1/24 scale DH Mosquito for rubber power.

[Piecost]

Interesting experiments. I too have thought best to not cover in extreme conditions. We are back to the usual cool and humid enviroment. What are you using to glue the tissue down with?

[Jmk89]

P.S. I see that when posting, people can place images within text - some text; a photo; more text; another image, etc. How does one do this?

Stephen
Let's assume you've written all the text and clicked/dragged your photos into the box at the end of this he draft post.

If you look at the thumbnail of a photo you will see in the top RH corner an arrow symbol.
Now put the cursor in the text where you want to locate that photo and click
Then click the arrow symbol on the photo
A box will pop up - just click in INSERT and that will put the photo in the text where you clicked the cursor

[Prosper]

Thanks Jeremy! Will try this on my next post with multiple piccies.

Tim, I'm a long-time adherent (cough) to wallpaper paste glue. In my case this is something called UHU Glue Pen. It's gloopy, transparent (apply with an artist-type paintbrush of the relevant size), and water-based. Whatever it is chemically, it dries to an astoundingly tough transparent, flexible membrane. I've sometimes wondered whether it could be layered onto a form to make a cockpit canopy. I guess the answer is yes - but it dissolves when wet, so probably not very practical!

Stephen.

[Prosper]

I've been unable to do any work on this for the last 3 weeks, but after my last post, I had started on the demoralising chore of making the exhaust stacks. I tried everything - twizzling some balsa dowel then shaping it and trying to bend it with heat . . . carving each stub independently (too inconsistent, too time-consuming) . . . short forays into shaping plastic tube; moulding, casting different materials etc . . . all of this hampered by the stipulation that each exhaust stub must weigh not more than 0.0 grams . . .

One immediate difficulty is that I don't know what their exact shape is, in the first place. Few wartime Mosquitos seemed to have this type of stack. I've leant heavily on a New-Zealand 'late-production' example, even tho' this is brand new and I prefer to model from original examples. Curiously, look at lots of period Mosquito photos and the great majority of day Mossies had exhaust anti-glare shrouds, whereas most night Mossies pictured have bare exhausts - hmmm - wrong way round, surely? Maybe to do with performance - shrouds reduced engine power output.

The pictures are just to suggest what kind of things I was trying.

[Prosper]

The last pic is where I'd got to when I had to stop work. Sort of mass-production with individual finishing. There are twenty of these suckers to make.

Never mind - I've got all winter to do this . . .

Stephen.

[RolandD6]

Seems to me to be a prime candidate for making a good pattern out of firm polished wood, making a silicon rubber mold and then press molding replicas from lightweight paper clay. The type of silicon rubber used is very expensive for little jobs like this but there are people on YouTube etc. who will try to convince you to make a mold from adulterated silicon sealant. I have not tried this because I already have more than enough genuine silicon rubber from past projects. Another possibility is latex rubber which is relatively cheap. I believe the normal method of making a latex mold is successive thin coats allowing the coats to dry before applying the next coat. You have to provide sufficient time for the water content in each layer to evaporate.

Just a suggestion

Paul

[Jmk89]

If you're going to try moulding using paper clay, perhaps the pattern could be moulded from wax, like a piece of jewellery being made using last wax casting.
I've never tried it, it's just a thought that popped into my head when I read RolandD6's post. Forming wax might be easier than carving firm wood, especially as you could make the basic round rod by pouring warmed wax into a split tube. ISTR that Bill Dennis wrote an article in AM in the 80s on wax patterns that he used to make exhausts by electrolysis with copper solution. Adapting those techniques might get you to a good result and leave you more winter for other things, Stephen

[Jmk89]

I mean electroplating not electrolysis and the article was in March 1983.
I apologise for the mistakes

[Prosper]

Many thanks Paul and Jeremy - I had considered 'lost wax' but these exhaust stubs are so small and thin that I doubted my ability to make wax examples (examples, plural, because there must be one left-hand and one right-hand example). I have RTV silicone from other, full-size uses, but . . .duuuuhhh . . . from my previous use of RTV silicone I only thought of moulds split into two halves - again, too awkward for these tiny components. But - of course given the felxibilty of silicone, perhaps a lost-wax or lost-balsa or something form could be pushed out of a solid (one-piece) silicone mould . . . Thanks for energising all three of my brain cells . . .

What is 'paper clay'? It's all right; I won't feel betrayed if you tell me that it weighs more than 0.0 grams per CC.

Stephen ps yes i do have other (aeromodelling)things in mind Jeremy, for the winter

[OZPAF]

Instead of carving - perhaps bending insulated wire of the required thickness would work for plugs for your mould. It could be flattened as required and a bank of them attached to a baseplate, and moulded as a unit.

I like Jeremy's idea of using electrolysis onto wax - but at this scale it could be flimsy. I believe this was used on a French aero engine of the first world war to make the copper water jackets around the cylinders.

John

[RolandD6]

The following are examples of paper clay that I have. Two are made in Japan and the clay in the round tub is made in Australia. So far I have only used the middle example. I was able to press mould it and cast it by thinning with water. All of them are very light weight. The two examples on the right come in a variety of colours and all can be painted.

Paul

[OZPAF]

electrolysis

Whoops! copied Jeremy's mistake - electroplating is the right word.

John

[SP250]

What about making the plug from Stainless rod of suitable diameter, bending and flattening one end for the splayed exhaust exit.  But leave that end too long so it can be rigidly mounted onto a base of some sort.  Then use thick wall heat-shrink tube and shrink onto the plug, once cooled, can be slipped off the plug and do the next one.  Should be stiff enough by itself to mount the round end onto a plate of 5 (or 6) depending upon which version of Merlin engined Mosquito you are modelling.
John M

[billdennis747]

Bill Dennis wrote an article in AM in the 80s on wax patterns that he used to make exhausts by electrolysis with copper solution. Adapting those techniques might get you to a good result and leave you more winter for other things, Stephen

Crikey, that's good memory. I was once told by someone that they only looked at the pictures! It was copper sulphate and I used it to make one of those convoluted exhausts for a WW1 Mercedes engine. You can get good results from heat shrink tubing. You can buy a 'selection box' of very different sizes and it will shrink quite a lot around a mould. I've made an exhaust and strut-end boots for a Bucker Jungmann.
PS just noticed SP250's similar post - sorry John
PPS if looking for that paper clay stuff, it's called Hearty Clay (as on the photo) and it weighs 0.0001g/cubic mile

[Prosper]

Well at 0.0001g/cubic mile that comes well within my specification. Amazing stuff! You'd think that the factory where they make it would float out to space!

But seriously thanks for all the suggestions, gents. Electroplating wax is a very smart idea. Funnily enough I found just days ago that I'd run out of heatshrink of the right size to perform an electronic task - but I didn't have a lightbulb go on above my head regarding Mosquito exhausts ;( Anyway, now I'll be ordering a selection box, both for electronics and exhaust experiments. One thing I did find out right at the start of this nightmare excercise, is that flattening tube doesn't make the flared, fishtail outlet. You'd think that that would be how they made the full-size exhaust stubs, but apparently not, since flattening tube doesn't give the width of exhaust slot observed in photos. Not to worry, if I only have to shape one left master and one right, that'll be a relief.

More anon,
Stephen.