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Old Hobbico Avistar big time modding

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Old Hobbico Avistar big time modding

Old 03-24-2008, 09:08 PM
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Default Old Hobbico Avistar big time modding

I have a older Hobbico Avistar 40 ARF that I found in an estate sale. The plane was brand new never flown and not fully finished. The wing had taken some rib dammage. I decided to completely strip it down and make me a Piper Cub wanna be. I cut the wings in half and took out all the diehedral and made a flat wing. I am making some wing tips out of 1/4" balsa I cut them out to approx 5" and glued them to the last rib. The origanal wingspan was 57" now its going to be 67" . My question is the 5" wing tips are they going to be too big? (5" tips on each side of the wing total 10 extra inches.) Or is this going to be ok? I also an going to 2" aileron stock and adding flaps. Will also be doing a much larger rudder . Maybe something like a Taylorcraft. What do you all think?
Old 03-24-2008, 09:45 PM
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Default RE: Old Hobbico Avistar big time modding

Go for it. With flaps deployed, it may float along and not want to settle for landing. Something about the increased lift and ground effect. Always fun to experiment. We have a fellow in our club who takes Kadet Senior kits and uses the wood in them to make airplanes that do not resemble the Kadet. One was a mid wing pre WW1 looking type plane. Another looked like a DeHaviland Beaver. You are only limited by your imagination. Have fun.
Old 03-25-2008, 06:08 AM
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Default RE: Old Hobbico Avistar big time modding

Great, I was afraid the wing tips might be too large. Any more suggestions?
Old 03-25-2008, 10:06 PM
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Default RE: Old Hobbico Avistar big time modding

It will work. I would cut 3 1" lightening holes in the wing tips. Two in the wide part and one out farther on the tip. Make more if it looks like they will fit. Trace an outline of the tip on paper first so you can lay out where you want to put the holes. Make sure you leave at least 1/4" of wood between the holes and between the holes and the edge of the tips. If you feel that will be too many holes in the tips, then make fewer hole and space them evenly. You want to remove weight but not the strength. If you don't want to add the holes. it should be fine, but you could need a larger engine than you planned. Sometimes these trainers were heavy already and would just barely fly with the minimum recommended engine. A .40 - .46 is recommended for this plane. With the modifications, I wouldn't go below a .46
Old 03-26-2008, 06:02 AM
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Default RE: Old Hobbico Avistar big time modding

I plan to power with a 56 os 4 stroke .thanks for the advice.
Old 03-27-2008, 10:49 PM
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Default RE: Old Hobbico Avistar big time modding

One thing I've noticed with people throwing flaps on their RC planes is that the flaps are more flaps than what is really needed.

Lets see here, The reasoning for flaps is:
#1) Increase lift
#2) Increase Drag
#3) Increase AOA

With flaps deployed on the approach, you need to figure out what your best approach speed is and either trim that out for landings or hold the nose down. The more flaps you have, the higher your nose wants to ride. To keep the aircraft from descending and losing too much altitude too fast, keep in a click or two of power during your final approach. Your distance for your final will be much shorter with flap and the aircraft will appear to be sinking like a brick, but when you pull that plane onto the runway, hit some ground effect, and pull the nose up to flair.. your speed will bleed off fast in this configuration and your landing will be as smooth of a landing as you can get.

I fly the real thing, and knowing the configuration and way various full scales work, can translate into being one of the best RC plane landers at your field.

I've only been flying RC for about a year, but I can land smoother and slicker than 90% at our field, mainly because I fly the real things and I've applied that to my RC flying.

Too many people come in too fast, trying to cut the throttle right at the numbers on the runway and land flat or balloon their landings. Come in steeper, pull it back when your 2-3 feet off the ground and you will impress daily
Old 03-28-2008, 05:59 AM
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Default RE: Old Hobbico Avistar big time modding

Great advice there. I have been running different types of landings through my head and trying to figure out how flaps work. I have never used flaps before but one of the guys in our club flies the real thing and is thebest pilot there. he has the super cub and can make superb landings just like you stated.
Old 03-28-2008, 09:25 AM
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Default RE: Old Hobbico Avistar big time modding


ORIGINAL: Sempiterna

I fly the real thing, and knowing the configuration and way various full scales work, can translate into being one of the best RC plane landers at your field.

I've only been flying RC for about a year, but I can land smoother and slicker than 90% at our field, mainly because I fly the real things and I've applied that to my RC flying.

Too many people come in too fast, trying to cut the throttle right at the numbers on the runway and land flat or balloon their landings. Come in steeper, pull it back when your 2-3 feet off the ground and you will impress daily
Ditto. Flying full scale really helps.

Those are some BIG wingtips, but the airplane will fly. Flaps should not be used as speed brakes, but they will allow you to descend at a steep angle without increasing airspeed. The flaps will essentially increase the camber and AOA of the airfoil. The effect of this is similar lift at slower speeds.

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