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  #471  
Old 02-28-2020, 09:12 PM
jamlip jamlip is offline
 
Join Date: Jun 2017
Location: Palm Springs, CA
Posts: 83
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Hi Dave,

What grit are you using on your block?

I'd start off heavy on the mud, then cut it to shape with 40 grit. Going super coarse gives a good cut, which stops the block riding along on the surface, creating waves. Once you have the shape sorted and can't feel any weirdness, move up the grits until you're where you need to be (120?).

If you're already doing this, ignore me.
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Palm Springs CA
Flying a 1987 O-360 RV-4, rebuilding a 1992 O-360 CS RV-6
2020 paid
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  #472  
Old 02-29-2020, 08:33 AM
David Paule David Paule is offline
 
Join Date: Dec 2009
Location: Boulder, CO
Posts: 4,238
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I shaped the foam in the middle, even though it'll get cut away, just because when I started, I didn't know how wide my canopy would be and what the shape of the opening was going to be. Since then, I marked some areas where I didn't need to fiberglass.

Except for using 36 grit as the first sanding cut, jamlip described the process well. The final shaping was in areas, sanding with about 120 grit and adding slight layers of mud here and there.

3M has a nice sanding board for the open drywall sandpaper. It's a decent longboard except for not being very long. But it was perfect for this. Got it at Home Depot in the paint section.

Right now the shape is where I want it, or as close as I'm going to get anyway, and it's as smooth as needs be. The plastic that I'll be covering it with can bridge scratches worse than 120 grit leaves.

Dave
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  #473  
Old 03-09-2020, 02:59 PM
David Paule David Paule is offline
 
Join Date: Dec 2009
Location: Boulder, CO
Posts: 4,238
Default Second Fiberglass Practice

The fiberglass layup of the avionics shelf reminded me the hard way of several things I’d forgotten. As a result, it is barely useable and I haven’t decided whether to make another or fix this one.

Some of the details are -

1. Leave enough extra peel ply that doesn’t get epoxied so that you have a handle by which to pull it off.

2. Ditto with the perf ply, if you’re vacuum bagging it.

3. The absorber layer doesn’t need to be oversize but that’s a whole lot better than undersize.

4. Even using plastic, try to work out excess epoxy before laying down the peel play and the perf ply and absorber layer.

I was somewhat surprised that the Jeffco epoxy I was using had ample pot life. I thought it would be a race and it wasn’t too bad. I got by with one batch. Wirejock’s epoxy quantity calculator was a bit generous. Wirejock's Epoxy Calculator

The layers I used turned out to be just right. That was uni 90, bid 0/90, bid 0/90, bid 0/90, uni 90, with 0 being the side-side direction. However, afterwards, I decided that some more uni would be better.

How did it turn out? There are a few places that aren’t exactly bubbles but more like nicely-laid-up hills. Small ones. Outside of that, not so bad. Here it is, roughly trimmed.



After that, I covered the cockpit area in plastic, using duct tape. There were a few ripples remaining in the plastic. I chose the worst place for another practice lay-up, using some scrap cut-offs from the earlier work. This was vertical and was centered over the left corner with the fairing mold, the cockpit side, the turtledeck and the tailcone side all intersecting.

The lay-up was uni 0, bid 0/90, uni 0 this time, with 0 being the longitudinal direction, left/right. That used up the scrap pieces. I used Wirejock’s epoxy calculator again, and it was generous this time, too. Memo to self - knock it down by something like maybe 10%. Here it is shortly after laying it up with the epoxy still wet and peel-ply pressed into it.



It certainly looks to me like I’ll have to work out all the ripples in the plastic, once this is off.

Dave

Last edited by David Paule : 03-09-2020 at 03:09 PM.
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  #474  
Old 03-17-2020, 09:07 AM
yarddart yarddart is offline
 
Join Date: Jun 2006
Posts: 129
Default Rv3b

Looks great nice workmanship you are going to love it.
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  #475  
Old 03-20-2020, 06:19 PM
David Paule David Paule is offline
 
Join Date: Dec 2009
Location: Boulder, CO
Posts: 4,238
Default Cutting Fabric

Thanks!

Lately it seems as if all I've been doing was cutting fiberglass fabric for the canopy fairing. I'm using the same lay-up that I used on the avionics shelf, 1 uni, 3 bid, 1 uni, with peel ply this time on both sides. At the front and the back, the unit runs laterally, but on the sides, it follows the contour of the fairing, very roughly parallel to the canopy edge. Let's make that very, very roughly.



The cutting tool I've been using is the Olfa pizza cutter. I've used it right on the table with little damage, and the blade cuts as well now as it did when I started. It's much easier than scissors, but I do have to put pressure on it.

Here is the fabric all organized and ready. I expect that as I go there might be a bit more trimming, hope not, but it's probably likely.



The box is the canopy box.

The lay-up appears as if it'll take about all the remaining epoxy I have left of that gallon I bought.

Now all I need is the gumption to do this.

Dave
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  #476  
Old 03-22-2020, 07:33 PM
David Paule David Paule is offline
 
Join Date: Dec 2009
Location: Boulder, CO
Posts: 4,238
Default Gumption Found

I laminated the canopy fairing today, all by myself. Took all afternoon and went fairly well considering everything. I must have gone through half a dozen pairs of gloves.

Right now the epoxy is curing. Iíll leave the laminate in place for at least a couple days, donít want it to warp after I remove it.

After I was done, I noticed that the cup with residual epoxy, about 3/4Ē of it, was getting warm. I checked with my IR thermometer and it was 118 F. A moment later it was 127, so I carefully took it outside and left it on the patio, away from anything. Shortly afterwards, it measured 337, but the next measurement was less. Evidently I missed the peak. At least it didnít ignite; I'd wondered if it would. The fairing itself was roughly at shop temperature and now, an hour later, does seem to be curing.

And hereís what it looks like. The peel ply is still on, and the various defect artifacts seem to be related strictly to the peel ply.



Dave
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  #477  
Old 03-23-2020, 05:10 PM
RV3Kev RV3Kev is offline
 
Join Date: Sep 2017
Location: Traralgon Australia
Posts: 34
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Is the glass fire that you laid down going to be structural or are you making a mold?
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  #478  
Old 03-23-2020, 05:41 PM
David Paule David Paule is offline
 
Join Date: Dec 2009
Location: Boulder, CO
Posts: 4,238
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The canopy fairing I am making will also be the integral canopy frame. At least that's the plan. Some head scratching needed here - I seem to do a lot of that.

Why? I wanted to make something out of composite, so I decided that this would be it and didn't order the canopy frame. As I was laminating it yesterday, I had second thoughts about that idea. I seem to do a lot of that, too, lately.

Dave
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  #479  
Old 03-26-2020, 09:03 AM
Larry DeCamp's Avatar
Larry DeCamp Larry DeCamp is offline
 
Join Date: Apr 2010
Location: Clinton, Indiana
Posts: 962
Default Head scratching

David,
One option that might materialize is to use your glass fairing as the inner shell . Then to accommodate the plex/glass intersection thickness , just lay-up an outer shell. Lastofom laminated to your inner-shell and glass over that will give it good section modulus and a slot for sealant to bond the plex into. Just a thought .
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RV-3B flying w/7:1 0320 / carb / Pmags / Catto 3b / digital steam
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Clinton, IN
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  #480  
Old 03-30-2020, 06:32 PM
David Paule David Paule is offline
 
Join Date: Dec 2009
Location: Boulder, CO
Posts: 4,238
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Larry, that's a good idea, and sort of what I'm planning, except on the inside, at least at the cockpit. I'd intended that this be the exterior and with some work I think it can be.

The fairing came off the fuselage easily enough, since I’d used plastic sheet and duct tape for a mold release. The first layer of the lay-up was peel ply, and that’s firmly glued on. It’s a major pain to remove and comes off in strips and pieces. The outside was easier and now it’s all off, but it took parts of three work sessions to do it.

The fairing isn’t perfect at all, not even nearly so, but I think it’ll work. After I removed the mold and rough-trimmed the edges so that I wouldn’t get slashed by the fiberglass, I put it on the fuselage. Good place to store it for now. The far side, forward of the roll bar, looks discontinuous because it's a trimmed edge that'll eventually be cut away so that I can sit in it.



Here’s the canopy mold after removing it from the fuselage. If you look closely at the upper right edge, you’ll see a small black tab. That’s a couple layers of Gorilla Tape that I put there for a pull handle to remove it. Since it fits flush on all sides, there wasn’t any other place to grab it. The pull tab worked well.



The black line was a mark to indicate where the glass should stop on the top.

I made a canopy support cradle to hold it while I trim it. Haven’t tried it yet. Because of the working height, I’ll use the canopy box as its base.

The shop has overhead radiant heating. Under the heaters, it can get pretty warm. But about 25% of the shop isn’t directly affected by that since only three of the four heaters are connected right now - I’ve left a gap in the coverage for this. I’ll be working on the canopy in that area. Since the heaters, in aggregate, are about 75% of the power of my house furnace, and the shop is 1/4 the size and better insulated, I can heat the entire shop to any safe temperature and still not melt the canopy with the direct heat. All I have to do is pay the electric bill.

The nutplates for the aft deck are finally riveted on. It was less of a job than I’d thought it would be and came out pretty well.

Dave

Last edited by David Paule : 03-30-2020 at 06:35 PM.
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