• If You Are Having Trouble Logging In with Your Old Username and Password, Please use this Forgot Your Password link to get re-established.
  • Hey! Be sure to login or register!

Yes, another Javron cub

Thanks, guys. Do you use something like a 10 oz cloth or what? How do you finish it? Gel coat or just fill and sand or something else?

Wayne
Use Rutan Bi-directional 7725 cloth. I think is 8.8oz fabric. google 7725 fiberglass and youll see its common. Spruce has it. Cutting on the bias means cut it on a 45 degree diagonal. If you are worrying about waist when you cut it off the roll your doing it right.

Finishing it....
You would get a lot out of going to EAA Sport Air Workshop "Composites for Vans Aircraft" class taught by Scott VanderVeen. If you go to it you'll do this task in class and have a stronger lighter windshield fairing. I cant do it justice using this type of communicating.

But you asked.....when you order your cloth buy a pound of flocked cotton and a pound of glass bubbles aka micro balloons. Micro Balloons aka Micro is like dust particles of glass beads. So use a mask, do not breath it in. Mix up your epoxy like you lay up some glass cloth, then start adding in the Micro. it will take about 5X volume of Micro to Epoxy. ABout 5.5OZ of Micro to 1 pump of West System Epoxy. mix in a little at at ime until its like cake frosting and the tips of it done fall over. We call the mixture of Epoxy and Micro Balloons "Dry Mirco" when the mixture has so much Micro that the mixture looks dull for 3 to 5 seconds after you stop mixing it.

Now frost your window fairing like your frosting a cake and let it cure. 8 hours at 70F or 3 hours at 120 F if you can get it warm. Then sand it with 80 grit and the corner of a small block of wood as your sanding block on 45 degree pattern across the line of the fairing.

I attached a photo. I did this last week. Its not for the windshield. I'm modifying a vans cowl scoop to fit my cowl. I first fabricated a sharp fillet of 50-50 ratio of Flox and Micro mixture becuase Micro is not structural, Flox is. But flox wont sand much at all, Micro sands fabulously. I then immediatly applied two layers of Epoxy impregnated cloth over the fillet let it cure. Then I applied a 20-80 ratio of Flox - micro over the top of the sanded glass cloth to form a gentle fillet and immediatley applied two more layers of glass cloth. Let it cure. Then I frosted it, sanded it, and did it two more times to get it looking good. I dont have a photo of that part handy.

If you dont sandwhich the fillet then I'd use more than 4 layers of cloth. Bob Barrows calls for 8-10 layers for the Bearhawk Patrol fairing. I bet the sandwhiched process is lighter and stronger and and better looking.
 

Attachments

  • Screenshot 2024-04-08 at 12.11.01 PM.png
    Screenshot 2024-04-08 at 12.11.01 PM.png
    2.2 MB · Views: 34
  • Screenshot 2024-04-08 at 12.20.04 PM.png
    Screenshot 2024-04-08 at 12.20.04 PM.png
    1.2 MB · Views: 30
. ABout 5.5OZ of Micro to 1 pump of West System Epoxy. mix in a little at at ime until its like cake frosting and the tips of it done fall over. We call the mixture of Epoxy and Micro Balloons "Dry Mirco" when the mixture has so much Micro that the mixture looks dull for 3 to 5 seconds after you stop mixing it.
Not 5.5OZ, rather units should be Grams. 5.5g to one pump.
 
When adding filler to epoxy adding too much filler means pumping up another minimum batch of epoxy to liquify the mix a bit. So you waste time creeping up to a mixture that will not run. (Thixotropic mixture) Somtimes I think its too thick and it still runs. Adding colloidal silica when you get close makes a reliably thixotropic mixture that still seems sorta wet. Much less critical. West has it , the boat builders call it Cab-O-Sil.
 
I used the standard 3 inch wide clotch on a roller aircraft spruce sells. Went 8 layers deep, just rolled and padded the cloth together. Came out about .125-.140 thick, some hand sanding when done and wiped a skim coat of the beads and voila, ready for primer. Sure its a little heavier then getting all fancy with bagging it or other methods, and the standard weave laid down just fine. Its hell for stout too. Stiffens the boot cowl up a lot. Make sure the windshield is lightly strapped with a strap or bungees back into the bootcowl and backup strip when laying up the outer strip. Once you add felt and subtract the masking tape and packing tape the gap fits snug with the windshield. Also oversized the holes slightly to allow some movement for alignment. Once I bit the bullet on masking it all off, I really only had 3 hrs or so into getting it all laid up to cure. Another 2 for clean up and drilling/sanding. Less time and frustration then farting around with those aluminum strips... To make the inside backup strip you can just make a foam block that fits into that area snug and well, then use that to make the piece on the bench. Worked great! Next time I would make a slightly wider backup about 14 inches maybe 15 inches wide, and use plaster and waxpaper to make a very tight fit piece.
 
Thanks guys, for all the helpful suggestions. Put down a layer of blue painters tape and a layer of clear packing tape. I marked on the blue tape the limits of where I wanted the new retainer to be with a black sharpy.20240501_084504.jpg Put 3 layers of wax on the packing tape. I ordered some 7725 and started cutting strips on the diagonal. I figured I needed about a 2.5 in strip so I measured and cut a strip. Took it to the windshield and all of a sudden, it was maybe 1.5 in. Turns out there is a lot of pliability in this fabric which is probably why it was suggested. So back to the cutting table and I figured out how many threads I wanted (about 32 gave me the width I wanted). I wound up using the narrow fabric strip (plus another one) below the windshield so I didn't have as big of a step. My next mistake was to mix up a 6 oz batch in a solo cup. Started laying tapes and it seemed OK at first but the batch cooked off, melted the solo cup, and made a mess. I'm in Phoenix area where it is currently pretty warm and very dry and I think that made it go sooner. Mixed another 6 oz batch (I never learn) but at least this time I used a paint mixing cup. Still cooked off before I was done but didn't melt the cup and didn't make as big a mess. Made a smaller batch and finally finished laying 8 layers (not counting the narrow layers I put below the windshield).20240501_110306.jpg I think 8 layers is too much. Four probably would have been plenty. Rolled it with a ridged roller to get the air out and let it set for a day. Came off pretty well. I did some initial trimming with a multi-tool using a saw blade and then a sander. Put it back up and used a hole finder to drill all the mount holes. Marked where I wanted to trim to and trimmed again with the multi-tool. Mixed some micro balloons with resin and hardener and did a skim coat on the out side and sanded that to a finish. I'll have to drill the holes out again. 20240620_121324.jpg Seems to be ok. It's a bit heavy but not too bad.

Also worked on a sight glass. Looks like this 20240614_094227.jpg which I believe is more or less how atlee dodge does it. I took mine all the way over to the fittings in the tank. I'll have to check it often to make sure it works out.

Wayne
 
Cutting the fabric on the 45 degree bias is exactly right. Next time
-put a large piece of 4-6 mil plastic down on your work bench,
-cut a piece of glas cloth oversize and weigh it (lets say you have 6 oz of fabric),
-mix up only that much epoxy (6 oz in this example) and dump it on to the fabric.
-place a top piece of plastic over this mess.
-Push the epoxy into the fabric using a bondo spreader or hotel key card (or your drivers license...haha) a 1 in diameter steel tube rolls it out nice too.
-Now, mark out the shape you want...like you wanted a 3.5 inch strip to cover your 2.5 inch wide finish dimension of your windshlied retainer.
-so far you have no mess....just cloth and epoxy between visqueen plastic.
-cut the shape you marked out with scissors, and take it over to your windshield joint....remove one side of the plastic and lay it down as you remove the top piece.
-Take a throw away paint "chip brush" and make sure your glas/e[poxy fabric is free of bubbles and in exactyl thte right location.

I don't like to pre-impregnate more than two layers of glass cloth at a time. But you can impregnate a number of strips at one time. Also, when you dump out your epoxy it cools so it wont thermally run away and get hot on you.

You will have very little waist epoxy by weighing what you will use. 95%.of the time will not need to add more to the layup. I try to leave a small amount in the cup so when I hit with the chip brush I can add a bit more epoxy to the layup if its dry.
 
Thanks bcone.
Covering turns out to be somewhat therapeutic for me. Kind of like doing it. I decided to use Stewart's system. All of the control surfaces have now been covered plus the door through silver. Started with the bottom side of the stabilizers which won't be seen so much. I definitely learned as I went and the last pieces are better than the first. As soon as I get the wings back off, I'll start on the fuselage and prep the wings.

Things I've learned so far - I ordered direct from Stewart's and went by their recommended super cub quantities. It said it should take 50 yards of fabric. That probably is plenty if you know what you are doing but I don't. I'd probably say order at least 55 yards, maybe more. Fabric is fairly cheap per yard but shipping it is not, so order plenty. You can probably get 5 more yards for the price of that second shipment. I probably use more anti chafe tape than I should but I also found this quantity to be low. I used up the single roll pretty quickly. I could also see that I would run out of grommets pretty quickly. Their list included 50 seaplane grommets. I ordered a bunch of standard grommets and will put those anywhere I don't think water will be such an issue. For instance, I used seaplane grommets on the flaps but used standards on the ailerons. I've also wound up buying more 2 inch pinked tape. Again, I probably use too much but there it is.

I am a cheap skate which sometimes translates into I spend more than I would have if I wasn't. I decided to try to save money on the iron and bought a Toko T14 ski wax iron. It's a great iron, digital and all, but will only go up to 330 degrees. Since pretty much every system says to take the fabric to 350, I questioned myself for about a month before I finally just broke down and bought a Fabric Pro iron.
20240118_133235.jpg
On the surfaces done so far, I brushed diluted glue over all of the white like the directions said. I sprayed the silver outside the hangar one side at a time.20240401_130205.jpg Picked up some crap in it but it all gets sanded anyway. Sanded between each of 3 coats. I will sand the last coat when I'm ready to prime it.20240417_091238.jpg

I've used poly fiber a little bit and it's great but it can be difficult here in Phoenix to get the fabric to the glue while it's still wet. That stuff flashes pretty fast when it's over 100. That's not an issue for a lot of the time with Stewart's. You let the glue tack up anyway before positioning the fabric. You lay tapes in to wet glue but you can do it in small enough lengths that it doesn't seem to be an issue. Then there the mask thing. Using mek, you should mask up every time. I've been able to go all the way until spraying silver without masking up. I pretty much decided not to use polyfiber early on but waffled between Stewart's and Aerotech for quite awhile. I think acetone is a lot better than mek but it's nor exactly benign so I eventually settled on Stewart's.

Bad things about Stewart's, the glue cleanup can be a little bit of a pain. Literally. The easiest way to remove it is with the glue eraser and it works very well, but if there's any hair where you have to erase glue, there won't be when you are done. Also, if you get it on your clothes, it's there forever. Also also, if you are like me, you will inevitably spill a little cup of glue on the floor. If that happens, just plan on spending some time cleaning it up. Other than that, I really don't have much negative to say. I can't speak to longevity of the cover yet, of course.

Wayne
 
Tools for Glue application.....
I ditched the cup/paper plate thing after I knocked it/spilled it a few times. I switched to using 30ml dropper botttles. I used less glue, it was quicker with the bottle. Just apply it on the parts and then spread it with the chip brush. when I knock it over its ok. When I forget to place the cap back on, its easy to clean out and no glue dries inside. With the cap on the bottle the glue stays fresh for months. I bet glue consumption when down +15%
 

Attachments

  • Screenshot 2024-06-29 at 8.45.15 AM.png
    Screenshot 2024-06-29 at 8.45.15 AM.png
    552.7 KB · Views: 9
I have just bought a set of wings from Javron for my experimental PA-11. I really like the workmen-ship. I am also using Stewart system. I am not ready to cover them yet but was wondering if there is any prep to the aluminum before covering?
Thanks
 
I usually just wipe it down with acetone prior to glue application to make sure it's clean. I couldn't find anything in the manual saying to do anything special but I figure cleaning is a good thing.

Wayne
 
Back
Top