[Snapon]

Anyone got any ideas how to stop my Funtana tucking towards its belly in knife. I can mix it out on the tranny but even then when the rudder gets towards the end of its throw there's so much elevator mixed in she just snaps. It can get pretty hairy especially when low.

I read in another thread about rigging some up on the ailerons but the author didn't say whether his plane tucked to the canopy or the belly. It's really pissing me off as it's a good ship otherwise. Any ideas?

 

[Snapon]

Ooops! Sorry guys. Meant to say HI to all the other Bros as it's my first post here.

 

[matlok]

Welcome to the forum Wowbagger!

Someone back me up, but I believe you raise both ailerons to help correct tuck to the belly. It would be easy just to dial in some sub trim and try it. If it works - great, if not - take it back out! Also you may also want to look at this: http://www.rcuniverse.com/forum/Low-wing_aircraft_and_knife-edge/m_120014/tm.htm Check post #11 I believe, by George Hicks. (I haven't read the whole thing, but it looks interesting)

 

[Gordo]

If it was tucking to the belly, wouldn't moving the alerons up be adding to the problem?

My knife pulled to the canopy and I did the "up" thing. My sledge pulls VERY slightly and I was gonna mix it out, but decided not to.

 

[TailTwister]

I think Matlok has it backwards too. Knife edge tucking to the belly would need ailerons lowered, pushing the wing up (relative to the belly of the plane), right?

 

[Gary Seeloff]

All this talk of moving the ailerons seems like fixing your car's front end alignment by bending the steering wheel. :lol:

I'll admit that I don't know of any good way to fix the Knife's coupling, I've always just accepted it as nature of the beast. I would think moving the ailerons up or down would cause all sorts of tracking and trim problems.
Have you fellers using this technique noticed any side effects? Just curious....

Gary

 

[Snapon]

Matlok, thanks for the welcome bro, and thanks for the great link. It's explained stuff I never even knew was going on... I'm gonna try the aileron thing first but I can see it affecting other stuff too, but I'll try it first cos everything else means hacking stuff around. Yeah, I think they should go down too. Seems there's a lot of variation with Funtana's - some people say they have little pitch coupling and other say they get a lot so I guess it's down to the stab angle or maybe the CG as everything else will be exactly the same. Anyway, thanks for the help guys and I'll let you know if any of this stuff fixes the problem.

 

[TailTwister]

This may be related or just a coincidence.

When I first flew my Funtana, the landing was a bitch, because it would balloon and rock like mad as it slowed down. I raised both ailerons by an eyeball 1/16 of an inch. The ballooning stopped.

My Funtana is straight as an arrow in KE. I use full (all but touching the elevators) rudder and full power, as the fuselage area of the Funtana doesn't seem to like KE at all. I get no pitch coupling, and almost no roll coupling.

I do not recall flying KE before the aileron (spoiler) change. It basically works like changing the wing incidence.

I'd also check the thrust line. The Funtana has a ton of right thrust on purpose, and perhaps this one has a bit too much down.

Also, does CG effect this at all? My CG is at 6 inches back, if you think it does.

Good Luck and keep us up to date,

 

[Snapon]

Thanks for the info TailTwister. Okay, I'll try rigging the ailerons up a bit and see what happens.

Just fitted it with an ASP 91 four stroke and 15x4 which has put the CG back to 6 inches so, everything being equal, it should now fly knife just fine! :roll:

Just eyeballed for downthrust and there's about a degree. So I guess I'll have to fix that too. Didn't someone say that upthrust helped when hovering? Maybe I should have a degree of up instead...

 

[citation X]

Hey guys-I have reflexed my ailerons on a few profile's and have reduced alot of coupling issue's by this method, which did not induce any other problems that I noticed. I have flown a few different funtana's and none of them had any coupling issuse's what so ever. My guess is you should be able to correct this problem by reflexing the ailerons. As long as everything else was set-up as per the plans. Just my 1 1/2 cents. Ricky

 

[Jim T]

I picked the tip up off of RCO back when I started but raising the ailerons slightly will stop the belly tuck and give the wing some washout (which is good). I have done it on every plane I own.

 

[Snapon]

Bro's, never got to the rigging the ailerons up, reason was I found the wing dowels were getting chewed up pretty bad with vibration. My cure was to fit alloy tube over them (s'what I had lying around) and bore out the holes in the former. While I was at it I was thinking of this knife tuck under problem and decided to file the holes in the former without touching the bottom of the hole, this way I'd get more wing incidence. And ya' know what? It worked!!

It's still there slightly so I programmed in 10% up elevator with full rudder and it knifes like an arrow! There's a fair bit of roll coupling but I can manage to fly that off.

Also, as everyone on RCU told me, fitting the 91 four stroke has transformed it. Thanks for all the help. Appreciate it. I now have the Funtana I always wanted!

 

[TailTwister]

A member of mt club just let me fly his with a Saito 91 and an APC 15x4W, and it was awesome. Even climbing from a hover, there was no need to go over 1/2 power. Most flying, including big loops was done at about 1/3 power.

Mine has a 72, and it's amazing how much difference there is.

Man, I wish I had a Saito 91 or 100...

I'm glad to hear that the wing incidence fix worked out so well.

 

[Gordo]

I can't say enough good about the saito .91. I haven't had a 100 but I have heard all dood, and the 2 I have seen are great. I'm totaly in the market for annother .91.