sweet, if that is hafl throttle then it is going to be hauling when you go full

Don't know if it will be possible to go full throttle. The torque problem is so bad that you can do consecutive rolls just by applying power very rapidly. Got some advice from pompebled over on RC Groups so I think I'll try this:

1. I'll position both 4 cell packs on the left

2. Unfortunately this will push the CG back so I'll open up the bow and add some lead, I doubt the weight will make much difference as the boat seem overpowered as it is... truth be told the boat was never balanced anywhere near 33% .. more like 26% so I 'll try to get it right

3. I pull the tabs off and try the X430 again ... maybe the cavitation will calm down and hopefully the smaller prop will ease the torque roll.

If anyone has other suggestions I'd be glad to hear them

Might have to build a Catamaran to make full use of this motor setup .... do they torque roll badly as well?

PS: Any idea how much boats of this size generally weight?

iwouldnt put them both on the left but more like a shift an inch over
i wouldnt add wieght to the front either because once you get it set up correctly then it will be robbing you of speed.
you dont need trim tabs if you set your boat up correctly.
btw can we see a pic with all of the electronics and batts in it please, thanks then maybe we can help you more.
mike

how high up in your hull do the batteries sit? if they could be moved lower you could try that

I'll take a pic tonight, but the bats are straddling the keel and stuffing tube thery're as low as the can go. I'll have to play around with the balance but I'm pretty sure it's going to need quite a bit of weight on the left ... the rolloing is very severe .. it rolls better than some of planes!

idk wat the problem is, when you put it in the water does it balance level?

She floats level at rest and runs level till just past 1/2 throttle .... like I said if you just blip the throttle to full power it will roll over. I figure she will have to be set up to float right side high in order to correct the problem.

well if i were u i would pm taylor, or some other guy that knows more than i do, usually boats onnly torque roll at take off i think atleast but i may be wrong

another thing you could try is movving the trim tabs outward so that you get more leverage and that would most likely help

Here's an interior pic .... a bit messy

http://s183.photobucket.com/albums/x...t=layout-1.jpg

The batts are actually a bit high .... tried to squzee them around the motor, I was trying to get close to an acceptable CG.

Suggestions welcome

Oh ... I've also got some AquaCraft Nitro Hammer props ... they look almost exactly like the Octura x432's ... could the reduced mass affect the rolling?

i would try moving the tabs out more so that it stabilizes the boat more.

Well made some changes and did a few more runs today.

1. Cut down my trim tabs and moved them outboard … right to the chine line.

2. Shifted the battery packs .. one now lies across the keel the other just squeezed past the motor. The boat now leans significantly to the left (from the back) but once you apply power it flattens out but wants to turn left all the time.

3. Added a little lead to the bow


http://s183.photobucket.com/albums/x...nt=newtabs.jpg

http://s183.photobucket.com/albums/x...t=newbatts.jpg


For my first run I bent the tabs way up out of the water flow and put on the X 430 … once she got up to about 1/2 throttle she started to porpoise. But most important there was no torque roll.

Adjusted the tabs down, probably a bit too much she ran very wet but I managed to get it up to full throttle. Not very fast with the 430 but no bouncing or rolling.

Decided to switch props, put an AquaCraft Nitro Hammer prop; its plastic but looks just like a X432 it’s specs: diameter: 1.25" (32mm) - pitch: 1.65
Actually did some checking …. that’s a bit more pitch than the X432

That seemed to produce the best runs; I also ran the X432 …. The hammer prop cavitates a bit more than the 432 but it seems to run faster. Problem is you either have to jam it down with the tabs or you go the aerial route.

Generally I’m pretty pleased, but the hull has to trimmed down into the water if I want to get to full throttle.

Yes, it’s kind of cool watching it do a run where it spends 50% of the time in the air; but it’s not that quick.


Is there any way to stop the porpoising without resorting to trim tabs? Nose weight?

Suggestions welcome …..

Might get some video tomorrow ….

Very nice. Whered you get the fountain decals?

Pulled the image off the fountain site and got a sign guy to cut them fo me.

crashbuilder,what is the length of the prop tube from the transom to the prop tip?What angle is that prop tube comming out of the transom at?The reason i ask is because i am converting a submerged drive to one like yours and i need some help thank you.

ridgewalker

2 3/16" from transom and if my robart is correct -5.5 degrees

thank you.Nice work hows it running?

Quickish but not great .... I think my shaft angle might be a bit severe ... just posted about that ....I think I've seen suggestions (flex drive) that the angle should be between 0 and 2 degrees .. impossible with my hull and motor set up. BOUNCE, BOUNCE, BOUNCE!

The only way to reduce the propshaft angle, using a rigid shaft, is to move the motor as far forward as possible.

In your case that would be major surgery as the deck will have to come off, or at least the hatch should be extended forward.

The motor would have to sit on the wood, as low down as possible.

With this size boat the bouncing (called porpoising) will stay, unless the angle is reduce significantly.

Regards, Jan.

if sh is bouncing. create a ride pad at the back and make sure your strut is LEVEL with the keel of the hull.

OK …. First step ... I need to reduce the shaft angle.

Graupner “U” joint or wire drive.

Option 1
Graupner “U” Joint:
I can slam the stuffing tube down to the keel and drive the solid shaft internally with the “U” joint. The drive angle won’t be zero but it will be significantly less than 5.5 degrees. The “U” joint has 2 ball things, 2 shaft couplers and a central section. I �m guessing it could be used externally in a strudder application, but it’s looks pretty draggy. Will there be an issue with the @6 degree bend?

Option 2
Wire Drive:
My preference, but I don’t think I have access to the key material. I’ve access to a lathe and can add 1/8 shafts to both end of the wire. I’ve got brass tubing in the required sizes. But music wire is a problem.

Welding rod is widely available … can this be a substitute? I fly gliders and I’ve been forced to use welding rod for my push rods. There’s an aluminum rod that’s very soft, I use it as a servo saver linkage …. it bends before damage to gears etc. Then there’s this brassy looking rod … it’s quite stiff but it fatigues easily … you can’t do multiple bends at the same point it’ll snap.

I did a mock-up with the brassy looking rod and it’s surprisingly smooth over a 5-degree bend. My fear it’ll snap after a few runs.

Why don’t people sell wire in small quantities?

Anyway suggestions welcome.

Are you going with the wire drive or u joints?

The u joint is simpler but hey ....live and learn; I'll give the wire a go.

I really want to tap the full potential of this boat and I figure a true zero drive angle is a step it that direction.

Only problem is that I'll have to use steel welding rod, I can only find coiled music wire here. Anyone tried this?

most people use 1/16 stainless steel music wire.the have it on towerhobbies for around 10 bucks for alot of them.
btw if you go with a wiredrive, make sure the wire rolls good(not bent)

I did a little mockup a few days ago, it bent thru 10 degrees and still rolled pretty smoothly. My final design only has to bend @6 degrees so it should work out.

Could you post up a pic of the wire drive that you are building.I'm trying to do the same thing.I have a 1/8 prop shaft,how do i attach a wire to a 1/8 shaft?Your pics may help me thank you

After last weeks runs it was suggested that I get my drive angle down. So I built a wire drive.

I’ve been researching these for a while but didn’t really grasp the concept till Easy Rider set me straight.

However, Easy’s set-up posed several challenges for me :
1. The external bend would have set my prop back to @4.5”; a bit far on a 15” boat
2. My rudder stand-off would have to be beefed up to serve as a strut support
3. I’d have to build a strut and all that stuff

From Easy’s pic it was clear that all you need to do is to support the drive at both ends and provide a frictionless path for the drive wire. Excuse me if this seems obvious, but it took me a while to get my head round it …

So I went the K.I.S.S. route … I just built a bent stuffing tube, 5 degree deflection and straight at both ends. The motor end of the drive has a 1/8” shaft that connects to the coupler and sticks about 1/4” into the stuffing tube. The prop end has a 2.25” long 1/8” shaft that rides in a straight section of the stuffing tube. The tube bend matches the bend required by the wire so effectively the wire is floating in space .. and a bit of grease… just in case.

The shafts are just standard 1/8” Dumas stock with a 1/16” hole drilled through. The wire is steel welding rod and is bonded to the shafts with “Permatex” sleeve retainer … couldn’t find Loctite 603.

The only thing in contact with the stuffing tube is @ 3” of 1/8” shaft so it rolls smoother than the original solid shaft.

After the runs today, I pulled it down and it’s apparent that the wire is running free and smooth. The welding rod has a bronze finish on it that’s easy to sand off …. I sanded both ends before bonding. Anyway the centre / bend section of the wire still has the coating on it.

Unfortunately, this drive is fixed but hey …it’s my second boat!


http://s183.photobucket.com/albums/x...urrent=key.jpg

http://s183.photobucket.com/albums/x...rent=angle.jpg

http://s183.photobucket.com/albums/x...rent=drive.jpg


Oh .. how did it run? Chalk and cheese .. this is a different boat! I get a bit of porpoising at about 1/2 throttle, but the solution .... just go faster, then she settles down completely. I’m still using the trim tabs, but ever so slightly. She’ll do full throttle without them but that’s iffy; she starts riding on the prop and chine walking .. fun to watch.

What’s next …. maybe 9 cells. balance the prop, sand the bottom.

Actually I need a new pond, I thought this one was ok but I can’t run full out for more than 7secs … just when every things have aired out and settled down.

Don’t know when I can get video…..