Atom Ant

I have completed fiberglassing a fuselage with 3/4 oz. cloth and water-based polyU. Everything went fairly well. Two questions. I have a couple of creases and seams that I did not do a very good job on. How do I remove them by sanding down to the level of the main fiber or ssanding to the wood and ppatching with fiberglass. Second what kind of filler do I use to get ridd of high and low spots?

Campy

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Be advised that waterbase poly is FUEL RESISTANT, not fuel proof. If you let a clear coat dry for a minimum of a week AND wipe your plane down at the end of the day you should be OK. If you let the residue sit on the plane for several hours it will soften the poly.

Here is a "How To" on using water base poly for glassing. This is all stuff I learned "the hard way"

Atom Ant

Thanks Campy. I have pretty much folowwed this method to this point. I am going to make sure I use use fuel proof paints. But, I still have a question on how to get rid of the mistake areas mentioned above.

Atom Ant

My bad, I did not read through your entire post. Thank you

techsarge

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Campy...

Had a question about fiberglassing. In your attachment you said to overlap adjoining sections of fiberglass about 1/2" - 3/4". On the overlap and using lightweight fiberglass, will that overlap leave enough of a bump to be noticeable? If so, than I would have to sand through the top layer of the overlap? Haven't tried fiberglassing yet, but trying to gather enough info to make intelligent decisions.

Thanks...

Ed

Campy

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Using 1/2 - 3/4 oz glass cloth the bump you get is hardly noticeable noticeable. Then, by the time you apply another coat of poly AND a poly/microballoon mix and sand, I sincerely doubt you will see any bump.

You might want to read the "How To" I put together on glassing with polyurethane. It should answer a lot of your questions. As far as weight/strength for resin vs polyurethane, the polyurethane is going to be ABOUT 1/2 the weight of a similar resin fiberglassing job. The poly, however, is only going to have about 60% of the strength of a resin job.

What this translates to in everyday talk is:

The resin job is going to be HIGHLY resistant to dings, chips, etc., but very hard to sand.

The polyurethane job is going to be a lot more resistant to dings, etc than your regular film covering or "silk/dope" finishes. It is more flexable and easier to sand than the resin since it is a "softer" finish. Because it is a "softer finish", it is not as resistant to HARD dings and knocks as the resin is. Think of it as a piece of plastic and a piece of metal. Both will resist scratches, but the plastic is going to scratch before the metal does.

techsarge

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[quote]ORIGINAL: Campy

Campy

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[quote]ORIGINAL: techsarge

[quote]ORIGINAL: Campy

[quote]ORIGINAL: techsarge



Campy...

Thanks for the clarifications. You really broke it down into basic terms. I've built several kits and in each instance glassed the center section. I went to Home Depot and bought 6 oz glass cloth and polyester resin whish included a little bottle of hardener. Unfortunately, that stuff really smelled horrible. I have a townhome and relegate all my building to the basement. There is one window so the ventilation is not good at all. Anyway, that's why I thought of using water-based poly. I have read that the odor is minimal and that would please me and my better half. Did you use minwax or any particular brand of water poly?

>I have used the Minwax waterbase polyurethane, however, any
>of the waterbase polyurethanes will work fine. The only "smelly"
>part is the sanding sealer.

I have a couple of building projects in mind. One is the L-4 (J-3 Cub) kinda modeled after another fella on RC Universe, KHodges. The other alternatives are the Top Flite P-47 (60 size) or the Shyshark SBD Dauntless. I don't know much about Skyshark kits but the few things I've read about them were good.

>I have built the Skyshark Tempest kit. The quality of the
>materials is excellent and the parts cutting is super. I will
>offer a couple of suggestions on their kits, especially if you
>will be doing retracts and/or glassing it. Use the maximum
>size engine (or a little larger ) that is suggested. Glassing
>and/or retracts adds weight really quickly. Glassing
>especially adds weight in the tail no matter how careful you
>are. You need to be aware of this if the plane is a short
>nose/long tail type (Tempest among others ). If you
>opt for mechanical retracts (or a different brand of retract )
>make sure that the retract will fit the cutout in the plywood
>support and the retract has the proper clearances BEFORE
>epoxying them in place.
>
>The control surfaces are a 1/16" balsa sheet with slotted
>ribs slid over them. This assembly is then CA to a 1/4"
>thick piece of balsa. You will want to CA pieces of scrap
>3/32" balsa on BOTH sides of the 1/16" backbone in the
>areas where you plan to place your hinges.
>
>Several of their models recommend/suggest covering the
>control surfaces with fabric or film. What I found that worked
>very well, especially for glassing/painting, was 1/64" plywood.

Haven't had a plane with retracts before and read alot of posts on RC Universe discussing lots of problems. And I fly from a grass field although it is rolled and pretty well maintained.

>If you do decide to go with retracts, get ones that have the 3/16"
>diameter struts instead of the typical 5/32" diameter, especially
>if you fly off a grass field. Also, when flying off grass, be aware
>that you will most likely be doing frequent adjustments to the
>struts, especially if you have a "hard" landing and are using 5/32"
>struts.
>
>I know Robart makes retracts with 3/16" struts and I also believe
>the brand that SkyShark suggests have 3/16" struts. I would
>double check to be sure though.

There is a club that flies at a nearby county forest preserve that has an asphalt runway as well as grass. Might be worthwhile to look into that. Were you satisfied with your Skyshark kit and the durability of the retracts?

>I used a set of Robart mechanical retracts I already had. If
>I were to do it again, I would go with the 3/16" strut retracts.
>As for air vs mechanical, unless the retracts are something
>like the SpringAir brand (fail open ), I won't even consider
>them. The other thing you will need to look at is the degree
>of complexity in the air system (and potential for leaks ) vs
>the complexity of the linkage in the mechanical system.
>
>I found that the total weight of the mechanical system was
>less than the total weight of an air system. That may have
>changed in the last couple of years though.

After you use filler and the surface looks good, you said to use primer. Would I use latex primer since I don't have any spray equipment and would probably use latex paint from a spray for the finish coat? I'm not sure they sell latex paint in a spray can so I might have to brush it on.

>I use automotive primer in a spray can. The type I use is the
>"High Build" type of primer. The advantage to this type of
>primer is that it will fill in the little scratches that are next to
>impossible to get out. The down side to this primer is that if
>you are not careful it will add weight quickly.
>
>They do sell latex in spray cans. I know Krylon has some.
>You may want to check some paint stores. Some stores
>(usually the smaller ones ) will not only custom mix the paint
>but put it in spray cans for you.
>
>An option you may want to consider, especially if you plan on
>painting more than one plane is a Husky brand compressor
>($100 @ Home Depot ) and an airbrush (about $20 - $30 ).
>
>If you decide to brush the paint on, I have gotten some decent
>results using foam brushes and FloTrol. FloTrol retards the drying
>of the paint slightly so it has a better chance to level itself out
>and hide and brush marks.

If I do that, what would I use for a clear coat for fuel protection that would not damage the latex finish coat or even the polyurethane which attached the glass cloth to the fuse? I don't know, maybe I'm confused.

>For a clear coat you are safe with just about anything. Just
>about anything is compatible with latex ONCE IT HAS CURED.

>If you want a FUEL PROOF clear coat, use something like
>Ultracote clear. Oil base polyurethane is also fuel proof,
>however it will "yellow" after about 6 months. Water base poly
>is FUEL RESISTANT. Let is dry for a week, and as long as you clean
>your plane at the end of the day you should be OK. If you let
>the residue sit on the surface for 3 or 4 hours, it will soften the
>poly.


Thanks again for your help....

Ed

Here is a little "How To" on using latex. It is geared primarily towards spraying, however there is a lot of good information there.

Ted

techsarge

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Hi, Campy...

Thanks for the real thorough responses to my questions. It looks like whichever kit I decide to go with will be a good winter project. I think the water poly would be best in my case because of the ventilation in the basement and the other alternative would be finishing resin. I imagine that finishing resin would be heavier than poly. How much glass cloth did you use for the Tempest? I guess the best way would be to use the largest pieces possible for the fewest seams? I'm still a little nervous about the retracts. I read some posts where guys used 5/16" wire and Robostruts. I don't know if Robostruts can be used with mechanical retracts. Maybe the extra load on the servo would cause problems. Would you say that the mechanical retracts are simpler to install than comparable pneumatics and probably less expensive, too? I'll make a decision in the next couple of weeks on the kit because I'd like to have it completed by Spring. Thanks again...

Ed