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Geoff Sleath11/11/2018 13:04:52
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3017 forum posts
247 photos

As you'll see Robert, the sides are merely 1/16" balsa sheet supported by 1/8" square stringers. Not really adequate to support anything like a tailplane.

I found the magnetic blocks made a very firm support for the inverted fuselage half.

fuselage 7.jpg

Putting a few blocks inside held the structure despite the 1/16" gap to the steel base and the others acted to keep it all level.

Here is the finished structure so far. It's quite straight and using the magntic block with a bit of imagination holds it steady enough to add the internal parts I've made for elevator and rudder servos, battery tray and motor mount.

fuselage 8.jpg

This shows the drawing with zero indication of tailplane support and without showing the stringers which go through the tailplane location and will need to be removed.

drg empanage.jpg

I've inserted a piece of 6mm medium soft balsa between the last 2 formers. I'll fit the second once I've built the wing so I can get the alignment of both exactly right.

fuselage 9.jpg

Another problem to be solved is the mounting of the fin. The top crutch is right down the centre spine of the model and thus exactly where the fin goes! Just glueing the fin onto the crutch would ne'y be sufficiently strong. So the crutch must be removed at the back to fit the fin. I intend to push the fin right down on to tailplane, then add strips at the top to replace the parts of the crutch cut away and sandwich the fin. At least, that's the plan.

More later.

Geoff

Geoff Sleath11/11/2018 14:46:47
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3017 forum posts
247 photos

I've needed a few mods to the front of the fuselage to accommodate a LiPo (probably a 4S 4AH but I may experiment with a smaller 3S). I've given myself plenty of room to play with position.

drg front fus 2.jpg

It's just a matter of where I install an access hatch.

fuselage 11.jpg

fuselage 12.jpg

I had intended to make the front cockpit removable and that may still be the way to go but if the battery needs to be well forward it will make it difficult to access and secure properly. So I may have to make a hatch in front of the cockpit.

I've made arrangements to mount the Axi motor on former 2, which is 1/8" plywood. On the original design to motor (probably a cobalt Astro geared) was held (by elastic bands!) on a pair of 1/4" ramin dowels which stretched from former 4, through formers 3 and 2 to former 1. The 2 front formers are 1/8" birch ply (though labelled 1/16"! The inaccuracies multiply). This would be quite rigid. In the absence of the dowels I intend to support the motor mount with some 1/8" ply extending from the 1/8" ply battery tray. They're as yet not fitted. I've added an extra piece of 1/8" ply to give thickness for the 4mm T nuts. Note the extensive use of my hole saw to keep weigh down and for ventilation.

fuselage 10.jpg

Now it's a matter of building the wing. The somewhat obscure instructions deviate somewhat from the drawing, which itself is barely more than an outline. So what's new? At least it's an interesting and challenging build and I'm enjoying interpretting/adapting/designing. It's a lot more difficult than building from one of Peter Miller's plans - at least they're quite complete and the designer's on tap with help

Geoff

Geoff Sleath11/11/2018 21:59:42
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3017 forum posts
247 photos

The undercarriage is wing mounted and there are blocks fitted between the ribs to support it. I'm almost sure when I've seen this done before, ply doublers are glued to the balsa ribs to strengthen and spread the landing loads. The ribs are 1/8" balsa.

Is fitting doublers a good idea? If so, what thickness should they be? Would 1/16" ply be sufficient and how far along the ribs should they extend. The blocks are in the area between the spars and glued to them (1/4" square as the main spar and 1/8" towards the rear. There are top and bottom spars in both cases)

Geoff

Robert Parker12/11/2018 21:52:55
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835 forum posts
1088 photos

Hi Geoff,

Add strength, much easier to do now than in a repair later.

Certainly go past both spars or even make new ones from 1/8th lite ply. 1/16th sounds OK to me as a doubler.

Regards

Robert

Geoff Sleath12/11/2018 23:52:15
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3017 forum posts
247 photos

Well I've made some 1/16" ply doublers but only between the spars. I have, however, made sure there's space for spar webs so there's ample room for the u/c blocks.

As usual with this 'kit' the wing build is as big a creative challenge to the builder (me) as the rest but it is happening albeit slower than I'd anticipated - which is about par for me anyway

Geoff

Geoff Sleath13/11/2018 09:55:47
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3017 forum posts
247 photos

I managed to find these Softbore tools recently amongst the modelling 'detritus' left to the club by a deceased member. I don't think they're sold now but I remember them being mentioned in the magazines some years ago. They're designed to make clean holes in soft balsa which usually tears when normal drills are used - at least it does when I try to do it.

They looked to be unused. Anyway I tried one last night to drill through the wing ribs so I can fit a paper tube to feed the aileron servo leads through. It worked really well as can be seen here showing both top and bottom sides of wing ribs. I was a bit ambitious and tried to drill through 6 at once; it worked OK but got a bit hot and scorched the balsa but no more than laser CNC cuts do. It even cut through the ribs with 1/16" ply doublers without problem.

soft bore tools.jpg

Geoff

Dwain Dibley.13/11/2018 10:39:46
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958 forum posts
938 photos

Geoff,

go with the doublers, as thick as possible, well, up to an 1/8th at least, they do not have to be rib shaped, but large enough to prevent the bearer "crushing" the rib on a heavy landing, by spreading the load.

Nice looking build so far Matey. wink

D.D.

Geoff Sleath17/11/2018 17:55:05
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3017 forum posts
247 photos

It always surprises me just how many separate parts there are to build a wing - the ribs are just a small part of the build. I had to modify some of the ribs to cut notches for the undercarriage mounts and add doublers to give it some strength. I didn't want one slightly heavy landing to result in lots of repairs.

I also cut slots in the ribs for the dihedral braces which seem to be very substantial - 2 X 3.2 mm plywood and 10mm deep. The drawing says 1/16" but the wood supplied is 1/8". Both had to be cut out from a piece of sheet. The steep angle worried me at first until I realised 10 degrees meant 5 degrees/side - I can be a bit slow sometimes.

I also made an extra rib for a half bay near the root just where the wing exits the fuselage. As the design stood, all the pressure of tightening the wing in place would have born directly on 1/16" sheet half way between ribs. I also needed the centre open for servo lead access and to build secure mounts for the wing support dowels at the L/E. The drawing shows just one in the centre but, as that's where the centre ribs meet on the wing and where the crutch is on the fuselage, I think I'm going to go for 2 dowels and leave the centre free.

wing 1.jpg

The drawing and the instructions seem to deviate and, as Robert warned me about wings warping when ailerons are applied because of the flimsy structure, I decided to build a conventional wing with a 'D' section l/e and capping strips on the ribs themselves. I saved some weight on the t/e by just using 30mm x 1.5mm sheet top and bottom rather than sold wood - they are more secure than sold butt-joined to the rib ends.

(the dark square is a Sleath bodge after I inadvertently broke the sheet in handling! I'm pretty clumsy)

I've also made the aileron which is also built up on a sheet of 1/8" balsa - the aerofoil is flat bottomed. As the drawing calls for one carved from solid that's more weight saving to offset the extra I've introduced with full l/e sheeting.

The wing as it stands with the dihedral braces fitted weighs 118 gms so the complete wing (uncovered) with servo mounts should be under 250 gms. So not too heavy so far.

Geoff

Edited By Geoff Sleath on 17/11/2018 17:55:39

Robert Parker18/11/2018 09:25:40
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835 forum posts
1088 photos

Hi Geoff.

Coming along nicely yes

Regards

Robert

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