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fiberglass question

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Old 04-01-2012, 09:00 AM
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mesaflyer
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Default fiberglass question

When fiberglassing a wing or control surface, how important is getting the cloth material wrapped around the surface edge? For example, the control surface TE is about 1/8" thick, and the leading edge is about 1/2" thick. And the wing TE is just over 1/2" thick. If I apply the cloth on the flat surface, and trim it at the edge of the wing TE (after the epoxy dries), will this be ok? I was going to coat the edges with epoxy just to fill the wood grain.

I did a few searches and read a few articles, but could not find any detailed info on this. I presume that wrapping the part would be "stronger", but only if the balsa LE on the control surface was edge glued to the control surface so that the fiberglass cloth covered both the sheeting and LE. As opposed to having the sheeting installed over all the internal pieces (ribs, LE, and TE), in this condition the fiberglass cloth would be epoxied to just sheeting. I hope this makes sense.

I did read one article where the wing TE had the cloth applied after fiberglassing the top and bottom of the wing. I just could not see what the advantage was to applying the cloth using this method. The cloth does not really do anything, it's not wrapped around, just applied to the LE of the wing.
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Old 04-01-2012, 10:28 AM
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Default RE: fiberglass question

You have the right Idea, the glass won't make a 90 degree ish bend at the sharp TE, so let it hang over the sharp edges and trim it after it hardens. 1/2 radius is doable with medium to light cloth

I wouldn't try and glass the TEs either,, not worth the trouble, just epoxy and sand it smooth is what I always do

good luck
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Old 04-01-2012, 11:14 AM
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Default RE: fiberglass question

yea , i found out while trying to get the glass arround a leading edge on a stab , so i just cut it off about an 8th inch from the
edge , and just epoxied and sanded the rest.
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Old 04-01-2012, 03:33 PM
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Default RE: fiberglass question

I noticed you said CUT it off. If you use sand paper, 220 to 120 grit it comes off smoother and cleaner so you can blend in the other side and not notice any seams. Try it and see what you think.
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Old 04-01-2012, 09:57 PM
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Default RE: fiberglass question

I have only glassed with WB poly but what I have done is similar to what has been posted I laid a pre cut piece of cloth on the surface,then after brushing the material out so the cloth sags over the edge, I allow the poly to dry for about 45 min.,then I brush on another coat.

after it dry's over night I gently sand the edge to remove the excess glass with 220,the lighter grit only removes the scrap cloth leaving a small layer of resin and cloth at the trailing edge, the leading edge should be round enough to allow the cloth to wrap around the curve, this should allow for a slight overlap at the LE.

I then glass the other side same method, 2 coats, over night dry, lightly remove excess,this leaves a decent amount of resin and cloth at the TE to protect it.

now that the excess cloth is cleaned up I give the object another 3-5 coats of clear WB poly as needed to fill the weave,I use Varathane Diamond finish WB poly so you can do several coats if there done within a hours time for each coat, if left longer then it needs to dry over night and a light sanding of the surface for the next coats is needed, this helps make for a smoother surface with the WBP any way, so I usually do 3 coats then a sanding before applying another couple of coats,I only apply enough to fill the weave and give the surface a smooth feel,usually 6 coats gets the results I am after but +or- a coat is to be expected depending on how well I sand it.

there is usually plenty of material built up on the TE to protect the area and allow for painting, my P 47 wing right after peeling the paint masks and my spit both glassed this way .
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Old 04-02-2012, 02:47 PM
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Default RE: fiberglass question

yea gray i'll try that out, it makes sense that it would blend in
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Old 04-02-2012, 03:34 PM
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Default RE: fiberglass question


Quote:
ORIGINAL: WhiteRook

yea gray i'll try that out, it makes sense that it would blend in
I'm sort of like Tim, I use Deft Sanding Lacquer for glassing, gave up epoxy a long time ago. There are beter things on the market today, maybe not better but easier and lighter. Sanding is just one of the little things that helps give you a better smoother looking job.
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Old 04-03-2012, 03:42 PM
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Default RE: fiberglass question

i tried just plain clear lacquer for glassing , but it seemed like it would pull off the balsa , i just didnt trust it
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Old 04-03-2012, 06:07 PM
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Default RE: fiberglass question

I tried water base poly and it was OK and could be used in my shop. A friend put me onto the Deft and it works great, just stinks so bad it's breath taking. To be used in open spces only!! I also don't use cloth thicker then 3/4 ounce, 1/2 ounce usually. The trick with the Deft Sanding Lacquer is to put on two coats to the wood before you glass and lightly sand. This keeps the lacquer used to glass from soaking into the wood. Then I glass with about three to four coats then mix up a batch of the deft about 50/50 with talc/baby powder to fill in the weave. sometimes a second coat of fill may be needed but almost all of the finish coat sands off. It doesn't pull off!!
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Old 04-03-2012, 06:35 PM
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Default RE: fiberglass question

I've always used polyester resin for glassing (which is a pain to sand and use)but it yields a very durable surface. Ihappen to have some Deft laquer sanding sealer and am just starting to finish a model and might try the sanding sealer.My question is: does using sanding sealer yield the hard, durable finish that you get with resin? I can see that it would be much faster and easier and certainly doesn't smell any worse than resin.
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Old 04-04-2012, 03:45 AM
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Default RE: fiberglass question

If you are really worried about added weight, you could use deployed air bags from cars... this is what I use and the weave is tighter(and wont show through with less coats) and is much lighter and stronger than the fiberglass cloth. The doping agent is irrelevant, resin or epoxy work equally well.
dan
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Old 04-04-2012, 09:29 AM
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Default RE: fiberglass question


Quote:
ORIGINAL: thomas.crown

I've always used polyester resin for glassing (which is a pain to sand and use) but it yields a very durable surface. I happen to have some Deft laquer sanding sealer and am just starting to finish a model and might try the sanding sealer. My question is: does using sanding sealer yield the hard, durable finish that you get with resin? I can see that it would be much faster and easier and certainly doesn't smell any worse than resin.
It's a very hard surface just like resin. Lighter and easier to sand. Just take some scrap balsa and do a test. After the filler coat let it sit over night and sand it smooth. Last plane I built and glassed was a gasser so I used water based latex house paint so it didn't even require any primer. I really liked using the latex, easy to work with, cheap to buy and it makes clean up of my guns so easy!!!
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Old 04-04-2012, 11:32 AM
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Default RE: fiberglass question

Thanks. I did a test last night and WOW! I did one with just sanding sealer on the balsa with 2 coats on the glass. The second test I mixed in some microballons in the second coat on the glass. Both trimmed easily with a blade or sandpaper. The one with microballons had the weave filled better, but not by much.

What really shocked me was how much easier it was to sand - effortless. Definitely lighter than resin too. I'm sure it isn't quite as durable as glass/resin, but I'll gladly spend the time on repairs (if needed) down the road (runway would be more appropriate). It yields a smooth as glass surface too.

I wasn't looking forward to the task of glassing my current project (a .60 sized plane that has almost no flat surfaces). With this technique I can't wait to start. Just a bit of final sanding and I can get the entire plane covered in a couple evenings and get it painted. I'll be done painting sooner than I would have had it glassed and sanded using resin.

Many thanks for the tip. I'll reserve using resin for times when I really need the extra strength or fuel proofing that resin provides. I'll probably do a test to see how much strength resin really provides vs. the added weight. I'll let you know if the results are really significant.

The last plane I glassed had a flame-out at the worst possible time and overshot the runway and hit a tree about a third of the way out from the wings root 8 feet off the ground. This was a heavy .60 size plane and I expected to have nothing left. Imagine my surprise when the only damage was a crushed LE and sheeting. This was partly due to the balsa sheeted foam wing (and the glass/resin bonding everything together). It would have had much worse damage had it been monocoated without the glass/resin and/or a built-up wing.

I started using polyurethane (Gorilla glue) to sheet foam and it really works great. I sheet everything and then cut out the ailerons etc. which perfectly match the wing. Easier and lighter than built-up and faster too. Too bad I love to build, so I'm still building a lot of my wings.

Thanks for the tip, Tom.
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Old 04-04-2012, 11:39 AM
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Default RE: fiberglass question

Where do you get used airbags? Autobody shops, car dealers? I assume this is a no cost item since they are not reusable to my knowledge. Is the weight comparable to 3/4 oz glass cloth? Glass cloth isn't too expensive but I really like free!
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Old 04-04-2012, 01:55 PM
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Default RE: fiberglass question

You get air bags at the junk yard. The bags are carbon fiber. For glassing I prefer 1/2 ounce glass. OK, if your really going to glass with deft I will print out the instructions one more time. Slap on two coats to the bare wood, let it gas off then lightly sand so the wood is smooth. Now start glassing like normal. I use those cheap paint brushes from the hardware store. I do use thin CA and dribble some onto the fibers where the bristles go into the brush. That keeps the bristles from coming out and sticking onto the glass. I give at least three coats of the deft then sand with 220. At this point I decide if it needs anoter coat of deft. If not then I mix up the deft 50/50 with talc or baby powder, I have never used the micro balloons doing the fill. I lay on coat number one then sand. If I need another coat I decide then. Sanding removes almost all of the 50/50 fill coat so you aren't adding much weight at all.
My last plane I did was the 80 inch 1/4 scale Sukhoi 29. Pretty big plane. Glassing added almost one pound of weight, about the same as covering. The paint added about one pound too. Not too bad for a plane that size. After the Deft has cured for about 3 days it is every bit as stiff as resin. If you want it to feel like resin does then keep adding the deft. It is thinner then resin, like resin it doesn't chip so you get very little hanger rash. If you crash then just like resin you will have a lot of small parts clinging to the glass. Glassing adds strength to the air frame, it helps a lot against things like vibration but doesn't help at all in a crash.
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Old 04-04-2012, 03:15 PM
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Default RE: fiberglass question

can i get the deft sealer at lowes or h depot? sounds like its worth a try.
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Old 04-04-2012, 04:34 PM
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Quote:
ORIGINAL: WhiteRook

can i get the deft sealer at lowes or h depot? sounds like its worth a try.
I get it at Lowe's. They have sanding lacquer and sanding lacquer sealer. The difference between the two products is the sealer has more of the floatsum that does the sealing. Both products work the same but the sealer seems to fill in the weave better so it doesn't require as much of the finish/filler coat.
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Old 04-06-2012, 06:36 PM
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Default RE: fiberglass question

Been away from my computer for a few days. Thanks for the responses. I did just cut away most of the fiberglass, and then sand it down to the edge. This is my second fiberglass job, but the first time with resin. My first attempt I used the WB poly, and for some reason it bubbled up in a few places when the plane sat out in the hot sun. This has been discussed a few times on here, and in my case the plane sat for almost a year after I fiberglassed it until I painted it, so it had plenty of time to out gas. I think the sanding sealer that I used to seal the balsa just couldn’t handle the heat.
This time I used 3M fiberglass resin from Home Depot. Worked fine, sands easy enough, in fact I sanded right through the cloth in a few places where I guess I had high spots. No biggie, just going to wipe on a coat of resin.
I’m going to try Gray Beards Deft method next time. Only problem is that lacquer is not available in CA, so guess I’m going to have to take a road trip to Vegas. Now there is a new reason to visit Vegas!
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Old 04-06-2012, 06:47 PM
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Default RE: fiberglass question

most of the time I get mine at the auto body shop... the ones I get are usually kevlar and it is about 75% of the weight of glass. I also use it as filler in my indoor targets for my .22 and .45 in the house. Works great and it is light and easy to maintain.
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Old 04-07-2012, 02:28 AM
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Default RE: fiberglass question


Quote:
ORIGINAL: mesaflyer

Been away from my computer for a few days. Thanks for the responses. I did just cut away most of the fiberglass, and then sand it down to the edge. This is my second fiberglass job, but the first time with resin. My first attempt I used the WB poly, and for some reason it bubbled up in a few places when the plane sat out in the hot sun. This has been discussed a few times on here, and in my case the plane sat for almost a year after I fiberglassed it until I painted it, so it had plenty of time to out gas. I think the sanding sealer that I used to seal the balsa just couldn’t handle the heat.
This time I used 3M fiberglass resin from Home Depot. Worked fine, sands easy enough, in fact I sanded right through the cloth in a few places where I guess I had high spots. No biggie, just going to wipe on a coat of resin.
I’m going to try Gray Beards Deft method next time. Only problem is that lacquer is not available in CA, so guess I’m going to have to take a road trip to Vegas. Now there is a new reason to visit Vegas!

How long did you let the model sit, after the sanding searler, before the poly ?

If you could still smell the sanding sealer, it wasn't dry. If your poly was applied over it, bubbles would occur when you place the model in the sun.

The sanding sealer will handle the sun, but make sure that it is completely dry before you apply anything over it.

The same is true with the poly. Give it plenty of time to dry before you put anything over it.
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Old 04-07-2012, 08:11 AM
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Default RE: fiberglass question


Quote:
ORIGINAL: TomCrump


Quote:
ORIGINAL: mesaflyer

Been away from my computer for a few days. Thanks for the responses. I did just cut away most of the fiberglass, and then sand it down to the edge. This is my second fiberglass job, but the first time with resin. My first attempt I used the WB poly, and for some reason it bubbled up in a few places when the plane sat out in the hot sun. This has been discussed a few times on here, and in my case the plane sat for almost a year after I fiberglassed it until I painted it, so it had plenty of time to out gas. I think the sanding sealer that I used to seal the balsa just couldn’t handle the heat.
This time I used 3M fiberglass resin from Home Depot. Worked fine, sands easy enough, in fact I sanded right through the cloth in a few places where I guess I had high spots. No biggie, just going to wipe on a coat of resin.
I’m going to try Gray Beards Deft method next time. Only problem is that lacquer is not available in CA, so guess I’m going to have to take a road trip to Vegas. Now there is a new reason to visit Vegas!

How long did you let the model sit, after the sanding searler, before the poly ?

If you could still smell the sanding sealer, it wasn't dry. If your poly was applied over it, bubbles would occur when you place the model in the sun.

The sanding sealer will handle the sun, but make sure that it is completely dry before you apply anything over it.

The same is true with the poly. Give it plenty of time to dry before you put anything over it.
That could have been the problem, but I don't believe so. It was a few years ago, so I can't say exactly how long I waited before starting the poly. I am pretty sure it was at least a few hours before I lightly sanded, and then started applying the poly. I know it was dry, but perhaps I suppose it still could have been gassing off. Hard to tell though being water based, it doesn't smell bad, and water based products dry real fast.

One thing though, at first it only blistered where the surfaces are sealed on the other side, or were solid/thick surfaces. For example, it blistered on top of the wing where the split flaps are painted on the other side of the top of the wing, and at the wing tips where the is a solid block of balsa. It was this way for a long time, but now there are several very small blisters appearing in other places.

I cut away one of the blisters, and everything (paint, primer, fiberglass, and sealer maybe?) pealed away from the wood in one big solid paint chip.

The "silver lining" is that when I scrape the wing tips on landing, I don't feel so bad . It's a heavy plane and hard to land, but it makes for a good "warbird trainer".
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Old 04-07-2012, 06:31 PM
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Default RE: fiberglass question


Quote:
ORIGINAL: Gray Beard


Quote:
ORIGINAL: WhiteRook

can i get the deft sealer at lowes or h depot? sounds like its worth a try.
I get it at Lowe's. They have sanding lacquer and sanding lacquer sealer. The difference between the two products is the sealer has more of the floatsum that does the sealing. Both products work the same but the sealer seems to fill in the weave better so it doesn't require as much of the finish/filler coat.
Gray Beard,
Read and copied your instructions above, but just wanted to verify one thing. You use just the sanding lacquer sealer for all of the coats, including the last coats mixed with talc or baby powder? You do not use the sanding lacquer at all? Is that correct?
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Old 04-07-2012, 07:09 PM
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Default RE: fiberglass question

I did some experiments with the light glass/deft technique and my old glass/resin to determine strength and weight. I also compared them to monocoat for a frame of reference.



 

I used a powder scale that measures in grains because my 4” X 4” test pieces were so light I couldn’t get significant measurements on the electronic scale. I converted to ounces but I’m just going to give relative values. My paint could have been lighter too. This was 4 coats of lacquer. I think the resin would also be heavier in practice since I was able to sand it down farther than might be practical on curved surfaces. The deft is faster, easier and you don’t have to worry about pot life.

These are not meant to be absolute values. I just wanted to get an idea of what to expect.



 

These numbers are for materials only (no wood) for a single test piece. Due to different amounts and materials (or math errors) the results could differ.

Monocoat = .22 oz per square foot.

Glass/deft = .36 oz per square foot. With paint = .67 oz per square foot.

Glass/resin = .78 oz per square foot. With paint = 1.09 oz per square foot.



 

I knew the deft would be lighter than resin. Half the weight is not bad. Since you can’t paint over monocoat that number is meaningless really. I’ll have to try silkspan/dope sometime just for grins.



 

I tested the strength by dropping lead weights from various heights. The resin is definitely stronger (perhaps as much as twice as resistant), but the glass/deft protects well too. Another coat or two might help, but I’m not sure it’s worth the weight.



 

Unless I really need the protection or fuel proofing that resin provides I will never use it for glassing again – the deft is so much easier to work with and lighter too. My thanks to Gray Beard for this tip.



 

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Old 04-07-2012, 07:27 PM
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Default RE: fiberglass question

I use both Defts, makes no difference. the sealer has more filler in it so it fills the weave a bit better. Whatever the hardware store has on hand. Photos of my last one I glassed. Had a slight RF problem show up. OOPS!!!!!!! As you can see, Deft is veery strong and doesn't chip easily. Good stuff. Glass and Deft on this plane added one pound. Don't ovewr think the weight, it comes out pretty light!!
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Old 04-08-2012, 03:11 AM
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Default RE: fiberglass question

mesaflyer: Waiting a few hours isn't nearly long enough. I wait a week.
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