Preparing a fuselage for a former - question
 

Guys currently building a Skygate Hawk and wanted to check something with you pros.
The fuselage is a sandwich construction with a layer of foam (guess nomex or similar) between the outer skin and the glassed inner surface finish - should I just scuff well (120 grit) clean and fit with Aeropoxy or does the foam need removing in the glueing areas to make a good joint?

marcs

RE: Preparing a fuselage for a former - question
 

If the foam is sandwiched between layers of glass I would see no reason to remove the foam. Is the inner layer of glass really thin?

RE: Preparing a fuselage for a former - question
 

I'm guessing it will be OK fitting it as is with good surface prep, the glass on the surface is of reasonable thickness. Looking at the Stage 1 option from Skygate it looks as if this is how they do so at the factory.

marcs

RE: Preparing a fuselage for a former - question
 

I've often seen this with some of the pattern planes.. and have typically just glued it to prepped inner layer of glass. I vaguely remember someone mentioning (on another forum) to drill a few small holes on either side of the bulkhead position thru the inner layer of glass and foam to the outer layers to give the glue some extra "bite" to all 3 layers. Not sure if this was good advice or not, but it made sense to me. i just haven't had a chance to try it..

RE: Preparing a fuselage for a former - question
 

Without some pic's, I'm not sure exactly what you are facing.

Depending on the material, I sometimes just scuff it up a bit ; other times I use a 'Woodpecker" to make a bunch of small holes in the foam to allow for better epoxy penetration.

Woodpecker : http://www3.towerhobbies.com/cgi-bin...P?I=LXHZ26&P=8

RE: Preparing a fuselage for a former - question
 

Marc, keep things simple and just scuff and aeropoxy. That's how Skygate did mine.

Also, all the bits I glued in like that stuck like s**t to a blanket!!

Cheers
mark

RE: Preparing a fuselage for a former - question
 

Marc, as far as I remember, the Skygate Hawk has a vacuumed sandwich. This basically means that the inner layer has been layed up and covered with bidim/peel ply/absorbing falter.
The inner surface shall look slightly grainy. If not you can scuff it lightly with a perma-grit drum/ball passed at slow speed before gluing. In any case do not remove the inner layup.


By the way, the foam is called Airex. Nomex is an aramid honeycomb.

RE: Preparing a fuselage for a former - question
 

Thanks Mark, did suspect this was the case but wanted to double check.

marcs

Pics for those who wanted to see.

RE: Preparing a fuselage for a former - question
 

Yes that is Airex, and yes you need to scuff it.

RE: Preparing a fuselage for a former - question
 

Cheers all.

marcs

RE: Preparing a fuselage for a former - question
 

I was under the impression that essentially if you use peel ply then the inner surface is ready for bonding, no scuffing necessary Oliver? Isn't the purpose of the peel ply to remove the waxy surface layer that forms when the epoxy cures ?

RE: Preparing a fuselage for a former - question
 

Marc, Do so scuff it but do not drill it. Drilling that would be the same as preffing it to tear.

RE: Preparing a fuselage for a former - question
 

Alcohol wipe, scuff it, alcohol wipe and go....

Dan

RE: Preparing a fuselage for a former - question
 

Yes absolutely Ian.
The purpose of the peel ply in the sandwich process is not to remove the waxy surface but to isolate the bidim from the absorbing falter so that you can remove everything when the bonding is completed. The grainy surface is only a consequence of that.

However if you look at the pictures provided by Marc, it looks like the inner layup was laid down by hand ( technical choice ). In that case the inner layup has to be prepared before the gluing process, of course.

RE: Preparing a fuselage for a former - question
 

Speaking of which you guys, If you have to buy just one or two diff types of hysol, Which (number) one would you get? I have not used any yet but looks like I might as well take the plung!!!