[NSRCA-discussion] An education in balsa usage for pattern

[Earl Haury]

Sig's catalog contains a good description of the various grades / cuts (grain) / applications of balsa. 

The effort required to get the proper grades of balsa and the building involved drives most folks to composites. A few years ago I needed another Hydeout kit when they were out of production - so I scratch built a Hydeout from balsa - lighter than the composite version. Competed with it for a couple years / Nats, most folks didn't know that it was a "woody".  As has been suggested - building a balsa model from plans is very informative and rewarding.

Earl
  ----- Original Message ----- 
  From: Mike Hester 
  To: NSRCA Mailing List 
  Sent: Tuesday, March 28, 2006 5:53 PM
  Subject: Re: [NSRCA-discussion] An education in balsa usage for pattern


  ""It seems that everything I read of late seems to indicate that light weight and strength only come with composite construction.""

  What in the devil have you been reading? Ads for composite planes? =)

  Composites are easier to market, manufacture and sell. (Unless you're in dire need of carbon...you could be in deep dookie soon, if you're not already). Wood, for the purposes that we need it for, is impractical to mass pruduce. only about 1 of 100 balsa trees are in the 4-6 lb (contest) range, and the quality and weight vary wildly within that range. large well funded overseas companies can buy up large supplies and go through it, selling off the wood they can't use to other sources who aren't as picky. It's not that practical here in the states.

  However, sometimes you just can't beat a dead tree. I've heard you can't get a partner sized plane to 9.5 lbs with glow (hogwash) or that you can't make weight with an electric wood plane (also complete garbage, even with the heaviset equipment). Anyone that tells you that in this day, at this time, is either full of crap or trying to sell you something. Nothing wrong with the latter, as long as you know what you're really getting and why.

  Truth is, if you want the kind of plane that the japanese fly, you have to either build it or have it built. yeah I know about the Tojiero from a long time ago, and I also know it's light now (although a couple years ago it was rare to hear of one under 10.75)....but the design is a little lacking. Probably just fine for AMA classes I would suppose. 

  The best crash course would be to get a set of 2 meter plans from someone who sells 2 meter wood plane/parts stuff. To name a few, Mark hunt's Insight, Bryan hevbert's Patriot (slightly overbuilt, but still very awesome), or....well just look around. *cough* =)

  Here's a few weights to go by:

  1/16x4x36    12-16 grams
  3/32x4x36    18-22 grams
  1/8x4x36      24-28 grams

  For leading edges and 1/4 squares, buy sheets of 4-6 lb and cut your own stuff. if you buy 1/4" square sticks, they can be between 4 and 22 grams(!!!!) If you cut it out of a good piece of 1/4x4x36, it'll be about 3-4 (or less). Stay on the lower end of the scale for electrics, but examine each piece carefully. Some of the really light stuff is too brittle and cracks easily.

  In general, for sheeting you want A-grain. For stronger/stiffer stuff, you want C-grain. A bends easily across the sheet, C is stiffer.

  Wood reinforced strategically with carbon and a couple of odd composite parts make for an extremely light, strong and great lasting airframe. 

  BTW when you order it, don't be afraid to have it hand picked. Order more than you need, and weigh each and every sheet. use the best. there's sometimes a fee for hand picking, but you have some accountability if it's boat lumber.

  -Mike
    ----- Original Message ----- 
    From: White, Chris 
    To: NSRCA Mailing List 
    Sent: Tuesday, March 28, 2006 5:37 PM
    Subject: [NSRCA-discussion] An education in balsa usage for pattern


     

    Can anyone tell me where  a person can get a "Crash" course in learning about balsa weights and strength and its proper use in balsa pattern models.

    I notice a few years ago that in the 99 world champs most of the Japanese pilots models were balsa and light weight too.  It seems that everything I read of late seems to indicate that light weight and strength only come with composite construction.

     

    Thanks..Chris

     



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