Message-Id: <199812010117.TAA04489@arnet.arn.net>
Date: Mon, 30 Nov 1998 19:16:05 -0600
To: Marvin Kaye <lancair.list@olsusa.com>
From: Hannes & Benita TRNKA <hbtrnka@arn.net>
Subject: Re:De-Ice Boots
In-Reply-To: <3.0.3.32.19981130012032.02bdbe50@olsusa.com>
Mime-Version: 1.0

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>I have purchased de-ice boots but so far have only fitted them to the
>surfaces and made the openings for the air/vacuum fittings.  Expect to
>install them March/April.  I purchased them from Chuck.  I understand
>that they are designed for laminar flow wing, Beech Star Ship, I think.
>Chuck reports no significant change in handling or speed.  Hope he is
>right, but normally there is a few knots given up for the benefit.
>
>Regards,
>
>Gary Rodgers

In 1995 I considered installing the BFG boots on my IV-P, but had concerns
about them disrupting the laminar flow over the wing. I called Rick
McWilliams, the designer of the IV's wing, to ask  about his opinion of
boots on the IV, and he was very much in doubt of the wing maintainig
laminar flow with boots installed. He told me that the maximum "ridge" or
discontinuity on the forward part of the wing has to be 0.002" or less to
maintain laminar flow. As far as remember the TE of the BFG boot, even
though it is a low drag faired boot, is 0.007". The boot itself is also not
totally smooth. Even with vacuum applied it is wavy which can disrupt
laminar flow.

Back then I also talked to a Starship support engineer at Beechcraft and if
my memory serves me right he told me that the starship wing cannot maintain
laminar flow with the boots.

According to Lancair the IV loses about 25 mph flying through rain - the
raindrops disrupt laminar flow (I'd be interested in hearing numbers from
people other than Lancair)

I don't know for sure that the boots will have a negative effect on
performance - the only way to find out would be an actual flight test.
That's why I was wondering if somebody on this maillist knows of anybody
who has flown a IV equipped with the boots.

Hannes TRNKA