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How to reinforce plastic cowls?

Old 07-12-2002, 01:41 PM
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Default How to reinforce plastic cowls?

I have a Lanier Stinger 120 kit. It has an ABS plastic cowl as well as the whole top of the fuselage is plastic.

Now I know one of you aspiring people are going to say, throw the plastic cowl away and put a fiberglass on it. And I may do that, but I also have the whole top of the plane to worry about.

I remember reading in a model mag some years ago about using two oz. fiberglass cloth. You glue the halves together using plumber's ABS/PVC cement. Then still using the swab that's attached to the can lid, you stick the fiberglass to the inside of the cowl.

My problem is, how do you keep the cement from melting the shape of the plastic? Could you use epoxy if you roughed it up a little?

I have already glued the cowl together using the Oatey PVC cement and where I got it on a little heavy, it distorted the outside shape of the plastic a slight amount. Also the drying time is in excess of 24 hrs.

I'm of the opinion that if I glue anymore pieces together, that I will use the PVC cement but use it sparingly so as not to soften the plastic all the way through.

How do you use the PVC cement to attach the fiberglass without distorting the plastic?

Jim
Old 07-12-2002, 02:07 PM
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Default How to reinforce plastic cowls?

Epoxy won't stick to the PVC, but CA will. You can use CA to attach fiberglass to PVC without distorting the PVC.
Old 07-12-2002, 02:15 PM
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Default How to reinforce plastic cowls?

Jim:

I use a combination of the lighter cloth as well as the 2 oz. You
do not need to cloth the entire area, but make reinforcing strips
and little squares wherever you have screw holes. The thin and
medium Ca works great on the styrene. Wipe down the inside
with rubbing alcohol and the thin Ca will soak thru the cloth and
adhere great.

Randy
Old 07-12-2002, 02:53 PM
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Default How to reinforce plastic cowls?

While I was building the wing mfg p-38 they suggested the pvc glue method. It worked great as far as building and beefing up. Havent flown it yet so cant speak to that. I was light handed with the pvc glue while I was beding the 6 oz glass (because thats what I had on hand) inside the cowl. My next step is to use finish reson on the inside because the cloth isnt soaked thru and thru (due to putting is on light, naturally). I did that on boom radiators and it worked like a champ. I expect this to work much better than the ca I used on previous cowls. Over time, those still cracked and came apart. But they do last longer than without.
Edwin
Old 07-13-2002, 01:26 AM
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Default PVC

I have and still use the PVC with glass cloth. It works and is bullet proof......crash confirmed. Just don't soak the cloth and the plastic will not melt. Just go lightly is enough. It is, in my experience, not necessary to go over it with any additional cement or epoxy.
After the "Experimental landing" to test the effectivness of this method, the plastic failed where I had not reinforced...That is my story and I am sticking to it!!!!!
Old 07-13-2002, 02:45 AM
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Default How to reinforce plastic cowls?

w8ye,
I have a lanier giles 35% that I reinforced the cowl with fiberglass and epoxy resin. I used a 6oz cloth(Had it left over form another project) and finishing resin. I know that alot of guys go through the expense of fiberglass parts(for a lighter cowl) only to add lead to the nose of the plane so it balances. I used a rather light engine (zdz 80) so the added weight of the cowl was actually helpful. I was able to balance the plane simply by shifting the battery pack around. A lighter cloth would have also worked but in any event the result is a very strong and durable cowl. I also used a strip of cloth w/ epoxy to finish the wheel pants. I prefer not to use CA for laminating since the fumes are bothersome and it sets up to fast.
Old 07-13-2002, 03:53 AM
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Default W8ye

I have a bunch of these things. Stingers I am referring to. I use gel super glue to tack the nylon cloth into place. The gel is really easy to handle. I also installed the wooden pieces into place with the gel. I also glue the plastic pieces together with gel. I also installed the plastic pieces in their permanent location with the gel. If you don't get the plastic in just the right location. without a gap the gel will fill the gap.
Back to the nylon or fiberglass cloth. After tacking the cloth in place I apply the pvc glue in very light coats as not to melt the ABS plastic. use the pvc glue spairingly. The use of the gel makes the plastic with the cloth very hard while the pvc glue leaves it flexible.
About gel ca. You can buy a large tube at the hobby shop and have most of the glue go bad before you get a chance to use it.
I visit my local Wal Mart and buy a bunch of the very small tubes from them. Then the gel does not go bad before I can use it. I also make field repairs using these small tubes of gel and all sorts of other things. I try and never go to the flying field without it. I have included a photo of the Gel CA that I get at Wal Mart. Before you complain about the cost of the small tubes remember you will use all of the tube before any of it has a chance to go bad.
Lee
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Old 07-13-2002, 04:42 PM
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Default Glass & PVC cement

My experience with glass cloth & PVC cement was bad. I used it on a Great Planes ARF Spitfire. After a number of flights, the inside of the cowl was gummy and slimey. It would clean up OK but just do it again with the raw fuel (from front bearing) and exhaust residue that the engine throws out. Maybe I used the wrong stuff but it was what I was using in the yard on my sprinkler system. I tore out the PVC'd glass (easily, as it didn't stick all that well either) and redid it in epoxy.

Yes epoxy doesn't much stick to the plastic. However, I have found it sticks well enough, particularly if you glass the whole inside and it endures normal wear and tear and the occasional nose over. It isn't hard to do. Takes maybe 30 minutes with 2 oz cloth and your choice of epoxy. I use EZ Lam, others use Z-poxy or West system. I used to use polyester resin but it melts certain types of plastic. I'm allergic to CA, but can use it sparingly, and the thought of using that much CA on glass cloth bugs me.
Old 07-14-2002, 02:35 AM
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Default Plastic cowls

Well, I've been reading all the posts on the plastic cowl. After reading them all, I decided that me and Mr. Oatey was going to put the 2 oz cloth in today. It went on in a few minutes. I put the Oatey PVC cement on no heavier than it took to bond the fiberglass down. It turned out real neat. It didn't melt through anywhere. I just used the swaub thats attached to the can lid.

I suppose I should now put a couple coats of 30 min epoxy in there to try to stiffen it up a little and maybe fuel proofing if it's going to do like Mr. Thud_Driver says? With the way this cement attacks the PVC, I cannot help but think that it will bond well.

I was wanting to put another layor of glass along the sides where the screw will be and all accross the fron inside because that's where the plastic isa the thinest. 2 oz cloth is rather light weight stuff.

I also went to Walmart and bought some CA Gel after I had glassed the cowl. But there are several other pieces of plastic on this jewel. They will all get their chance.

Thanks to everyone who voiced advice here.

Jim
Old 07-14-2002, 07:02 PM
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Default PVC & Glass cloth

That was the other thing I noticed about the PVC cement and glass cloth was that the cowl didn't get a whole lot stiffer or stronger. After I ripped it out (like I said, it didn't stick any better than the epoxy to the Great Planes plastic cowl) and put a new epoxy & cloth job inside the cowl, everything got nice and stiff, almost like a rock. Actually, your're making a second cowl inside and in contact with the plastic one. If it delaminates, you can always shoot some thin CA in there as you would when you bang it up.

For me, the epoxy & cloth goes in just as fast and the result was better with no worries. It must take almost an extra minute to mix the epoxy. I also had to wait for the PVC cement to set so the time element was about a push.

To reinforce the screw holes, take an EZ hinge and zap it over the area where the hole is going to be on the inside of the cowl. Can do either before or after the glass cloth job, or just add extra layers of cloth. There's usually enough trimings for around the nose and attach points.

I've not tried epoxy over the PVC/glass job so I don't know. I do know that I didn't get the cloth completely sealed with the cement (I think it need two light coats) and ended up with oil seepage under the cloth.

Just my experiences!

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