had flex/cable savers. New motors have 8mm shafts. The new couplers reduced the space for the flex savers. I will trim the flex tube for them to fit so I am not going through this again.

I mainly built it for straight speed but it will turn decent. Keep in mind I have small turn fins on it that are about right for a 26" mono. I don't have many turning videos but here you go.

[kfxguy]

This is 50 something and not letting off towards the end. I'll reiterate tho, small turn fins and they are swept back

[Finest Racing]

Excellent running boat. I would be racing with other boats which will cause rough conditions. Thank you for posting the videos. I need to think if this would be the best boat for racing.

[kfxguy]

Excellent running boat. I would be racing with other boats which will cause rough conditions. Thank you for posting the videos. I need to think if this would be the best boat for racing.

I would highly consider it for what your doing. I have some other videos of it running around about 60 mph and turning well. It can do much better but I had a short rudder on it, drag prop, trim tabs way far into the middle and short turn fins. I guarantee it's got a lot of potential. It has some weight to this hull too, it's very heavily and nicely laid up.

[Bduncan]

running 86 here on 8s. http://youtu.be/8rpnSrjC_-8