D.H. Dragon Rapide pattern

[Mothman]

Hi all,
here's the current state of play on the Dragon Rapide.  So far, I've made the left tailplane and elevator, nose cowling and engine nacelle halves.  Today I also roughed out the fuselage halves on the bandsaw and started the clean up, when the sky went black and the thunder came and I was needed to calm the Shar-Pei down. He was left alone as a pup in an empty house and doesn't like the noises.

So here's a couple of shots of progress so far on the DR.

Martin

[Peter]

Looks good so far Martin, what type of wood are you using? I have a new four month old puppy that jumps and loud noises then piddles on the floor.

Peter

[Mothman]

Peter,  it's not wood, it's a material known as Ureol.  Also known as CIBATool, Axxson, Ebalta or Renshape. It's a dense epoxy foam.  At the hardest level the foam nature isn't noticeable. This is not quite at that point, but was all I could get.  If I used wood it would be steamed pear or Swiss pear.

Our latest doggy is a Shar-Pei pup of about 13 months, but he was badly treated so needs some work and a lot of fuss.

Martin

[Peter]

Thanks for the quick response Martin! I'll keep my eye out for Ureol or its Canadian equivalent.

Peter

[Balsabasher]

Martin I note your progress on the Rapide with great interest,I see that you are using the 'Aeromodeller' George Cox drawing as a basis for the build,a good choice as it is a very good drawing.
Out of interest where did you obtain your Ureol from ? do you have to order large amounts of this stuff as I understand that it is expensive,up until now I have only used this interesting material for wheel spats etc for which it excells,my precious few pieces are used with care,it certainly takes paint very well.
Another question ? do you have to make these masters so that they come apart,ie for the eventual rubber moulds to break down into sections ?
Barry.

[Mothman]

Peter, in Canada, it is probably known as Renshape. That's what it is known as all over America.

Barry, I always go to the users of these things and beg offcuts.  What I did with the Ureol was to find a company that do the rapid prototyping that it's used for and ask if they had any short bits, telling him that I was an "old fashioned" modeller, making a joke that, come the glorious powercut brother, I would be working with my hands while they fixed the generators.  Seemed to work.  I was sent a large piece which they had as a sample and only had to pay the the postage which, at £10 for a next day courier, seemed very reasonable.  Then I found a local company who also had a sample twice the size and he gave me that when I visited and asked for my card as they need people to clean up the products of rapid prototyping, something I have to see him about next week, so it's worked out well.  I also buy my brass from a local engraver for scrap value.  A few quids-worth will last me an age.

I keep all the scrap Ureol in a box.  If you need a few bits, let me know.

Cheers,
Martin

[Balsabasher]

Thank you Martin,I will have to ask around this area to see if anyone uses it ? we have few if any pattern shops now not like the seventies when the car factories etc were using lots of small companies to do work for them,pattern making has changed dramatically like draughting has,old skills and old methods went out of the door literally overnight,for example a friend purchased a draughting board from his company for a tenner,the boards probably cost hundreds of pounds initially,nobody wants them as it is all done on computer now,I still draw up by hand and always will do just like my days at school in technical drawing.

Thank you for the kind offer on the offcuts.

Barry.

[Mothman]

Barry, those same pattern shops will now be using rapid prototyping if they've survived.
I'd try one of them.  Tell them what you do, that always gets them!

So long as nobody on here starts having their models made by "3D printing", SLS, LOM or any of the other push button modelmaking techniques.

Martin

[Mothman]

Barry, forgot to answer the point about masters.
Yes, they have to be kept in component form and designed to locate to each other positively.
Remember the old Airfix kits..."Locate and cement..."
They also have to be designed for different materials as "multi-media kits".
Plastic kit pins and small holes doesn't work in resin, so the norm is slots and tabs that won't break in the moulds.

And yes, those drawings struck me as the best of several and I'm quite happy with them. They check out well with the photos.

Cheers,
Martin

[lastvautour]

I recall you talking about the stitching, but cannot find the post. How did you simulate the stitching on the control surface?

Lou

[Mothman]

Lou,
I used self adhesive aluminium tape, Selotape Aluminium, which I embossed from below with a chisel made from an old Swiss file, then I cut the strip with a very sharp scalpel blade (I sharpen my own on my diamond dust block).
I then cover the strip with a scale width piece of fine tissue and  seal it with a little dope.
However, both I and the client think it a little heavy looking, so I'm going to try a lesser degree of embossing with a wider spacing. The tissue works well as a covering strip though and we'll keep that.
In anything smaller than 1/32nd scale I think the stitching would have to be left off and just the covering tissue used.
Martin

[Ivanhoe76]

Looking good, Martin, I'm glad that Aeromodeller drawing panned-out for you.

Wilf

[Balsabasher]

Martin please take this in the spirit that it is intended,try and make the rib tapes more subtle,I think that at 1=32nd scale even the stitching can be omitted as it is only certain angles on the real thing that you can see it,better just a representation I think,these things are difficult to get just right.
Thanks for the explanation on the method of assembly of these type of kits,very interesting.
Barry.

[Mothman]

This particular guy wants something akin to the ridiculously detailed Wingnuts Wings plastic kits from New Zealand, but he has to understand that something CAD drawn and CNC produced will have detail even the best pattern maker can't reproduce.  Those kits are 1/32nd scale WW1 and all have rib taping, but with longitudinal stitching which is so much easier to make so subtle it's almost not there. I think it looks a little too subtle and therefore a bit mushy, but it meant I had to try to do something similar on the DR.  I think just the tissue covering tapes would be sufficient.  Otherwise on such a big plane there would be too much fussy detail.

Wilf, I can't thank you enough for sending those drawings through.  So much better than any of the others I found.

I'll try the tape only version on the tailplane that goes with the elevator I did.
Pics. once I've done it. I'm working on the fuselage currently.  Oh and making another 15 paper briquettes for our stove to supplement expensive coal this Winter.  I'm up to 100 now.  Every little helps!

Martin