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TD-3 , wing issue

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TD-3 , wing issue

Post  swift53 on Sat Oct 14, 2017 2:13 pm

I have a NOS TD-3, only problem is that there was weight on one of the wings, and has slightly lost the
convex shape. Any suggestions on how to take the concave out back to convex?

Thank you.

Regards, Alberto
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Re: TD-3 , wing issue

Post  Marleysky on Sat Oct 14, 2017 3:09 pm

Hey Alberto!  Welcome to the forum.  The TD -3 is the one with the thin plastic hollow airfoil wing?  That would be difficult to try to re-shape. Hopefully someone who's done that type of repair will jump in and help you out!

Here's a linc to the owners manual with tips on how to repair the plastic body.
http://www.mh-aerotools.de/airfoils/documents/cox_td3_instructions.pdf


Last edited by Marleysky on Sat Oct 14, 2017 3:14 pm; edited 1 time in total (Reason for editing : Owner manual linc)
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Re: TD-3 , wing issue

Post  swift53 on Sat Oct 14, 2017 4:30 pm

Hello Marlesky, good tips on the manual, but nothing on this.

On a squeezed plastic bottle, you can just blow it back to shape,

but this will not work on the wing, and even if manage to inflate, it will shrink back.

There has to be someone out there with the 'knowledge'

Thank you.

Regards, Alberto
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Re: TD-3 , wing issue

Post  NEW222 on Sat Oct 14, 2017 7:52 pm

The thing I would try is to have something solid in the shape you want, a bit smaller may be better. Then, carefully heat up the wing and hold around the shape you had earlier. You can also secure the wing to your object then heat carefully and evenly. Allow to cool and remove.
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Re: TD-3 , wing issue

Post  NEW222 on Sat Oct 14, 2017 7:54 pm

Sorry, please disregard my post. I was thinking one piece in an airfoil. I did not realize it was hollow and airfoiled on top and bottom.
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Re: TD-3 , wing issue

Post  swift53 on Sat Oct 14, 2017 8:04 pm

Only thing that popped in my mind, was 2 part foam that would expand, but possibly very difficult to control,
not to mention the inner cables for the bellcrank.

Regards, Alberto
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Re: TD-3 , wing issue

Post  Oldenginerod on Sat Oct 14, 2017 10:38 pm

I like the idea of inflating the wing back into shape. If you were able to induce a regulated supply of air, say 2-3 psi (just below the pressure that the concave section will pop out at), then heat the area gently until it expands into shape, take away the heat and it should reharden quickly with the constant airflow. You could try to seal leaks in the wing with tape, depending on how much air leaks out, but as long as you have a reasonable flow from a compressor that you can regulate the pressure of, I think it should work.

Rod.
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Re: TD-3 , wing issue

Post  KariFS on Sun Oct 15, 2017 3:13 am

How about using a suction cup to pull up the area in question, and then gently heating the edges of the dent with a hair dryer or such?
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Re: TD-3 , wing issue

Post  swift53 on Sun Oct 15, 2017 3:31 pm

Will try both, the suction cup and the gradual inflation. So far, the best solutions Smile

Cannot try it until next month, but will post results.

Thank you!

Regards, Alberto
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Re: TD-3 , wing issue

Post  pkrankow on Sun Oct 15, 2017 5:15 pm

Oldenginerod wrote:I like the idea of inflating the wing back into shape.  If you were able to induce a regulated supply of air, say 2-3 psi (just below the pressure that the concave section will pop out at), then heat the area gently until it expands into shape, take away the heat and it should reharden quickly with the constant airflow.  You could try to seal leaks in the wing with tape, depending on how much air leaks out, but as long as you have a reasonable flow from a compressor that you can regulate the pressure of, I think it should work.

Rod.

A blower puts out that kind of pressure. A hair dryer maybe, if it has a cold cycle.

Phil
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Re: TD-3 , wing issue

Post  swift53 on Sun Oct 15, 2017 7:22 pm

A hair dryer will work well for the heating part. For the inflating, a compressor with a football needle will have to
be the way to go (I think)...

Thank you.

Regards, Alberto
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Re: TD-3 , wing issue

Post  Oldenginerod on Sun Oct 15, 2017 7:37 pm

swift53 wrote:A hair dryer will work well for the heating part. For the inflating, a compressor with a football needle will have to
be the way to go (I think)...

Thank you.

Regards, Alberto
If using a compressor be very careful. You don't want to split the wing with too much pressure. The compressor will need to have an adjustable regulator, like for spray painting. I would gradually increase the pressure from zero until the dent just starts to come out, not more than a couple of psi, then turn back the pressure so that it's just below that point. Once the dented area is heated it should inflate into shape without overdoing it. Once it comes into shape, stop heating but allow the air to keep flowing to cool it. If it pops back to where it was when the pressure is off, try just a little more heat.

*Please note, this is only a theory and hasn't been tried by me, but it makes sense to my way of thinking.
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Re: TD-3 , wing issue

Post  swift53 on Sun Oct 15, 2017 7:56 pm

Extremely careful...

first week on Nov. we shall know. Smile

Kind regards, Alberto
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Re: TD-3 , wing issue

Post  dckrsn on Sun Oct 15, 2017 8:30 pm

Hi Alberto, and welcome.
This is an interesting topic. I don't have much to add, except
you might consider using a bicycle or air mattress pump.
A hand pump should give you plenty of airflow control.
Bob
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Re: TD-3 , wing issue

Post  roddie on Mon Oct 16, 2017 9:45 am

dckrsn wrote:Hi Alberto, and welcome.
This is an interesting topic. I don't have much to add, except
you might consider using a bicycle or air mattress pump.    
A hand pump should give you plenty of airflow control.
Bob

As anxious as I am (and probably the rest of us too..) to see if you can fix that wing.. I'm actually glad that you're waiting until next month. In the meantime you may get more replies to this topic with other ideas to consider.

I think that the "needle" for inflating footballs etc. is a good idea.. as long as you can seal the wing airtight.

I'm known for my crazy ideas.. so here's one to consider..

Firstly............ the wing should be warm.. and your workshop should also be warm. If the wing is cold.. there's more risk of cracking it when trying to reform it.

You may not need to internally-inflate the wing with compressed air. Suction cups were mentioned. Craft-stores would likely have these in different sizes. Try to find a small one that you can tie a length of string to.. so that you can get a "straight-pull" on it. Secure the string above your workbench on a hook and hang/suspend the wing an inch or two above your workbench. Moisten the suction-cup and apply it to the dented area. You now have both hands-free to work. Obtain a wash-cloth and wet it to the point of saturation.. but not dripping. Fold it into quarters and lay it on the wing for a bit of weight. Then heat the dented-area "gently" and "gradually" using a hair-dryer and watch to see if the dent begins to release. Be patient and don't overheat the panel. If the dent levels completely out.. stop the process and just leave it hanging with the weight on it. After several hours, the washcloth will dry-out; gradually releasing the tension.

If the dent "reforms".. you could alternately try a rapid-cooling method by reheating.. followed by quenching with a small container of cold water. It shouldn't take much to cool the panel. Place a large cookie-sheet under the wing to catch the water. If using water.. be sure to drain any if it gets inside the wing.
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Re: TD-3 , wing issue

Post  fredvon4 on Mon Oct 16, 2017 11:58 am

Just had to google TD-3 and take a look

Gonna be tough with the vacuum formed ribs on the top of the formed hollow wing

Good idea to post a few pics of the deformity

I think I would be tempted to make one or more Lite foam or balsa internal ribs, slit the underside of the airfoil and sneak them in then glue/ tape the slits closed

Of course a replacement TD3 in good condition is usually a $200+ investment
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Re: TD-3 , wing issue

Post  Mudhen on Mon Oct 16, 2017 3:52 pm

If you don't intend to fly the model then I'd recommend not repairing it.
It's very thin sheet plastic. The only access to the internal structure is through the hole in the firewall, but the model is not sealed.
I don't think enough pressure can be generated, even with heat, to restore the shape of the airfoil without possibly damaging other parts of the airplane.
And I'm not sure that one could control the pressure enough to reshape the airfoil to its original design.
Sometimes with restorations you have to let some things go. This may be one of them.
On the other hand, if you do find a workable solution, I'm all ears. I have a couple of TD-3's in the same condition.
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Re: TD-3 , wing issue

Post  swift53 on Mon Oct 16, 2017 6:34 pm

fredvon4 wrote:Just had to google TD-3 and take a look

Gonna be tough with the vacuum formed ribs on the top of the formed hollow wing

Good idea to post a few pics of the deformity

I think I would be tempted to make one or more Lite foam or balsa internal ribs, slit the underside of the airfoil and sneak them in then glue/ tape the slits closed

Of course a replacement TD3 in good condition is usually a $200+ investment

I would be weary cutting or otherwise doing any major surgery. My TD-3 is NOS and except for this 'small issue',
It would be a 100 point plane. Virgin.

Tried squeezing together the leading and trailing edges together, and it will regain the original shape,
but as soon as you let go, boing, back to hollow..
if that is of any help...

Absolutely thrilled about all the great replies , still have 2 more weeks before experimenting begins.

Regards, Alberto
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Re: TD-3 , wing issue

Post  Mark Boesen on Mon Oct 16, 2017 11:06 pm

you might try using hot water, stick wing under faucet while holding as described earlier, letting it cool while holding, when i comes to reshaping plastics, i prefer steam or hot water to hairdryer or heatgun and even then it's still kind of a crap shoot reforming plastic.
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Re: TD-3 , wing issue

Post  dckrsn on Mon Oct 16, 2017 11:39 pm

TD-3

lifted photo Smoking
Bob
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Re: TD-3 , wing issue

Post  roddie on Tue Oct 17, 2017 12:06 pm

TD-3

lifted photo  Smoking  
Roddie
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