My concern would be the effect on flutter characteristics of the wing.  In the certified/military world when external stores are added to a wing it requires analysis and testing to check the new modes that are introduced.  I don't know what analysis and/or testing Lancair did on the original design.  General aviation is much less stringent in flutter analysis than are commercial transport and military.  Ground vibration and instrumented flight test would be a good idea.

The following paper contains a number of flutter case studies some of which involved adding stores to wings.

http://www.n91cz.com/Flutter/Flutter-ADA328059.pdf

 

Chris Zavatson

N91CZ

360std

http://www.n91cz.net/

On Friday, November 1, 2013 7:15 AM, Ted Noel <tednoel@cfl.rr.com> wrote:

I asked this basic question a few years ago. In essence, Beech did this with some Bonanzas and Cessna did it with 310's. It turned out to increase acceptable gross weight because it changed the spanwise weight distribution to reduce flexing loads on the wing. With proper design, the tanks also acted like winglets to reduce drag in some flight regimes.

Ted Noel

On 11/1/2013 7:24 AM, JIM HANKINS wrote:

Does anyone know of a valid reason for not installing 15 gal tip tanks on a Lancair IVP turboprop?  I made provisions for

this when I was building, but to my knowledge it has not been widely done.  Adjustment of the angle of attack on the tanks would be welcome.

 

Most comments on this would be appreciated.

 

Jim Hankins

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