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  #21  
Old 01-13-2007, 09:43 PM
John Brohm's Avatar
John Brohm John Brohm is offline
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Quote:
Originally Posted by CPMcGraw
I actually was thinking of aluminum instead of plastic. You're using paper clamps, which probably work just as good; but I still like the idea of the thumbscrew adjustment, meaning I can set the pressure instead of taking all-or-nothing.

Nice looking jig!


I've never liked the Estes Fin Alignment jig (even though they seem to be much sought after on eBay!) because, like Craig, I've found them finicky and somewhat imprecise; and being vertical, I don't like the potential for glue runs and sags. For a number of years, I've been using the tried & true matte board method. I've been picking up 8"x10" and 11"x14" matte boards at Michael's (in their framing department - you can usually get leftovers on the cheap). I've made up a family of templates (eg: BT-60/3 fin/3/32"; BT-60/4 fin/1/8"; etc, etc) that I use to hold the rocket and fins in a horizontal position (this by itself is not a new idea).

I layout the template as precisely as I can with compass and straight edge; I cut out all three (or four) fins, and then chamfer the points where the fin cutouts interface with the body tube (this allows the template to slide over the assembly without interfering with any glue alongside the fin joint). It's a method that's worked very well over the years and usually provides me with very precisely aligned, equally spaced fins. Since I like to surface my fins with tissue and dope before I glue them to the airframe, I find that the fin slots in the template have to be just a slight tad over-size so that the template will slide on without any binding.

I said all of that to say this: it would seem to me that Carl could generate an extremely accurate and comparatively inexpensive family of fin alignment templates with his laser cutter; with a bit of ingenuity, these could be setup on a horizontal bed with sliders, making the whole fin alignment process very fast and accurate; being horizontal makes it much easier to manage the glue (of whatever type one chooses to use). This setup allows the modeler to tailor his alignment jig to his liking (more or less sophistication), while keeping the whole thing inexepensive.

I'll offer up a couple of photos of my usual setup once I manage to get home to my shop.
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  #22  
Old 01-13-2007, 10:58 PM
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dwmzmm dwmzmm is offline
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Default LAUNCH Magazine # 3; SEMROC Ad on Page 20

Carl,

When I saw this ad, my first thought was the goodies shown on the right was a SEMROC
version of the "Designer's Special." Heck, you may want to gather up all those parts shown,
throw them in a box and sell it as such. I know I could find plenty of uses in building my own
designs! How about it?
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  #23  
Old 01-13-2007, 11:12 PM
James Pierson James Pierson is offline
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Lightbulb More Parts Choices.

More Parts Carl, Please.

I would like to see PNC from Semroc. Yep, thats right PNC from Semroc, at least two in every size from ST-5 to ST-16. The big reason WHY, is that some of my freaky designs are only flight stable if I add alot of nose wieght and this can only be done by using the PNC's and stuff them with clay. I don't believe I can get that many WL-7 on for enough wieght.

I would also like a little design variety as well using some hollow Transitions. Some of my designs lately have used the BMS Boattail in Rocksim. This boattail is great for a more retro rocket look. The main reason WHY is that you should never attach fins to a paper transition and solid transitions can only be used above the recovery device if they are solid.

What about a Semroc tube marking guide. Well at least have a small aluminum or brass angle stock. Be for warned about your door jams gentlemen, they are not all pertectly straight . Wasn't Me! Just a little carpenter joke.

What I really need access to buy is a 3/16" x 48" Maxi-Rod for those design that just won't take to a diet well.

Thanks,

James Pierson
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  #24  
Old 01-13-2007, 11:19 PM
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Carl@Semroc Carl@Semroc is offline
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Quote:
Originally Posted by dwmzmm
Carl,

When I saw this ad, my first thought was the goodies shown on the right was a SEMROC
version of the "Designer's Special." Heck, you may want to gather up all those parts shown,
throw them in a box and sell it as such. I know I could find plenty of uses in building my own
designs! How about it?
Did not think of that! We just gathered up some "blems" that were laying around and "posed" them.

The lack of larger printed chutes and manuals have kept us from doing the "specials."

One special I always wanted was a set of all the body tube sizes in very short (2-3") lengths. I have access to that now. When I am building a rocket, I use a short piece of tube to fit the nose cone, then sand it, fill it, and paint it. THEN I finsih the actual body tube. This keeps all the sanding and layers of filler coat off the final tube. The short piece is then thrown away. I used to think that everyone did that.
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  #25  
Old 01-13-2007, 11:22 PM
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Tau Zero Tau Zero is offline
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Thumbs up Preview: "Tau Zero" Fin Guides

Quote:
Originally Posted by John Brohm
I said all of that to say this: it would seem to me that Carl could generate an extremely accurate and comparatively inexpensive family of fin alignment templates with his laser cutter
Yeah, he's, uh (cough) workin' on it. (See photo below.)


Quote:
I find that the fin slots in the template have to be just a slight tad over-size so that the template will slide on without any binding.
I was thinking just today that I need to go down to the tool store and pick up some Dial Calipers to determine what the tolerance should be, since the prototype guides below fit *real* (i.e., "too") snugly.

We need to cut some "triangles" to allow room for the fillets, so the fin guide doesn't get glued to the rocket.


Cheers,
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  #26  
Old 01-13-2007, 11:24 PM
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CPMcGraw CPMcGraw is offline
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Quote:
Originally Posted by James Pierson
What about a Semroc tube marking guide. Well at least have a small aluminum or brass angle stock. Be for warned about your door jams gentlemen, they are not all pertectly straight . Wasn't Me! Just a little carpenter joke.


The house I live in was built in stages, in different decades, and I think they used a rattlesnake for a chalk line...

As for the marking guide, I'd like to see one as well.

Quote:
What I really need access to buy is a 3/16" x 48" Maxi-Rod for those design that just won't take to a diet well.


I just picked one of these up at Home Depot. You have to be careful, though, as not all of them are straight, either. Employees and customers don't always appreciate the model rocket flyer's need for a solid 48" of steel rod with NO KINKS.
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  #27  
Old 01-13-2007, 11:28 PM
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CPMcGraw CPMcGraw is offline
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Quote:
Originally Posted by Carl@Semroc
Did not think of that! We just gathered up some "blems" that were laying around and "posed" them.

The lack of larger printed chutes and manuals have kept us from doing the "specials."

One special I always wanted was a set of all the body tube sizes in very short (2-3") lengths. I have access to that now. When I am building a rocket, I use a short piece of tube to fit the nose cone, then sand it, fill it, and paint it. THEN I finsih the actual body tube. This keeps all the sanding and layers of filler coat off the final tube. The short piece is then thrown away. I used to think that everyone did that.


Call it a Motor Tube Assortment, with "lots of additional uses"...
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  #28  
Old 01-13-2007, 11:29 PM
James Pierson James Pierson is offline
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Talking Good one Craig

That guy using a rattlesnake for a chalkline "isn't the sharpest tool in the shed" now is he. LOL

I going to have to use that one at work Craig, that a good one.

For fin allignment, I have printed out the Centuri fin guide, set it on the floor and aline the BT on it with fin glued but not dry, look down from about and adjust the fins as necessary. Use the Force Luke, or your carpenter eye .

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  #29  
Old 01-13-2007, 11:33 PM
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CPMcGraw CPMcGraw is offline
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Quote:
Originally Posted by John Brohm
...I said all of that to say this: it would seem to me that Carl could generate an extremely accurate and comparatively inexpensive family of fin alignment templates with his laser cutter...


I made it a habit with the BARCLONE PDF plans to draw a fin guide like the one Jay has in his photo. (In fact, I think that's one I drew up for him on that project... ) I have found these simple cardstock holders to be just about as accurate, although I wished my own had been a bit thicker (and stiffer) at times. Carl's 0.07" cardstock would make ideal disposable guides which could be included in every kit at a nominal premium.
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  #30  
Old 01-13-2007, 11:34 PM
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Carl@Semroc Carl@Semroc is offline
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Quote:
Originally Posted by James Pierson
More Parts Carl, Please.

I would like to see PNC from Semroc.
We have checked into molds for nose cones. The best price I could find was $5K per nose cone! When I mentioned that to Bill Stine, he said I could get those in China for about $800. I mumbled that it did not look like we would be doing nose cones. I refuse to deal with China. I think I am too old to start trying to get along with them now.
/rant

We have done some work with resin cones using roto-casting. They work well, but are very labor-intensive. We are working on a resin cast nose cone similar to the PNC-50K, but it is not a high priority.


Quote:
I would also like a little design variety as well using some hollow Transitions.
We have done the BTC-55Z and are working on the BTC-70HZ that are hollow balsa.

Quote:
What about a Semroc tube marking guide. Well at least have a small aluminum or brass angle stock.
We do have a plastic angle we use with Scout groups, but it is not online. We are thinking of providing fin marking rings like Estes used to provide on some kits.

Quote:
What I really need access to buy is a 3/16" x 48" Maxi-Rod for those design that just won't take to a diet well.
When we do launch equipment, that will be added. The SLS series really needs that.
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