REFLECTOR: Hatch and Seatbelt attachment points

[Chuck Harbert]

Darrell, sounds like your system would work well for attachment of the big 
hatch. I don't think the loads are that great and you're using the bolts in 
shear.  Just be sure that the front of the hatch attachment can't ever come 
up. I recently saw a Velocity that had the whole section (turtle deck?) 
above the canard removable. I wondered if in turbulent conditions if it 
might stress these attachment points. Again, if it broke off, it would ruin 
your day.

I take off my moderate size hatch very often so I'm glad all I have to do is 
pull a cable to release it. I wonder if you could use spring loaded pins 
with a cable to release it, so you wouldn't have to crawl under the panel?

Al said he was concerned with the seatbelt attachments and I agree with him 
that they were troubling. I went to 3/8" aluminum and extra layups over 
these hardpoints, but still not sure it's adequate. I wonder if these held 
in the crashes of Velocities? That would be the true test.

Chuck H

------------------------------------------------------
I am building an XLRG with the fast build fuselage and I did the "really big
hatch" mod.  I want to have the hatch cover secured with no visible hardware
from the outside.  I made a molded flange along the leading edge of the
hatch to hold the front in place.  Now I am going to put 2 or 3 hardpoints
along the aft edge to hold it in place from underneath.  I am going to use
large thumbscrews that I can reach from behind the panel.  I am thinking
1/4-20 will be strong enough but I may use 1/2-13 thumbscrews because they
have a larger head and would be easier to tighten by hand.  I may use fine
thread if I can find a fine thread thumbscrew I like.

Darrell Kufalk
> -----------------------------------------
> One important place in our airplanes where we have small bolt (I think it 
> is
> 5/16) threaded into ¼" aluminum, is the seatbelt anchors. The highest
> loading would be on the ones on the keel side (standard 3-point 
> restraint).
> I have doubts that this anchor would handle the roughly 12-15 g loading 
> that
> I think a restraint system should handle (I don't remember now where I got
> that number).  The threads may not be the weak point; it may be the glass
> plys holding the hardpoint.
>
>
>
> I had discussed this with Mark Machado at Velocity some years back, and he
> said they would do a test; but I guess that idea left when he did.
>
>
>
> Al
>
> -------------- next part --------------
> An HTML attachment was scrubbed...
> URL: 
> http://www.tvbf.org/mailman/private/reflector/attachments/20050721/81940aa7/attachment.html
>
> ------------------------------
>
> _______________________________________________
> Visit the gallery!  tvbf:jamaicangoose
>
> End of Reflector Digest, Vol 14, Issue 55
> *****************************************