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Apr 16, 2014, 10:47 AM
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Fred Sanford's Avatar

Control Throws


Getting ready to maiden my Ka8b via aero-tow. Any recommendations on the amount of throw? How close are the manual recommendations?
Also wondering what thickness of a shim should I use underneath the forward horizontal stabilizer hold down screw?
Thanks in advance!!!
Fred
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Apr 16, 2014, 12:12 PM
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SZD16's Avatar
You should be at 1.5-2 degrees between the wing and the stab....shim to suit.
As far as throws......I always set as much as possible along with 50% EXPO so you have the full throw if needed but around neutral the sticks aren't twitchy.
Apr 16, 2014, 01:35 PM
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I believe my shim was about 4mm at the leading edge of the stab seat. As stated above, just shim until the wing incidece says +1.5-2 degrees with the stab set at 0 degrees. Fly with it there temporarily until your are satisfied with the plane's performance then glue it in place.
Apr 17, 2014, 05:45 PM
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Thread OP
I agree with SZD16, i usually start of with lots of throw and enough expo to smooth it out, this gives enough control authority to counter any severely out of trim issues. Although it still did not help me save my KB when i flew it with the COG and the incidence incorrect!
Set up correctly this is an amazingly docile plane
Apr 21, 2014, 05:06 PM
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For you aerotow guys, how much weight in the nose was needed to balance at 80mm? Does this count battery?
Last edited by sleep4; Apr 21, 2014 at 05:52 PM.
Apr 25, 2014, 07:13 PM
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Fred Sanford's Avatar

Aero-tow Maiden Flights Revisited


My flying buddy Graham and I had very interesting maiden aero-tows! We both flew with the G of G at 80mm. Wow! Tip stalls galore, we both managed to get the planes back on the ground. Graham's without damage and mine with some wrinkles in the nose. Today we both towed with altered horizontal stabilizer incidence. Graham has about 4mm and I ended up with 1/4" and an additional 4 ounces of lead in the nose(total of 34 ounces which includes the battery) . We both had good flights, three each, but still had to add some down trim. We both had a flight where we were able to thermal and the plane shows potential once it gets sorted out.
Apr 25, 2014, 09:04 PM
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Did you measure the decalage (incidence difference between stab and wing) before and after shimming up the stab? If so, what was the stock vs. altered values?

Scott
Apr 26, 2014, 05:40 AM
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Fred Sanford's Avatar
Quote:
Originally Posted by shinck
Did you measure the decalage (incidence difference between stab and wing) before and after shimming up the stab? If so, what was the stock vs. altered values?

Scott
I did not measure the decalage.
Apr 26, 2014, 05:26 PM
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Quote:
Originally Posted by Fred Sanford
I did not measure the decalage.
I don't know why, but much of the scale stuff coming out of asia tends to have incidence issues. I have a minimoa that had 5-6 degrees in it.
Apr 26, 2014, 07:35 PM
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Fred Sanford's Avatar
Quote:
Originally Posted by rcsoar4fun
I don't know why, but much of the scale stuff coming out of asia tends to have incidence issues. I have a minimoa that had 5-6 degrees in it.
My Chinese 4M "Ventus" from Nitro planes needed a 1/4" also! Guess manufacturers don't test fly their stuff.
Apr 26, 2014, 07:49 PM
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Quote:
Originally Posted by Fred Sanford
My Chinese 4M "Ventus" from Nitro planes needed a 1/4" also! Guess manufacturers don't test fly their stuff.
Scary, ain't it?

I own two of the Robart meters, I don't see how people get along without them. With any knew plane I can set it up so at least I know it will be flyable.
Apr 27, 2014, 12:35 AM
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Thread OP
Maybe they use the factory floor as the datum and the floor is on a slope
May 03, 2014, 09:46 AM
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Fred Sanford - where did you get your replacement pilot figure. Also are you using magnets to secure canopy?
May 03, 2014, 10:22 PM
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Fred Sanford's Avatar
Quote:
Originally Posted by sleep4
Fred Sanford - where did you get your replacement pilot figure. Also are you using magnets to secure canopy?
The pilot came from a swap meet. It was about 3 1/4" high. The figure had earphones so I modified it as follows. Used a Dremel and shaped the earphones into ears. Added a 1/32" plywood ball cap visor, then used Bondo to shape the head into a cap. Added a 1" balsa "riser" to the base of the pilot. Narrowed the shoulders and capped with balsa. Painted with artists acrylic paint.
The canopy was not removed. I cut the canopy base from the bottom using a single edged razor blade making multiple cuts. The cut out allowed the positioning of the pilot figure and is secured with a screw from the bottom
I have magnets glued into the canopy base and tabs.
May 06, 2014, 09:07 AM
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K8b ready for maiden


Finished up the K8b 3500. Here are a couple of photos.

Battery - 8oz.

Lead - used 4 oz. lead fishing weights secured in recesses between the formers with epoxy and microballoons . - 22 oz. added

Tow release - Graupner

CG - set @ 82 mm from leading edge at the wing root for initial flight.

Incidence - wing @ +2 degrees with stab set to zero.

Hope to fly it soon.


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