Aeromarine Sprintcat 40

[Jeff Wohlt]

Many BL motors will stop completely when thriottle is off so the prop then becomes kinda like a brake. Feigos may not as they turn very easily at off. You will never see a drag boat just pull off the throttle...they come off slowly. I guess the stopped prop could cause some transom to lift. Combine that with a fast reduction of tunnel air and yes you could almost go end over end in some cases.

For my bassboat coming off some serious speed (near 70 in an 18 ft boat) you always watch the third hop if you are taking some big waves. That is my experience with fast real boats. It can stuff you real damn fast. Just the right combo and it then pushes the transom up and in you go. I have come very close. I did spin it out at around 50 and almost broke my ribs. I was trimming down as I went into the turn...that is a no-no. IOGP/Formula One boats (Seebolds that I get to be around ) used 24v down trim systems.

[DISAR]

Interesting experience, I wish I had a real fast boat. It must be the sudden speed reduction that caused the diving.

[Jeff Wohlt]

That or a combo of three good waves that you went over and the last one threw the transom up and stuffed it.

Yes, a buddy was behind me and said all he saw was a big spray and actually thought I barrel rolled it.

Charger bassboats do not like trimming down thru a turn and it is because it has such a deep v at the front. Had I stayed trimmed up I may have been ok just some porpising. We actually run them thru turns pretty damn fast. I do not have the kahoonas but at Truman Lake is is nothing but 15 foot wide channels as you get backin the arms and fish for spawning bass...these guys fly thru there and all you see is a big rooster tail coming thru the woods since it is nothing but trees in the lake. Two boats meet and no kidding you can give them a 5 smack holding your hand out and they hardly back down below 40 mph. If you get out of the channel you can go from 15 feet to 3 feet in nothing flat. Already replaced one lower unit on mine from hitting bottm. All you can do as you see the depth finder getting very shallow is keep it wide open and trimmed all the way up...never come of the plane as you will bury it in the rocky bottom....I not only took the lower unit out but actually hit the bottom with my boat at around 40 mph so I figure I went in to about 1' of water. Only a $3500 screw up.

Here is a friend of my sons little weekend catch.

[bustitup]

Just a heads up
there is a guy on ebay selling the molds for this boat...hull, top, cowl, radio box

[Fluid]

Just a heads upthere is a guy on ebay selling the molds for this boat...hull, top, cowl, radio box

Nope, a completely different boat. It's 42" long (not 34" like the SC40) and it is definately NOT an Aeromarine hull. I don't know what hull it is a splash of.


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[Joern Markset]

The size does not matter.

That`s not what I`ve heard....

Interesting to watch your project, I have pretty good experience with this hulls but powered with .45 nitro. They can be incredible fast with a proper setup.
I have plans for building an electric cat in that size my self, just don`t have the time at the moment...
Keep on posting, and provide us a video when you`re done

[DISAR]

New test today on 6s2p with 447/3 again with cog about 32-33%. It was a bit windy and choppy and did not run at full throtlle only once or twice for about 2 secs. No dive today which I believe was due to sudden speed decrease, but quite the opposite. The boat has the tendency to be air-borne when I hit full throttle and quite loose on the water. Only aft part touching the water but the bow lifts quite a lot. Maybe I have to transfer the cog a bit fwd again 34-35% or add some weight somewhere to adjust the cog easily. Because of the hull's design the batteries are quite difficult to reach and have cut some part of the rails and deck edges. I have the following questions:
a) Does anybody know where the cog should be for this boat? Joern?
b) My bottom of strut is above 1/4" from bottom of sponsons shall I lower it or lift it to keep the boat on the water?
c) Or shall I change the angle of the strut, now I have it parallel.

Needs some more testing but not much time.

[EPower]

I don't understand why the ETTI will not handle it. It is for 7s, I will go 6s first, it is for 150A I aim to go about 100-130A.
The size does not matter.

Your Etti will handle it just start with a small prop i was told that a Hydra 120 could handle that motor LOL i bet you the Hydra would go up in smoke first

[DISAR]

You know what, I took out the ETTI and put a HM200A 3-7S (my last one) which has worked satisfactorily till now in my other boats. See how it goes and then put the ETTI in. I don't have the money to go for an expensive one now.

[Joern Markset]

I was running my cats with about 33 - 34 % cog. I had a 16 oz fueltank in front and the .45 engine was mounted right behind the fueltank. Bashing around throttling up and down makes this boat dive in the end because of the very low bow. Your struthight seems fine to me, maybe you should try a slightly positive angel. It is no problem to run in the 60`s and still become stable. Just get yourself experience with this boat and you will be satisfied. Hours and hours with testing will get you on the top

[DISAR]

Many many Thanks, appreciate Joern.

[Jesse J]

Disar, when I get mine together Im gonna try small props until I learn how to drive it. I wonder if you propped back some and found a less windy day, if that would help to get the feel of how she handles, then prop back up once you have her dialed. I'll be curious to see how things go, good luck!

[DISAR]

Are you going to build a Sprintcat? That will be nice.
I know that the conditions were not good for testing but I wanted to see first the temps of ESC,motor & batteries. Everything was cool. Handling was of secondary importance which will be now first. The 447/3 is considered quite "small" for this setup and I think I can go upto a prather 235-240, 452/3 for max.speed.

[Fluid]

a) Does anybody know where the cog should be for this boat?

This depends on the speed and weight. The faster the boat, the further forward the CG needs to be. On 80+ mph SAW passes my SC40 needed the CG near 35%. With 4S power and 50 mph, 32% was good. If the CG is too far forward the boat may hook in the turns.

b) My bottom of strut is above 1/4" from bottom of sponsons shall I lower it or lift it to keep the boat on the water?

You will probably need to raise the strut to keep the boat down on the water - between 5/16" and 3/8" worked well for me but it is prop-dependent. The deeper the strut, the higher the boat rides, and usually when the strut is that low the boat tends to skip over the water rather than ride on it.

c) Or shall I change the angle of the strut, now I have it parallel.

The angle will probably need to be between flat and two degrees up at the prop end. Set the boat on a flat surface to measure the depth and the angle, don't 'eyeball it'.




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[DISAR]

Mr.Fluid I don't know what to say

Thank you very much for your excellent advice