Finish Glass Work Tips

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Top deck installation. Photo: Zach Chase/FiberTech Composites
Top deck installation. Photo: Zach Chase/FiberTech Composites

Glassing the top on: When glassing the tail of the top deck to the aft part of the fuselage there is a problem area. The manual is a bit unclear re. whether to add all the extra layers of glass at the same time you use mill fiber (and flox) to attach the tail to the joggle in the fuselage. I chose to do it in two steps, so I could clamp the tail to the fuselage and keep everything level and smooth. When you add the glass layers underneath, there is an air pocket from the offset of the fuselage and top deck of almost 1/8 inch. This is almost impossible to totally stipple out UNLESS you add some mill fiber/ flox/micro mixture to fair that in a bit before add your glass cloth. I used a piece of DBM tape with one layer of glass over the top (over the fiber mix) instead of the 4 layers of cloth.

–Paul Hansen

Main gear pant fabrication:
When glassing the interior seam of the main gear pant, there is very little room to get in there and work in the aft end, especially the very aft (vertical) joint/seam. Trying to get two layers of stick cloth in there without getting all bunched up and messed up is next to impossible. Cut a short (about 3-4 inches) piece of DBM tape to use in that aft end. Trim the ends to match the curvature of the corners, and use that instead. Resin it, and then fold it to install it. Much, Much easier!! Then apply your regular cloth on the horizontal seams as instructed, lapping the cloth over on to the DBM a little.

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–Paul Hansen

NACA scoop:
After receiving my fuselage ventilation kit and reading the directions I cut out the NACA inlets 3.5 inches aft of the forward fuselage joggle. I discovered that the inside part would not fit between the cage and wall of fuselage. I ended up making my own part as we did with the my Long EZ experience, splicing it to the S-H part and happily it will work, however it cost most of a week end in time. The sh part will work if you start the NACA cutout 4.5 inches aft of the forward fuselage joggle.

–George Best

SHAI reply to NACA scoop:
We have heard from George and one other builder that the 3.5″ dimension given in the option instructions for the NACA cutout led to interference between the air box and the cage. I certainly apologize to George and anyone else who was led astray by this, and we’re revising the instructions to warn against cutting the NACA opening without first checking for clearance inside the shell. However, I’d be very cautious about using the 4.5″ dimension that worked for George. The problem here is not that our 3.5″ dimension is ALWAYS wrong (’cause it was taken right off Harry DeLong’s well-ventilated airplane). Rather, there is just a certain amount of variation from GlaStar to GlaStar in the relation of the shells to the cage. I should have recognized that when I called out 3.5″. As Reagan said to Gorbachev, “trust, but verify.”

–Craig O’Neill, S-H Tech Pubs

Strut/fuselage fairings:
The early months of GlaStar production were a bit . . . frantic. The strut fairings you and many other early kit purchasers received were never intended to be a standard part of the kit, but rather were supposed to be options. However, they were mistakenly added to early versions of the kit parts list. By the time we succeeded in getting them removed from the parts list, we had also had a chance to step back and take a good look at the fairings (as first installed on Jim Londo’s taildragger), and we decided they were really kinda crappy anyway in terms of fit, sturdiness, ease of installation, etc. The upshot is that no instructions have ever been written for these things, they are not now available either as an option or as a standard kit part, and frankly, if they were mine, I’d pitch ’em in the trash. Particularly if you intend to fold your wings at all frequently, they’ll always be in the way, and any performance gain is likely to be pretty minimal. Nevertheless, if you want to go ahead and monkey with them, as I recall Jim Londo’s installation, the forward halves were bonded to the shell just like the stabilizer strakes, and the aft halves were secured with screws and nutplates.

–Craig O’Neill S-H Tech Pubs

Spraying on gelcoat: I tried brushing the gelcoat. Didn’t work. I tried spraying the gelcoat over an area partly masked by PVA as SHAI describes in the manual. What a mess! That didn’t work either because I found that in trying to sand to the feather edge that just removes the underlying PVA, I removed too much of the original gelcoat and exposed the glass under the gelcoat. After I’d removed all the gelcoat top layer, I tried the following: I thinned the gelcoat with about 10 percent acetone, then catalyzed it with 2 percent MEKP. Then I just sprayed over the now well-sanded fuse belly seam (after masking off all but about an 8″-wide gap centered on the belly seam). I needed about 50 psi to move the gelcoat with my cheap little “touch up” gun. I tried to keep the spray centered in the gap so that there would be only a little overspray at the masked edge (to minimize any “edge” that might build up). Then, after letting the gelcoat cure for about two hours, I applied a layer of PVA to allow the surface to cure hard.

I will wash off the PVA and sand smooth with wet 320, 400, 600, 800, 1200, and finally 1500-grit paper, then polish it. Based on what it looks like now, I think this will work well.

–Dennis Douglas

More on gelcoat: [note: Gelcoat is not to be used as a filler- SHAI] I tried brushing on the gelcoat to fill dips. After sanding back to bare glass on the remaining high points before I got through the brush strokes, I gave up. I even thinned it a lot with acetone to make it spread better; no big help. I ended up using 3M acrylic red putty to fill the low spots: it dries fast and sands readily. Over this I sprayed gelcoat. I added a styrene monomer/paraffin wax additive that a local fiberglass shop uses to produce a hard fast surface; I also sprayed on PVA two hours later. PVA can be sprayed with a hand-pumped household spray bottle if you dilute it; the mix that worked well for me was 2 parts PVA : 1 part rubbing alcohol : 1 part water. The result was that 20 hours later I was able to wet sand it by hand starting with 320-grit emery paper. It came out beautifully.

All this work was done, by the way on my belly seam. I though my belly seam was pretty cool until I turned the plane upside down (I had done the dorsal seam with the plane upright) and started checking it with straight edges and tangential lighting. By the time I got it halfway to fairly fair, I was most of the way thought the shell edges and able to see the DBM. There were some low spots almost 3/64″ deep along the long axis of the midline. So I filled any gaps in the seam with mill fiber, laid some DBM over the low spots and BID over the high spots and sanded and filled (with Q-cell/resin paste) and sanded and filled until I thought I was close enough to try brushing on Gelcoat. Typical me, the process took twice as long as I thought it would. The movie “Karate Kid” where the kid sanded and scrubbed his way to karate fitness came to mind.

In the end though, it came out beautifully. As a test, I recessed a few shell attach screw heads (the ones that ended up a bit puckered in from over torquing), glassed over them, smoothed over with Q-cell and putty, and gel-coated them. You can’t see them. Time will tell if one layer of BID is enough to prevent cracking of the Gelcoat over the screw heads.

–Brad Cruz

Filling seams: I have found that the easiest way to apply the resin mix to a seam is to mix about a 50 gram batch and drop it into a tight cone made from an 8″ square of kraft paper with the exterior overlapping edge taped. Make the cone first and leave it tightly closed at the point. After you have the mix dropped glob by glob into the cone, fold the upper part closed (several 1/2″ folds) and cut off the tip to the desired opening. Then you use the thing like a cake decorator, laying neat seams wherever you like, which can then be tooled to the desired radius with a tongue depressor or whatever. Don’t dally too long, because the heat of your hand warms the mixture through the paper and you might find it going off before you’re through.

–Al Sibley

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