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Old Nov 25, 2012, 12:31 AM
UMs & parkflyers... for now.
davidterrell80's Avatar
United States, VA, Herndon
Joined Apr 2012
2,920 Posts
I'm planning to use a technique I've done before.

I'm going to take some 1/32 sheet and make a partial profile section between the two sides, placing a panel before and after the cockpit area. In the cockpit area, I'm going to use some 1/16 basswood to make a battery/avionics tray by spanning the main stringers. Then I'll tie it together with a piece of 1/8 square, running a "motor stick" from the firewall to the horizontal stab. This should carry the loads and leave the formers and stringers for air loads.

Pictures tomorrow.
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Old Nov 25, 2012, 01:16 AM
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gupi's Avatar
Vienna, Austria
Joined Jul 2010
811 Posts
Looking very cool already! Interesting idea with the "motor stick".

Nevertheless i think if the fuselage was designed to handle the stress of a rubber motor going through all its length it'll handle electric motor flight, too. At least that's what i experienced with my free flight to RC conversion. The strength of the wings, fuselage, controls was never the problem. Adding too much weight definitely was.

At least in flight that is. If you plan to cartwheel often then you might need reenforcements.
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Old Nov 25, 2012, 07:19 AM
UMs & parkflyers... for now.
davidterrell80's Avatar
United States, VA, Herndon
Joined Apr 2012
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The rubber motor applies compression and torsion to the fuselage, to be sure. What I'm concerned about are my own piloting skills, my desire to fly this as a sport plane, and previous experiences with cartwheeling and sudden stops.

A lack of faith, I suppose. But, I am planning to use 1/32 for the fuselage stiffening, when my mind is telling me 1/16.

I guess that makes me a Kantian, rather than a follower of Spinoza.
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Old Nov 25, 2012, 07:42 AM
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I had looked at an old late 30's era TBD-1 Devastator. I already have enlarged the plans 200% and studied them quite a bit for a conversion build. The fuselage formers looked very similar to yours. I loved the look, but wasn't sure how to approach the build, so I am enjoying watching you do this.

Conrad
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Old Nov 25, 2012, 08:00 AM
UMs & parkflyers... for now.
davidterrell80's Avatar
United States, VA, Herndon
Joined Apr 2012
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The keys to building the formers are:

-- using a light coat of spray adhesive to affix the patterns to the wood. The paper adds strength need when pulling a blade across the grain.

-- affixing the pattern to the wood immediately before cutting, so the adhesive does not set and makes the removal difficult.

-- keeping fingers close to the cutting tip, pressing down, again being mindful of the grain direction. When you are pulling the knife through a thin section, you fingers can keep the former from pulling apart in tension.

Nevertheless, I have left the paper on the formers. They add a great deal additional fracture resistance without too much weight... and may provide additional strength in a crash, ensuring I have a repairable pile of sticks.
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Old Nov 25, 2012, 06:24 PM
UMs & parkflyers... for now.
davidterrell80's Avatar
United States, VA, Herndon
Joined Apr 2012
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I downloaded my good camera and found some early Skua photos. Attached here for the record.
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Old Nov 29, 2012, 09:34 PM
UMs & parkflyers... for now.
davidterrell80's Avatar
United States, VA, Herndon
Joined Apr 2012
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I had some very full days, lately; and not all of them pleasant. I'm still having problem with the pinched nerve.

I finally made some progress on the fuselage. I finished adding the stringers. I'm thinking that I will apply 1/32 sheet from the forward edge of the cowling all the way back to the wing root trailing edge; and also in the wing saddle.
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Old Dec 02, 2012, 11:36 AM
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This plane is going to be a beauty. I like the idea of leaving the paper glued to the balsa formers. May need to dust off those Devastator plans again. Like the Skua, The Devastator had a very generous cockpit area. I had visions of a video camera in the cockpit, maybe even some experimenting with FPV. Ideas for another day.

Nice work David.

Conrad
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Old Dec 02, 2012, 05:04 PM
UMs & parkflyers... for now.
davidterrell80's Avatar
United States, VA, Herndon
Joined Apr 2012
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Thanks, Conrad! The paper has already saved two of the formers in the cockpit area. A diminished motor control in my right hand led me to apply too much force and the former bent double. I was able to straighten it out and touch a microscopic line of thin CA on the wood side.firmed it right up. It also led me to think I'll reinforce future formers at thin points the same way.

Although I'm not through with the fuselage, I worked on the vertical stabilizer and rudder, tonight. I tried something new, in that I used white gorilla glue, in very small quantities, to make the laminations. It worked quite well.
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Old Dec 03, 2012, 09:51 PM
UMs & parkflyers... for now.
davidterrell80's Avatar
United States, VA, Herndon
Joined Apr 2012
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Adding some soft stringers to the vertical stab and rudder, to provide a symmetric airfoil shape.
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Old Dec 04, 2012, 11:36 PM
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Vienna, Austria
Joined Jul 2010
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Looking very good!
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Old Dec 06, 2012, 04:47 PM
UMs & parkflyers... for now.
davidterrell80's Avatar
United States, VA, Herndon
Joined Apr 2012
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Thank you, gupi! I've been watching your build with real pleasure.

I returned to the wing today. I installed two Common Sense RC 3.5 g servos for the ailerons. Then, I touched up the sanding on all the flying surfaces.

Since I intend this to be a "belly lander" I see the need to place some servo covers on the underside of the wing, perhaps like those used on the UMX Carbon Cub.

The flying surfaces are now ready for covering.

Hooray!
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Old Dec 06, 2012, 08:55 PM
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That is an interesting airfoil shape. Looks like it should give lots of lift without much speed.
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Old Dec 07, 2012, 05:20 AM
UMs & parkflyers... for now.
davidterrell80's Avatar
United States, VA, Herndon
Joined Apr 2012
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I kept the FF airfoil.

I felt this decision proper, as my normal style of flying is more scale than acrobatic. Had I meant this to be more of a "pattern" style plane, I would have change the airfoil profile to one having more symmetry. If it proves unsatisfactory, I have a couple of options:

-- Mix in down elevator with throttle, after I get the plane trimmed.
-- Reflex the ailerons, to reduce the CLmax and change the Pitching moment; adjusting the down thrust to re balance the forces.
-- Build a second wing that keeps the upper profile, making it compatible with the fuselage, but that uses a different lower profile.
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