40% Extra 260: Own-design build thread

[OnTheEdge]

Dave, in the wing construction part, it looks like you sheet the servo wires into the wings. Looks like they are not removable...??? Any reason for not cutting a tube wide enough to fish the extensions through?

[OnTheEdge]

	Quote: Originally Posted by paffy
	Also - you should slow down the posting frequency. You make me look real slow with my build P.

Paul, you better get busy. Dave's #72 post shows he's done covering the fuse already. You better get going. I'll bet that as of this Friday, Dave will have some flights on this plane.

.........Mark

[dmichael]

Xed and Mark,

Yes, you are both correct, the servo extensions are glued permanently into the wing. If they were damaged I'd have to cut them and make a new hole then fish the new wires through. As to why, I don't like having to drill a long hole through the center of the wing. If I had to do it to fix it then I guess I would at that time but I haven't had any issues doing it this way.

Dave

[dmichael]

Cut out ailerons next. In these pictures you can see that I have imbedded additional balsa into the center of the wing facing at the hinge line and glued them in place with pro-bond. On top of this I then glue on the balsa that will get beveled. The hinges penetrate through both this piece that runs the length of the aileron and these imbedded blocks for maximum gluing strength.

[dmichael]

I faced the ailerons- looks like from the picture that I used a couple different pieces to do this job (not sure why- must have been using up the balsa I had on hand). Here are pics of the first piece going on. I find that when you cut out the ailerons, if you aren't careful to keep them straight when gluing on the facing, you can put a warp into the aileron. To make sure this doesn't happen, I set the aileron down on a flat surface and lay some straight aluminum with weight on it to keep the aileron straight while the glue dries.

As you can see I have only the best and most hi-tech equipment there. Three bricks, a vice and a partial jug of YS 20/20!

[Aerotech]

Dave,

Nice job on your build. I always like to see new things. Have fun with it and I hope to catch up with you sometime.

Thanks

John

www.aerotech-rcmodels.com

[dmichael]

Anti-rotation pins.

I started using this method about 8 years ago when I built a Carden Cap. I found that the dowel anti-rotation pins work fine but i wanted to be able to drill a hole in them and insert a safety pin (not a real safety pin but a pin to keep the wing from coming out in the case where my wing bolts backed out.

So- I started using hardwood railing instead of dowels- plenty of meat to drill through.

I also found that it was easier to set up the plane when setting incidence because I could use two straight edged pieces of plywood on the inside of the fuse instead of trying to make a hole that fit my anti-rotation dowel perfectly so that there was no looseness. I've used this method ever since and it has saved a plane on one occassion.

[dmichael]

Not because of great planning, I stumbled upon the need to glue a strip of 3/32 plywood along the sides of the fuse where the hatch matches up. I needed to do this because the hatch needed to clear the 3/32 ply reinforcements I glued in at all of the joints. This did the trick but also gave me a really nice clean corner for covering and it never gets dented- it stays very neat looking.

[dmichael]

Engine and cannister installation.

I used a ZDZ160 Champion and JMB mufflers. I liked both of these and flew the plane well through the Unlimited sequence.

Something I didn't like was the way I connected the headers to the cannisters. Because the headers didn't drop low enough to be in-line with the cannisters and because I couldn't move the cannisters up (no room) I elected to insert some flexible tubing between the two. While this did connect them and the engine ran well this way it resulted in a very sloppy engine and muffler area with plenty of leaks. It also allowed the cannister mufflers to rotate from vibration resulting in the down tubes constantly rotating to the left (from the point of view of the cockpit facing forward.) I addressed problem #2 but I never was happy with the whole attachment method.

I should have used a spacer between the header and the cylinder and, in fact, did just that when I retrofitted a ZDZ Super 160 at the beginning of this year. Here are pics that explain.

[paffy]

	Quote: Originally Posted by dmichael
	Ha! I had a four year head start on the build! It takes me longer to reduce the picture size than anything else! I bailed on the foam ribbed wing because I encountered difficulty cutting the bottom of the wing with my very crappy homemade foam cutting apparatus. I am sure that it would be easy to do with a decent bow that would cut 50-60". The sheer length of the cut makes it difficult for the neophyte foam cutter like myself. I think it would be great to do a 40% wing that way someday. Dave

I remember long time ago (when I was a kid and Sinclair Spektrum 48 was the top of the line PC) somebody showed me how he builds sailplanes - he computer generated the first and last airfoil, made plywood templates, then put bunch of balsa sheets in between and shaped the whole thing to make the whole span worth of ribs. Maybe you could use similar method for making the foam ribs ?

Butt all the blanks together on two rods, sandwich them between the templates and hotwire along the perimeter. You'd be dealing with 7" instead of 60" deep cut ... You could probably make the indents for sparcaps and alignment tabs part of the templates as well.

P.

[dmichael]

OK- we're nearing completion. At this point there's just radio and tank installation. Of course, there are lots of details I never covered but I either didn't have any pics or didn't want to bore you!

Here are some pics of the initial cannister install with the ZDZ 160 Champion. If you have never seen the JMB mufflers here is a picture. They provide no power increase nor require any tuning so they can be installed without a specific length header. In fact, you're better off with a shorter header than a longer one so they work well in tight installations. I have also used and am currently using in a different plane the more traditional type MTW 110K cannister mufflers. These provide some boost and require specific header length. I like both types- but I have noticed that the JMBs produce a deeper rumble (more pleasing) than the MTWs- I perceive these as a bit "tinny".

The JMBs are a few more ounces but have a very cool mounting lug on the end. I am surprised that other manufacturers haven't done the same.

[dmichael]

Installed pics.

[dmichael]

OK- would you believe that this picture was the first time I put the whole thing together?

If you do, I have a bridge to sell you! I am constantly putting my planes together as I am building them. At the end of the building day I might put it together just to see the progress.

[dmichael]

OK- last series of shots for the night. These pics are in my back yard and I have primed and painted the cowl white. Still have to paint the wheelpants, gear and the remaining colors on the cowl. Also have graphics and gear cuffs to put on.

Tomorrow, I'll post the final pics with some shots from the field and in flight.

Please fire away with any questions or comments between now and then.

Thanks-

Dave Michael

[dmichael]

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