REFLECTOR: Strake construction

Keith Hallsten KeithHallsten at quiknet.com
Sun Jul 29 00:46:26 CDT 2007


Doug,

 

You don't need to convince me of anything - it's your plane.  However, I
have a bit clearer idea of your intent.  

 

Be aware that the angle joints between the bulkhead pieces (and between the
bulkheads and the baffles, and between the baffle pieces) provide a bracing
effect for the bulkheads.  The closer to right angles they are, the better.
They are also a lot easier to fit when they are close to right angles.  The
baffle pieces should line up on either side so stresses will pass straight
through, without tending to bend the bulkheads or baffles.  I think you will
find that's harder to achieve when things don't intersect at nearly right
angles.

 

While the baffles are not heavily stressed, they are key to dividing the
strakes into cells - thereby bracing the top and bottom strake skins, and
helping to pass air and fuel loads from the strake skins to the spar.

 

Regards,

 

Keith

    

 

  _____  

From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Douglas Holub
Sent: Saturday, July 28, 2007 7:19 PM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Strake construction

 

Keith,

 

Maybe the bulkheads in my plans are different than yours. I've attached a
little sketch that shows the change. (The new bulkheads are in red; the
plans bulkheads are in black.) All I'm doing is eliminating a couple of
angles and running two bulkheads where four used to go. I'm giving up about
10 gallons of fuel by scooting the aft bulkhead forward a little bit, but
50-55 gallons is plenty for me. Plus it moves the fuel a little closer to
the center of gravity, which is a good thing. The more shallow angle of the
front bulkhead still allows the back seat passengers room for their elbows.

 

As far as a composite structures expert goes, Danny Maher says on the tapes,
"The baffles aren't that structural." That's why they only get 1 ply of bid
instead of two.

 

Doug

----- Original Message ----- 

From: Keith <mailto:KeithHallsten at quiknet.com>  Hallsten 

To: 'Velocity Aircraft Owners and Builders list' <mailto:reflector at tvbf.org>


Sent: Saturday, July 28, 2007 6:47 PM

Subject: Re: REFLECTOR: Strake construction

 

Doug,

 

I don't know exactly how you are planning to arrange the baffles, so I can't
comment on whether or not your arrangement will provide an equivalent
structural system to that specified in the plans.  However, it is your
responsibility to completely understand all of the implications of the
change.  If you don't have the background in composite structures design to
fully analyze the two systems for equivalency, get some professional help to
do so.  I suspect you will find that there are serious problems you haven't
recognized.  This is a major change, and cannot be done lightly.

 

Keith

  

 


  _____  


From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Douglas Holub
Sent: Saturday, July 28, 2007 12:55 PM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Strake construction

 

   Thank-you for your concern, Keith. When I said I was only using two fuel
bulkheads, I didn't mean that I wasn't using the normal number of fuel
baffles, and I'll still be installing those two small non-fuel bulkheads
(with the 5" access holes) between the spar and the aft fuel bulkhead. I'm
just using two fuel bulkheads that need to be sealed instead of the four my
plans call for. 

 

Doug

----- Original Message ----- 

From: Keith <mailto:KeithHallsten at quiknet.com>  Hallsten 

To: 'Velocity Aircraft Owners and Builders list' <mailto:reflector at tvbf.org>


Sent: Saturday, July 28, 2007 2:42 PM

Subject: Re: REFLECTOR: Strake construction

 

Doug,

 

Your photo shows that you are making a significant deviation from the plans
with your strake bulkhead arrangement, and I hope you have fully evaluated
the consequences!  Reducing the number of bulkheads will increase the loads
on the remaining bulkheads, and will also increase the bending moment in the
strake skins due to the increased span between supports.  The anti-slosh
effect of the bulkheads will also be reduced, increasing risk of structural
failure in turbulence.  The bond to foam is very weak, so increasing the
thickness of the foam core of a bulkhead will have only a very small effect
on the strength of the joint.  I suggest that you either do a complete
structural analysis to prove that the arrangement will be adequate, or else
go back to the plans!

 

Keith Hallsten

 

 


  _____  


From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Douglas Holub
Sent: Saturday, July 28, 2007 7:01 AM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Floaters

 

Thanks for the info. I found the red balls at www.fletchair.com. The new
part number is 401129-5. It's in section 28 of their online catalog. Below
it in the catalog is a seal with a hole in it (called "U-cup seal for AA1
fuel gauge") which might work well to keep the ball in the tube.

 

I hope to install my sight gauges next week. Attached is a picture of my
fuel tank. I wanted to keep it simple so that it would be easy to seal. So I
have only two fuel bulkheads, and I used 1" foam instead of 3/8" foam so
that there would be plenty of room for lots of goop on the top edge.

 

Doug Holub

----- Original Message ----- 

From: David <mailto:Dastaten at earthlink.net>  Staten 

To: Velocity Aircraft <mailto:reflector at tvbf.org>  Owners and Builders list 

Sent: Saturday, July 28, 2007 12:47 AM

Subject: Re: REFLECTOR: Floaters

 

Fletcher's and Fletchair were bought by Wilson a year or two again. The
number should work, but googling for fletcher's may be a dead end. 
I'd met mister Fletcher several times in the past, and admired him for
keepin the business up even into his 80's. 

Dave

PUSHERPILOT at wmconnect.com wrote: 

Chuck, 
I found the info on where I bought the red fuel balls: 

Fletchair, Inc 
9000 Randolph St 
Houston, TX 77061 
713  641- 2023 

Part No 5407 4001 4097 0757 
AA1 Fuel Float Ball 

I think that these are for a Grumman A/C 

This info is seven years old, but you can give it a try.  I installed wires
to keep the ball from going out the top or bottom. 

Good Luck, 
Mel Bina 

 
 
 
 
 





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