Easy to make fin sanding jig.

[bradycros]

The additional weight will only be in the very low grams range. So, no worries.

 

[Doggonewild]

So how did you do it? Would it work on the stubby elliptical cones they use on some of their kits?

 

[bradycros]

So how did you do it? Would it work on the stubby elliptical cones they use on some of their kits?

I am still putting information together. As you now know it's easyer to just do a task then it is to discribe doing the task.
I haven't worked one of their stubby cones yet, but yes it could work if you made a tool for the purpose.

 

[bradycros]

Go to the Scratch Built section. Open "Homemade Logo Rocket", go to page 2, post #53 and start reading. I'll probly do one more post to finish, but all the information you'll need to get started is there. Let me know if this works for you.

 

[bradycros]

The additional weight will only be in the very low grams range. So, no worries.

The cones are being weigh'd in grams.
#1: Out of the bag, surface sanded and hole put in the top.
#2: Finished making cone pointy.
#3: Still needs final sanding. Then will be ready for paint.

A differance of 6 grams from stock to modifiyed.

 

[sodmeister]

Geeze.....I missed this info.I was wondering how you made the NC pointy without the hat ,but did not want to ask for fear of hijacking this thread and going into another direction.
I`ll check the LOGO thread.


Paul

 

[sodmeister]

Very good build article you have going there.I don`t know how I missed it ,but sure am glad I found it !! You have some very good ideas and many of them pertain to Launch pad kits (one of my favorites)

And yet another use for JB weld....BRAVO !

Paul

 

[bradycros]

Are you going to show your build?

 

[Doggonewild]

I didn't plan on it, heheh. The tail cone is done, I think it will look really nice when it's painted. The thing holding me up is a little warpage when I put the CA on the fins, trying to get that straightened out. Plus I have a couple little things left on the other two rockets I'm working on, mainly the conduit on the little 1/23 scale WAC Corporal. Maybe I'll do a build thread for the Indigo when I start that. I sure would like to launch the Lance first before I start that though, to see how it holds up building very light. So many rockets, so little time.

 

[bradycros]

Here's another Lance photo for ya, www.wsmr-history.org/lance.htm

 

[Doggonewild]

Thanks again Bradycros for all your interest, pictures, and help. I still haven't gotten the warp out of the fins, my CA application technique needs to improve. I hurried too much, the cause of most shoddy jobs no matter what you are doing. I'm about to try a water mist and clamping over night. I do have confidence in my jig though, things were going great until shortly after using it.

 

[pcotcher]

Thanks for this thread guys - and for the ideas Doggonewild!

I've been working on a scratchbuilt Nike Ajax, and have been struggling with how to taper the fins. It's actually one of the biggest barriers that I face in wrapping up the project (that and the electronics for staging, DD, etc.)

It began life as a TLP kit, but if you read the thread, you'll see that I chose to pretty much scrap that kit and move on with a scratch effort.

https://www.rocketryforum.com/showthread.php?t=4222

I'm going to try and employ this technique to get the right tapers on all of the fins - the main sustainer fins are going to be a treat as they're LARGE, but with this, it should be doable!

Of course the bigger trick will be my SCUD fins, as those have to be double tapered to match to the vinyl details that I designed as the airframe details (the fins have to fit inside for it to look right!

Of course the question becomes - what do you do with diamond cross-section fins, once you get to that fourth edge? How would you mount something like that, and keep it flat?

Will post to my build thread as I make progress...

Of course, other ideas and suggestions for jigs are always welcome - I noted at least one mention of a jig for a circular sander...

Paul

 

[bradycros]

Thanks again Bradycros for all your interest, pictures, and help. I still haven't gotten the warp out of the fins, my CA application technique needs to improve. I hurried too much, the cause of most shoddy jobs no matter what you are doing. I'm about to try a water mist and clamping over night. I do have confidence in my jig though, things were going great until shortly after using it.

Bummer man. Now is the time to run around in circles screaming and pulling your hair.

I don't know if CA will soften up any when heat is apply'd. Most things do. Maybe you could blast it with a hand blower. If that soften'd it up to any degree you could place some thing hard on it immediately and then use your fingers for clamps, since the CA would cool of fast and get hard again. Hold the fin over the stove's heating element, just don't burn it up. Dip edge in boiling water? Just throwing out some plan B's for ya.

What's the stuff that's used on people that glue them selfs together? Nail polish remover I belive. If it softens up CA on people, it should soften up your CA soaked wood fin enough to bend it back into shape until it evaporates, yes? No? I'd wear some kind of rubber glove to avoid getting stuck to the fin. If the glove gets stuck you can sand it off. That's plan C.

I know you don't want to start over, but that might be plan D.

If it comes to that, I would soak the fin real good with CA BEFORE sand paper even touches the fin. Apply more if you sand into bare wood during the sanding. That might/could work.

 

[judo]

This may be the answer to my Doorknob fins as well. And since my daughter has taken up the guitar, strings should not be a problem. Which string is half of 3/16th of an inch?

 

[Doggonewild]

This is how I thought a diamond bevel could be done. You'd need three shims as Bradycros suggested earlier in the thread. Here's another one of my world famous Paint drawings, a side view. I think some rubber cement would keep things from moving around, and of course, this would be clamped onto the jig board, not just the shims and fin clamped together.

I certainly don't want to do the fins over, I'll get them straightend out somehow. Thanks for the suggestions on how I might do that. I have some acetone, which is basically fingernail poilish remover. That will be a last resort. I'll experiment on that demo fin first.

 

[Doggonewild]

For a 3/16" fin, you'd need a bass string, a .095 A. The actual diameter called for is .09375", but that's very close. Anything steel of that thickness would work. You might be able to buy a single A string at your local music shop, I don't know. I buy a whole set of four bass strings at a time for 20 bucks. They might even be doing a string job for a customer, so they might have some old ones for free.

 

[judo]

Thanks.

 

[Doggonewild]

I took the fins to the hot water tap and gave them a good shower for a minute or two on the trailing edge, where the warp problem is. The water ran right off, CA seems to be waterproof. I was skeptical but quickly sandwiched them between my carpenter's square and a piece of balsa scrap, clamped everywhere I could, and left for 24 hours. I couldn't believe it actually worked pretty well. It is very slight now on just two of the fins. Dipping in boiling water for a minute might be the ticket. I think it was the heat more than the water for sure.

 

[Doggonewild]

Here are the strings needed for fin thicknesses from 1/16 to 1/4 inch. A piano shop might have cheaper wire than buying guitar strings, I guess that part is up to you to check out

Fin thickness/ Wire gauge needed/ Closest guitar gauge
1/16" .031 .030 D
3/32 .047 .046 E
1/8 .063 .060 D bass
5/32 .078 .075 D bass
3/16 .094 .095 A bass
7/32 .109 .110 E bass
1/4 .125 .125 B bass

 

[bradycros]

I think it was the heat more than the water for sure.

How 'bout that. Water transfers heat. Who'da thunk it.

 

[judo]

Here are the strings needed for fin thicknesses from 1/16 to 1/4 inch. A piano shop might have cheaper wire than buying guitar strings, I guess that part is up to you to check out

My daughter says I can pick up a single string for a buck. I can afford that.

 

[Doggonewild]

How 'bout that. Water transfers heat. Who'da thunk it.

It was a slow experiment, just clamping didn't work, just cool water and clamping didn't work, next step was hot tap water. Boiling water I suspect works best, but I haven't tried it yet. A hot heavy iron might work, but I don't own an iron, I am a slob. I do own some water though I am also cheap, if this thread hasn't revealed that already, heheh. I haven't used CA much in the past, it makes me cry, so this is a learning thing. It does make a pretty sturdy fin though soaked into balsa.

Bass strings do cost more than regular guitar strings, but still shouldn't break the bank. But as a cheapskate, it's the principle of the thing.

 

[bradycros]

Let me know how it works out.

 

[judo]

Bass strings do cost more than regular guitar strings, but still shouldn't break the bank. But as a cheapskate, it's the principle of the thing.

Dang straight! It cost me $7.62 for a single string! There's a figure best expressed in millimeters!

The jig worked just as advertised though. I've got the "Seriously Beveled Fins" I've been looking for with out the ribs and sheet styrene.

 

[Doggonewild]

That's great! Glad it worked for you. Yeah, that's a lot for a string, I'll have to check into cheaper alternatives and post it. Cut into segments though, a guitar string could be used for a lot of fins.

Since I'm posting, I boiled the two worst warped fins, and it seemed to make it worse. I have one more idea with boiling to try, then I'm on to acetone.