Bolt together construction-L3 Again!

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denverdoc

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For some of you who subscribe to other forums, I apologize, I know I have beat this subject weary, if not dead, but before risking a few hundred in materials, I'd like to run the almost finalized concept past you all. Bear with me if this is a bit tedious.

About 3 feet up the 6 inch bottom half, is a 1/2 inch CR which is epoxied in place(thrust
ring). This is the only piece epoxied to the airframe. The MMT is pretty much conventional,
three CR's around a 98mm by 42" motor tube: it slides into place and butts
up against the thrust ring. Between the bottom two CR's the fins sit per usual practice.
But the fins are not epoxied to the MMT. The fins resemble an I beam: strips of
1 inch spruce are epoxied to the G-10 at the top and bottom of the fin tabs on both
sides, and are drilled out to accept threaded inserts which are epoxied in place.
The fins are then screwed down vertically thru the respective CR's using good SS
bolts.

The airframe is obviously slotted to the end. The MMT slides in now that fins are
affixed, and 4 bolts secure the MMT in place, (I could use more obviously). As the
AF is Kevlar wrapped I dont think shearing at the bolt holes will be an issue. Finally
the tailcone is fitted into place and bolted to the aft CR thru sleeves running
parallel to its long axis. It has attached to its CR four AF wall thickness tabs
that fill the 1/4 inch exposed slots. The airframe bolts to it as well to provide
a little rigidity at the end.

Folks wonder why go to the trouble. Well the modular concept has appealed to me
for a while--and with the expense in fabric reinforcing the airframe ito say nothing
of the AF itsself in these dimensions. I want to be able to accomodate most any
k thru M motor made including hybrids. I want to be able to replace fins if I bust
one, and swap out FIN planforms depending on my mood and mission. G-10 ain't cheap
either though I found a great source for .125 (about 9 bucks a sq ft). Plus it
provides flexibility--say I want to fly with strap ons--simple just poxy on a pylon
with internal threading l(ike the fins) to the MMT of the strap-ons and bolt into
place from the inside of the AF. You get the idea.

So I open the floor to debate! Criticism, name calling, whatever--I want this to
be a good L3 job--some innovation yet SAF Eand successful!

John S
 
I'm going to guess your assembly will look a bit like this.

https://homepage.mac.com/wesrudy/NikeMMT.jpg
https://homepage.mac.com/wesrudy/NikeMMT2.jpg

This belongs to Jerry O'Sullivan. This quick switch MMT assembly gave him the latitude to change from Three M motors, to a pair of Ns or an O, or just a single M. He's been flying this setup for a while as these photos are three years old (at least) and it's worked very well for him. If you poke around his site www.vahpr.com he *may* have some build tips. He's changed the site a bit and I believe he dropped it on somewhere but you have to peruse a tad to find it.

Some of the ring build is here.

https://www.vahpr.com/n3_p1.htm

Chuck
 
Thanks a bunch--figured something this simple wasn't original, but on the other hand knowing its been done gives me some peace of mind and a reference for my sometimes skeptical (righjtfully so) TAP. Thanks again,
John S
 
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