faceman

Building a Sig Kobra (the smaller one) and during the build decided to cut off the cowl to make it easier to mount engine, nose gear etc. Anyone have any idea if there is a fiberglass or ABS cowl available for this plane, or of any other cowl that may fit it. Using a tru-turn 2.25" spinner on it. Thanks for any help. Worst case i'll rebuild one for it out of balsa and ply ring but was hoping for a quicker solution.

SeamusG

Have you checked Fiberglass Specialties?

speedracerntrixie

My Feedback: (29)

I have molds for a .60 size Dalotel cowl that uses that size spinner. If you give me the firewall dimentions I will check to see how close it is.

faceman

Fiberglass specialties I checked already had nothing. Speedracer I'll check those dimensions. Thanks

SeamusG

The basic shape reminds me of a Chaos front end treatment.

I can throw a measuring stick on the plans if you need dimensions.

rcscott101

I don't blame you for taking it off, I built one and it was probably one of the hardest engine instalations ever! but it is possible. if you carve a piece of foam to the shape of the cowl in place , now with wax paper on the fuselage wrap the foam with fiberglass gloth and coat with epoxy 30 min works good. doe this 3-times and when cured remove and soak entire cowl with foam in a medal can of gasoline and the foam will melt without hurting the fiberglass. now trim and remove where needed for engine, prop., and nosewheel, then mount with 4 small screws. *note* make foam block about 3/8th of an inch bigger on firewall side so the finished cowling can be screwed to fuse. sided.

faceman

RS scott: Interesting method of making a cowl. I never thought of it but I actually have all the materials on hand to do the cowl. One question how heavy is the fiberglass you use to do it? Speedracer my firewall dimensions are 3 3/8" top to bottom and 2 7/8" side to side. Pretty small firewall with a 2.25" spinner isn't it? Wish I saved the one I cut off, could have shaped it and make a glass one out of it!! Thanks guys for all the help.

speedracerntrixie

My Feedback: (29)

Face, the cowl I have is much bigger then that. There are many ways to make one though. The above works but for something that small I would just make it out of balsa. Once you have the shape you can cover it with Monokote or Utracote, wax it with a good carnuba wax, apply 3 layers of 4 oz cloth and epoxy. I prefer to use epoxy laminating resin. Once cured, you can sand smooth while still on the balsa cowl. Make a slit at the bottom and then peel away from the balsa form. You will end up with a glass cowl that should weigh 1 to 1.5 oz.

faceman

Thanks Speed. Gonna give that a try. Think im gonna get it all set and make sure it flies OK then i'll work on the cowl. Unless of course winter hangs around longer and i'm grounded. thanks again.

GarySS

My Feedback: (13)

Here's a shot of my Kobra with a balsa cowl and side mounted engine. Fuel lines had to run out the side of the fuselage and then into the engine compartment it was so tight.

rcscott101

a medium fiberglass weight, not the weave wing tape, but if you do use a thinner one just do a couple more layers, this work great, I have done a couple and there just fine. learned this in a old model aviation magizine, '82 I believe, back when people actually built every plane frome plans or a kit... I stuffed a OS 32sx in it, was very tight and frustrating but it works excellent now. hope this will help your decision, oh and don't stand over the gas container when melting foam. some fumes... have fun!

faceman

Guys I can't thank you enough. Gary your Kobra looks awesome. Im putting an older OS35 in mine. Been working on this darn plane for 4 years now and between work and rc heli's peaking my interest I have layed off from finishing it. I did RC back when I was a kid (when ARFs just started coming out) and used to build all my planes. Think I enjoy building and tinkering with them just as much as flying. Again many thanks guys for helping out. Always amazed at how much info you can gain on these forms. Sure makes the hobby that much more enjoyable.