Cracking Fiberglass Top, Engine Cowling

[N601RX]

Has anyone used these to repair enlarged holes?

http://www.skybolt.com/images/pdf/Mooney%20Cowling%20Kit%20Instructions%20REV%201%206-7-11.pdf

[Yetti]

Back to the OP topic.  I grew up breaking and repairing fiberglass sailboats.   About 10 years ago I built a kit kayak with epoxy.  I have played around with vacuum bagging some parts and carbon fiber lay ups (for of all things bike shoe sole repair).  The mixing of carbon fiber mat and fiberglass may not be the best idea as the two expand and contract at a different rate.   What may be good is to glass in some carbon fiber rods or aluminum if high strength is desired.  Or thin plywood would work also.   You would want to saturate the plywood first in epoxy. This is normal boat building technique.   I found these guys that can do a Class 1 fire retardant epoxy.   http://www.interplastic.com/resinwizard_TR.asp?chemical=&conpercent=&maxtemp=400&degree=on&deg=F&btnSubmit=+Search+

What would be slick is to epoxy the repair area with mat and epoxy and then vacuum bag it to get the excess epoxy out and increase the strength of the bond. 

For the time people are spending on repairing, it may make sense to create a Master mold and then lay up new pieces.   Anyone want to lend a cowl?

While doing all this it would make sense to run a backing strip of mat and epoxy along the screw line and reinforce that area too.

I have 4 oz cloth, some carbon fiber cloth and a vacuum pump.

 

I am in Houston and Brenham and would help out for a ride in a Mooney.  

[triple8s]

I worked on a homebuilt for several years and learned a little about woking with composites. My C model has a 201 cowling mod and had the cracking upper cowl so I added a layer of bi-directional inside the cowling on a 45 to the cracks as they ran longitudally along the top center of my cowl. I believe it was .58 S cloth, also put one layer of 45 cloth in the center part of the cowl where it arches in a point running back aft. I always had Aeropoxy 2032 and 3660 around for the kit so I used it. Repairs around the fasteners? I used a little cotton flox with the same. On the inside of the cowl I didnt but should've used peel-ply because it wouldve given a much smoother finish for the baffling to rub against. Engine baffling wears out faster on a rough finish. I ended up resanding all the areas the engine baffling fits against, then replacing all the rubber baffling. This greatly helped on engine cooling. Someone posted previously about using polyester resin..... no one uses it on aircraft. http://www.amtcomposites.co.za/sites/default/files/media/howto/Advantages%20of%20Epoxy%20over%20Polyester.pdf  The resin/hardner must be mixed more accurately or you'll end up with either a gooie mess that will never cure or a part that turns brown and brittle, I've seen Vinylester mixed hot enough to spontaneously combust. Another thing resin has very little strength by itself and a layup that is too wet is heavy and brittle, its going to crack again. There are books on this. If you are going to take the time to make a repair take the time to read up on it, talk to folks in the know and make a proper repair.

[M20F-1968]

I have a spare J model cowling which I saved after my rebuild project.  I had two different cowlings to choose from and rebuilt one completely which is on my airplane.  I saved the second cowling and it could be used to make a mold if anyone were interested in doing that.  I have it in Massachusetts. 

 

Regarding the Skybolt fasteners, I used them throughout the cowling.  They make a nice product.  The cam locks are adjustable and I would recommend them.

 

John Breda