PAU Ultimate assembly

[acerc]

Those metal L brackets are bolted to 1/4" ply on the sides and the bottom, if it goes so goes the rest of the plane.
The cans are in, the front holder will get epoxied in here shortly. Now it is time to go back to a few things I skipped.

 

[Rusty 73]

Just warning you the plywood in the PAU doesn't have the same strength of the plywood we get here , don't tighten the motor mount bolts too tight as the firewall wood will compress.
It doesn't take much to damage the landing block or crack the glue joints .

 

[49dimes]

That's a good point. A lot of airframes have soft ply in the motor box. That's why I use blind nuts and back it with a nylon lock nut when mounting engines.

 

[acerc]

The engine is held in place with one inch diameter stand off's with the same size washer on the other side.

 

[Snoopy1]

If I may ask why did you go with a two stroke I know you avid four stroke person.

 

[acerc]

If I may ask why did you go with a two stroke I know you avid four stroke person.

One word, weight. I did not want to add that kind of weight to this particular airframe. If it goes well and at some point I think it can handle it, the Valach 120 can always be added later.

 

[acerc]

I spent the first part of the day trying to figure out why the heat kept throwing the breaker in the shop. Turned out to be a simple miscalculation as to breaker sizes, it's all good now. The nose has had a coating of epoxy for oil proofing, some ply pieces were made to cover holes, and some finish work on the ele servos. Pics to come after epoxy dries, but the nose part might be in the morning as it is slow curing.

 

[Rusty 73]

That's a good point. A lot of airframes have soft ply in the motor box. That's why I use blind nuts and back it with a nylon lock nut when mounting engines.

I use a two washer method with the wide against the firewall and narrow one on top with a nylon fiber 1/4 nut ,7/16 socket .
Even after 10-15 flights I open the battery bay and check the bolts , usually get an 1/8 of a turn on the nuts till its snug , from vibration and compression of the wood.

The reason I brought up the wood quality is the aircraft ply 1/16 3 ply and 3/16 5 plywood i used to rebuild my damage Extra was alot more torsional stronger than the Chinese ply wood they use, won't even call it wood maybe something recycled from the forest .
Its quite easy to cheap out on the wood quality but after 100-200 flights the plane just won't track and fly the same as it did new .
These are disposable airframes the won't last a long time

 

[Snoopy1]

I have had my share of bad fire walls. The only way to get around it, is that I made 2 - 3mm flat plates on either side of the fire wall. The plates were cut and fitted to the motor and firewall and drilled out to lighten it as much as possible.

 

[acerc]

You guys are paranoid!!!! lol This one seem's to be of good wood and glued well as nothing is giving or looking weak.
Here is a few shots from today starting with the wing turnbuckle noting how it is to long, Herve sent another set out. The engine is mounted on 1" dowel for stand-offs, with 1/16" x 1-1/4" washers, one in front and two behind with double lock out nuts. What I mean buy lock out is there are two nuts but the second one is a lock nut in and of itself and not the plastic type. I dropped one of the standard nuts and be damned if I can not find it.
Next up is the fuel tank tray which doubles as a top cover for the can tunnel. Then the front tunnel opening is closed up but held with 4-40 and blind nuts, might need to get in there some day.