Rate1

My latest kit, Lanier Extra 300 1/4 scale, has foam core main wings and tailplane. The instructions is calling for the two foam stab panels to be joined together with epoxy and then fiberglassed with a 2 oz cloth.

QUESTION; how do I best glass this area?

Is there different glassing techniques out there? How much epoxy is considered to be just the right amount? Is it crucial to use 1 hr cure epoxy or even longer, or could I just use my regular 30 min epoxy? When the instructions call for 2 oz cloth glassing I assume this means one layer of a fiberglass cloth that has the weight of 2 oz.

The way I though of how to fiberglass was to first apply a thin layer of epoxy on the surface to be glassed. Then put the cloth in place, nice and smooth, to following up by apply additional epoxy ontop of the fiberglass, just enough to sink into the fibers of the cloth.
Another method I have heard of would be to first apply the epoxy direct on the cloth and then place the epoxied cloth onto the surface, epoxy down agains the foam, and after it has cured apply another layer of epoxy ontop of the raw fiberglass.
I don't know wich of the two way I just meantioned that is the correct/best way of doing it?
Further, I am only assuming that I should glass one side first , eg top side of stab, to let it cure before letting my self lose on the other side of the stab? Then there is a matter of the LE and TE where the two layers meet. How big should the overlap be on a 1/4 scale stab?

I am trying to make this kit as light weight as I possibly can so using the right technique to obtain the best result is crucial to me. I even bought 1,5 oz cloth, instead of a 2 ox, that I intend to use (there was no 2 oz cloth avilable). Wanting as light glassing as possible, but still rigid enough, could I mix in 50% alcohol into the epoxy to obtain a thinner epoxy mix that is easier to spread out as a thin layer???
Being a relatively inexperienced builder with only one kit under my belt, GP Extra .60 kit, I am hoping to recive some help on this matter.

Best regards,

Edwin

My Feedback: (2)

I dont know anybody that glasses using the two methods you mentioned. I'm assuming the panels are already wood sheeted. I've had real good luck using polyurethan glue to join wing panels, it expands into every crack and crevis. Or unthined epoxy works too. After they are glued together and the seam sanded smooth, I lay the glass down first over the seam, dry. Then mix up the epoxy and pour it onto the glass. Use an old credit card or similar as a squeegy to spread the epoxy and push it into the glass. No dry spots. Mix a little at a time, not too much or it will harden up on you. Dont use it if it does that. Mix more. For wing joining glass, epoxy needs to be strong, I wouldnt thin it too much. Just enough to make it a little runny and use denatured alcohol from the hardware store (Home Depot or such). It has less water content. I do only one coat of epoxy. Feather the edges best you can. Some of the hobby fiberglass thats sold specifically for wing joining is crap. It has a seam on it that needs to be cut off. Even then its still too stiff. I get my heavy stuff from walmart. After spreading, roll a roll of toilet paper on the epoxied glass to soak up any excess and use the card again to smooth it out some more. Use a paper towel with alcohol on it to clean the card from time to time. Once cured I use lieght weight spackling mixed with water to a hair thicker than milk (more like syrup) and rub it into the glass with my fingers making sure it fills the weave. Sand it down to the glass and fill it again. Do this until its smooth as you want and cant feel the featherd edges. Then you do the finish coat of glass (.5 to .75 oz) over the whole wing in basically the same fashion.

If weight is of utmost importance and this is your first time glassing, wouldnt it be better to use ultracoat instead? Just a thought. It IS possible for a glass job to be as light as an mylar finish but it takes a little practice. Once its on, its a b*tch to get off if you dont like it. You have to use a hot air gun to soften the glass/epoxy and slowly pull it up. Redoing the surface for another attempt can drive some guys to suicide.

Edwin

Rate1

Edwin, thank you. I only need this fiberglass for joining two stab panels, left stab is joined with epoxy together with right stab at their root ends. Glassing the two stab halfs, over the epoxied seam, is called for by the instructions as a meassure of reinforcing the two stab panels to become one unit. The glassing will not show on the finished kit as it will be inside the aft fuz under the fin. Yes the foam stab panels will be sheeted before epoxy them together and then reinforced with fiberglass. Can I assume that your describtion on how to glass also applies to my purposes?
The plane will be covered with reg plastic covering film inorder to save weight.

Christian

chris_in_montreal

My Feedback: (1)

Rate1, there's a really good how-to on glassing here: [link=http://airfieldmodels.com/information_source/how_to_articles_for_model_builders/finishing_techniques/apply_fiberglass_finish/index.htm]Airfield Models[/link]

I followed the guidance here for reinforcing the wing joint and for general glassing for my first attempt with great results.

Rate1

Merci.

da Rock

If you're only reinforcing a joint, and not covering the entire surface here are a couple of suggestions/ideas.

There is strip glass cloth available. The 1" wide works for butt joints. Look for some that has flat edges. There is some that has edges that're mfg'd such that they're much thicker than the cloth itself. That's a problem when the cloth is out where it can be seen. It wouldn't be a problem if inside the fuselage, but why buy it when there is better.

You can CA glass down and needless to say that's lots quicker. It's also not as messy to do. And it'll be lots lighter, just the thing you want to happen around the tail of any aircraft.

The slower epoxies are often thinner. Look for bottled epoxy and tilt the set up to find the most liquid you can find. I often use an acid brush and paint on the 30min ZPoxy I favor. It can also be thinned slightly with acetone or with denatured alcohol. Don't use drugstore alcohol as there is little reason to use it when it'll put water into the mix and acetone and denatured is almost as cheap and as easy to find. I don't often need to thin the 30min ZPoxy. Just did what you describe with 1" cloth and 30min and it took about 5 minutes to do.

Rate1

darock,

Thanks. That seams easy enough. I like...

The more I am investigating and searching the RCU for techniques and how to do the more cluttered am I turning. Not in aspect of actually doing new building steps as RCU is full of people like you guys that want to help out and share your experience. But it is full of so many different ways of doing things. Basically the more I dig the more routes to go I find.
Initially I had decided to covering my kit with reg plastic film to keep the weight down. However, I have now gathered that fiberglassing a plane does not necessary means a much heavier structure, but also gets many other benefits plastic covering is not offering.

Question to you guys, would you cover a 1/4 scale extra kit with reg plastic covering or fiberglass and why so?

da Rock

If you know what weights of glass cloth to use and where to use it, and how to apply it with the right amount of resin, a glasscloth finish will not add too much weight. But almost nobody can finish an airplane the lightest with a glass finish. Remember, that unless you put pigment into the resin, you've still got to paint the airplane.

da Rock

Would I finish a model with glass instead of film?

You bet. I've chosen epoxy/cloth over film every opportunity where I had the time to do the epoxy/cloth.

Why?

The airplane is a lot stronger, a LOT stronger structurally. And it's more durable. It gets lots less hangar rash.

And the size of the airplane isn't important to the decision. I've got a "little" Hots I built back in the 80s and glass/epoxied entirely. It is actually about the same weight as the kit built ones my buddies covered with MonoKote. I scratch built it and selected the wood. And I sheeted the wing instead of building it open-bay, and did the tips with block. But like I said, I selected the wood and used contest balsa where I wanted it to be light. But that's comparing apples and oranges.

da Rock

BTW, have you read the HOW TO articles about painting on glasscloth with polyurethane?

It takes less skill to paint than to apply epoxy. It's lighter for sure. And it's quite strong. Most of the structural strength of "fiberglass" comes from the glass fibers being trapped and becoming rigid. And polyurethane does that.

Rate1

Well this link Chris in Montreal gave me (Airfield Models) is an excellent source of information. That page is recomending to use 0,58 oz cloth and by following the easy instructions...I mean what could possibly go wrong?

Rate1

Darock,

No I havn't read the "articles about painting on glasscloth with polyurethane". Where do I find it?

Rate1

It so happend that I did put in an order for contets balsa to replace all the sheeting and leading edges in my kit. I also trew in a couple of slabs of 1/8" lite ply to replace those heavy fuz side ply. The reason is obviously to save weight.
If to fiberglass instead, assuming the entire plane needs to be covered with sheeting or ply, how much work are we talking about. As someother guy meantion, after he is done fiberglassing he use very thin balsafiller on top of the glassing and then sand it down. He keeps repeting this moment to obtain desired finish. However, this step of sanding the finish is recomended to not do in this article. Instead the article is recomending the fiberglass to be primed to fill out the weave. After all this left to do is to paint for a finished job. To me the step that seams hardest is to paint.
Left to cover on my kit to be fully covered with wood is some openings in the fuze sides. The rest is allready covered by either balsa sheets or ply as per plans.

Edwin

My Feedback: (2)

Rate1,
Yes, that method would work for just wing joining.

As far as your last post, there ARE primers that do a good job of filling the weave. The whole point here is just to fill the weave before the final paint. Whether you use coats of primer or filler doesnt really matter. There are some differences in weight, but you find that out doing what you are already doing, asking around. I personally like glassing the whole plane, no wrinkles in the heat.
Edwin

Rate1

Edwin,

What weight penalty do you think I will get glassing and painiting a 25% Extra compered to plastic covering. Assuming I am doing a proper job glassing and painting.

Edwin

My Feedback: (2)

Somebody better than me should answer that question. I dont really have any idea, too many dependencies. I have 2 philosophies for covering. My scale and warbirds larger than 72" ws get glass work. Smaller planes get mylar. On aerobatic planes, they all get ultracoat. Lightweight is my goal for aerobats. But I've never had one that large, I like them around 60" to 70". Thats just my preference. My aerobats generally get a lot more dings and mylar is easier to repair (just my opinion). I get more dings cause I think I'm better than I really am.<g>
Edwin

Rate1

Well I suppose that has settle this issue then. This since the aerobat I am going to build has a 72" wingspan and needs to be as light as I can get it.