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Retractable fins

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: Ragnarok » Thu Apr 17, 2008 9:38 am

TwitchTheAussie wrote:Its easy with the right metals and an oxy torch

Would you really want to invest that much effort into a round that will be completely obliterated on impact?
I'd be prepared to make saboted finned round that I know I won't get back, but the effort required to make spring loaded fins is more than I would want to invest for a one use projectile.

Using fins (for enhancing accuracy) on a full bore projectile (higher drag) that could only be fired relatively slowly (thus with limited practical aimed range anyway).

The advantage of saboted rounds is that the fins are fixed, velocity is higher, drag is lower.
It's an easier to make round that will go further... no competition for me.
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Does that thing kinda look like a big cat to you?
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Unread postAuthor: Antonio » Thu Apr 17, 2008 9:46 am

jackssmirkingrevenge wrote:I think in the case of us humble amateurs, it's not really worth the trouble. Fold-out fins are undeniably cool, but you never get to see them work and you can achieve the same stability by simply hollowing out the tail of your projectile.


Yeah I think its easier to make the projectile stable by moving the center of mass forwards instead of moving the center of pressure(due to the air flowing past it) using the fins backwards.
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Unread postAuthor: daccel » Thu Apr 17, 2008 9:08 pm

Some good points, a sabot does seem to win out on this one. If it aint broke... One note though, the fins do add rotation which increases accuracy over a non-rotating mass forward design. However, that slight increase in accuracy would probably be negated by imprecise construction, and only noticeable at long range.
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Unread postAuthor: TwitchTheAussie » Thu Apr 17, 2008 11:59 pm

Ragnarok wrote:
TwitchTheAussie wrote:Its easy with the right metals and an oxy torch

Would you really want to invest that much effort into a round that will be completely obliterated on impact?
I'd be prepared to make saboted finned round that I know I won't get back, but the effort required to make spring loaded fins is more than I would want to invest for a one use projectile.
.


Itd still be a good job to do
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Unread postAuthor: Lentamentalisk » Fri Apr 18, 2008 2:48 am

daccel wrote:Some good points, a sabot does seem to win out on this one. If it aint broke... One note though, the fins do add rotation which increases accuracy over a non-rotating mass forward design. However, that slight increase in accuracy would probably be negated by imprecise construction, and only noticeable at long range.


This is not the case. The only way that the fins would add even a slight rotation (at the cost of forward velocity) would be if the fins were slanted, which is much easier to do on static fins, such as seen in saboted ammo, or if your spring fins were put on crooked, in which case it won't fly straight no matter what.
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Unread postAuthor: jackssmirkingrevenge » Fri Apr 18, 2008 4:42 am

Lentamentalisk wrote:This is not the case. The only way that the fins would add even a slight rotation (at the cost of forward velocity) would be if the fins were slanted


Not necessarily, if you give the fins an aerofoil shape the projectile will spin too.
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Unread postAuthor: tmacd995 » Fri Apr 18, 2008 10:50 am

I think what Blitz posted would be amazing, somebody make it and I will be happy to use it.
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