Beveling Hardwood Fins without a Router

[gdjsky01]

I just spent a good portion of two hours searching TRF (which is in and of itself often quite futile) looking for how people might put a symmetrical 1/4 inch bevel on the leading edge of hardwood fins (aka harder than balsa or basswood).
I have a Delta belt sander. You know, the kind with a 6 inch disc and a 4 inch wide belt. That is it. No table saw. No router table. Oh... I guess I do have a dremel as well.

And of course various sanding blocks and such.

My current idea (and I think its a bad one) is mark the 1/4 inch line, put several layers of masking tape along it, and manually hold it to the belt until TLAR on one side. Lather rinse and repeat.
Anyone have a lot better idea (other than buy something).

If there is a great thread on this, just let me know.

Cheers.

 

[cls]

I built a jig for the disk sander. It has a wide block at the bottom, and a piece of plywood at an angle in a slot on the block. The block was clamped to the disk sander table, near the down going edge. That way I can slide the fin edge across the disk edge.

Egads, terrible description, so sorry. Pretty sure I got the idea from one of the Apogee videos or books or newsletters.

Ok, I got first prize here for worst post ever, sorry.

 

[gdjsky01]

I built a jig for the disk sander. It has a wide block at the bottom, and a piece of plywood at an angle in a slot on the block. The block was clamped to the disk sander table, near the down going edge. That way I can slide the fin edge across the disk edge.

Egads, terrible description, so sorry. Pretty sure I got the idea from one of the Apogee videos or books or newsletters.

Ok, I got first prize here for worst post ever, sorry.

Picture worth a 1000 (or more) words?

 

[David_Stack]

John Coker put together a page showing how he does it (disc sander):

http://www.jcrocket.com/finbevels.shtml

 

[cls]

Ah great! John Coker to the rescue! Yes, one picture is what you need.

(Whew, so relieved I don't have to go in to storage to find the jig.)

 

[lakeroadster]

John Coker put together a page showing how he does it (disc sander):

http://www.jcrocket.com/finbevels.shtml

Thanks for posting this. Excellent!

 

[user 35280]

NCR has these,
https://northcoastrocketry.com/products/airfoil-assistants

 

[TheBob]

I glue down 60 grit to a flat piece of mdf. Tack with ca a spacer, cover with tape (so it glides better) and then I sand it by hand.

 

[TheBob]

That was 5ply 1/8. Mark a line parallel to the trailing or leading edge for setting the spacer. I use a scrap piece of ply first to set an angle that looks good (how far to set back the spacer). Spacer is 1/8 sq
Trailing edge I do two angles. Leading edge I router a radius then one angle.

 

[TheBob]

Finished profile

 

[gdjsky01]

@TheBob Your way seems WAY WAY WAY simpler. I don't have the inclination (pun intended) to build a jig. Thats a lot of work. I'll try the low tech approach. Thank you for sharing. (Plus coker's site barely loads. I had to hit the wayback machine)

 

[4regt4]

NCR has these,
https://northcoastrocketry.com/products/airfoil-assistants

I've used these. Found them a bit difficult to use. It's hard to hold the sandpaper in place, unless it's tacked down with a bit of adhesive. And if the wood is hard, it's a very slow go with 80 grit. I don't have anything coarser on hand.

What I did was to draw a line (this is for a 1/8" thick fin) maybe 1/16" from the edge. Take a sanding drum in a Dremel at the lowest speed and make quick passes at a 45deg bevel on each side. Don't even try to take it down to what would be a "finished" level. Just knock the corners off the edge of the fin. Then I use Apogee's T-bar aluminum sanding block to continue the process of just crudely establishing the contour. Then the NCR blocks to finish it up.

(Aerotech's plastic fins keep getting more appealing....)

Hans.

 

[Paul Howard]

I glue down 60 grit to a flat piece of mdf. Tack with ca a spacer, cover with tape (so it glides better) and then I sand it by hand.
View attachment 540883View attachment 540884View attachment 540885

As an RC Glider builder/flyer and Free-Flight Glider and Rocket-Glider builder, I really appreciate the Lo-Tech simpler approach. I've hand-sanded airfoils since being a kid using line marks, tape, sanding blocks, etc. I also like to put hardwood trailing edges on my RC Glider wings and sand them to a pretty sharp edge, it's all part of making something fly better! That said, the more 'bigger production jigs and power tools" is great too, I just don't have the room in my dinky house full of backpacking, skateboard and bow-making tools/paraphernalia Good thread!

 

[augendoc]

I’m one of the people who contributed to John Coker’s fin beveling page. The simple low-tech idea of gluing a spacer to your fin and hand sanding on a block should work great, but consider this: 1) the spacers need to be the exact same size and position on both sides of the fin, 2) mark the intended position of the rear edge of the bevel before you start sanding so you know how much to sand off on each side, and 3) consider using a small sharp block plane to remove the bulk of the material you would otherwise have to sand off by planing almost to the line in #2.

A tool like this sliding square from Lee Valley should work great for laying each spacer in the exact same spot on each side of the fin. Or you could make something similar. Here’s a pic of the tool.

 

[David_Stack]

I’m one of the people who contributed to John Coker’s fin beveling page. The simple low-tech idea of gluing a spacer to your fin and hand sanding on a block should work great, but consider this: 1) the spacers need to be the exact same size and position on both sides of the fin, 2) mark the intended position of the rear edge of the bevel before you start sanding so you know how much to sand off on each side,

I did something similar to @TheBob, but instead of placing the spacer on the fin I secured it to the same surface that I adhered the sandpaper to. That way I didn't have to worry about the bevel angle not being consistent from one side to the other...

The fin was affixed to a sanding bar, the edge of which rode against a 'fence', sliding the fin across the spacer and the sandpaper.

https://www.rocketryforum.com/threa...-dual-deployment-trainer.172528/#post-2274389

 

[gdjsky01]

@David_Stack
David that is a nice setup. I may try something similar. Confusion. Transfer tape is one sided. Like that used in vinyl cutting. What were you using? It suggests it had to be two sided tape... like carpet tape???? Maybe using rubber cement?

 

[David_Stack]

'Transfer tape' in the context I used it is the way 3M refers to their #924/926 tapes. It is a double-sided tape, effectively two removable paper carriers on either side of an adhesive layer/film:

https://www.3m.com/3M/en_US/p/d/b40065866/
I first began using it too many years ago to apply balsa skins to foam core R/C sailplane wings (nod of credit to Bob Dodgson/Dodgson Designs).

Something similar is packaged in those window winterizing film kits that you can get at places like Lowes and Home Depot (https://www.lowes.com/search?searchTerm=window winterizing film). I don't know if you can buy that tape separately, but the 3M 924/926 is available from various retailers (disclaimer: for what 3M charges per roll, it may be less costly to buy one of those window winterizing kits).

 

[TheBob]

Paper is glued down to a mdf board with medium strength contact cement spray.
Spacer thickness and placement have to match on both sides.
Run the fin on the sand paper, not the spacer.

 

[TheBob]

I tack the spacer on with CA. The CA can be removed with acetone

 

[gdjsky01]

@TheBob and @David_Stack Thank you both. I do not have a wide piece of aluminum as shown, but think I have a suitable substitute. I do have some aluminum angle channel that should work. Amazon tells me I'll have the 'Transfer Tape' tomorrow. I'll try an find something to practice on. The angle is not really too important as its an 'own design' scratch build. But I am using some 3D rocketry fins I bought years ago. Not like I can replace em.

Too bad I don't have my ceiling tiles where I used to build by wooden sailplanes... long gone... it and the sailplanes... no place to fly em. I might add THIS IS WHY TRF is so great and deserves our support. (IMO)

OT: Who runs TRF these days?