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        Build Log The JS1 B/C in 1/4 scale

#1 mikegbogh Sep 21, 2012 03:14 AM

The JS1 B/C in 1/4 scale
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Hi There,
Having had a break from building and doing some balsa bashing in between during winter, its now time to start a new project.
I have done several threads before and often go back and check the earlier ones, the main reason is that each one going forward is that much better, with practice and new ideas always improving on the last.
So once again my goal is to produce a nice flying Scale sailplane using composites and very basic techniques that the average modeller could use.

Project JS1 1/4 scale

This was chosen for various reasons 1/4 scale means it can be easily transported , even in a normal car, JS1 because its new, leading edge sailplane technology and its made In South Africa .

I visited the Jonker Brothers factory in Potch and found these guys friendly and willing to assist, I was humbled by their generousity and when you see what they have achieved, it is nothing short of remarkable.:)

Recently they unveiled a 21 mtr "C" version and both the B and C did very well at the recent World gliding Champs in Ulvade Texas.

Johan Bosman of the JS 1 revelation team sent me a PDF 3 view and I had this enlarged to 1/4 scale. This will be the working drawings for patterns etc. No CAD/CAM fancy stuff I am afraid , just hand shaping and template accuracy.

I am doing a plug first and will then make a mold so I can produce a few fuselages, I know I want at least 2 and I am sure if they fly well , I have some flying buddies who may also want a JS1.


#2 mikegbogh Sep 21, 2012 04:58 AM

Lets get started then
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Hi All,
Intro over , lets get going, I have over the last few months collected some sheets of extruded polystyrene foam , and a few litres of epoxy, and some rolls
of glass and carbon cloth, the first part of the build is making an accurate plug,
which can be molded, obviousely the better the plug the better the end result.
so some pictures of early work to date.

#3 mikegbogh Sep 21, 2012 06:24 AM

Foam cutting
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Hi all,
So after making some templates, the shape was transferred to a foam block and using my cutting bow clamped verticle on a flat table the shape is cut out. First the side view , then the two sheets glued together and then the top view.
The next move was to cut out a slice and tranfer the cross section to it, this will act as a guide when sanding later.

#4 yyz Sep 21, 2012 11:21 AM


#5 Titus ZA Sep 21, 2012 02:42 PM

And he is at it again. :D
This is going to be awesome.

Subscribed! :popcorn:


#6 mikegbogh Sep 23, 2012 01:43 AM

Saterday's goin to be dusty
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Hi All,
Just some peekchas of saterdays efforts, once again stressing that this is right at the beginning and there is lots of work ahead and no real plan, it just evolves as we go.


#7 mikegbogh Sep 23, 2012 01:57 AM

Saterday night fever
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A bad case of build fever,
I decided to cut a small wing panel and use this as the base of the wing saddle area. This will allow both wing roots to a. the same shape.
b. easy to align in all dimensions. c speed up plug making.

So I cut out a piece of foam, marked the fuselage and hand cut out the wing roots/saddle and epoxied in the piece after checking it and using small foam wedges for adjustment.
Sunday I will focus on the boom and fin area.

pictures attached.

#8 swarrans Sep 23, 2012 04:11 AM

Great stuff Mike - reading with interest.

I am going to be building some new ASG29 wings (4.8m) so I look forward to when you get onto that bit (which by your past standards won't be all that long!)



#9 Shedofdread Sep 23, 2012 11:40 AM

Really looking forward to seeing this one come together. By your normal rate, I'd be expecting to see the first fuz by ohhhh, end of the week? ;)

#10 mikegbogh Sep 24, 2012 02:10 AM

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Hi There,
So sunday I cut the remaining bits and late in the afternoon joined them up, ops a small piece missing , so I grafted in a piece of foam and sanded to shape. Overall I am pretty pleased with the basic shape, so today I will lock in that shape with some glass/epoxy. The plug will only need to be strong enough to sand, paint and mold so less glass required than an actual flying fuselage I hope.

I am sure this question will come up at some stage so let me pre-empt it.
Does the JS1 use and ASH26 fuselage, I never really got a straight answer to this question, and I would say that the JS1 A did, the B and C have a remodelled tail fin and although slight, it is different, it is this fuselage I am building.

Anyway the secret of its success lies in the wing design and airfoils.:)

Pictures attached.

#11 Shedofdread Sep 24, 2012 05:24 AM

From my experience of using foam cored plugs - don't skimp on the glass. 4 layers 200g would be a minimum. That way it stands life in the workshop, stays true and you can attack it with whatever machinery / tools you need to.

I don't know if its available where you are but I like a product called 'Reface'. It's a polyester based brushable / sprayable ultra high build primer (more like liquid filler than primer).


#12 Sutton Bank Sep 24, 2012 03:41 PM

I've missed you Mike. Your fast-forward masterclass builds. Your amazing why-didn't-I-think-of-that ingenuity. Your perfect astro-turf lawn.

Beautiful subject too. I'll relish every post.


#13 AllanK1 Sep 24, 2012 04:32 PM

Go Mike go.
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Me Too! look at that boy go. You make me feel like my feet are in mud, no way I can get through building this quick even using similar methods.

It's going to be good to watch Mike.

All the best


PS I attach a shot of Woo with his scratch built JS1. This one did use an ASH 26 fuse though. It looks fantastic in the air with that wing and flies pretty well too. I think he said he handed the Tx to someone called Joe Wurts at an aero tow meeting in Hawkes Bay and Joe had it up to over 3000 feet. I suspect that would be out of sight for us mere mortals!

#14 swarrans Sep 25, 2012 01:09 AM

Apologies if this is seen as a hijack Mike, but I'm planning to use your thread to guide me through making a 4.8m wing for an ASG29 I'm going to build and I wondered if you had any advice of wing section? It would be about 220mm at the root and I want it to be able to roll nicely. I had been thinking of going with a trusty HQ3/13 but I wondered if you were planning something zippier for your JS1?..



#15 Titus ZA Sep 25, 2012 01:11 AM

Yup, another warp speed build on the way again. Fantastic! Keep it up Mike.


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