REFLECTOR: Hatch and Seatbelt attachment points

[Pat Shea]

Most of the force from a crash will be in sheer.
That's what the filleted layups over the hard points
provide for.

Pat

--- Jim Agnew <jim_agnew_2 at yahoo.com> wrote:

> Chuck,
>  
> As far as the seat belt anchor points in the keel, I
> put the plates on the inside of the keel with the
> metal attaching construction adhesive (  Aeropoxy
> ES6228 ) and then did the bid layups on the outside
> of the keel.  You would have to rip the plate
> through the keel and extra bid layups.
>  
> Jim
> 
> Chuck Harbert <c.harbert at comcast.net> wrote:
> 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.

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