Building Tips and technical articles. > 1/2 A building.

#2 wood screws

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Ken Culbertson:
Screws are fine.  Just make sure that you plan for the oil soaking.  Consider giving the mount a CA bath before you fly it.  Make sure it has soaked in and set before you try the screw!  Alternatively, if the plane lives long enough you can drill out the holes and put a wood dowel in the hole then drill and screw into it.  That is what I used to do after my flying skills increased to the point that the 1/2 life of the plane was not used up by the trip to the field!

Ken

944_Jim:
Mr. Jim,

If you don't mind deviating from the stock firewall, you could employ a plastic mount. Cox International may have them still, as should EX Model Engines (and I bet Mecoa too). Also quite easy to find on the 'Bay. It would have a slot between flanges that straddles your fuselage, and a plastic firewall. They are usually molded to take a Babe Bee or horseshoe backplate product engine.

I only show this as another avenue to consider. If you slot the fuselage (or drill one hole oversize), you get the added benefit of being able to adjust your up/down thrust by simply loosening screws and pivoting the mount.

https://coxengines.ca/building-supplies/cox--049-engine-firewall-mount-control-line.html

kenneth cook:
             Jim, the Skyray ALWAYS breaks it's nose off at the front of the leading edge. The engine stays on the firewall with wood screws just fine. I CA the nose  back on and it's good until the next knockout. About the 3-4 time the sensitivity calms down a bit which is good.  Essentially, where the cheek blocks stop which is the front of the leading edge. I'm not certain if they're built yet but adding some 1/64" ply or even 1/32" to both sides of the fuse and extending it back onto the wing a minimum of 1/2" works wonders.

Paul Smith:
I built some Skyrays for the Sig contest and used 2/56 Allen head capscrews and blind nuts.  In retrospect, #2 lag screws would have been good enough.

I extended the engine reinforcement some and it worked OK.  If I did it again (unlikely) I would extend it more.

The wing warped because I covered it with iron on plastic.  I replaced the warped wing with a bigger and thicker wing with dope.  Even with a small weight penalty, it flew a lot better.

Jim Roselle:

--- Quote from: kenneth cook on April 17, 2024, 06:05:27 PM ---             Jim, the Skyray ALWAYS breaks it's nose off at the front of the leading edge. The engine stays on the firewall with wood screws just fine. I CA the nose  back on and it's good until the next knockout. About the 3-4 time the sensitivity calms down a bit which is good.  Essentially, where the cheek blocks stop which is the front of the leading edge. I'm not certain if they're built yet but adding some 1/64" ply or even 1/32" to both sides of the fuse and extending it back onto the wing a minimum of 1/2" works wonders.

--- End quote ---


I’m adding 1/32 ply doublers to 1/2” past the LE. Also extending the nose 1/2” to address the balance issues with a product engine or tee dee. I figure the 1/2” nose extension on my sons will slow down the responsiveness with a babe bee and make it a suitable trainer.

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