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Green house canopy construction

JU88 Glazing

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John Dennier12/10/2014 18:45:03
35 forum posts
7 photos

I am confronted with the need to construct cockpit and nose glazing for my scratch build JU88. I am hoping to get some words of wisdom from experienced members before I attempt to re-invent a mousetrap.

Cheers JD

stu knowles13/10/2014 09:44:01
558 forum posts
44 photos

Hi JD,

You have picked a tricky one there! There's no easy answer that I know of and to some extent it depends on how big the model / canopy will be,

Rough & Ready, Make the shape out of balsa or blue foam if bigger, finish with glasscloth 7 resin & paint. If you made the plug from wood, you could also Vac Form a clear plastic using a pop bottle (small canopy) or a home cooked vac former, or send the plug off to someone like Saric Vacform who will use it to pull a couple of copies.

Got any pics of the build so far? How big will the finished model be?

Like the choice of prototype, sorting out cowls / canopies is often the most tricky part of the build....... be there done that!

Peter Miller13/10/2014 09:50:16
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10006 forum posts
1164 photos
10 articles

Many years ago (i could add a couple of Manys) there was was a control line Dornier 17 (Plans probaly in hte X list) I actually bought a kit for this model in 61 in Aden.

The glass house nose was built up with frames of 1/16" ply and cross members. then all the glazing was fitted, one panel at a time.

Slow and painstaking work from start toi finish but Boy! didn't it look fantastic!

The frames were only about 1/8" wide and had a bulge at each intersecting joint so that a slot coul be cut in for the cross members.

I suppose you could describe it as "egg box " construction in 3D

 

Edited By Peter Miller on 13/10/2014 10:12:27

Philip Ogden13/10/2014 11:01:32
67 forum posts

I have seen the cockpit made from sections of model railway track silver soldered together which gives a very strong assembly and also has a ready made groove to hold the glazing panels. Also puts some weight where you need it. Looked very neat.

Percy Verance13/10/2014 21:53:45
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8109 forum posts
155 photos

I think Sig still do a kit for a C/L Dornier 17. I don't suppose it's a much later version of the one you had Peter?

The JU88 is certainly an unusual subject. Many moons ago, we had a chap in the club of which I was a member who designed and built a model of the Blohm & Voss BV141 assymmetric bomber. It actually flew too, but it was rather unstable. I recall that model having the nose constructed with many flat panels of glazing.

Colin Leighfield13/10/2014 22:07:29
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5886 forum posts
2457 photos

Chris Golds has got a build feature for his 120' span Ju88 G-1 in the September and October Q&EF mag. He made a balsa plug for the canopy and Sarik made some prototypes for him. He says that a resin-based plug will be made for a production version, which will be available from Traplet.

Another fantastic looking model from Chris, although it looks as if he"s made the wing-tips broader than scale to make the handling easier, which to me is too obvious visually, the wing shape is such a characteristic of the 88.

Good luck John, a great choice and one of the greatest combat aircraft of all time.

Peter Miller14/10/2014 08:48:17
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10006 forum posts
1164 photos
10 articles
Posted by Percy Verance on 13/10/2014 21:53:45:

I think Sig still do a kit for a C/L Dornier 17. I don't suppose it's a much later version of the one you had Peter?

I didn't know Sig ever did a Dornier 17.

The kit I had was German, possibly Hegi, certainly not Graupner. That was bought in 1961 because I brought the kit home from Aden and built it here.

The original model was built by the then doyen of scale builders, Captain Milani who, I believe owned and ran a hotel in London.

Peter Miller14/10/2014 09:05:44
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10006 forum posts
1164 photos
10 articles

Just looked at the Sig Dornier construction manual. UGH!

Nothing like Milani's. Wrong version, very crude construction, Just a bubble canopy.

Milani's was covered in 1/16" sheet all over, took a lot of care to get it on properly but a work of art when finished.

John Dennier15/10/2014 02:20:38
35 forum posts
7 photos

Yes the JU88 project has raised some eyebrows among the members of my club. Builds among my colleagues tend to be the popular war birds which have been done to death! I only hope of course that I don't get skunked come Maiden day. However as an eternal optimist I am planning as if for success...The cockpit and nose glazing details will become an issue after a successful maiden, attempted in a somewhat primitive "boilerplate"configuration with canopy and nose fashioned from foam. The model has a six foot wingspan and is modified for electric power from the original drawing so the build so far has involved some redesign and posed some interesting issues. I have had great support from my colleagues some of whom are "Master Builders". The comments that you all have taken the trouble to offer are very much appreciated and eventually I hope to post some viuals.

Many thanks to all contributors. JD

cymaz15/10/2014 06:24:50
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8530 forum posts
1150 photos

The JU 88 R1 had nose guns and a radio array. This version might save you building the glazed nose.

Colin Leighfield15/10/2014 07:49:20
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5886 forum posts
2457 photos

Good luck John. If you use an accurate wing shape, don't forget the wash-out, although I'm sure you don't need me to mention that.

Dave Hopkin15/10/2014 07:55:50
3672 forum posts
294 photos

Lindsey Todd did a build log on a Bristol Blenheim, which has an equally difficult glazed snout, might be worth looking at the log - pages 3 to about 8 are relevant - **LINK**

Charles (Model Airplane Graphics)22/11/2014 01:27:10
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9 forum posts
11 photos

John,

The JU 88 is a great aircraft to model. I'm sure it will be a chalange and an interesting project.

I know little about it so I went on line.

I found this site. I hope this site will be of some interest to you.

**LINK**

Good luck with the JU 88 project.

Charles

John Dennier26/11/2014 04:37:53
35 forum posts
7 photos

ju88 nose 1.jpgju88 nose 2.jpgju88nose 3.jpgHere are some pics of my efforts to create the nose glazing for my JU88 in build.mold on the vacuum box.jpg

cymaz26/11/2014 06:48:55
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8530 forum posts
1150 photos

Wow, superb effort thereyes

stu knowles26/11/2014 07:26:06
558 forum posts
44 photos

I'd say that that was a winner! I don't know about you but I get a real buzz from taking on a problem like this and overcoming it. I've had some small success with canopies, a friend does brilliant grp cowls. Being able to produce bespoke items opens up all sorts of possibilities for interesting aeroplanes.

What did you use to make the plug? How thick was the glazing material?

John Dennier27/11/2014 06:02:14
35 forum posts
7 photos

Thanks for your comments gents. So far so good the transparent medium is only 1mm thick including the protective film adhering on both sides. I think it is pollycarbonate and it was acquired at my hobby supply shop as canopy medium. I have been advised of another industrial plastic supplier here in town who has stocks of this material in various thicknesses. Something to be considered for the next challenge will be the main cabin canopy which has very complex curvatures and is pretty big.

Returning to the nose glazing, the plug was plaster of paris built up on a 1/16 th ply structure. The frame is a plywood sandwich following the outline of the plug leaving approximately 3/4 inch extra material all around. The transparent sheet being stapled within the sandwich. I discovered that the medium which was being heated in a toaster oven cooled very quickly during initial efforts and lost plasticity before the pull was complete. The answer was to heat up the mold in the oven. The mold has to be placed on a stand of sufficient height to allow the frame to be lowered completely over the mold to contact the vacuum box. The determination of this height is a judgement issue.

I hope this helps anybody contemplating a canopy pull.

Cheers JD

Tony Bennett27/11/2014 08:39:06
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5074 forum posts
129 photos

Brilliant sir.

just brilliant.yes

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