Tee Bee Help
If you've flown one of the Todd's Models "Tee Bee"s I need some trimming help from you. If not, could you put me in touch with some one who can? I think the design originally came from "Team Evolution", but I can't find a way to contact them.
I finished up building and balancing the Tee Bee with 3 Tadiran 430 mAh lithiums, the JMP HF9 ESC, the WES-Techik MICRO DC 5-2.4 motor, and the WES-Technik 23cm x12cm (9" x 5") carbon fiber prop. Rx is a GWS R-4P and both servos are Hitec HS-55. Balance was 70mm back from the LE of the wing (BTW, this is about 29% MAC), as per plans, motor thrust line was 8deg downthrust, and stabilator neutral incidence was lined up with its mounting slot. Final weight was 110 gram; heavy I know, but it has lots of power and a decent glide with power off.
I've tried stabilator neutral positions of +15deg, 0deg, -15deg. I've tried thrust line positions of 4deg downthrust, 8deg downthrust, 15deg downthrust. It appears to like the stabilator somewhere around 15deg of "up elevator" for "power-off" glide. But, at that setting, it will loop!, even with 15deg of downthrust, at full power.
I'm finally looking for some advice on trimming this 4oz bucking bronco, before I beat it into a pile of plastic and balsa dust.
I do not know the Tee Bee, but it seems to me that you really need to put the CG more back until the glide is ok and then choose a downtrust angle again. BTW, glide is normally not too good with these extremely slow planes.
Thanks to ALL who answered. The final consensus solution came from Rick Page, John Arbo, and Todd Long; who said:
From: "Rick Page" <email@example.com>
Subject: RE: Tee Bee Help
Date: Fri, 22 Jun 2001 23:36:58 -0700
X-Priority: 3 (Normal)
I don't have the Tee Bee myself, but those designs tend to go down fast
with power off. If you try to trim it for unpowered level flight it has way
too much up (as you've found). Your original settings were probably correct
and expect to keep some power on all the time.
Date: Sat, 23 Jun 2001 20:09:02 EDT
Subject: Re: Tee Bee Help
I do know the plane and though it appears to be conventional, it has a
LOT of under camber, about 12% as does the V-tail version, the Little Bee.
That much makes for an extreme trim difference between power on and off.
The three models that I've seen or flown will drop at about a 45 degree angle
with no power when adjusted for proper powered flight. Only a slight amount
of power is required for a "glide" but always a little is needed.
I think that it has something to do with the air flow under the wing and
the amount of drag. Don Stackhouse can probably give a technical explanation
about it. I have read somewhere that 8% under camber is the maximum that
should be used to prevent excessive drag.
From: "Todd Long" <firstname.lastname@example.org>
To: "Robert \(Bob\) P. Andris" <email@example.com>
Subject: Re: Tee Bee Help
Date: Sun, 24 Jun 2001 08:50:21 -0700
> I'm finally looking for some advice on trimming this 4oz bucking
> bronco, before I beat it into a pile of plastic and balsa dust.
Sorry you are having such a tough time. I would try moving the CG back to
about 40% and 4 deg. of downthrust.
The Tee Bee will not glide, it comes down at about a 45 deg. angle.
I'm at Todd's settings and it flys great with power-on and somewhat "stonelike" with power-off.
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