Scratchie

I've never read about anyone using sanding sealer before painting. Obviously fiberglass is stronger, but if wieght is an issue why not use sealer?

planebuilder66

My Feedback: (8)

I did just that on my HOB fw-190, I didn't want to glass it due to weight and I wanted to paint it so I could blend the plastic top to the balsa fuselage. But in hind-sight, I should have just glassed it, I spent soo much time laying down sanding sealer and sanding,...repeat the process and eventually, I was able to get the wood grain filled and gone. Glass would have been faster. Unless your talking about filling the weave of the 1st coat of glass with sanding primer/sealer, then that would work just fine, your paint will be thicker, but getting the smooth surface will be easier to achieve. Primer sands way easier than epoxy finishing resin.

eddyc

My Feedback: (11)

What a coincidence, back in the late 70's I built a HOB 190. I surfaced it with a technique I believe I read from the late Jim Meister. Brush on polyester resin with no glass then wipe off as much as possible with paper towels. After it hardens fill the remaining wood grain with vinyl spackle, which is a lot easier to sand than the hard resin. Once the spackle dries sand, prime then paint. Was actually quick and easy.

planebuilder66

My Feedback: (8)

I still have mine from the late 90's, here's the result. All I can say is be carefull of some plastics, the paint I used on this was lusterkote, it didn't happen right away, but the thinner used in lusterkote will attach some plastics, the top plastic top deformed and started to shrink from the paint, it eventually stopped shrinking, but not too happy with what happened. If I had to do it over again, I wouold do the resin sealing first, then use the sanding sealer to finish it off.

Scratchie

I guess that I'm used to a lot of sanding (boats) I always woudl put on 3-4 coats of sealer before glassing (roughing up the laast coat of sealer first), then filler and more sealer after.

Scratchie

eddyc, what do you mean by "polyester resin"? Do you mean a polyester varnish-type product, or a two-part epoxy?

planebuilder66

My Feedback: (8)

STD fiberglass resin, Polyester is true fiberglass, we all converted to epoxyglass, using epoxy resin. The polyester is what you find in homedepot, walmart or boat stores for general repairs and layup's of cloth. Stinks like heck and has a short pot life of around 15 minutes, it's pretty brittle and heavy.

Scratchie

doesn't sound like a good building matrrial. Perhaps sealer and a little elbow grease is the way to go.

Gray Beard

My Feedback: (-1)

I just did a plane using sealer instead of glassing, like PB66, from now on I will just glass, it comes out a lot smoother in the end. I do put on two coats of sealer and sand before I glass.

Bax

My Feedback: (11)

Sanding sealer is used to seal the wood so that additional coats will not soak in. Usually, after a coat of sanding sealer, you'd lightly smooth-off the surface and then use Balsa Fillercoat (that's if you were using dope), otherwise, something like K&B Primer was used. Now, you want to use any kind of primer/filler that will do the job. As long as whatever paint you use to go over it is compatible, you'll be OK.

NM2K

My Feedback: (14)

And, the gas bubbles generated during curing can leave microchannels that will permit water to be introduced to the wood, if only one coat is applied. Multiple coats of polyester are mandatory in order to prevent this phenomenon from occurring. Yes, it surely does stink. I doubt if it is as bad for your body as epoxy, but that is only a guess on my part.


Ed Cregger

Gray Beard

My Feedback: (-1)

I also use deft sanding Lacquer for the glassing. Two coats then sand, then I mix the Deft about 50/50 with baby powder and coat the plane and sand between coats until all the weave is gone. The deft gasses off as it cures so you loose about 80% of the weight. Comes out very smooth and light but the fumes of the Deft can get you if you don't have an open area to work in. Sanding down the baby powder coats is also a big mess so should be done outdoors. It's worth the effort though.

planebuilder66

My Feedback: (8)

GREYBEARD, how do you think I keep the misses out of my mancave?, all the dust! It works great for me.

madtrev

Why not mix up some dope and talcum powder?

Gray Beard

My Feedback: (-1)

Talcum powder is another good mix but the baby powder is a lot cheaper at my local drug store. PB, the problem with the baby powder is the foot prints and the smell, as well as it works it still smells like baby powder and you track it in and out, nice white foot prints. My wife and I both smoke {sin, sin!!} but we never smoke in the house, this time of year the shop is also our smoking room. I no longer have a real hanger so my planes are all right there hanging up in the shop. It's silly to have to clean a plane before you go to the dry lake bed to fly them!! It really is a mess!! Just works so well!!

planebuilder66

My Feedback: (8)

Don't feel bad about the SIN,SIN!!!, I do it too, and not the funny little green trees some on here think I'm on, but almost every plane I have is covered in balsa, filler or stagnant dust here in the basement?! So I'm not worried about that, just the fragrant smell of baby powder would get my butt kicked at work. It's kinda hard to be a "In Charge" kinda guy when you smell young, if you know what I mean? But I see the dust as a sign of progress or regress in sometimes, but at least I do notice the little balsa shavings being tracked upstairs into the livingroom everytime I go outside to sin. So I see where your coming from, if your interested in quitting, check out this phone # 1877-4-quitting, it's pfizers personal campain on helping people quit. I plan on calling them soon, I made a plan, when I finally get to building the hostetler skybolt, I'm getting the medication and going to build that plane to keep myself occupied while I do it. I'm going to need it if I plan on putting a gemini 4 cyl os in there, that's like 1/4 a year of smoking the nails.

Top_Gunn

My Feedback: (6)

Some "sanding sealers" (the Pactra version, for instance) aren't good sealers; they're really more of a filler. If you use them without sealing first, you can get cracks developing later and it will take many, many coats to fill the grain. Thinned nitrate dope makes a good sealer. Especially over silkspan. Then you can use a mix of dope and talcum powder as a lightweight filler. It won't give you the strength of fiberglass, but it's light and smooth and compatible with just about any kind of color coat.

MTK

Polyester resin and MEKP hardener form simple polyester surface coating when mixed, used to laminate glass cloth and other things....fiberglass is fiberglass just like carbon cloth is carbon cloth. Polyester and glass are totally different materials. There is another material, vinyl ester, that is much less brittle but you typically need to mail order this stuff. Can be used to laminate the glass cloth the same as polyester. The curing mechanism is based on free radical chemistry which means simple sunlight (ultraviolet) will cure it without adding the peroxide

Epoxy is similar in certain sense, but totally different chemically...it's a two part system also and certain types of it can be used to laminate glass, carbon, etc to wood or other surfaces. Other types are much thicker and are used as adhesives. Epoxy is much more versatile than polyester and vinyl ester. Depending on the type of part B one uses (hardener) pot life can be anything from a few minutes to 12 hours or more. Much less brittle than polyester, much much stronger (tensile strength is around 10KPSI as opposed to around 3-5 KPSI), it is typically used by many to laminate all kinds of structures. Polyester on the other hand is very inexpensive comparatively speaking

Did you know that the most of the current fighters in the US Air Force arsenal are basically epoxy/carbon laminates?

MattK

MTK

This is what I occasionally use on my wood models or surfaces...nitrate and silkspan. I like talcum but calcium stearate is lighter and fills faster.

An alternate technique is epoxy clear paint like Klass Kote thinned 50:50 as a wood sealer and silkspan bedder. Slight increase in weight but much more bullet proof finish than nitrate. I used clear epoxy paint to bed fiberglass cloth for years in the 70s, 80s, and 90s. Much lighter than regular surfacing epoxy

BTW- The best surfacing epoxy I have found is Pro Set. It's the thinnest around and the 125 resin and 229 hardener give around 70 minutes of pot life at room temp. Just started using a J. Greer product, 300/21, which is sligthly thicker than Pro Set but half the cost for similar quantity. FWIW2U

MattK