Hardshell on the Tub

[macleodm3]

I can't figure out what happened, and we don't really know what caused it, but about one year ago we realized my wife was pregnant. So... ever since our brand new second duaghter was born in November 08 (and she is Perfect!) the Cozy has been on hold. Its been a nice steady progression from taking turns sleeping while staying up with the baby, making bottles at 2:30 am, but now actually she sleeps all night.

 

So, lately I've been getting back out in to the shop. Not as much as before, cause we're still rearranging our bedrooms for our new Carlie.

 

My current stage is the tub is upside down and the bottom is contoured. I really can't see a big window of time soon to micro the bottom and glass it in one step, so I've been mircoing and sanding a little bit at a time. I really like what I learned from Marc Zeitlin's posts on the mail list about his experience with denatured alcohol, and I've been adding that into the mix as well.

 

There has been no trouble at all spreading the micro, including some small fillets in areas where builders have had problems with the glass lifting, such as the recess around the landing break, and the joggle near the front of the tub. Sanding is going well, and I'll have a nice surface to apply the glass.

 

I am concerned about the soft foam in the back near the naca duct, should I hard shell that foam? It seems like it might get all messed up from sanding the hardshell. Marc Z had troubles with that same foam around the nose.

 

Also, when applying the glass to the cured micro, do I need to wet the surface with epoxy first? It seems I would, but then that defeats part of the purpose of hard shelling.... having an easy time alone getting the glass straight before wetting it out.

[Steve Innova]

Also, when applying the glass to the cured micro, do I need to wet the surface with epoxy first? It seems I would, but then that defeats part of the purpose of hard shelling.... having an easy time alone getting the glass straight before wetting it out.

I always brush epoxy on the part before laying down the glass. I think you get better wetting out when the epoxy soaks up through the glass. And you ensure that the glass-foam bond is fully wetted out.

 

If you're working with UNI, that actually makes it easier to slide the UNI around. (The best way to apply UNI to large surfaces, IMHO, is to cut the required length, then roll it onto a smaller roll for easier handling, then roll it out onto the surface.)

[TMann]

I am concerned about the soft foam in the back near the naca duct, should I hard shell that foam?

I didn't run into that issue on the Long-EZ but I have found that the hard shell goes a long way towards protecting the integrity of the softer foams. I would hardshell it.

 

Also, when applying the glass to the cured micro, do I need to wet the surface with epoxy first?

You are dealing with a very large area here. As such I would suggest laying your glass out over the hardshell, get it situated and then wet it out. Once you hit it with the hairdryer it will be wetted throughout and bond just fine to the hardshell. If you are working solo on this big layup, go with the all slow to get as much working time as possible. I did my fuselage exterior in on step working solo. I used one of those little skinny paint rollers (about 6 inches wide) to wet out the large areas quicker and then squegee like crazy.

[macleodm3]

I used one of those little skinny paint rollers (about 6 inches wide) to wet out the large areas quicker and then squegee like crazy.

So did you actually use the nappy roller used to apply paint to walls? If so, did you have better luck with the shorter nap or the longer nap? Were you able to wring out the excess ($$) epoxy when you were done?

 

(The best way to apply UNI to large surfaces, IMHO, is to cut the required length, then roll it onto a smaller roll for easier handling, then roll it out onto the surface.)

Yeah, this actually sounds like a great idea! I have rolled up the glass (as well as folded then unfolded) before, but never on to a small tube... I think I will give this a try!

[TMann]

Use the short nap roller covers.

 

I marked the fuse to ssist in aligning the edges to the proper orientation.

I also use 3/4" masking tape over my cut lines for the UNI. After cutting you have a 3/8" tape at the ends to help keep the stuff together while you are handling it an then trim them off with your scissors trin step.

 

It's a big layup so get your peel ply on as soon as you can and continue to squegee it out.

[Big Steve]

I have glassed a Longeze fuselage and a cozy fuselage the cozy was a lot easier than the Long. The Long took from 8:00 in the morning till Midnight one side was totally cured while doing the other side. The cozy you do in steps and it takes about 6 hours per step. I dont hardshell just get the foam right before you start,. Steve build on

[ErlendM]

It seems like it might get all messed up from sanding the hardshell.

Sorry for interupting - but beeing new to this, what is hardshell?

[GuinnessGuy74]

Hardshelling is applying a micro slurry to your foam, and allowing it to cure completely. You then sand the cured micro and continue on with your layup. It is useful when doing very large layups by yourself.

 

If you do a search in the archives you can find out more, and how heated a topic it can be....

 

Jim