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Old Jun 14, 2009, 06:26 AM
Promoting Model Aviation...
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EJ,

That's a great sheeting technique. I've added that to my Tips and Tricks thread if you don't mind. http://www.rcgroups.com/forums/showt...2&page=3&pp=25

Great work on both the build and the thread. I have really enjoyed following your progress.

Frank
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Old Jun 14, 2009, 11:31 AM
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Frank,

Thank you for the kind words.

Of course you should add the wing sheeting technique to the list. That goes for any other technique you see fit to add to the list.

As I noted, the iron-on sheeting technique is not my idea, just one of many in one of the building books that I have. I just wish I had remembered it before I attached the bottom sheeting.

Thanks for following along!

EJWash
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Old Jun 14, 2009, 11:31 AM
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The latest snag:

Let me start by saying that I have always enjoyed Sig kits. The quality is there, and the ease of building is there. They were among the first to publish build/instruction manuals and they manufacture their own wood and hardware.

The above being said, I dont like the aileron linkage-to-servo set-up.

The aileron set-up utilizes one servo driving both ailerons by way of a 1/16 music wire pushrod out to bellcranks in the wing. A short pushrod is used from each bellcrank out to its aileron panel.

My concern and reason for modification comes in the instructed method of tying the aileron pushrod to the aileron servo. With the servo mounted in place, a 1/16 music wire spur is bent to form wrapped with copper wire, and soldered to the aileron pushrod. The spur is connected to the servo horn with a Z bend. There is where I have a problem. With this method, I see two pitfalls:

1- There is no way to remove the aileron servo (if needed) without de-soldering the spur and removing it.

2- The soldering of the spur is going to heat and deform the plastic servo horn.

Bottom line, Im not going this route.

Id like to use a Du-Bro Ball-joint aileron connector instead. Much cleaner, and Ill be able to remove the servo if needed.

Im open to other ideas, and would appreciate input.

Thanks!

EJWash
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Old Jun 14, 2009, 04:11 PM
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Ohh....they've changed it then from what mine shows. My plans (remember this is an old kit) shows just a normal 90* bend and the nylon keeper on the end of the music wire. Now I'm going to actually change it to a non-adjustable (probably metal) clevis on the servo side, and then go with an adjustable clevis on the aileron itself.
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Old Jun 14, 2009, 06:34 PM
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BillyP,

Would you please post a shot of that?

Thanks!

EJWash
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Old Jun 14, 2009, 06:59 PM
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Sure, it's the same setup my father-in-law is running on his 4*40 that he has, I'm going down to pick up the cub this week and I'll grab a pic of it.

Allthough, I do like the looks of that Du-bro setup
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Old Jun 15, 2009, 08:22 AM
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While not the most economical solution, in my opinion, the best route is to go with wing mounted servos for each aileron. This allows for a short pushrod connection, and a more positive response.

The mod takes little time, and can be done with scrap materials that you already have.

The additional costs come from adding a servo, Y-harness and servo extensions.

Unless you are going for a scale look, the servos can be surface mounted in the rib bays, surrounded by balsa sheeting. The sheeting provides surface area so the covering has ample area for adhesion.
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Old Jun 15, 2009, 10:23 AM
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Thanks Tom,

I'm going to keep the bellcrank/servo configuration. This will be a basic air-knocker kind of machine.

I made a servo mount in wing's mid-section and a servo tray. I really needed to take care of this issue now, because the the mid-section is sheeted top and bottom. Not as easy to apply clamps or get my hands in there later.

I worked out a solution to the pushrod-to-servo link. I'll run a 'Z' bend from the pushrod to the servo. One end of the 'Z' will be wrapped in wire and soldered to the music wire pushrod, and the other end will have a solder-on threaded coupler with ball joint connection at the servo. At least, this is what's in my head for now.

EJWash
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Old Jun 15, 2009, 11:25 PM
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I think I have the aileron servo situation handled.

I cut out a servo tray mount (3/32 ply) that is firmly attached to the wing mid-section. Dang subliminal thought! I was listening to music on my iPod while laying out and cutting the tray mount, and, well, I guess the rest speaks for itself...

A detachable servo tray was fabricated (3/32 ply). Basswood servo rails with rabbet cuts overlapping the sides to get maximum glueing surface area.

Lighting holes were cut into both of these pieces. The tray mount weighed-in at 12 grams before the holes, and 6 grams after. The servo tray weighed-in at 12 grams as well, and 6 grams after. The plan calls for a 3/32 servo mount, so Im guessing things weight-wise is pretty much a wash here.

Instead of the Z bend, I opted for a U-shaped linkage from the aileron pushrod to the servo. I used heat-shrink tubing to secure the pushrod ends to the servo linkage and tested the throw with a servo tester. Not a solid bind with the tubing, but things looked pretty good.

After the top and bottom sheeting is glued-in, the aileron servo area of the sheeting is cut away. When this is done, Ill bind the two ends of the aileron pushrods together with the U-shaped linkage to the aileron servo and solder everything together.

I am using :30 minute epoxy on this build instead of faster setting time epoxy because I prefer the longer set time in the Southwest USA summertime.

Thanks for following along!

EJWash
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Old Jun 16, 2009, 01:10 AM
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A little ore time in the shop tonight, so I decided to take a little more weight off of the aileron servo tray.

I trimmed the servo mounting rails to get rid of some of the bulk. The reason for the size was for an ample bonding footprint.

EJWash
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Old Jun 16, 2009, 03:51 AM
Zor
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Quote:
Originally Posted by EJWash1

I think I have the aileron servo situation handled.
>
> Etc . . .
>
Thanks for following along!

EJWash
EJW,

I have been following along but could not visualize the arrangment from the text.

The pictures clarified everything. Thanks.

I see that you do believe that binding area in a glue joint is a big advantage for strength. Thus my often mentioned fillets in the corners. I see that you do have small fillets.

Your arrangement is very ingenious.

Congratulations on your progress (if you read this posting) .

Zor
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Old Jun 17, 2009, 01:13 AM
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It was a long and enjoyable day in the shop. Since it gets hot out here, it helps to take a break now and then and dunk in the pool.

Fitted and ironed-on the top and bottom wingtip sheeting. I really love the iron-on method. It's a no-brainer, right up my alley!

Brought the ailerons up to finish sanding. The ailerons are laid-out and constructed as part of the wing, and then cut away. Afterwards, bracing ribs, leading edge, and cap strips are added. It seemed like it was taking some time to get them done, so I counted the pieces. Thirty (30) wooden pieces make up the ailerons, plus the nylon control horn. No wonder...

Braced the aileron bellcrank mounts against their adjoining ribs with :30 minute epoxy.

By the way, I learned a trick years ago about mixing two-part epoxy. I mix it on a playing card. If its about a dime-sized blob per part, I use a popsicle stick to mix it. If its just a drop or two, I use a flat toothpick.

When I started the build, I laid-out all the wing wood in the top half of the box the model came in. The box is getting sparse. I must be getting close...

Thanks for following along!

EJWash
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Old Jun 17, 2009, 05:25 AM
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We had a heat wave yesterday, too. It got up to 80 !!! LOL

After your comments, last Winter, about my snow blower, it's my turn to gloat. LOL

Nice work on the wing, EJ.

I love it when the kit box is nearly empty. That means that it's nearly time to start a new build !!!
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Old Jun 17, 2009, 07:30 AM
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Bellcranks for aileron actuation? How old fashion! The 1/4th scale Champ I built in the mid 1980s had two aileron servos, mounted up close to the center section and push rods running out to bellcranks and the ailerons were actuated the same as your doing. At the time it was rumored that long servo leads would cause interferance and I think the Y-connector had chokes on them to help with this problem, also. If all the connections are tight; but, smooth actuating, this method is certainly viable.

Like someone previously stated; I would have used two aileron servos, as I think this is the easier method, now.
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Old Jun 17, 2009, 09:52 AM
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Tom,

Turn-about is fair play, and I asked for it...

EJWash
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