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Author Topic: Why not use thicker wood for the tail?  (Read 3364 times)

Offline frank mccune

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Why not use thicker wood for the tail?
« on: March 22, 2016, 06:28:54 AM »
      Hello All:

      One of the things that bother me when I build a kit, is the 1/8" wood supplied to make the stab, elevator and rudder for a plane.  I usually add a bit of tail weight to get the plane to balance.  The weight often takes the form of 1/2" bolts, lead weight weights etc.  I have never had a profile that did not turn out to be nose heavy!

       Would it not be a better idea to make the tail parts from thicker balsa or perhaps a hard wood that would be heavier?  If the new wood would turn out to be too much weight, one could cut lightening in the tail parts and cover them for a finish. This would be stronger and avoid those unsightly add on weights.

      Anybody ever do this?

                                                                                                                  Be well,

                                                                                                                  Frank McCune
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Online Dave_Trible

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Re: Why not use thicker wood for the tail?
« Reply #1 on: March 22, 2016, 07:09:32 AM »
It wouldn't hurt at all to go a little thicker as long as you don't make the airplane tail heavy.  The stab would be more rigid too,  preventing flutter and flexing.  Kit makers have found thinning sections saves money even if it's not the best for the design.  Thin twisting wing flaps was the bigger problem in earlier times/kits unless the wood was rock hard.  If building a classic ship and wanting to maintain the original dimensions a layer of carbon veil will stiffen thin sheets pretty well.  This might be common where you are building a scratch copy from nice light wood of an old kit design that came furnished with harder heavier wood in the kit (maybe intentionally to use thinner sections).

Dave
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Offline Motorman

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Re: Why not use thicker wood for the tail?
« Reply #2 on: March 22, 2016, 08:23:02 AM »
I always use thicker wood than the kit has if only to get dubro 5/8" hinges installed see my post below. On my RSM Ringmaster kit I replaced the stab/elev with harder wood and used the supplied wood to make a hand launch glider, it was that punky. Ringmaster is a force in old time now.

http://stunthanger.com/smf/stunt-design/profile-tail-fail/

MM
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Offline MikeyPratt

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Re: Why not use thicker wood for the tail?
« Reply #3 on: March 22, 2016, 06:07:35 PM »
Quote from: Ty Marcucci on March 22, 2016, 12:45:58 PM
Two models I always replace the thin wood with are the Magician and Flite Streak. Those stabs are just too thin. Walter Umland puts out a 35 Magician with a thicker stab..3/3" is about the right size so the LE can be made sharper vs round for more stable flights. D>K

Hi Ty old buddy,
Yep your right on (on this subject anyway lol).  The last Magician I built was in the late 60'S and I used 1/4" balsa for the stab, and 3/16" for elevators.  Balance was almost perfect after that and flew really good with out flaps.

Later,
Mikey
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Offline Steve Helmick

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Re: Why not use thicker wood for the tail?
« Reply #4 on: March 23, 2016, 01:11:51 PM »
The Fast Richard "Excalibur" is another that just begs for thicker flaps and tail surfaces. The plans called for 1/8" for all that stuff. Dick probably had some really good light "C" grain for his. The one I built in '67-'68 got 3/16", but it was a mite tailheavy, too. Do what you think is right.  H^^ Steve
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Offline Dennis Toth

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Re: Why not use thicker wood for the tail?
« Reply #5 on: March 29, 2016, 04:33:24 PM »
For OTS and Classic I like to use rock hard wood of the same size as the original and cover it with 1/2 oz glass with epoxy which I scrape and toilet paper roll off. This helps with the balance, gives very stiff surfaces. For those ships that don't need a specific thickness I like to go thicker, shape the surface then to the 1/2 oz glass/epoxy/TP roll off, same for flaps. The scrape/TP roll off really reduces the weight and gives very good stiffness.

Best,    DennisT
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Offline Avaiojet

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Re: Why not use thicker wood for the tail?
« Reply #6 on: March 29, 2016, 05:54:50 PM »
Quote from: Dennis Toth on March 29, 2016, 04:33:24 PM
For OTS and Classic I like to use rock hard wood of the same size as the original and cover it with 1/2 oz glass with epoxy which I scrape and toilet paper roll off. This helps with the balance, gives very stiff surfaces. For those ships that don't need a specific thickness I like to go thicker, shape the surface then to the 1/2 oz glass/epoxy/TP roll off, same for flaps. The scrape/TP roll off really reduces the weight and gives very good stiffness.

Best,    DennisT

Dennis,

I used to do the same thing with polyester resin. It could be cut with acetone and brushed.

What Epoxy are you using? How do you thin it?

Charles
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Offline Mark Scarborough

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Re: Why not use thicker wood for the tail?
« Reply #7 on: March 29, 2016, 06:21:45 PM »
Quote from: Avaiojet on March 29, 2016, 05:54:50 PM
Dennis,

I used to do the same thing with polyester resin. It could be cut with acetone and brushed.

What Epoxy are you using? How do you thin it?

Charles
The problem with Polyester resin is that it shrinks,, and on thin material it will cause warpage,, along with polyester being rather painfull to work with as opposed to something like Zpoxy or other finishing resins ( EPOXY)
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Offline Target

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Re: Why not use thicker wood for the tail?
« Reply #8 on: March 29, 2016, 06:39:01 PM »
Charles-
I recommend not thinning epoxy. Just buy real epoxy, used for molded aircraft, such as Pro-Set, MGS (really great stuff) or even West Systems if you slum with any boat guys.
All of the above are much thinner than 1:1 epoxy that comes in bottles for glue. MGS is damn near like thin fruit juice in viscosity.
They all wet out fabric beautifully. If you need them thicker for some application, it's easy to toss in some colloidal silica, but it's hard to make epoxy resin thinner by adding a chemical without weakening it substantially.
R
Chris
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Offline Avaiojet

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Re: Why not use thicker wood for the tail?
« Reply #9 on: March 29, 2016, 09:28:31 PM »
Quote from: Mark Scarborough on March 29, 2016, 06:21:45 PM
The problem with Polyester resin is that it shrinks,, and on thin material it will cause warpage,, along with polyester being rather painfull to work with as opposed to something like Zpoxy or other finishing resins ( EPOXY)

Mark,

I haven't used Polyester resin in years. I've been using just silk or silkspan and applying it with clear dope, followed by repeated coats of dope.

I have also used Minwax over clear dope. No issues there. More weight?

I would like to try what Dennis does and uses on the ARGO II's flaps. I'm guessing that method is becomming popular. I'm trying to keep that model as light as possible. Be nice to have one really good airplane.

Chris, I wouldn't know what to thin Epoxy with? I only used it as glue. 5 minute and 20 minute.

I will do a search of the products you suggested and have a conversation with Dennis.

Guys, thanks for the replies and information.

Charles
 
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