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Chris Williams 1/4 Scale T21

Let us all watch your new project progress.
SedB
Posts: 52
Joined: 14 Nov 2019, 09:17
Location: Netherlands

Re: Chris Williams 1/4 Scale T21

Post by SedB »

Looks good so far!
I just got my copy of the exact same model today, so will be looking forward to see the progress in this topic :D !

Daniel

Sean Fitzgibbon
Posts: 86
Joined: 11 Oct 2017, 18:53
Location: Mitcheldean

Re: Chris Williams 1/4 Scale T21

Post by Sean Fitzgibbon »

So, after declaring that I intended to invest at least one hour a day on this build, circumstances dictated that I didn't touch it for months!!
I am now back in the saddle and have rediscovered the motivation to press on with the project, having seriously considered packing up this hobby after over 30 years of building and flying.
Over a week or so of evenings in the workshop, the tailplane is pretty much completed and I'll probably move on to the fin and rudder this week.
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Sean Fitzgibbon
Posts: 86
Joined: 11 Oct 2017, 18:53
Location: Mitcheldean

Re: Chris Williams 1/4 Scale T21

Post by Sean Fitzgibbon »

With the tailplane and elevators completed, I've moved on to the fin and rudder.
The upper forward ribs of the rudder balance aren't shown on the plan, but it's fairly straightforward to work the shapes out. As for the elevators, the rudder ribs are made from balsa triangles, again easy process of marking out and cutting.
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Sean Fitzgibbon
Posts: 86
Joined: 11 Oct 2017, 18:53
Location: Mitcheldean

Re: Chris Williams 1/4 Scale T21

Post by Sean Fitzgibbon »

I'm really enjoying this build so far, the fin and rudder are now complete and put to one side with the tailplane and elevators. Next jib is to clear the board and set up to start the fuselage.
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Jolly Roger
Posts: 427
Joined: 30 May 2015, 20:35
Location: Sutton Bank, North Yorkshire

Re: Chris Williams 1/4 Scale T21

Post by Jolly Roger »

Looks great Sean. You're really cracking on.

The T21 is one of those snub-nosed chubby-winged cartoon gliders you just want to pick up and cuddle!

We had the Yorkshire Gliding Club T21 crawling around the sky above our house all Saturday. It's going nowhere fast and at times just sits, parked in the sky. Adorable.
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Sean Fitzgibbon
Posts: 86
Joined: 11 Oct 2017, 18:53
Location: Mitcheldean

Re: Chris Williams 1/4 Scale T21

Post by Sean Fitzgibbon »

Hi Roger,
I know what you mean, there's so much character in the vintage gliders. I popped down to our club field on Saturday after Frank Skilbeck told me that he and Dave Keen were going to try towing Dave's T21.
This is a 1/5th scale model, from the Mike Trew plan I believe, that Dave acquired second hand fairly recently.
Our field at Newent isn't the largest or exactly obstacle free, but they did a great job and managed three flights, although Frank's Laser 150 powered tug was operating at it's limit! Watching the T21 arcing around in the sky certainly gave me more incentive to crack on with mine.
Chris' design is very well thought out and although a lot of the tail end parts are not included in the short kit, it still has been a straightforward process so far.
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Sean Fitzgibbon
Posts: 86
Joined: 11 Oct 2017, 18:53
Location: Mitcheldean

Re: Chris Williams 1/4 Scale T21

Post by Sean Fitzgibbon »

So, moving on to the start of laying down the fuselage sides, I was pondering the issue raised on a parallel thread by Sebd. This refers to the force required to pull in the longerons at the nose following a fairly dramatic curve. I also have the issue of not being able to source spruce strip long enough to make them in one piece.
So I decided to scarf the longerons in the area where they will be supported by doublers and then split them longitudinally from the nose back to just in front of F4.
Chris had commented that his preferred method now is to use doubled 3 x 6mm strip rather than one 6 x 6mm, so I'm hoping this hybrid method will address the problem.
I have to say that this process and then cutting in the diagonal strips is made so much easier with the little Proxxon table saw.
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RobbieB
Posts: 599
Joined: 07 Mar 2015, 22:22
Location: North West

Re: Chris Williams 1/4 Scale T21

Post by RobbieB »

Sean,
I too use the 2 x half thickness method to wrap spruce longerons around difficult bends - so much easier than forcing or steaming and you end up with a structure just as strong. Just make sure that when you are scarfing, the joint faces mate accurately and are in the length to thickness ratio of 12:1 or thereabouts for a longeron, 15:1 for a wing spar flange; and as you say, preferably in the region of a former but most full size boys would say if the joint is done correctly that shouldn't matter.

Sean Fitzgibbon
Posts: 86
Joined: 11 Oct 2017, 18:53
Location: Mitcheldean

Re: Chris Williams 1/4 Scale T21

Post by Sean Fitzgibbon »

RobbieB wrote:
18 Jul 2020, 11:08
Sean,
I too use the 2 x half thickness method to wrap spruce longerons around difficult bends - so much easier than forcing or steaming and you end up with a structure just as strong. Just make sure that when you are scarfing, the joint faces mate accurately and are in the length to thickness ratio of 15:1 or thereabouts; and as you say, preferably in the region of a former but most full size boys would say if the joint is done correctly that shouldn't matter.
Hi Robbie,
Good to hear that other people concur!
The scarf joints I made were about 80mm long for the 6mm section and cut on the Proxxon table saw before a light sanding with the Permagrit. I used the clear, non foaming Gorilla glue to form the joint and a test piece that I made failed outside of the glued area.
The design has a double longeron for a portion of the length of the fuselage, and the joint is completely covered by this for more security.
It's a very satisfying process to build this so far, lots of lovely traditional wood modelling.

Sean Fitzgibbon
Posts: 86
Joined: 11 Oct 2017, 18:53
Location: Mitcheldean

Re: Chris Williams 1/4 Scale T21

Post by Sean Fitzgibbon »

The formers are nearly finished and the fuselage sides just need the longeron doublers adding before I can start looking at starting putting the fuselage together.
The only slight modification I made was to infill the top of the pylon formers with 1/4 ply beneath the hardwood insert.
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