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ezgb59a
09-04-2008, 08:33 PM
Talked to someone familiar with our area's 4H judging and got the scoop. They are looking for fin alignment and finsih.

Regarding the finish ...

What steps do you take to have a finsih where the lines on the rocket tube are not visible?

How many coats of paint do you normally put on?

What steps do you take for the fins and nose cone? Especially given some are cardboard and others are balsa wood.

Trying to get ideas of what I'm not having my son doing.

Thanks
ez

stefanj
09-04-2008, 08:41 PM
There are so many possibilities . . .

I tend to go overboard and make "catalog perfect" models, especially when I'm working on a special clone. This means filling in balsa until it is smooth, filling and sanding the body tube spirals, several coats of primer, compounding the paint, and waxing the final finish.

On the other hand, sometimes I build a sport model where I only do a minimum of each step. I still fill in the balsa, but don't go crazy. I only use one coat of primer. Two coats of paint. No buffing or waxing.

Royatl
09-04-2008, 09:59 PM
Talked to someone familiar with our area's 4H judging and got the scoop. They are looking for fin alignment and finsih.

Regarding the finish ...

What steps do you take to have a finsih where the lines on the rocket tube are not visible?

How many coats of paint do you normally put on?

What steps do you take for the fins and nose cone? Especially given some are cardboard and others are balsa wood.

Trying to get ideas of what I'm not having my son doing.

Thanks
ez

For body tube spirals, get some Elmers Carpenters Wood filler (if you can find the Fill'n'Finish style, that's the best, but they don't seem to be distributing that as much). Don't need much. Thin it with a *tiny* amount of water, and apply it to the external spiral. Don't glob it on, just lightly coat it along the gap. When it is dry, use 320 grit sandpaper and lightly sand most of it away, going across the gap, not with it.

Now, use a spray sandable primer. I prefer a "spot filling" primer that you can get at auto parts stores. Spray a light coat evenly over the tube, let it dry a few minutes, and spray another light coat. again using a 320 or 400 grit sandpaper, lightly sand the entire tube. Then one more light coat and that should do it.

For balsa, use the same filler, don't thin it quite so much. You can do this with bare fingers but I prefer to use a nitrile or thin latex glove (especially if you use the fill'n'finish. Just use your fingers and rub the filler into the balsa, leaving a thin coat, but making sure any deep veins in the balsa are covered. Let it dry and lightly sand. Sometimes I'll start with a 120 grit wet-or-dry paper, dry. Then switch to 320. Use the primer as above, but you may want to use one or two more coat/sand cycles to be sure the surfaces are smooth and hard.

This can all be done *before* the rocket is completely assembled. Just be sure any balsa surfaces that need to be glued don't get filled/coated. And scrape the coating away from the body tube just where you need to glue.

First one or two rockets may not turn out absolutely perfect, or they may end up with too thick a coat of paint. But eventually you'll be able to do it with just the right amount of filler, primer and paint.

Solomoriah
09-04-2008, 11:09 PM
I thin the filler out to the consistency of a thick paint (think tempura) and brush it on the fins, leaving the root edge clean of course. I do both sides at one time to avoid warping. When the filler is dry, I sand it off with fine or very fine sandpaper, following the grain, until I have a smooth surface.

The same thinned filler gets brushed over the spiral lines, generally a bit sloppily. Again, when it's dry I sand it, across the lines (lengthwise along the tube), until I get down to the body tube. This leaves the spirals filled, obviously.

Generally, this is perfect, but I have a hard time seeing the remaining grain or grooves. This isn't a problem, though. After the rocket is entirely assembled and ready to paint, I give it a coat of spray primer. I use the cheap stuff, Wal-Mart ColorPlace Gray Primer or Dollar General Miracal Gray or Red Oxide. Sometimes I apply a coat of red oxide, then follow it with a coat of gray (without sanding in between). This makes it a bit easier to see where I'm sanding through the gray primer.

When the primer is dry I take the rocket out in the sunshine, where I can readily see the places the filler didn't quite fill. I sand the rocket down as smooth as possible, paying special attention to the problem areas. It's okay to sand through the primer to the balsa or paper on all primer coats except the last... you want it complete so there are no places where the paint coats/sticks unevenly.

When, at last, I have a smooth and blemish-free primer coat showing, I apply my first coat of paint. Since I'm using the cheap stuff, I have that "recoat within one hour or after a week" thing going. Not a problem for me, since I tend to be finishing several rockets at one time and generally get to paint only every few days at most. I apply a coat just heavy enough to cover, let it set half an hour or so, and recoat. This coat I apply pretty heavy, standing in the sunshine and getting the rocket just shiny wet. I avoid runs by constantly turning the rocket (I paint on the end of a dowel with an expended engine affixed) and get a heavy coat by applying thin layers round and round again. Applying a heavy coat in a single spot with the paint can moving slowly makes a run every time.

If I succeed in getting it as wet as I want, I generally have to stand and turn the rocket a minute or so until the shine begins to fade to be sure it won't run when I put it on the rack to dry.

This generally gives a nice gloss. If I want to paint a second color, I have to wait at least 5 days, preferably a full week, before masking and painting. I learned the trick of sealing the mask with the base coat color from someone on YORF... just paint the edges of the mask with the first color, let it dry half an hour or so, and then hit it with the second color. Often I can apply that second color in a "wet" coat on the first pass, though I'm not sure I understand why this works.

I try to pull off the mask fairly early; when I put it on, I fold the ends over where I'll need to pull to get it off. It's either pull it off early, or wait a week, and I'm terrible at waiting to pull off the mask. If you pull it off after an hour but before a week, the second color tends to want to pull off in sheets!

It gets another week to dry before decals and clearcoat are added. I apply Future with a damp paper towel, let it dry half an hour to an hour, apply any decals, and put another coat of Future on (basically to protect the decals, as the second coat won't really thicken the Future anywhere else on the rocket). However, laser-printed decals are destroyed by wet Future, so when I use them I must first apply Future and let it dry, then the decals, then a coat of rattlecan clearcoat.

I think that's it. Quite a production, isn't it?

We all have different methods and prefer different paints and clearcoats and whatnot. You really need to screw a few up before you develop a method that works for you. Practice makes perfect.