Go Back  RCU Forums > RC Airplanes > ARF or RTF
Reload this Page >

Warped ARF Stab- How to fix it?

Notices
ARF or RTF Discuss ARF (Almost Ready to Fly) radio control airplanes here.

Warped ARF Stab- How to fix it?

Old 11-30-2008, 06:14 PM
  #1  
Jeff Worsham
Thread Starter
My Feedback: (28)
 
Join Date: Oct 2007
Location: Saratoga Springs, UT
Posts: 406
Likes: 0
Received 0 Likes on 0 Posts
Default Warped ARF Stab- How to fix it?

Hi All-
Finally getting around to assembling a 4 Star 60 ARF purchased back in March. Working a few mods 'glass cowling, enlarged rudder, CF pushrods, Venture 60 landing gear with pants, etc. So you can imagine my disappointment upon seeing the warped stab when I started to glue the hinges. Trailing edge of stab is bowed nearly 3/16". The Plastruct piece in pic is 3/16" stock. It's a built-up flat stab, sheeted with about 1/16" balsa. Is there any hope of straightening this out? Or do I have to build another stab? Thanks for any suggestions....Jeff
Attached Thumbnails Click image for larger version

Name:	Mk26017.jpg
Views:	12
Size:	61.8 KB
ID:	1081625  
Old 11-30-2008, 06:16 PM
  #2  
ChuckW
Senior Member
 
ChuckW's Avatar
 
Join Date: Jun 2006
Location: Clovis, CA
Posts: 5,165
Likes: 0
Received 2 Likes on 2 Posts
Default RE: Warped ARF Stab- How to fix it?

You can try bending it opposite of the warp and re-shrinking the covering but that may not help since it is sheeted. I would Contact Sig. They generally stand behind all of their products.
Old 11-30-2008, 07:05 PM
  #3  
flaminheli
Senior Member
 
Join Date: Dec 2005
Location: iola, TX
Posts: 1,345
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Warped ARF Stab- How to fix it?

I had the same problem once before. I removed the covering in the recommended area that was to be glued into the rear of the fuse. I then used a wet rag and applied a liberal amount of water to the balsa and then laid a heavy book on it over night and that removed the warp. I am not saying it will help your problem, but it did mine. Or you could do what ChuckW said and contact Sig.
Old 11-30-2008, 07:32 PM
  #4  
Jeff Worsham
Thread Starter
My Feedback: (28)
 
Join Date: Oct 2007
Location: Saratoga Springs, UT
Posts: 406
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Warped ARF Stab- How to fix it?

Thanks Chuck and Heli- I hadn't thought about calling Sig, will do that in the morning as they've always been known to be good people. If no help there, will try to re-warp it straight like Heli did before the last resort of building another stab. It's my first arf so would seem ironic to have to scratch-build a stab.
Old 11-30-2008, 07:40 PM
  #5  
red head
 
Join Date: Feb 2005
Location: Zephyrhills, FL
Posts: 2,102
Likes: 0
Received 1 Like on 1 Post
Default RE: Warped ARF Stab- How to fix it?

Both of the above answers are good ones. I'd inject some water ammonia mix and weight the heck out of it over night. If you have access to an injection needle you might be able to just inject, weight, and then seal the injection holes with an iron ENJOY !!! RED
Old 11-30-2008, 07:45 PM
  #6  
jrf
My Feedback: (551)
 
Join Date: Dec 2001
Location: Burbank, CA
Posts: 2,901
Likes: 0
Received 4 Likes on 2 Posts
Default RE: Warped ARF Stab- How to fix it?

If the stab were twisted, you would have to fix it. But why do you feel that a bowed stab is a problem? As I recall the 4 star has separate elevators, so you don't have to worry about a one piece elevator not fitting the warp. 3/16" of total dihedral (or anhedral) in the stab will have no effect on the way it flies. A number of full scales have dihedral in the stab and a few have anhedral. Old style pattern models often had anhedral, and a whole lot more than 3/16".

If heli's trick doesn't work, use it as is.

Jim
Old 11-30-2008, 10:36 PM
  #7  
ram3500-RCU
My Feedback: (221)
 
ram3500-RCU's Avatar
 
Join Date: Aug 2002
Location: n. canton, OH
Posts: 9,703
Received 8 Likes on 4 Posts
Default RE: Warped ARF Stab- How to fix it?

Personally, I would twist it just past straight and re-shrink the covering. It just might be all you need. You can usually put it between your knees and twist with one hand while heating with the other. I think it will work, but if not, you can always move on the some of the other good ideas listed above.
Old 11-30-2008, 10:38 PM
  #8  
captinjohn
 
Join Date: Jan 2002
Location: Hesperia Michigan, MI
Posts: 12,957
Received 4 Likes on 4 Posts
Default RE: Warped ARF Stab- How to fix it?


ORIGINAL: red head

Both of the above answers are good ones. I'd inject some water ammonia mix and weight the heck out of it over night. If you have access to an injection needle you might be able to just inject, weight, and then seal the injection holes with an iron ENJOY !!! RED
Is a mix better than strait ammonia liKe say a 50/50 mix? Thanks Capt,n
Old 11-30-2008, 11:03 PM
  #9  
ram3500-RCU
My Feedback: (221)
 
ram3500-RCU's Avatar
 
Join Date: Aug 2002
Location: n. canton, OH
Posts: 9,703
Received 8 Likes on 4 Posts
Default RE: Warped ARF Stab- How to fix it?

Ammonia bending is an art and not without its hazards. It is anhydrous ammonia (not your home stuff) that is used to soften the matrix that holds wood fibers together. It breaks down the hydrogen bonds within cell walls and within the lining matrix. This allows molecular movement when subjected to tensile or compressive forces (bending). Once the ammonia evaporates from the wood, new bonds are made creating a permanent set; in simple terms, this can be considered similar to the process of adding a permanent wave to hair. It is corrosive to some metals and hazardous to handle and breath. Also, it vaporizes and dissipates at atmospheric pressures and temperatures above -28F, so it is usually used under pressure in specially constructed tanks. Otherwise it is gone before the wood is plasticized. It can also be used in closed tank (baths), but not in open air. It just has no time to do it's thing at room temperature in open air. There is a lot to using this stuff and really, in this situation, water combined with heat (as in your sealing iron), would do just fine if you want to 'chemically' bend the wood. The ammonia method is more for plasticizing the wood and really making it pliable so it can be curved and shaped, and this takes a full bath in the stuff to work. You just want to take a slight curve out and straighten the wood. Just inject warm water and apply heat as you bend it back to straight. No ammonia is needed.

I am a carpenter by trade and have actually worked with wood in this way. It is fun and rewarding, but just not the best fix in your situation IMO. Way overkill.
Old 11-30-2008, 11:28 PM
  #10  
Jeff Worsham
Thread Starter
My Feedback: (28)
 
Join Date: Oct 2007
Location: Saratoga Springs, UT
Posts: 406
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Warped ARF Stab- How to fix it?

Thanks- I'd heard about ammonia way back in my free flight days 30yrs ago, seems people then thought it helped form balsa when soaked in a mix of ammonia/water. I am partial to a method which will be long lasting. The bow isn't centered in the middle of the stab, and I'm afraid that heating the covering alone while holding opposite bend will not be a long term fix, especially once it sets in the sun a few hours. Injecting warm water sounds like it might work, along with some heat during the "re-cure." Thanks for all the ideas!
Old 11-30-2008, 11:37 PM
  #11  
ram3500-RCU
My Feedback: (221)
 
ram3500-RCU's Avatar
 
Join Date: Aug 2002
Location: n. canton, OH
Posts: 9,703
Received 8 Likes on 4 Posts
Default RE: Warped ARF Stab- How to fix it?

If you use water and heat, just use a flat surface to (iron) it. It will be easy to over do it. I have, though, straitened wings using just the covering. It holds remarkably well under the pressure of shrinking, but that was more for twists.
Old 12-01-2008, 08:33 PM
  #12  
red head
 
Join Date: Feb 2005
Location: Zephyrhills, FL
Posts: 2,102
Likes: 0
Received 1 Like on 1 Post
Default RE: Warped ARF Stab- How to fix it?

Ram 3500, covered the use pretty good. I've used a mix ( about 50/50 ) and had good luck with it but that's me. I agree that it can be dangerous if you don't pay attention to what you are doing. ENJOY !!! RED
Old 02-16-2010, 11:24 AM
  #13  
Jeff Worsham
Thread Starter
My Feedback: (28)
 
Join Date: Oct 2007
Location: Saratoga Springs, UT
Posts: 406
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Warped ARF Stab- How to fix it?

Overdue Update- After trying all the ideas above (and more than once) I ended up calling Sig, explained the situation, and they replaced the warped stab. I can't say enough about how relieved and refreshing it was to find out that after all these years Sig remains the great company it's always been by practicing great customer service. Let's hope they get enough of our business to avoid the path to non-existance that so many other kit manufacturers have gone.

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.