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Re: 1/4 scale T-21 CW

Posted: 09 Feb 2020, 20:51
by Dave still
I'll follow I'm looking to build a scale ship for next year not sure which to go for.
Can I ask what flying experience you have? I've only flown small flat field stuff and going to learn to slope fly this year and got 3 models to go through. Then maybe a scale build next winter.

Dave

Re: 1/4 scale T-21 CW

Posted: 18 Feb 2020, 11:07
by SedB
Thanks for your comments! Yes, I'll do my best to keep the aft as light as possible (scraping of glue residue, but doubt that will make the difference :D ).

My flying experience is 3 years with motorized gliders (up to 4meters span) and planes up to 3meters. Too I did some slope soaring.
I'll be building tow hook into this one so I can use it both on the field and slope. I haven't figured out where to put the tow hook yet. Looking at reference pictures it seems that the T21 had this installed on different locations (or the pics are misleading me).
I think I'll end up installing it next to the skid, on the belly of the glider.

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Starting with the tail section, here ribs 2 and 4 seem somewhat short:

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And while stuff is drying I started on the rudder too:

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Next time I think I will as a small ramp (is that correct English?) instead of building these curved parts on the plan. Haven't always figured out what the best technique for building straight..

Daniel

Re: 1/4 scale T-21 CW

Posted: 18 Feb 2020, 11:28
by chris williams
I usually do rudders like this...

Re: 1/4 scale T-21 CW

Posted: 13 Mar 2020, 20:21
by SedB
Preparations for the skid are underway;

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I'm not too sure yet on how to tackle this; The four layers of ply (drying here, but not glued yet) are okay and still give some flexibility. Though gluing them with epoxy and adding carbon strips seems a bit rude, as all the epoxy I'm used to gets rock hard. The way I understand skids is that they are supposed to have some flex, or is this only for full size gliders? Any thoughts are welcome!

Backspine preps:

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And the whole serie done:

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These will be glued to the inner sides of the frame, instead to on top of it.

Eventhough trying to keep the aft as light as possible, I felt the need for some extra meet on the rudder as the balsa base seems to be to soft for holding hinges. So, on the critical spots I added a small layer of ply:

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And the whole rudder done:

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I must say though looking at some other builds here, I do feel like a slowmover :oops:
But, the more I get done, the more fun it gets!

Cheers

Re: 1/4 scale T-21 CW

Posted: 14 Mar 2020, 09:11
by john greenfield
On my laminated skids, I always use PVA glue as it remains flexible. I have never had one fail by delamination so can commend the option as being well tried and tested.

AEB

Re: 1/4 scale T-21 CW

Posted: 15 Mar 2020, 09:42
by FrankS
Re Tow Hook, if this is for aerotowing it wants to be in the nose, our Mike Trew 1/5th scale T-21 aerotows lovely.

Friend has also just picked up a 2nd hand T-21 (1/5th scale) and it has a tow hook along side the skid, obviously for winch/bungee launch, but we haven't tried this yet.............

Re: 1/4 scale T-21 CW

Posted: 05 Apr 2020, 19:14
by SedB
Thanks AEB and Frank!
I'd love to hear how that tow hook alongside the skid works out eventually!

The rudder is nearing completion:

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The whole nose part is not as easy as I though it would be. Seems my method of working and pinning down things deviates from what I see on the forums.
For my next built I for sure will try to find a way to keep the whole model in position during the main part of the build.
For now it didn't work out for me since I had a hard time bending the longerons. I might see into a magnetic surface to build on, looks like a more easy way to keep the whole build straight

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Simple side question; did someone ever made successful use of one of these?:

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For some reason it seems impossible to cut longer straight strips with this simple tool..

Re: 1/4 scale T-21 CW

Posted: 05 Apr 2020, 19:35
by Peter Balcombe
Seb,
I expect that Chris Williams would have used “Bridson Jig” when he built his T21.
See https://scalesoaring.co.uk/phpBB3/view ... 826#p26826

I find that the balsa stripper seems to work better if you use a new blade and angle the blade as much as possible so that the tip end cuts much later than the top part
Peter

Re: 1/4 scale T-21 CW

Posted: 05 Apr 2020, 19:46
by chris williams
You shouldn't need a jig, really, for a slab-sided fuselage...These days I use horizontal liteply alignment plates to keep things straight

Re: 1/4 scale T-21 CW

Posted: 20 Apr 2020, 16:01
by SedB
Thanks again for the directions!

Here some more progress:

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Sorry, I did not setup a boot for taking pics :oops: ..

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Now with the sidepannels mounted it somewhat starts to feel like something more solid!

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I found this the easiest way the get the ribs glued in straight. It must be said that the trailing edge is of very soft balsa. I might reenforce, but will have to seen what the whole structure will feel like once completed.

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