Final sanding...how do you "see" the tiny irregularities?
01-10-2005, 09:57 PM
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Final sanding...how do you "see" the tiny irregularities?
I have sanded balsa down to 220 grit, and thought it looked perfectly fine. But then, If I were to spray on a quick coat of primer, suddenly all of the tiny imperfections that were masked in the grain and varying colors of the raw balsa, suddenly stand out. I would like to fill and sand all of these imperfections at this point...before glassing...so that the glass job will turn out clean and smooth, and not show the "print through" of any underlying bad spots in the balsa. My question is...whats the best way to show up these tiny spots, or unfair curves, needing fill and touch up, without adding a lot of unneccessary weight of paint/primer? Is the primer the only way to go? Also, I have used some balsa filler that was supposed to be easy to sand away, only to find it sands as tough as a blob of CA glue. What filler do you use to get an extremely fair, easy to sand away, surface?
Thank for the comments.
Jim
Thank for the comments.
Jim
01-10-2005, 10:25 PM
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RE: Final sanding...how do you "see" the tiny irregularities?
These tiny imperfections are nothing to worry about at this point. You'll have to do the same thing all over again after glassing the airframe. So why do things twice? All I would do is take care of the big stuff (dings, seam-lines, etc.) and then glass the airframe. Then primer fill and sand about four or five times using progressively finer grades of sandpaper.
It worked for me and gave a glass smooth surface.
It worked for me and gave a glass smooth surface.
01-10-2005, 10:30 PM
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RE: Final sanding...how do you "see" the tiny irregularities?
You can see more in natural light as opposed to florecent lights - sun shine is the best! Just rotate your item so only a light beam of light hits the surface at an angle and you will be surprised what you see!
Jerry
Jerry
01-10-2005, 10:32 PM
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RE: Final sanding...how do you "see" the tiny irregularities?
You might try just shooting a light coat of grey primer and then sand the airframe down with 220. Spots that need work will still have the grey primer...
01-10-2005, 10:51 PM
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RE: Final sanding...how do you "see" the tiny irregularities?
Don't try to fill all the grain before glassing. The glass will put an even layer over the grain and require much less filler and hence be lighter. YOu should fill gouges and such but that's all.
01-11-2005, 12:36 AM
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RE: Final sanding...how do you "see" the tiny irregularities?
ORIGINAL: tschuy
These tiny imperfections are nothing to worry about at this point. You'll have to do the same thing all over again after glassing the airframe. So why do things twice? All I would do is take care of the big stuff (dings, seam-lines, etc.) and then glass the airframe. Then primer fill and sand about four or five times using progressively finer grades of sandpaper.
It worked for me and gave a glass smooth surface.
These tiny imperfections are nothing to worry about at this point. You'll have to do the same thing all over again after glassing the airframe. So why do things twice? All I would do is take care of the big stuff (dings, seam-lines, etc.) and then glass the airframe. Then primer fill and sand about four or five times using progressively finer grades of sandpaper.
It worked for me and gave a glass smooth surface.
Cheers!
Jim
01-11-2005, 02:10 AM
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RE: Final sanding...how do you "see" the tiny irregularities?
Finishing before glassing -- I always use light spackle thined with a little water. Rub with fingers to complete coat the surface. This will raise the grain as well. Let dry completely (DAP has a pink spackle that turns white when dry). Sand all of the way back down to the wood. This will leave only a small amount of light spackle in the holes and low spots.
Glass the surface.
For surfacing after glassing. Use primer in multiple light coats. I have used grey primer that can be wet sanded. Another type which is cheap and sometime more compatible with agressive paints such as LusterKote is white flat latex 60%, 30% water and 10% microballs or talc. This is white and also can be wet sanded.
Marc
Glass the surface.
For surfacing after glassing. Use primer in multiple light coats. I have used grey primer that can be wet sanded. Another type which is cheap and sometime more compatible with agressive paints such as LusterKote is white flat latex 60%, 30% water and 10% microballs or talc. This is white and also can be wet sanded.
Marc
01-11-2005, 06:24 AM
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RE: Final sanding...how do you "see" the tiny irregularities?
Hey guys...good stuff, thanx very much. I guess with just a little more sanding of the rest of the parts...I'll be ready to do some glassing. That's encouraging. Progress is being made.
Just as an added note...I haven't built a kit in 20 years....now I am reminded of why ARFs became so popular. heh heh. In honesty, I have to say I am enjoying building this monster, (TF giant scale P-47) but in reality...much of it is just dull labor. I mean really....how much fun is sanding and sanding and sanding?
Thanks again for all the tips.
Jim
Just as an added note...I haven't built a kit in 20 years....now I am reminded of why ARFs became so popular. heh heh. In honesty, I have to say I am enjoying building this monster, (TF giant scale P-47) but in reality...much of it is just dull labor. I mean really....how much fun is sanding and sanding and sanding?
Thanks again for all the tips.
Jim
01-11-2005, 06:56 AM
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RE: Final sanding...how do you "see" the tiny irregularities?
ORIGINAL: Capt Jim
In honesty, I have to say I am enjoying building this monster, (TF giant scale P-47) but in reality...much of it is just dull labor. I mean really....how much fun is sanding and sanding and sanding?
Thanks again for all the tips.
Jim
In honesty, I have to say I am enjoying building this monster, (TF giant scale P-47) but in reality...much of it is just dull labor. I mean really....how much fun is sanding and sanding and sanding?
Thanks again for all the tips.
Jim
Sand for a little while -drink a beer and check work. Repeat process until either the beer is gone, or the balsa.
01-11-2005, 09:08 AM
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RE: Final sanding...how do you "see" the tiny irregularities?
Since you will be glassing the plane you may want to investigate applying the glass with waterbase polyurethane instead of epoxy.
My results have shown it is a lot easier to sand and a bit lighter in weight. The structural strength it adds is slightly less than epoxy, however the application is substantially easier and cleaner, not to mention NO FUMES.
My results have shown it is a lot easier to sand and a bit lighter in weight. The structural strength it adds is slightly less than epoxy, however the application is substantially easier and cleaner, not to mention NO FUMES.
01-11-2005, 09:20 AM
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RE: Final sanding...how do you "see" the tiny irregularities?
HI Campy...yes, I have heard about that water based polyurethane process, and there are thread(s) describing its pros and cons. I have never tried it, and so I am inclined to stick with the stuff I know, but it sounds like it has some merit. One guy talked about simply shooting polyurethane from a spray can, laying the cloth on, and spraying on subsequent coats. That really grabs my attention. I consider the polyurethane like a paint, rather than a glue. I wonder what the bond strength really is as compared to the usual epoxys and polyesters?
I have a lot of experience with polyester resins and would use them rather than epoxy resin....simply because the epoxys are about 5 or 6 times more expensive, and I have no problem dealing with the fumes from the styrene monomers. I don't yet have a decision on these options, and I have lots of time to think about it. I've only just gotten the tail feathers done, and there's lots of sticks still left in the box.
Jim
I have a lot of experience with polyester resins and would use them rather than epoxy resin....simply because the epoxys are about 5 or 6 times more expensive, and I have no problem dealing with the fumes from the styrene monomers. I don't yet have a decision on these options, and I have lots of time to think about it. I've only just gotten the tail feathers done, and there's lots of sticks still left in the box.
Jim
01-11-2005, 10:26 AM
#13
RE: Final sanding...how do you "see" the tiny irregularities?
ORIGINAL: ED STEFAN
Here's a good way to take the boredom out of sanding. Take the project outside on a nice sunny day. [8D] Take all sanding materials, a chair and position the work so the sunlight hits the balsa somewhere between you and the shaded cooler of beer. Sand for a little while -drink a beer and check work. Repeat process until either the beer is gone, or the balsa.
Here's a good way to take the boredom out of sanding. Take the project outside on a nice sunny day. [8D] Take all sanding materials, a chair and position the work so the sunlight hits the balsa somewhere between you and the shaded cooler of beer.
Sand for a little while -drink a beer and check work. Repeat process until either the beer is gone, or the balsa.
01-11-2005, 11:13 AM
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RE: Final sanding...how do you "see" the tiny irregularities?
What a wonderful set of ideas. It reminds me of an internet thing going around recently. It was a new plan, cleverly devised, to rid our country of terrorists, neighborhood, by neighborhood. As I recall it went like this....
As part of their ideology, all terrorists, having a number of extreme religious beliefs, must never allow there eyes to see a naked woman...other than perhaps their own wife. Their penalty for committing such a sin is death by suicide. Their religion also forbids the consumption of alcohol. So...until further notice, all american women, acting as true patriots, in a dedicated effort to help rid our country of terrorists, will undress and parade naked around their neighborhoods every weekend from 1:00 till 3:00 PM. The men, in order to prove they are not terroists, will position a comfy chair out on the front porch, lawn, or other good and conspicuous viewing location. The men are then required to sit and watch the parade; and of course the men will be drinking beer as further evidence of their non-terrorist beliefs. Any males not participating are highly suspect.
Now fellas...you ought to see this gal next door...Oh boy, I just can't wait till saturday.
Jim
As part of their ideology, all terrorists, having a number of extreme religious beliefs, must never allow there eyes to see a naked woman...other than perhaps their own wife. Their penalty for committing such a sin is death by suicide. Their religion also forbids the consumption of alcohol. So...until further notice, all american women, acting as true patriots, in a dedicated effort to help rid our country of terrorists, will undress and parade naked around their neighborhoods every weekend from 1:00 till 3:00 PM. The men, in order to prove they are not terroists, will position a comfy chair out on the front porch, lawn, or other good and conspicuous viewing location. The men are then required to sit and watch the parade; and of course the men will be drinking beer as further evidence of their non-terrorist beliefs. Any males not participating are highly suspect.
Now fellas...you ought to see this gal next door...Oh boy, I just can't wait till saturday.
Jim
