REFLECTOR: interference drag

[Douglas Holub]

I have been looking to doing something like this, but have struggled with how to make it all work with the cowling.  How will this fairing be carried through to the rear of the engine cover?
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I don't really know, yet. I'm just kind of winging it. I plan on butting the strake fillet up against the cowl fillet, with a 1" flange on the strake fillet overlapping the cowl fillet. I think I'll need to add a little triangle of fiberglass to the trailing edge of the wing where it meets the cowl so that the fillet radius will increase to infinity (become flat) there. I'll post some pictures when I'm done.

Doug
  ----- Original Message ----- 
  From: Brainard, Jerry 
  To: Velocity Aircraft Owners and Builders list 
  Sent: Tuesday, November 20, 2007 3:51 PM
  Subject: Re: REFLECTOR: interference drag


  It was my understanding that this was just cosmetic and not expected to have any structural capability.  As see it, it is a completed strake with shaped pour foam with some bid over it.  I guess the pour foam could break down over time, leaving a void that could be moisture collector.  Don't know if that's a real problem or not.  

  I have been looking to doing something like this, but have struggled with how to make it all work with the cowling.  How will this fairing be carried through to the rear of the engine cover?

  - jerry




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  From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On Behalf Of Ken C. Baker
  Sent: Tuesday, November 20, 2007 3:25 PM
  To: 'Velocity Aircraft Owners and Builders list'
  Subject: Re: REFLECTOR: interference drag


  Doug,

  Looks good! A word of caution though - most of the pour foams available on the market, even the very good ones, do not make good structural cores. They have very low pcf ratings, and during crystallization they form irregular cell structures. As well, they are prone to soft spots. They're great for shaping things that you will ultimately glass over - but it's important to remove the pour foam, and replace it with a structural core like 3/8" divinycell, then glass the other side. In other words, it's important to get that sandwich structure back in there - especially at a critical structural union like the strake/fuselage junction.

  Happy Building,

  -Ken Baker
  kenb at velocityaircraft.com
  XL-RG Hybrid-5 in Progress



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  From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On Behalf Of Douglas Holub
  Sent: Tuesday, November 20, 2007 12:00 PM
  To: reflector at tvbf.org
  Subject: REFLECTOR: interference drag


  I used pour foam to fill in the intersection between the strake and the fuselage, then shaped it with some 40 grit sand paper glued around a Clorox bottle. Here's what the fillet looks like with a Clorox bottle radius. By doing the top and bottom of the wings, strakes, and winglet intersections this way, I'm hoping to pick up a few extra mph.

  Doug Holub

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