questions about sand paper

[woundedbear]

Hi everybody I hope your 4th of July vacation was a good one. I have a few questions about sand paper. What type of abrasives work best for shaping and finishing balsa wood. What grits work the best? I was thinking that 150 would be a good grit to start with, then I thought balsa wood comes in different densities (contest, soft, medium, hard, and extra hard) So I guess what I'm asking here is which grit should I use for shaping the different grades of balsa wood and which grit I should do the finishing work with? When using sand-n-sealer what grit should I start with and what grit should I use for the final finish work to make the balsa wood surface very smooth for covering the frames? Thank you for your replies and time

[Mitch]

WB

I do not know the grit, as I do not use sandpaper from the hardware store.

I always have 3 grits ready on my sanding blocks. The sanding block is important, so I have Course Medium and Fine paper

It is also important to choose the right wood for the right place on your model if you are building to fly. The only place I can see using hard wood that needs a lot of sanding is the leading edge spar. Most of this gets trimmed down by drawing a no. 11 blade. Then course sand paper and I'm done, maybe a touch of the medium. What ever seems to be right. More art form here, getting a feel of it rather than science.

Mitch

[heywooood]

Balsa is considered a hardwood - it isnt heavy but it is dense..
Typical coarse grit is 60 - 80grit
Medium is 160 - 180grit
Fine can be from 220 - on into the 400grit range and beyond.
I use 60 then 80 then 100grit for shaping and 'rough' sanding.
Then 120 to prep for filling - apply the filler like a mud coating - then back to the
60 - 80 - 100 then 120grit. When it looks like its ready to begin paint prep
I use 160grit then 180 - then 220grit.
Then a primer coat of either matte white or light grey depending on the finish color.
Then I sand that with 180 then finish with 220.
If that looks good I sand with 320grit and then wipe with a micro fiber rag soaked in denatured alcohol.
Now the base color coat - sand with 320 then 400 grit.
Then the final color coats.

[Bill Gaylord]

Hi everybody I hope your 4th of July vacation was a good one. I have a few questions about sand paper. What type of abrasives work best for shaping and finishing balsa wood. What grits work the best? I was thinking that 150 would be a good grit to start with, then I thought balsa wood comes in different densities (contest, soft, medium, hard, and extra hard) So I guess what I'm asking here is which grit should I use for shaping the different grades of balsa wood and which grit I should do the finishing work with? When using sand-n-sealer what grit should I start with and what grit should I use for the final finish work to make the balsa wood surface very smooth for covering the frames? Thank you for your replies and time

150 probably is about the most useful grit that I use, which is what I generally keep on the block. The problem with using finer, is that it doesn't deck hard glue well, and tends to follow dips and curves, versus decking them flat. When sanding across dissimilar materials such as filler, using light pressure with 150 grit works well. Finer grits won't deck the surface evenly, while coarser grits are simply too harsh. I've found sanding belts, held by hand, to be quite useful. They're reasonably stiff, but can easily be manipulated to sculpt curved areas. I use them for rough sculpting LE stock, for example.

[NavyAD1]

220 and 400 wet or dry wrapped or cemented to a block works well. You can go up to 600 on a sealed/painted surface and have a glass like finish.

[heywooood]

I always use a sanding block..but I use different sizes and shapes. I have a 'large' one for the fuselage and wing initial shaping. It is 3"w x 7"Iong with a handle on top. I use this one to sand wing and tail leading and trailing edges - the top and bottom of the wings, the fuselage top, bottom and sides, and the tail pieces.
Then I use a smaller one 2.5" x 3.5" for final shaping of the leading and trailing edges and cleaning up around the cowlings, seam sanding on the plastic wheel pants and the like - and overall finish sanding. And I keep some different diameter wood dowel on hand to use as blocks for contour sanding. 1" dia. Down to 1/8" diameter cut to about 3" long