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Howto: Bevel Plywood Fins?

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shockwaveriderz

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what is the simplest, quickest easiest method to beveling the edges of 1/8" plywood fins..... All I have is a dremel moto-tool and sanding blocks and I hate sanding with blocks...... actually I just plain hate sanding .......

should I draw on the fins the area to beveled?
 

powderburner

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If you want nice, even, clean bevels, and you want to do it freehand, then you are going to have to practice first for about a thousand hours (if you are as coordinated as I am)

If you want to do it neatly, you will probably have to set up some form of a tool, or jig. You could use an existing spacer block, set back some measured distance from the edge to be sanded, so that your sanding block hits (and sands) at a consistent angle.

I have seen some people (on the web) make a tool that sits on the bed of their belt-sander and holds the fin at the right angle, but now you are into a fancy tool fixture, to say nothing of a good floor-standing belt-sander, and we are rapidly getting away from your attempt to find a simple, quick, easy way to do this . . .
 

vjp

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To bevel a fin free-hand, assuming the bevel isn't too acute, this is the best method that I know of.

- Lightly spray the back of a sheet of suitable sandpaper with 3M spray adhesive, and press it down on a flat hard surface, like a piece of particle board or finish plywood.

- Hold the fins you want to bevel in both hands, raising the back edge (the edge opposite where you want to bevel) to the proper angle with your thumbs, and spreading your fingers across the edge you want beveled to provide even pressure along that edge, push the fin back and forth to sand the bevel. Maintain a constant angle while sanding, for a flat bevel.

I've done this with pretty decent results on balsa, if should work on thin, lite ply, as well, with the proper grade of sandpaper. Leave a few inches of bare surface in front of the sandpapered area, so you can rest your thumbs there and not sand them raw.:D

If you're working with thicker ply, or tough ply like birch, this method probably won't be very practical.

A spacer block, underneath the lifted fin edge, may help to ensure consistency, as well (instead of just eyeballing it).
 

powderburner

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shockwaveriderz' process is a very good one, and his description is good.
I would humbly suggest one key addition to his idea.
Before sanding, on the opposite face of the fin (the side your fingers will be pushing on) from the sandpaper, add a temporary stiffening member by taping on a stick of wood that extends across the entire width. Make sure your reinforcing stick is hard, straight, and smooth, and try to use a tape that is not too gummy (or else you will have a whole 'nother problem to deal with when it is time to start priming and painting). Push down on the stick, and the stick will push more evenly on the fin.
This is to help keep the edge straight and flat where you are sanding. It is very easy to get a little too much edge sanded off where your fingertips are pushing down, and a bit too little left behind in the areas between your fingertips. The reinforcing stick should give you a much nicer, more even bevel.
 

KermieD

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That's an excellent article!! For me, I usually just do a rough sanding down with a Dremel and then follow up with a sanding block, since I don't have a disc or belt sander. Plywood is pretty easy, as you can just look to make sure the laminating lines are straight. This won't give you the tolerances of some other methods, but it's not that hard to make tolerable looking bevels.
 

edwardw

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Beveling fins....ick. I really hate sanding, I really really hate sanding.

Here is how I do it - though I realize I have a couple tools to help with it.

I have a bench belt sander, it's about 24" long of belt on a table.

I have different blocks I cut for different angles. I just put the fin on the block and then slide into the belt to sand that bevel.

I have been of late trying to figure a good way so that I could do circular bevels with something and rocks back and forth, but no success.

Once I get that down I will try airfoil shapes...


Edward
 

Ray Dunakin

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Originally posted by vjp
To bevel a fin free-hand, assuming the bevel isn't too acute, this is the best method that I know of.

- Lightly spray the back of a sheet of suitable sandpaper with 3M spray adhesive, and press it down on a flat hard surface, like a piece of particle board or finish plywood.

- Hold the fins you want to bevel in both hands, raising the back edge (the edge opposite where you want to bevel) to the proper angle with your thumbs, and spreading your fingers across the edge you want beveled to provide even pressure along that edge, push the fin back and forth to sand the bevel. Maintain a constant angle while sanding, for a flat bevel.
This is pretty much how I do it, even with G10 fins.
 

el chubbo

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using a quick router setup with a bevel bit...

but for 1/8" fins I would agree that the hand-sand method is best....
 
A

Austin

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Like previously stated, you can get a 1/4-Round Bit for your router and make really good round edges...I have used this for R/C aircraft for more years than I care to imagine and it works great, even on balsa. I am with Ray though...I still hand sand G-10 and most ply, although I recently made a beveling jig for my table sander and am going to try using it on the Tres ply fins.

Carl
 

swimmer

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shockie,

I've been wanting to bevel fins also especially on rockets with 3/16" ply fins. I did some practicing with scrap ply before trying it on my new fins. Up till now I've just rounded them off. I used an orbital sander and some 220 grit paper. As I sanded back and forth I watched two things:

1. The space between the sandpaper and the fin surface furtherest from the bevel. I tried to keep it at 1/8".

2. Watch the lamination line on the first ply. When it reached around 3/16" from the fin edge I stopped. It took me around 20 minutes to bevel three fins.

Filp it over and do the other side the same. A little sanding to blend it all in and you are through. Takes a little practice but it is fun and the fin looks terriffic. I only did the leading and trailing edges. Check out the pic and see what you think. It can be done.
 

astrowolf67

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One thing I've been wanting to try, is to get a dremel lawn mower blade sharpening attachment, and replace the grinding stone with a 1/4" sanding drum, and see how that would do for beveling the tips of fins. Any one else tried it yet? Thought about it yet?
 

swimmer

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David,

I didn't think of that, very good idea, but you would need a way to feed the fin to the sanding drum without gouging. I tried using my Dremel with the biggest sanding drum on it I could find but I couldn't control it enough to make it even the length of the bevel. I was able to control the orbital sander because of the amount of surface provided by the disc area. One thing I did try was laying an 1/8" steel rod on the fin at intervals perpendicular to the edge I was beveling and allowing the sander to rest on it while beveling the fin edge. The closer or farther the rod was from the edge changed the angle of the bevel. This worked somewhat but I opted to not use a rod. I hope this isn't too confusing. I just wanted to tell you what I did that worked for me. I'm open for any ideas that will make this job simpler.
 

sandman

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I've seen 'em cut on a table saw, I think that's what midpwrguy uses but that seemed dangerous to me. His came out really nice but he started out with thick fins.

I was going to try and make a "bevel cutting jig" to use on my benchtop band saw. That might be safer than a table saw.

Sort of like the jig that Norm Abrhams uses to cut tenon on the New Yankee Wrkshop TV show on PBS. Only with a band saw.

I think that might give you a consistantly straight cut.

Straightness and consistancy is the problem

I just never got around to it.

I will.

sandman
 

swimmer

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Here is a pic of my zipperless design with the beveled fins.
 

rbeckey

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I saw an aluminum sanding block at the hobby shop. It had a v shape on one side and a couple rounded channels next to it. The idea was to put the sand paper on the aluminum block and use the underlaying shape to form the wood. I believe it was for building aircraft wings. I could try to find out the name if you would like.
 

Orbital

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I like the table saw idea.. I was thinking of using a raised panel door cutting jig with an 80 tooth blade for a nice clean cut..

:rolleyes:
 

edwardw

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I was thinking about the table saw idea. At my work we have a DeWalt 12" compound sliding mitre saw. I would set the it to 30 degrees, then line the edge of the fin up with the cut and then put a bevel on them with that. I might try that. I also might want to clamp it down so I have some fingers left :)

Edward
 

Hospital_Rocket

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I just picked up a dremel jigsaw that has a sanding disk attachment. I made up a template that attaches to the table and I can easily cut the bevels. The trick is still patience.

This makes short work of fin bevels and as a bonus you get a tool to cut the fin stock out with!

I just checked eBay and found a couple more...

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2385065320
 

Ryan S.

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you could always downscale this and then use a sanding block. I just say sanding block because I think the sander might rip the balsa apart
 

Hospital_Rocket

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Try this out for size:

Go to WWW.Dremel.com and look at their shaper/router attachment. It is called:

#231 Shaper / Router Table

Combine this with a foot operated speed control and you could probablu go to town on fins.

Al
 

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