Hi Steve,
I went online and did some research on gluing delrin. First Delrin is a Dupont brand name for acetal plastic.
What I found was a somewhat mixed feed back on gluing delrin.
1. Some folks reccomended using a etching primer to delrin before gluing it.
Loctite prism 700 primer is an example. Other folks, said these primers
are nasty stuff and advised against using them.
2. Some people say delrin is unglueable and others say they glue just fine
within reasonable loads.
What did folks agree on, at most of the sites I looked at :
1. Rough up the surface to be glued to give glue a good mechanical bond to
grab on to.
2. Use alcohol to thoroughly clean all trace of the normal greasy coating
from the delrin.
3. Re-enforce the glue joint with some mechanical fasteners like bolts to insure the integrity of the glue joint.
The glues that people recommended were :
1." Loctite super glue for all plastics" thats available at Home Depot for $4.00
2. "Cyanopoxy" available at Cool-Chem.com . Go to mr hobby.com for
details on this glue stystem. It sells for $50.00 to $80.00 for complete
kits. This stuff is supposed to be the ultimate glue for delrin.
3. Another glue was listed when I looked up glues for delrin is at
www.thisglueworks.com, but I didn't see a specific reference to delrin.
So Steve, delrin can be glued if you follow th 3 steps above. This works into your idea of of bolting it to the airframe. You could bolt together a crutch like my design. Then you could glue and bolt the plywood doublers to the sides of the crutch. Then you could glue and bolt the plywood formers to the cross pieces and use normal glue to join the ply formers to the ply doublers.
Steve, one thing I found was a place selling delrin cutoffs. This stuff is expensive! You could probably drop $15.00 -$20.00+, just for a crutch.
If you have an inside source for delrin good but if not then price might be a factor to be considered.
Delrin is like phenolic in the fact that it hasn't been tried out and tested as a motor mount material. ( as far as I know) Both these materials are unknowns
for this application until someone actually trys them out.
My conclusion, delrin is an unknown but it may be a viable possibility as a motor mount material. I would test it throughly on the bench before I put it in an airplane.
It seems there are lots of possibilities for something as seemingly mundane as motor mounts.
Once again, Steve , thanks for your input.
Pat Robinson