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T31M build log


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With the basic wing structure completed it was time to move on to the fiddly bits, ailerons and airbrakes. Oh how I dread the faff of fitting airbrakes! It's often a tight squeeze for the servo and the linkage, and choosing to incorporate hatches also adds to the workload. I did contemplate leaving them off but, with a small airfield to operate from, I like my gliders to have some stopping power. Although I'm still undecided as to whether or not this is a glider .......... 

 

Servo shoe horned in to the unusually small D-box and secured with hot glue, a hatch below allows access to connect the linkage:

 

IMG_1425.thumb.jpeg.3cca0261a1f5b22af01a10f274588ceb.jpeg

 

 

Brake at full deflection:

 

IMG_1427.thumb.jpeg.b3ddd57b42039dc51975890d6ca399f5.jpeg

 

 

Ailerons hinged with Robert style point hinges, wing tip profiling completed:

 

IMG_1428.thumb.jpeg.74d5515f69f745686c15d877a3795ba5.jpeg

 

 

Aileron and brake hatches, wiring complete leaving only the wing joiner tubes to be fitted, sanding and covering. Note also the hard points for the struts:

 

1458432390_IMG_1426(1).thumb.jpeg.b96b5c5baf5b5a17623f81f1295ea6b4.jpeg

 

 

Just for fun I thought I'd trial fit the wings, they went on fairly smoothly but I have some wriggle room if needed before I epoxy the brass joiner tubes in place, without the struts they are very floppy:

 

IMG_1431.thumb.jpeg.f383ec4098b3fce8058e639f52b5515d.jpeg

 

 

 

 

 

 

Edited by Stephen Belshaw
Duplicated photos.
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I always knew Peter had done an 86” T31M but no matter how I searched the Sarik website over the years I could never find it. So I’ve been following this thread with interest. I reread the whole thread last night then did another search. As usual the only one that came up was a little one https://www.sarikhobbies.com/product/slingsby-t31m-47/

Well tonight the light bulb finally came on. First I read the fine print, then I realized the 47” wingspan they list is actually the fuselage length. I have to wonder how many other people were confused by this. I’ll be ordering a plan and short kit shortly.

Dave

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Continuing with the wings, the wing joiner tubes were bonded in by flooding the bays created by the sheer webs using 30 minute epoxy to give me some working time:

 

IMG_1433.thumb.jpeg.9f31ff16616ea6d0bd9fe4753a479e80.jpeg

 

 

After leaving overnight the wing panels were trial fitted to align the ply ribs that will face the central wing mount box, one wing slipped on easily the other was a tighter fit due to not quite perfect alignment of the mounting rods on one side - out of parallel fore and aft by 1mm. A little jiggling and fettling should sort this. I then faced the central box with 1/32" ply:

 

IMG_1434.thumb.jpeg.e79eaddd32383b70206190243baf1c22.jpeg

 

 

The wings were offered up again and marked through in to the newly applied ply ribs to align the holes that will be opened out to take the wing fixing "click" system:

 

IMG_1435.thumb.jpeg.81aa992919a14a8e80ece09e964779e2.jpeg

 

 

Once that was done I was able to sheet the wing root area:

 

IMG_1436.thumb.jpeg.0ce68cb25ba7f7a042ae3ea1fda24978.jpeg

 

 

Back to the fuselage, it was time to cut the battery hatch free but, like a numpty, I'd sanded over the cut lines I had marked out some time ago! A bit of pin pricking soon got me back on track and the razor saw produced a nice clean cut bang on target. Magnets were attached fore and aft:

 

IMG_1437.thumb.jpeg.46f71601e94cdea79b9cff98f40a49ea.jpeg

 

 

IMG_1438.thumb.jpeg.4b70f9e9e3e588b9415eace3e05eb3dc.jpeg

 

 

As luck would have it the prototype has a fuel filler cap handily placed to provide me with a way of pulling the hatch free:

 

IMG_1439.thumb.jpeg.87afc8c7bd097e27b3ef941b55aa8eea.jpeg

 

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A little bit of work on the cowl, I had already printed the dummy engine halves (VW air cooled boxer) and was wracking my brain as to how I could complete the exhaust system using only bits I could find knocking about the workshop. In the end a combination of brass tubing, piano wire, electrical cable, balsa and a yoghurt pot did the trick and gives a reasonable (I think) representation of the prototype.

 

First job was to cut out the area around the engine and fix some balsa on the inner face to give me something to glue to:

 

IMG_1440.thumb.jpeg.b823cf54db40f86f5ee2ae8dd122c514.jpeg

 

 

I fabricated the exhaust by soldering the brass tube parts in a simple jig:

 

IMG_1441.thumb.jpeg.0f7fbc4ca9f89a14aa74c19553a9749d.jpeg

 

 

The basic components:

 

IMG_1442.thumb.jpeg.c7b3e5f982f2385c9be56eb3e2c95b76.jpeg

 

 

A bit of painting .......................

 

IMG_1444.thumb.jpeg.06f4ec88c22fbacbd5568f8964ecb9b8.jpeg

 

 

.............. gives me something that looks like this:

 

G-BZLK.jpeg.484013de8e690c9bf35ab124e2976208.jpeg

 

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I've started on the covering. Flying surfaces in HobbyKing Carmine Red, I know a lot on here rave about the HK film but I always seem to struggle with it, the iron either too hot or too cold (Goldilocks). it goes on but it's a bit of a fight, in the end I seem to do best using the iron to tack and seal and the gun to shrink. 

 

Fuselage is covered in Diacov and is now ready for painting, this is a lovely material to work with, goes on a dream with the iron and quickly shrinks with the gun:

 

IMG_1446.thumb.jpeg.cb7566563f9b83c944ea3377b7212277.jpeg

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44 minutes ago, Peter Miller said:

Funny!  I love Hobbyking film. It is very similar and almost as good as Solarfilm Supershrink Polyester. I use a normal covering iron which is about 20 or more years old set at maximum heat and it works a treat.

Maximum heat! Do you use that temperature for tacking, sealing and shrinking? My covering iron is also of similar vintage with only a low to high setting rather than being marked in actual degrees of temperature.

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Yes.  Definitely for ironing down and also for shrinking.  I shrink the bottom of the first rib bay, the top of the next two, the bottom of the next two  .So I move out two rib bays at a time.

Like yours I have that pointer that goes from cool to hot.  On Solarfilm the hot could burn through. It never did on the Supershrink Polyester or the Hobbyking film.

 

Sometimes I use a big heat gun for shrinking but that doesn't give me as much control.

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Functional struts shaped to profile from spruce and wrapped in self adhesive vinyl. The "Robart" hinges will be bonded in to the hard points under each wing, the plans show modified plastic control horns for the fuselage attachment point, I chose to fit threaded eyes to give me some adjustment:

 

IMG_1450.thumb.jpeg.2baf1cd8ca3f474a5798a0baf6cad8f9.jpeg

 

 

 

IMG_1452.thumb.jpeg.cd8758c570c52d92ee8e71990593d814.jpeg

 

IMG_1451.thumb.jpeg.23c6a2d24324d6a94236a62cc3d2ae7a.jpeg

 

 

Fuselage has received a first coat of paint, Oracolor brush applied. After it had dried I couldn't resist a quick rig up to see what it all looked like:

 

IMG_1453.thumb.jpeg.fe3f41964e6652edc796ec795ed86072.jpeg

 

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Having calculated I had just enough Carmine Red to cover the wings I find I'm fractionally short so whilst I wait on HobbyKing it's back to the fuselage. After a further two coats of Oracolor I moved on to the fiddly bits, first I fabricated the leather cockpit coaming using some leftover log burner rope gasket covered in masking tape:

 

IMG_1455.thumb.jpeg.c9842cd0474d19d9ceb39bf2449212b3.jpeg

 

 

Along with some spruce finished with Danish oil and a piece of foam to simulate the head rest I have a reasonably atmospheric cockpit:

 

IMG_1462.thumb.jpeg.3b0ce6627d3711a07e39166f2deffe66.jpeg

 

 

Rudder servo installed and Rx mounted alongside:

 

IMG_1460.thumb.jpeg.6b89bf186872344cefb84deaa551e0ee.jpeg

 

 

Tailwheel and closed loop detail:

 

IMG_1461.thumb.jpeg.cdb7f0c371e27877fb29022390385b45.jpeg

 

 

Motor mounted and secured with thread lock, I've retained the side and down thrust, I can always change it if I feel the need. ESC floating free in the battery bay:

IMG_1459.thumb.jpeg.f3ee177aedde947d86f2261c04592111.jpeg

 

 

Registration lettering added:

 

IMG_1463.thumb.jpeg.069dea75356ad4dfca923916d7909146.jpeg

 

 

And with the wheels finally on that's the fuselage pretty much complete, apart from the windscreen which I haven't yet figured out how I'm going to secure it:

 

IMG_1465.thumb.jpeg.c51744afa0adc8259ae359b384904674.jpeg

 

 

 

 

 

 

 

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  • 2 weeks later...

With the arrival of the film from HK I was able to finish the covering, followed by the application of the registration lettering courtesy of my Silhouette vinyl cutter:

 

IMG_1468.thumb.jpeg.73232399e2336dcaaabda7ee18bffb4d.jpeg

 

 

Followed by glueing in the struts to the hard points:

 

IMG_1470.thumb.jpeg.7e01fdce43d5fa6aef842e1cdbfeb924.jpeg

 

 

Windscreen was fabricated from 0.5mm PETG fixed with UHU Por and silicone sealant and silver metallic vinyl film applied to simulate the aluminium support. Which, apart from radio setup, completes the build:

 

IMG_1473.thumb.jpeg.c951ec834c29896c32007307b177f6d7.jpeg

 

 

IMG_1471.thumb.jpeg.879d969d77e47966e0604e97908f345a.jpeg

 

 

IMG_1472.thumb.jpeg.0491c1e2f6a480550eb5c8b36a41c5dc.jpeg

 

AUW 2.2Kg (or 4.85lbs in old money), she balances easily without any lead and with room for adjustment on the battery if needs be. Maiden flight probably won't be until the spring.

 

Thanks to PM, she was a joy to build and I'm sure will be just as enjoyable to fly - looking forward to some low and slow flypasts!

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  • 9 months later...
On 26/01/2022 at 17:47, Stephen Belshaw said:

Wing retaining "click" fixings installed, female part bonded in and the male half threaded in to suit with the amount protruding varying the tension:

 

IMG_1448.thumb.jpeg.07ea83f212301d8e27117f6d8b4e9216.jpeg

 

 

They come with a wedge for prising them apart which will preclude the need for tugging on the more delicate parts of the wing:

 

IMG_1449.thumb.jpeg.b7f052f89467d52e9a79afc435c4af6e.jpeg

Stephen, given that you have been using this a/c for a while, what do you think of the wing joining system. Bas

 

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On 02/12/2022 at 17:13, Basil said:

Stephen, given that you have been using this a/c for a while, what do you think of the wing joining system. Bas

 

Hello Basil, I still haven't flown the model so no actual experience in the field with the fixing system to report. However, with multiple assembly/disassembly of the wing panels in the workshop I can affirm that it works as intended providing care is taken to set them up so as not too tight which can make it difficult to "unplug". 

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  • 6 months later...
On 18/01/2022 at 18:52, Stephen Belshaw said:

Continuing with the wings, the wing joiner tubes were bonded in by flooding the bays created by the sheer webs using 30 minute epoxy to give me some working time:

 

IMG_1433.thumb.jpeg.9f31ff16616ea6d0bd9fe4753a479e80.jpeg

 

 

After leaving overnight the wing panels were trial fitted to align the ply ribs that will face the central wing mount box, one wing slipped on easily the other was a tighter fit due to not quite perfect alignment of the mounting rods on one side - out of parallel fore and aft by 1mm. A little jiggling and fettling should sort this. I then faced the central box with 1/32" ply:

 

IMG_1434.thumb.jpeg.e79eaddd32383b70206190243baf1c22.jpeg

 

 

The wings were offered up again and marked through in to the newly applied ply ribs to align the holes that will be opened out to take the wing fixing "click" system:

 

IMG_1435.thumb.jpeg.81aa992919a14a8e80ece09e964779e2.jpeg

 

 

Once that was done I was able to sheet the wing root area:

 

IMG_1436.thumb.jpeg.0ce68cb25ba7f7a042ae3ea1fda24978.jpeg

 

 

Back to the fuselage, it was time to cut the battery hatch free but, like a numpty, I'd sanded over the cut lines I had marked out some time ago! A bit of pin pricking soon got me back on track and the razor saw produced a nice clean cut bang on target. Magnets were attached fore and aft:

 

IMG_1437.thumb.jpeg.46f71601e94cdea79b9cff98f40a49ea.jpeg

 

 

IMG_1438.thumb.jpeg.4b70f9e9e3e588b9415eace3e05eb3dc.jpeg

 

 

As luck would have it the prototype has a fuel filler cap handily placed to provide me with a way of pulling the hatch free:

 

IMG_1439.thumb.jpeg.87afc8c7bd097e27b3ef941b55aa8eea.jpeg

 

 

Stephen, I wonder if you could help me with the wing construction. I was under the impression that there is a definite dihedral present.there even appears to be shown a gap( Pic making hole for wing fixing) that would close up and give some dihedral. I may have overlooked the info, but I cant seem to find ant refeernce to one anywhere !!!!. Can you help please.  Bas

Edited by Basil
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Peter , thank you for your comments re the dihedral for the T31m. I am a novice to the hobby , as you may remember, so I have not the experience to take the initiative so will do as you suggest.  Am I correct in saying  that gliders dont have a dihedral.???

Bas

 

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