damfurst

I have a mini-v with following set-up
EMP 3500kv outrunner
Quark 33 esc
traxxas 2216 receiver
scanner mini servo (metal gears)
Apache metal ujoints
SW26rs prop shaft w/ 31mm prop
water cooling
75mm rudder (outdrive is braced to prevent turning & bottom fin removed)
homemade turn fin on left side

This boat runs very well now as far as handling goes (runs in a straight line at high speed) My problem is that because of the outrunner it lays to the right when running. In fact it looks like it's on it side when running flat out. It will turn over if you don't watch it or back off on the throttle. I've already tried adding 3oz of lead weight to the left hand side which did help, but it still will lay over alot. Would a trim tab on the right hand side make any difference with this problem? Or do I need to change to a different motor (inrunner?) to get away from the torqe of the outrunner? I've included some pics to help.

justintime2w8

My Feedback: (1)

I not an expert, but you generally have a few options when dealing with torque roll. First most people on a FE setup will offset the prop shaft from the center of the boat a fraction of an inch. Second lifting the prop up a bit can sometimes help (in your case I don't think you have much ability to do this) along this same thought you could run a smaller prop faster and reduce the roll. however this depends on you particular setup. Trim tabs are (for me) the last ditch effort to get the boat running right. Mainly because they rob speed the more adjustment you need the more drag. However this may be the right direction in your case. You could buy or home-make a set, all you need are some flexible aluminum bent in right angles. With that size boat you might try coke can aluminum. I would consider also adjusting the weight in the boat a bit, batteries, ect... Also try a smaller prop, if you can, and see what results. It all comes down to what works, you just have to start trying some things.
Hope my rambling isn't too off from what you were looking for.

headhunter23

Why do you have cooling tubes on it if it's an outrunner? Only way to cool is plate at front of motor where it would attach with screws. Just as the other guy said, switching to smaller prop would help but of course would mean less speed, unless you went with one with more blades to make up for reduction in size. Reason is the prop is tiping your boat to the side, a trim tab will help a little except for the initial rock.

Ivan.

HSVXU6

Hi, do a search on prop torque, you should find numerous ways of solving the problem tabs, smaller prop, more cells, different battery lay outs, turn fin angle, rudder angle, placement of weight on the transom, etc. etc. Hope it helps.

5lagd

would somehow fastening a small horizontal piece to the outrunner work? Like the Americas Cup sail boats do to their keel. Make it look like an upsidedown T.

pompebled

Hi damfurst,

Basically you've overpowered a small hull and you'll have to live with the consequences...

There are a few things you can do to counteract the resulting proptorque, as has been pointed out in earlier replies.

As you mentioned yourself, the main solution is your throttle finger/thumb, by going easy on the throttle when accellerating.
A small trimtab may help with the proptorque, but at the cost of some topspeed.

I have my doubts on the type and placement of the hardware though; the rudderblade is very thick for such a small hull, I use a knife blade to substantually reduce the drag.
The propwalk will give the boat a preference for right hand turns, I'd place a (smaller) turnfin on the starboard side.
The waterpickup has much less drag if it sits in the propwash in stead of under the hull (that's dragging a bucket through the water...)

Question: what are you cooling with the coil? Or is it a leftover from the stock brushed motor days?
If so, loose it!

Regards, Jan.

damfurst

I really appreciate all the replies so far. I guess I'll try a smaller prop and see what that does. But if not would an innerrunner be better than an outrunner?

Headhunter & pompled, I understand what you both are saying about the outrunner with a cooling coil on it. But this is a true outrunner with a can around it(factory built). I believe it is an 8 pole motor and my cooling coil is just around the end of it given how the motor mounting takes place. Nothing spins aside from the shaft on the outside of this can. But the poles rotate around the outside of the stationary wire coils. If you want better pics I could take some.

pompebled

Ah, I understand...
The closed can is for mounting only, in this case (and protection for the moving parts inside ofcourse).
Cooling should be done with a fan through the armature, as watercooling a can is rather pointless, as it has no connection to the parts of the motor that heat up.

I doubt, if an inrunner with the same rotor size would make the torque issues go away; on my 20"and 25"monohulls I have to be gentle on the throttle exiting the turns, as the (inrunner) motors are powerfull enough to make the boat barrelroll if ful lthrottle is applied instantly.

Regards, Jan.

SV27dayton

So Jan is saying that you would likely have the same problem w/ in in runner. I see what you are thinking: More rotating mass farther from the center of rotation is causing the torque roll rather than the tigher axis of an in runner. Might be true. I think in this small boat it may have more effect than in some of Jan's boats. My thought it go ahead and tab it. The others have some idea about increasing speed by reducing drag. You can do those things and the boat will probably be faster with trim tabs than it is now. I'd file that rudder down before swaping it off. Actually I might leave it alone. The SV has a similar rudder width and Grim claims it helps lift the tail in the turns in CW racing. I don't like the comment that you've overpowered the boat and have to live with it. You have to addjust for it and account for it. 9 out of ten guys on here whan to go faster which usually starts with overpowering a boat. Also there's a guy on here who has done BL conversion on several mV and a mC. I'll try to find him bc he may have some good advice. His boat are overpowered as well.

pompebled

Hi SV27dayton,

My 'overpowering' remark wasn't a comment, as we (nearly) all do the same thing to our boats...
It was merely an observation, followed by some suggestions to remedy the boats behaviour.

I've had wedge shaped rudders on my FE, changing the blade for a much thinner knifeblade make a noticable difference in speed, giving me the edge in competition running.
I agree it has an impact on how the boat will corner, you'll have to be more careful with the rudderthrow, due to the higher speed approaching the marker and the risk of flow breaking off the blade when turned in too sharp too sudden, most of the time resulting in a flip.

It seems every 'upgrade' has a downside too..., it usually takes me some (run)time to get used to the changed boatbehaviour after a modification, when I have the hang of it, it works out in the races for me.

Regards, Jan.

SV27dayton

This is a good statment. I use this forum to steer me the right way, which it usually does. I think you racing situation you typically live with some pretty wierd behavior and learn to control it if it means more speed or getting around the course faster. Much like a racecar driver has no problem with banging his head on the roll cage as he crawels though the window - My dad would not except that in his caddy. I think the same is true when you "over power" a small boat. It's kind of fun when your at the lake knowing that nobody else could handle your boat

pompebled

That's true indeed; my son runs his Hopf Lightning around the markers as if it runs on rails, it's a very easy boat to drive and with his hand/eye coordination usually good for a first place.
My own Hopf Baracuda is a two stepped hull and upgraded to the max, it is basically quicker than his boat, but a handful to control, we've switched boats for one heat and I could beat him with one hand tied behind my back, while he struggled to keep my temperamental Baracuda on the right track...

Regards, Jan.

damfurst

Well I've tried all things suggested here (which I really appreciate). The trim tab made no difference what so ever. I put the original prop back on and still was able to flip the boat right over, just not as quickly, so I think I need to look for a different motor with not so much torque or put an outrigger on the starboard side

pompebled

Could you show us a picture of the trimtab on the boat?

If it didn't have any effect, it's probably too small.

My son's first FE was a narrow hull, prone to torque roll, We solved the issue by adding a very long narrow trinmtab, angled down ever so slightly; the boat did handle better, but accellerating out of a turn still had to be executed with care.

Regards, Jan.

damfurst

After reading your last post Jan I decided to go & try it one more time. I put the x427 prop back on, bent the starboard trim tab a little down, and it didn't lean to starboard this time. It leaned to port instead & would still flip over. You are right this is a learning curve. So I took off the port turn fin & made a trim tab instead. I'm going to try it out today & see what happens. I also included some photos in this post. Thanks for the help.

pompebled

Adjusting the trimtabs is a matter of trial and error and should be done in very small steps.

Before you try again, set them to neutral and only bend down the one that should counteract the proptorque and work from there.

Let us know how thing work out.

Regards, Jan.

damfurst

Jan,
Went out Saturday and experimented working with the trim tabs. Which ever way I would bend it (just a little) it would lean the opposite from and sometimes flip over easier. I worked with it at a least a half dozen times. So I need to maybe do a little more research and then go from there. I do appreciate your help though. It's great to be able to ask questions here and get help from people who are half a world away.

pompebled

Hi damfurst,

If your adjustments made the boat lean the opposite way, the adjustments were to coarse...

I know it sound rediculous, but a fraction of an degree will make the difference between running upright, or crooked.

Half a dozen attempts is barely a first series of trials.

Keep it up and success (or what will pass as such) will come, make notes and measurements, take pictures, etc.

Regards, Jan.

sidav

iv got the same problem, 540 2700kv inrunner 2*7.2volts 5000mah makeing 14.8 volts 25" deep vee prince.
went out the other day i had no tourque roll but my flex shaft kepped sliping from my coupler, the proppeler was sticking out from the rudder about 20mm,so i pushed the flex shaft in as far as it would go witch ment the prop was inline with the rudder now iv got tourqe roll trim tabs dident make a difference, i now need a new flex shaft to make it a bit longer..i hope this helps im still new to this hobby and still learing

damfurst

I wanted to post a conclusion to this post since it now has one. I did take all the suggestions and tried them. I was attempting to try a different drive system when the boat fell onto the floor damaging the bow. I thought that would be no big deal to fix, but then my dog jumped on the boat severly damaging the starboard side. At that point I decided it was time to retire this vessel. I stripped all the parts and anything else useful out of the boat and sent it to the dumpster. I was never able to overcome the torque roll completely though little by little it was improving. Thanks for all of your help. Now on to the next project. Here are some pics of damage to my boat.