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Biulding the Perfect Sabots

Post about things you have launched or thought about launching. Also post about various materials used for building cannons. No posts about explosive projectiles!
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Unread postAuthor: Jared Haehnel » Thu Mar 20, 2008 7:58 pm

You see I was thinking about the cold and its affect on PVC when I initialy wrote it but I figured if I was wrong some one would let me know about it... so now that Carlman backing me up... I would wiat till it warms up a bit before testing it.
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Unread postAuthor: jackssmirkingrevenge » Fri Mar 21, 2008 4:46 am

Back when I was still into model aircraft I used to use blue foam for more peaceful purposes:

Image

Instead of a complex sabot, why not just use calibre width fins and a simple foam disk as a sabot, like so:

Image
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Last edited by jackssmirkingrevenge on Fri Mar 21, 2008 6:17 am, edited 1 time in total.
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Unread postAuthor: Jared Haehnel » Fri Mar 21, 2008 6:14 am

Nice plane Jack 8)
I'm afraid your image didn't quite pop up.
I was thinking about the cutting part and you might be able to make a coolie cutter by sharpening the edges of a section of PVC and tapping it down with a hammer. It should work for 1/2 and one 1 blue board anyway.
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Unread postAuthor: jackssmirkingrevenge » Fri Mar 21, 2008 6:17 am

There you go, fixed ;)

Jared Haehnel wrote:I was thinking about the cutting part and you might be able to make a cookie cutter by sharpening the edges of a section of PVC and tapping it down with a hammer. It should work for 1/2 and one 1 blue board anyway.


I use sharpened tubes quite a lot, I find that for expanded polystyrene type materials the best action is to cut in a circular motion like a hole saw rather than hammering it down, as this tends to cut rather than crush the material.
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Unread postAuthor: Jared Haehnel » Mon Mar 24, 2008 12:59 pm

If I understand this correctly...

If you have a two inch barrel using caliber width fins you are increasing the drag on the object...a trade off for stability. But if you want a higher velocity for longer distance smaller fins would be better.. the trade off is the dart is less stable...

In his case he is trying to get reasonable accuracy with a high velocity...
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Unread postAuthor: jimmy101 » Mon Mar 24, 2008 5:21 pm

Hey Jackssmirkingrevenge, any other thoughts on cutting blueboard?

Did you cut and shape the plane you posted yourself? How did you get it so smooth?

I've tried working with 3.5" blueboard and it always seems to tear and fragment. What is the best way to cut complex shapes?

My scroll saw seems to work OK but how do you do the more complex cuts, like shaping the oval of the fueselage or the airfoil shape of the wings? How do you smooth the surface after cutting?

Does anybody know if blueboard is strong enough to be used as a form in vacuum forming?
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Unread postAuthor: jackssmirkingrevenge » Mon Mar 24, 2008 11:41 pm

Jared Haehnel wrote:In his case he is trying to get reasonable accuracy with a high velocity...


It is a compromise, but if you're using a thin material for fins (say 1/64" ply sheet) the amound of drag you're adding for a wider fin is almost negligible.

Did you cut and shape the plane you posted yourself? How did you get it so smooth?


Yes I did. The fuselage was made in two halves, just like an airfix model, I cut the sheets to the correct thickness using a hot-wire cutter then used progressivly finer grades of sandpaper to shape it.

I've tried working with 3.5" blueboard and it always seems to tear and fragment. What is the best way to cut complex shapes?


For cutting I only use a hot wire cutter (I made it myself but you can easily buy one) or a very sharp surgical scalpel, the foam tends to dull the blades pretty quickly so you have to change them regularly to prevent it from tearing.

My scroll saw seems to work OK but how do you do the more complex cuts, like shaping the oval of the fueselage or the airfoil shape of the wings?


The fuselage is hollow by the way, as this was intended to be an indoor model I was doing my best to save weight. That was shaped with sandpaper. The wing on the other hand was cut from thin sheet (Which I made by having the hot wire cutter parallel to a flat surface and pushing the foam through, like a meat slicer) and I made the airfoil shape by wrapping it around some large diameter PVC tube then putting it in hot water to "fix" the shape.

I have a small booklet about the blue foam technique as applied to indoor model aircraft, if you're interested I'll try and find time to scan it.
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Unread postAuthor: Jared Haehnel » Tue Mar 25, 2008 6:26 am

Thats really cool Jack. I built the outdoor version of model airplanes. It was a lot of fun until you screw up and crashed them... then you have to pick up all those little balsa pieces and figure out a way to put everything put back together...

Its a fun hobby.
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Unread postAuthor: jackssmirkingrevenge » Tue Mar 25, 2008 6:37 am

Jared Haehnel wrote:Thats really cool Jack. I built the outdoor version of model airplanes. It was a lot of fun until you screw up and crashed them... then you have to pick up all those little balsa pieces and figure out a way to put everything put back together...


It used to be my major interest but it waned after I discovered spudding, somehow putting all that effort into a dainty little thing that flies around isn't as satisfying as blowing holes in things :roll: :D
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Unread postAuthor: Novacastrian » Tue Mar 25, 2008 6:43 am

jackssmirkingrevenge wrote:
Jared Haehnel wrote:Thats really cool Jack. I built the outdoor version of model airplanes. It was a lot of fun until you screw up and crashed them... then you have to pick up all those little balsa pieces and figure out a way to put everything put back together...


It used to be my major interest but it waned after I discovered spudding, somehow putting all that effort into a dainty little thing that flies around isn't as satisfying as blowing holes in things :roll: :D


BOOM i agree, however opening an already existing hole in a "Dainty" "thing" is much more pleasurable :wink:
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Unread postAuthor: Ryan00101101 » Tue Apr 24, 2012 10:56 pm

I found for a 2" air cannon I rip the blue foam board to pieces. The best method of shooting a big dart is to use paper towel and duct tape. Fold the paper towel in half then in half again wrap it around the dart till it makes a good gas seal and slides easily then duct tape it on there then use the blueboard foam on the front side of the projectile to hold it level with the barrel. I have made reebar arrows 4 - 5 feet long this way, and they do some serious damage. Plus everyone has paper towel and duck tape around. Another easy method for air cannons is to ball up plastic shopping bags so they fit perfectly then put whatever you want to blast out of it infront. Have fun and treat that potatoe gun like a firearm! :P
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