Re: droped booms construction, pors and cons from Bill Gowen on 2006-06-15 ([Indoor

From: Bill Gowen <b.gowen_at_earthlink.net>
Date: Thu, 15 Jun 2006 09:42:07 -0400

Ignacio
The recently deceased Ron Green had an article in INAV 110 that explains the droop boom concept. In case you don't have access to the article I'll try to hit some of the high points.

For an F1D, Bernie Hunt decided that a 10" vertical gap between wing and stab should be about optimal. Some models were built with 5" wing and stab posts to get this gap. The problem was the weight penalty of the posts - which had to be reinforced to be stiff enough at those lengths. The droop boom cuts the post length down. So you're actually trading the increased drag from the boom for the decreased drag and weight of the long posts.

If you follow the whole theory and trim the model to fly with the motorstick horizontal instead of the more common practice of flying in a nose-up attitude there will be some savings in drag there.

The thing that I like the most about the droop boom design is that I have much fewer problems with these models on high power launches. I use them on A6, F1L, EZB, F1M and LPP. This year I converted my open PP to this design with not very good results. I don't really know why the LPP works well and the PP doesn't.
Bill Gowen
Decatur, GA USA

  ----- Original Message -----
  From: izgo
  To: Indoor_Construction_at_yahoogroups.com
  Sent: Thursday, June 15, 2006 9:08 AM
  Subject: [Indoor_Construction] droped booms construction, pors and cons

  Hello

  I see Olbill is a fan of this configuration. I would like to hear
  about advantages and disdavantages on this tipe of construction. I try
  a search on the Don's yahoo goups archive and was little what I
  found. (probably because I used bad keywords to search).

  So far the droped boom can lower the CG, reducing the nose up moment
  because the propeller trust. Also, but dont know how important can be,
  the tail will be more (or less) affected from downwash, turning into
  an advantage or disadvantage.

  And a clear disadvantage is the increase of drag, because the droped
  boom and extra posts holding tail surface. If I dont reasemble bad,
  Don have told that "all other parts of model, not taking into acount
  surfaces, contrubutes in 1/3 of total drag".

  So.. what are the pros and cons from your point of view?

  Ignacio



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Received on Thu Jun 15 2006 - 06:43:44 CEST