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Old Apr 02, 2012, 12:00 PM
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Sure Keith, Perfect was very good, and the mods made it even better, but I believe evolution will go on
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Old Apr 02, 2012, 01:07 PM
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The larger the fin is, the more dihedral is needed to maintain spiral stability and vice versa. The popularity of Kolb joiners would then suggest that the Perfect had too large a fin.
Old Apr 02, 2012, 01:46 PM
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Quote:
Originally Posted by vespa View Post
The popularity of Kolb joiners would then suggest that the Perfect had too large a fin.
Or that people now prefer models with more lateral stability than was popular before Dr Drela popularised this.

Neil.
Old Apr 02, 2012, 03:15 PM
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Originally Posted by vespa View Post
The larger the fin is, the more dihedral is needed to maintain spiral stability and vice versa. The popularity of Kolb joiners would then suggest that the Perfect had too large a fin.
If I remember Perfect modifications right, it happened the other way round. More dihedral came first, larger rudder was relatively late mod.
Old Apr 02, 2012, 04:44 PM
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Anyone notice the fin "wobble" or flex in the video pointing towards the tail that Jojo posted?, seems like the fin/rudder removable portion looks almost loose.
Old Apr 02, 2012, 04:50 PM
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s2000 - your are right. I took a closer look at the video. That fin is wobbling all over the place. I hope they get that issue resolved in the production version. It would a shame to see such a beautiful plane go in because the fin blew off.
Old Apr 02, 2012, 05:00 PM
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I think it is just normal flex under flight loads. Early in the video where he shows the fin view during launch, there is a large rudder input. Under launch loads, things are going to flex. I'm pretty sure that none of this flex is visible from the ground. I'm sure that if you took a video of the tail of most modern F3J models you would see this type of flex. I think having the stab in front of the fin just makes it look worse than it really is.

Tom
Old Apr 02, 2012, 05:38 PM
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I feel fairly confident in saying if that fin was a permanent part of the fuselage it would not be wobbling that much, there are some strange Gremlin's at the base of that fin that are not natural flex. Yes sure any modern ship has some flex, but not this kind. I'll hang on to my Aspire for now.
Old Apr 02, 2012, 09:44 PM
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What are the aerodynamic, including airfoil, and structural differences between the Kolb Prestige and the Samba Pike Perfection?
Old Apr 02, 2012, 11:36 PM
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You could likely either glue the fin solid to the base, or temporarily with silicone type adhesive and tape as usual.
Either one should eliminate or minimize any wobbling from clearance between the tube and joiner, I would think.
Old Apr 02, 2012, 11:49 PM
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FWIW the new Supra have the same problem. The fin/rudder is slid on the back of the boom and a pin goes through the rear retaining ring. While practicing for the last F3J WC we noticed the severe movement of the fin, especially during launch. The fix was/is simple, tape around the front ring and partway up onto the fin to secure it. Probably all thats needed in this case as well.
Old Apr 03, 2012, 01:09 AM
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Guys, that very slight movement of the fin is a fraction of the slop that can be seen in every v-tail ever made. Furthermore, that slight movement pales in comparison to the boom flex. Don't worry about it.
Old Apr 03, 2012, 07:35 AM
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Originally Posted by lesterpk View Post
FWIW the new Supra have the same problem. The fin/rudder is slid on the back of the boom and a pin goes through the rear retaining ring. While practicing for the last F3J WC we noticed the severe movement of the fin, especially during launch. The fix was/is simple, tape around the front ring and partway up onto the fin to secure it. Probably all thats needed in this case as well.
Just to have a removeable fin, makes the Supra, special. It is worth the work to secure the fin.
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Old Apr 03, 2012, 08:15 AM
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Just to have a removeable fin, makes the Supra, special. It is worth the work to secure the fin.
The way how fin attachment is done in Perfection is actually very std F3X technology - same idea used in 2-piece v-tails all the time. The fin is quite large, but basically I see no reason why the attachment would not be reliable.
Old Apr 03, 2012, 08:43 AM
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So I guess the moral of the story is, I need to just go have fun with my airplanes and not worry about what a camera shows, and please, nobody stick a camera pointing at the tail of a V-tail! I don't want to know!


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