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From: Dale Rogers <rogersda@cox.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Subject: [FlyRotary] Re: foam-sicle (new ducts)
Date: Thu, 2 Sep 2004 10:41:34 -0400
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> From: "Marvin Kaye" <marv@lancaironline.net>
> Date: 2004/09/01 Wed PM 07:50:14 EDT
> To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>

...

> The term "BID" simply stands for bi-directional, and defines the cloth as 
> being woven with warp & weave at 90 degrees to each other.  This is in 
> contrast to "uni" (unidirectional) type cloth in which just about all of the 
> threads run in one direction, with single threads at 90 degrees every several 
> inches just to keep the primary ones intact.  

Ummm, Marv,

   What you gave is the description of "plain weave".
Rutan "BID" (RA7725) is not a plain weave.  It consists 
of paired strands of yarn crossing under/over crosswise 
pairs of yarn.  That's enough to make a major difference 
in the way the fabric "drapes".  It's like comparing 
gingham to challis.

Dale R.
COZY MkIV #1254


As for weights, you can find 
> much lighter fiberglass cloth at the local hobby shop, with material down into 
> the 1/2oz range.  For what you're doing, you would probably be well served 
> with some 2oz next to the mold, overlaid with several plies of 6 oz to add 
> strength to the exterior and the overall structure.  FWIW....
> 
>       <marv>
> 
> 
>   Since there are two ducts, you can surmise that I decided not to add another
>   scoop to the cowl.  I'm going to have one as an air box on the TB, with the
>   air horns inside.  The other goes on the bottom of the right radiator, where
>   the old hoses attached.  By the time I'm done, there will be about a 12 sq
>   in opening in the radiator duct where the new inlet duct will be added.  The
>   two new ducts will be joined by 3" ID tubing,  CEET for now, perhaps
>   something smooth walled later.  3" is just HUGE though, so it's hard to
>   imagine there will be any restriction now.  I may not get quite as much ram
>   air effect as I could with a dedicated scoop, but this system give me the
>   option of adding a scoop in a convenient location later, while still using
>   the air box that I'm making.
>   
>   Cheers,
>   Rusty (Frances turn North now)
> 
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