Straight shaft BBY SC21

[RPC1]

I spent about 2 1/2 hours today machining a rudder stand off bracket, fun but what a P.I.T.A.. It is a 2 inch extension and I milled the back mounting surface -2 degrees to offset the positive angle on the transom. It looks beefy but I made it 3/16" thick. Here are some pics, I am going to go put it on the boat now.

[Dr. Jet]

If you balance it correctly it can work but your cg will have to be back far. It will lift the front from weight and the prop will push the transom up...if right it can run very light...fine line on that but give it a try

I think Jeff is spot on. Keep the CG further back than the "normal" 30% and it may work well. The problem you will face is your motor must be forward by default, and this will make it more difficult to balance. Plan on having your batteries as far aft as possible.

Keep working on it, I like the idea of straight shafts to keep costs and complexity down.

[RPC1]

Thanks for the replies. I was going to put the CG forward more, but I think you guys may be right about putting it further back. Maybe I will try 25% first. Thanks for the suggestions. Here are some more pics of the rudder finally installed, I'm happy with the way it came out.

[RPC1]

Finally got it all done. The hull is joined, everything is put in its place, and ready for a test run tomorrow. I am going to run it without the ride pads first, then put them on and see how it goes. Although, there is a pretty bad hook in the bottom of the hull, oh well.
I had a lot of fun building this, and hopefully more driving it. But I got to say by the time you trim the hull, laminate it with fiberglass, make and install bulkheads, you would be better of just buying the damn FG hull to start with. I like the way the boat turned out, I just wish it were fiberglass. Maybe Randy does them in glass also, that would be nice. I'll post completed pics tomorrow and maybe a video.

[ED66677]

here's my idea... sorry if it comes a bit late in your project!
too much angle, this type of mounting require the prop to be further in the front!!!
as a mecanic engineer I don't like flex trans, I made mine out of 2 rigid shaft (look at my web page), and looking at what you are capable of doing/machining, this is a piece of cake, both shaft are linked with a short 1" piece of 4mm flex, no leakage at all, and ajustable, no thrust to the motor but to the stinger/strut! that's all we need!
regarding bearing, honestly you don't need them, because it's difficult to find some small size sealed ones and if availlable, they are expensive, they require after run oiling/greasing is not sealed!
IMHO bushing is the solution, mine are made of simple brass, no wear up to now, you can find some cheap teflon charged ones on e bay!!!

[RPC1]

OK. So I took it out today and ran it on 3s A123 4400Kv out runner and no ride pads on the bottom. It handled great, good attitude, but not the fastest 20-25mph . Then I put the ride pads on, which raised the prop 3/32", and ran it on 3s Neu energy lipos. It really came alive but seemed to take a bit to loosen up. It seemed looser with no ride pads . The strange thing is that it wanted to barrel roll really bad. Just as it would get loose the whole left sponson would lift dig the right sponson in the water and want to turn right. What is going on here? Any ideas? Here is the specs.

Scorpion 2821-6 4400Kv Outrunner (500 Watts cont.)
Mamba Max ESC
3s1p 3200 Neu Energy lipo
Reshaped Y535
Wedge rudder 1.75" deep
Neutral Balance left to right
CG 28%

Also the drive shaft, motor,and prop are offset 3/16" to the right and the rudder is centered. Should I move the rudder? Another thing is the wedge rudder is really thick, like at least 3/16".
Finally, the motor stayed relatively warm, and the Mamba Max thermalled continuously after 1 min. Thanks in advance for any solutions.

[RPC1]

I have a thought. Since the rudder is offset to the left from the prop, is it possible that the prop wash is hitting the lower portion of the rudder and that is causing it to torque roll? Any thoughts would be great.

[RPC1]

Time for an update. I took off the ride pads to put the prop lower in the water. It seems that the lower the prop is the more it holds the transom in the water. I also lengthened the prop shaft 1 inch, this helped the most. I also put Apogee 3s2p 2200Mah batts in also. Now it jumps out of the hole and on plane nice and level. Now the only problem is it is prop walking at top speed. I am thinking of a dual rudder set up with two of the Solinger micro rudders if the blade is long enough. Just waiting on a Himodel esc. the Mamba Max just keeps thermaling on 3s, and the little out runner is about maxed out, although it is doing better then the MM. So I think I will try a Medusa 2856-1400Kv on 6s1p.

[Avanti]

I would love to see some video and gps numbers
any idea what kind of speed you are running top end?

[RPC1]

When I get some extra time I'll shoot and post some video. I'd say speed would be 30ish. I'm surprised the motor is out performing the esc, it is out of my T-rex 450 helicopter.