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Permalink Reply by Zenith.Aero on November 4, 2009 at 8:01am

For technical model-specific discussions, we recommend that you start a new discussion under the model group, in this case: http://www.zenith.aero/group/ch750

This will keep discussions relevant to all members, and will make it easier to archive and access your post in the future.

Also, keep in mind that you can post a photo as part of your message as opposed to adding a photo attachment (attachments are generally used for documents or spreadsheets).

Thanks,
Zenith.Aero Admin

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Permalink Reply by Dr. Edward L. Olds III on November 4, 2009 at 8:57am

That's fair, thanks.

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Permalink Reply by Donnie Moore on November 4, 2009 at 6:46pm

Lay your square tubing lengthwise. One right behind the spar line clecoes and on right along the trailing edge. You want to be able to see 1/4 inch of the tubing when the flap is laying on it. Then cut some lumber the right length to keep The square tube spaced this way. Then use straps to bend the skin over the nose. (I used four straps.) Use hookless ratchet straps.

I still had the same problem with the holes lining up on the spar line so I drilled to A5

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Permalink Reply by Dr. Edward L. Olds III on November 12, 2009 at 4:15pm

Donnie,
Thanks for the idea, I hope I don't have to resort to too many A5s.
Ed

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Permalink Reply by Ken Sandine on November 8, 2009 at 9:45am

Edward, I've had the same problems. I have tried variations of Donnie Moore's method, still with no success. Before bending the leading edge with the parts "at rest," the bottom skin and spar holes align. But, as strap pressure is applied there is metal movement that pulls things out of alignment. I'm trying to think of another variation before calling buddies.

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Permalink Reply by Dr. Edward L. Olds III on November 12, 2009 at 4:18pm

Ken,

Yes, I have seen that problem. I hope I can get this part finished soon, it is driving me nuts. It seems like progress takes forever.

Ed

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Permalink Reply by Ken Sandine on November 19, 2009 at 10:34am

Ed, I have found success on my first flaperon. Attached are pics that I will refine on the second one.

To explain the basics: I secured the trailing edge with a 2X4 and a scrap strip loosly screwed to the top edge so that there was a gap into which the trailing edge would slide. I clamped that to my bench. The spar rests on steel tubes elevated with scrap wood to the same level as the trailing edge. I clamped both ends of the spar to the steel tube. To minimize the deflection between the spar and the bottom skin layer, I did two things: (1) I cut wood spacers to go between the hinge bracket (75A2-1) and the scrap strip on top of the 2X4 and (2) I put pins through the skin and spar holes at 8 locations that protruded 1/4 inch on the top. I used scrap A-4 rivet ends put through wood scrap and held in place from the bottom with the white foam packing material rolled up between the spar flanges. Crude! On my second one, I'll first try it without (2) in hopes that (1) will be sufficient.

To get the right pull with the rachet straps I secured the rachet high enough on the 2X4 so the strap was level with the top. To pull the skin, I used a 1X2 scrap piece of oak duct taped to the leading edge (at the bend point), fore to aft, in 8 places. My first attempt revealed that the duct tape stretched and the hinge bracket got in the way, so I notched that location. To hook the rachet strap to the 1X2, I put screws in the oak on the back corner so that they would add to a "bending moment" and not come off. (With what I have, the strap hook was "upside down" and the "loop" going over the screw). I also put a 1X3 along the top of the spar to hold the spacers as well as keep the spar in contact with the steel tube.

I did this with 4 straps, one at each rib, working the leading edge back a little at a time. As I started getting "closer" I used my hands to assist in "rolling" the edge around and taking up the slack in the straps. When it seemed like I was just "at the limit," I could push the metal to metal in place. There was sufficient hole alignment to work the three layers of holes so the clecos would go in.

The usual drill to #30, disassemble, and debur happened. On reassembly, I still felt I needed the hole alignment assistance on the spar to skin, so I cut 6 A4 rivit heads and inserted them into the #30 holes. Friction held them in place and I pushed them inside during riveting and dumped them via the space in the trailing edge.

I'll try #2 today and we'll see if I can duplicate #1. Thank you for sharing your journey.

Ken

Attachments:

• Flaperon assembly detail 2.JPG, 437 KB
• Flaperon assembly detail 1.jpg, 123 KB

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Permalink Reply by Dr. Edward L. Olds III on November 21, 2009 at 11:00am

Ken,

Looks like you found the secret! You did a great deal of thinking before you launched, I wish I had. I also see that you found a good way to use the straps with the ends still attached. I cut off my end hooks and that has led to some problems. I finally got two flaps done, with the help of two friends. Thanks for a great idea, I'm going to re-think my method.

Ed

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Permalink Reply by Ken Sandine on November 23, 2009 at 3:47pm

RE: Flaperons

Ed, I am website challenged when it comes to replies, discussions, forums, blogs, photos, albums, etc., so at the risk of redundancy, I'll tell you that it took me several hours of false starts to come up with something that worked for the flaperons. Despite being as careful as I can and matching predrilled holes, I'm still getting twists in the airfoils completed (horizontal stab, elev, slats, one flaperon). I hope a trim tab will compensate. I think that the 750 is still too new to have assembled enough new builder experience and refine feedback into a set of instructions that will save us time and braincells.

I'm going to try to finish #2 now and wish you luck on #3 and #4.

Ken

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Permalink Reply by Dr. Edward L. Olds III on November 23, 2009 at 9:52pm

Ken,

I would agree with your comments on "too new" and hope that it gets better. I hope we don't have the same problems as the 650 guys, with their FAA decree.

Ed

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Permalink Reply by Chumphol Sirinavin on November 24, 2009 at 12:58pm

Hi,

I am building new flaperons, CH 750 style, with nose skin folding under (and not folding over) for my 701 new wings. The new wings also have folded skin for trailing edge. I folded the flaperon skins and wing trailing edge skins with help of a wide 1" wooden plank screwed to edge of 6061T6 sheet, together with a number of C clamps. I leave the ends a few mm. too long to be trimmed off for proper fit after installing wings to fuselage. No photos until I am home again by mid December. I spent some time practicing flushed riveting with steel blind rivets and that slowed the work a bit.

Have fun.

Champ

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Permalink Reply by Dr. Edward L. Olds III on November 24, 2009 at 6:45pm

Champ,

Thanks for the idea. I'm trying Ken Sandine's method since it looks like something I might be able to adapt to my current situation. Are you trying to flush rivet the entire project?

Ed

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