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NJNike
05-04-2008, 11:15 PM
I'm a few days into construction of my Nike-Ajax by The Launch Pad and I'm sanding all the fins and filling, but I've come to a problem with the "booster" section fins. They need that diamond airfoil shape but I'm absolutely terrible at getting anything close to what it should look like :mad: . Any special tricks out there? :confused:

barone
05-05-2008, 07:33 AM
I'm a few days into construction of my Nike-Ajax by The Launch Pad and I'm sanding all the fins and filling, but I've come to a problem with the "booster" section fins. They need that diamond airfoil shape but I'm absolutely terrible at getting anything close to what it should look like :mad: . Any special tricks out there? :confused:
Well, I don't know if it's special......

Draw a line on each side of the fin at the high point of the diamond. Put some masking tape on the side of the line that won't be sanded first. Then draw a line on the fin edge where the tip of the diamond is. Then take a sanding block with some 150 grit sandpaper and start whacking away at the balsa. I'll switch to a 220 or 330 when I get it close to final shape. Then do the same for the other end of the fin. The first side ia easiest since the fin is flat. The second side gets to be a little tricky since you've got an uneven surface on the sanded side.

That's a nice bird to build. Still got to get mine completed. Shaping the fins for the nose cone.... ;)

MarkB.
05-06-2008, 09:03 AM
I got one . . . make the fin in halves.

1) Rather than one 1/8 balsa fin, cut two 1/16 balsa fins;

2) glue a 1/64 ply, 1/4 inch wide strip to the length of the leading and trailing edges on one half;

3) glue the halves together;

4) mark and put some tape on the high point as Don describes in the previous post;

5) sand to the ply leading (or trailing) edge;

6) amaze yourself with how easy this is!


The ply keeps you from "oversanding"; try it.


Alternatively, rather than making halves, you could carefully slit a thick balsa fin and press the 1/64 ply strip into the edges. My hand's not steady enough anymore for that but you could try.

sandman
05-06-2008, 10:04 AM
Yes, the TLP Nike Ajax is a great model. Shaping the fins is a PITA and I just sanded them to an edge front and back and gave up on the sharp bend in the middle. It kept wanting to be curved in the center so I just stopped fighting it.

A better way is to cut the fins in two halfs top and bottom. Sand the taper to a triangle cross section them edge glue the halfs together. That's the way i do it in my kit.

Build the TLP kit light! It flys beautiful.

Go to Excelcior for a really nice set of decals for it! http://excelsiorrocketry.com/

BTW notice the great boost on mine. It wasn't until I was packing for another launch that I noticed only two motors fired on that flight...It still flew fine! :rolleyes:

NJNike
05-06-2008, 12:14 PM
Thanks for all the great tips, guys. I think I'm going to give them all a shot at some point just for the sake of experiencing each method. And thanks, Sandman, for the link. I will definitely have to place an order for those decals.

scigs30
05-07-2008, 12:15 PM
Here is an easy way, let me see if I can explain it:
1. Put tape in the middle of the fin at the highest peak and on the side that is not sanded first.

2. Put double sided 3m tape on the edge of a table where you are going to sand the fin. Put a piece of music wire down on the double sided tape. The wire should be as long as the edge of the fin and dia. should come up to the middle of the balsa.

3. Place the fin on the double sided tape with the tapered to be end up against the wire.

4. Now start sanding away. The tape on the fin will stop you from sanding too much and you will hit the wire at the tapered end so you don't sand too much.

5. Now do the other side and flip over the fin and repeat the process.

6. You are done and should have a nice diamond shape airfoil in no time.