Rounding fin edges

[qquake2k]

Normally, I round the leading edges of plywood fins on a stationary belt sander. But I'm planning an upscale Sprint XL, and the shape of the fins don't lend themselves to easy rounding. Has anyone used a router with a piloted roundover bit for this? I have a router and table, but worry about controlling the fin as I run it around the bit. Does anybody use a Dremel router table? It looks like it would be ideal with a 1/8" radius bit.

https://www.amazon.com/dp/B0000302Y9/?tag=skimlinks_replacement-20

https://www.amazon.com/dp/B00004UDIJ/?tag=skimlinks_replacement-20



View attachment fin template.pdf

 

[ChrisAttebery]

I used a piloted 1/8" bit and a router table to shape the fins on my LOC Doorknob. It worked great.


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[JohnCoker]

+1 to the router table. I did the same thing with 1/8" thick G-10 fins for my Boosted Arcas.

 

[qquake2k]

I got the Dremel router table and a piloted 1/8" radius roundover bit. It works okay, but is a little flimsy. There is some movement of the Dremel when it's mounted. It "dug in" a little in places, and was easier to cut one side than the other, for some reason. A light touch and multiple passes is definitely in order. It works well around inside curves. I haven't tried outside curves yet. It will work, but I think a full size router and table would do better.

 

[ksaves2]

Geez, I wished I had the tools/stuff you guys have. Kurt

 

[qquake2k]

I spend way too much money on tools.

 

[afadeev]

Does anybody use a Dremel router table? It looks like it would be ideal with a 1/8" radius bit.

I used a piloted 1/8" bit and a router table to shape the fins on my LOC Doorknob. It worked great.

+1 to the router table. I did the same thing with 1/8" thick G-10 fins for my Boosted Arcas

Guys - thanks for the tool ideas and links!


I just ordered a router table setup for myself.

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[qquake2k]

Well, it works okay, but just okay. I think two of the problems are the relatively low speed of the Dremel, and the small diameter of the pilot. I need to dig out my big router and table. I'm convinced a carbide bit with a ball bearing pilot would be much smoother.

 

[JohnCoker]

It "dug in" a little in places, and was easier to cut one side than the other, for some reason.

After you do the first side, there isn't enough left on the other half for the pilot to ride against. That's why I taped a piece to the top side (see my pictures above); there's a solid surface for the pilot bit to ride against.

 

[qquake2k]

That makes sense. Thanks John!

 

[qquake2k]

The full sized router with a carbide bit and ball bearing pilot does work better. But I totally see what John is saying. So I lowered the bit a little which helped. It makes the radius slightly smaller, but does a better job overall.

 

[cjp]

Nice job on those fins Jim,really like the looks of this upscale.It's a great flier.:flyingpig:

 

[afadeev]

BTW, what's your take on rounding all four (4) fin edges of split fins vs. just two (2) leading and trailing edges of the split-pair?

I'm building my first split-fin rocket (MadCow Fire Flier), and the fins came pre-beveled only at the two leading and trailing edges of the pair (see pic below).
Was MC just lazy, or is there an aerodynamic reason for leaving interior edges square ?



a

 

[OverTheTop]

I have not done rounding of edges, but beveling using a Dremel on a router table with an angle jig works a treat.


Details here: https://forum.ausrocketry.com/viewtopic.php?f=6&t=5019&start=46

 

[qquake2k]

I have not done rounding of edges, but beveling using a Dremel on a router table with an angle jig works a treat.

What about using a Dremel chamfer bit?

https://www.amazon.com/dp/B000030305/?tag=skimlinks_replacement-20

 

[OverTheTop]

What about using a Dremel chamfer bit?

Looks good. Angle is a bit steep. Not sure how it would stand up to carbon fibre and G10. Sanding bobbins are cheap!

 

[qquake2k]

BTW, what's your take on rounding all four (4) fin edges of split fins vs. just two (2) leading and trailing edges of the split-pair?

I'm building my first split-fin rocket (MadCow Fire Flier), and the fins came pre-beveled only at the two leading and trailing edges of the pair (see pic below).
Was MC just lazy, or is there an aerodynamic reason for leaving interior edges square ?

I don't have any experience with this. I would leave the inner edges square, hoping to get the fins to whistle.

 

[jeff2space]

BTW, what's your take on rounding all four (4) fin edges of split fins vs. just two (2) leading and trailing edges of the split-pair?

I'm building my first split-fin rocket (MadCow Fire Flier), and the fins came pre-beveled only at the two leading and trailing edges of the pair (see pic below).
Was MC just lazy, or is there an aerodynamic reason for leaving interior edges square ?

View attachment 330245

a

Yes there's an aerodynamic reason not to bevel inside edges. I probably won't do a good job explaining it. The leading edge separates the airflow and the trailing edge brings that flow back together. If you bevel inside edges you are separating, joining, separating, joining the airflow. It would be a good project/experiment to see how that effects performance.

 

[amarillo_rocket]

This is what I use to round wood fins. Take a piece of 1" thick wood. Drill a hole 1/8" or so larger than the fin thickness and cut the hole in half. I place a piece of sand paper in the slot and hold the paper in place with my hand.

 

[qquake2k]

Now that's a clever idea.

 

[JohnCoker]

I had another opportunity to use a router to round fin edges, but this time I had to hold them in a vertical orientation with a jig because they had a profile applied.

 

[qquake2k]

Interesting method, John.

 

[blackwing94]

I just bought a Bosch router and jasper jig for cutting centering rings and bulkheads. For beveling fins, I was planning on trying a round over bit. Anyone else try that?

 

[qquake2k]

Yes. That's what this thread is about.

https://www.rocketryforum.com/showthread.php?142739-Rounding-fin-edges&p=1734002#post1734002