I am building my first kit. A goldberg protege.I have sanded it with 400 grit,then 600 grit,and then 1000 grit.
I am going to cover with oracoat.Just how smooth will it have to be?

I would have stopped with the 200, but then I am not looking for a perfect finish--just one good enough to not have pimples and potholes after it's covered.

400 is were I would normally stop for a film finish. Oracoat (ultracoat) works great - you'll like it.

Always feel free to do some side experiments - especially if this is your first time building. Take a sheet of balsa and sand different areas with different grit papers, then cover it. You'll see and decide for yourself just how smooth you wish to go. Beyond 1 foot away, most of us won't see much difference, if any, between 400, 600, and 1000 under a film covering. But that's just our opinion, not yours!

Good luck - it's alway great to see someone willing to put the time into a nice finish!

Gary

You should have great results with the finish. My last kit a Midstar 40 I went to 400 and it turned out ok, but next kit I will go further.

flynte

THE SMOOTHER THE BETTER THE FINISH.

Use your index finger or thumb and slowly draw it over the surface of your plane. It if feels smooth and doesn't catch anywhere then it is probably ready to cover. Where ribs meet spars are places that need fill or sanding work and if you don't do that your covering job looks poor.

I Stop At 400Then Wipe With A Tack Rag And Then Vacune The Frame.Dust Is The Enemey.
Rember To Cover From The Back To Front So The Seams Point To The Rear.
Good Luck And Take Your Time.To Me The Build Is One Job And Covering the Other Job So I Don't Get Tired Of The Build.
Keep Us Up to Date On How It Is Going.
John

Sanding balsa wood very smooth isn't going to help much, you need to fill the pores with primer or sanding sealer, then get out the fine grades of sand paper. But if covering with film, unless the wood is course grained, this isn't necessary.

I don't sand finer than 200 grit. The 200 grit "scratches" in the surface are smaller than the wood grain "canyons". I cemented a 4" wide piece of
1/16" balsa onto a pine two by four, and sanded one half with 200, the other half with 400, and I don't believe anyone can tell the difference after covering with Monokote.

The main thing is to make sure all protrusions are sanded flat, like lumps of glue, etc. And get all sanding dust off before covering. Good luck!

Clair

I'll go as far as 400 in most cases. The key is in the after sanding clean up for a good film finish. John s3 hit it pretty well in his post. The only thing I do different is to take the airframe outside and use an air hose to blow out all the dust before I use a tack cloth. Also clean all the loose and floating dust out of the shop before you start covering or painting for a better finish.