REFLECTOR: Strake construction

Sat Jul 28 21:19:22 CDT 2007

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 Hallsten 
  To: 'Velocity Aircraft Owners and Builders list' 
  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

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  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 Hallsten 

    To: 'Velocity Aircraft Owners and Builders list' 

    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

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    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 Staten 

      To: Velocity Aircraft 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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