Jig for sanding fin airfoils?

Anybody every see a jig for sanding quick and accurate airfoils and round overs in balsa fins?

I am generally lazy but expect perfection.

Not me, but I wanted to post so I wouldn't miss it in case someone posts.

Clamp a guide board over top of correctly sized sandpaper for type fin material.

Clamp properly sized shim for elevating fin to proper bevel and distance from guide to get it.

Slide fin stock back and forth till you get bevel on front.

Then flip to back and bevel also.

This was a large fin 11inch root. with 15 degree bevel. shim was 2inch from guide and thick paint stirrer used.

For smaller fins just scale it down.

For balsa this works pretty good once you get the hang of it – it takes practice to keep things even:

Master Airscrew Razor Plane

Credit goes to Tim from Apogee for the suggestion.

i use a mouse sander. works prettty good. no pressure just let it do the work

blackjack2564 said:

Clamp a guide board over top of correctly sized sandpaper for type fin material.

Clamp properly sized shim for elevating fin to proper bevel and distance from guide to get it.

Slide fin stock back and forth till you get bevel on front.

Then flip to back and bevel also.

This was a large fin 11inch root. with 15 degree bevel. shim was 2inch from guide and thick paint stirrer used.

For smaller fins just scale it down.

Click to expand...

I made one that is similar but does not use clamps. I will post pics next week.

I've wanted to create (or buy) a jig for airfoils and bevels for LPR birds but met with only limited success.

The best I've seen so far is the jig Bradycros showed in his post here. Scroll down to posts 73-85.

During the winter, or maybe spring, I attempted to create something similar that would work for me. Again, I'm going for smaller fins as I'm an LPR guy just barely peeking into MPR territory with the occasional E engine flight.

I started with something conceptually similar to what Bradycros did but had trouble holding the (small) fins steady while sanding them. I moved on to what I thought would be an improved design and it failed miserably. I then tried some implementations where the sandpaper was held stationary and the fin moved back and forth on some nice European-movement drawer glides. This had promise but still didn't do a better / more accurate / precise / easier job than just holding the fin at the edge of a table and using a sanding block manually.

In disgust I set the project aside until later. I think I had four prototypes, which mostly still sit in my build area, mocking me.

I think for small fins a manual approach tends to be easier; for me larger fins would be more ammenable to a jig approach as shown a few posts up. That shimming probably wouldn't work for a 1 inch fin for BT-20 :grin: . As I climb the ladder in power I will eventually get back to this project. But I'm in no hurry.

Meanwhile, I continue to watch this thread for any insights it may deliver.

Marc