Max Holste Broussard 1/72 Scratch Built Masters & Models

[Army_Air_Force]

Something that has been a concern from the start was resin shrinkage. The polyurethane resin has got virtually no shrinkage at all, by the clear polyester shrinks a great deal in a big block. The first cockpit was distorted from the heat, so it wasn't obvious. The second casting had the clear acrylic block hidden inside and that didn't have any significant shrinking. Because I only had some 6mm thick clear acrylic sheet to do the test with, the line of the block can be seen through the resin windows. OK, so that was better, the right size, but the block inside showing.

 

I cast another all resin cockpit with less catalyst and that didn't distort, but it did shrink quite a bit - around 0.5mm on width and 0.75 to 1mm on length as shown below. The front end of both the clear polyester and cream polyurethane cockpits, are both pushed up against the face of the 'V' block.

 

 

This is the second cockpit with the clear acrylic block inside, highlighted with the red dotted line. While this test block could be seen, it showed that the cockpit remained dimensonally uncompromised, as the lower quantity or resin around it, limited the effects of shrinkage.

 

Edited October 23, 2020 by Army_Air_Force

[Army_Air_Force]

Armed with that knowledge, I began with the plan 'C' test!! The shrunken clear cockpit was sanded down on the belt sander to give around a 1 to 1.5mm reduction in size all round. It was then wet sanded and polished.

 

 

It is seen on the original fuselage master, showing the clearance around the edges. This piece will be used as an insert in the next cockpit casting. It is the same polyester as the new casting will be, so should bond well. Its rounded, polished corners are a fairly close fit in the mould and so it should blend hopefully invisibly with the newly poured resin, not leaving eny edges showing. The limited thikness of the new resin should pick up the surface detail while minimising shrinkage to almost nothing.

 

Edited October 23, 2020 by Army_Air_Force

[Army_Air_Force]

Here's the clear block test fitted into the mould. If it works well to give me a clear cockpit without shrinkage, I'll make a new pattern for the insert and take a mould. I can then just pour the insert in clear resin, let it cure and then transfer it to the cockpit mould for final casting.

 

It's all part of the fun and challenge of scratch building and working with new materials. There's also a plan 'D' should it come to that!!!

 

 

Around 6pm, the silicone moulds for the fuselage, gear infill, landing light and wheels, had been cured for around 24 hours, so the plastic boxes removed the the master patterns pulled from the moulds. I'll probably leave them until tomorrow before casting any resin in them.

 

Edited October 23, 2020 by Army_Air_Force

[Army_Air_Force]

I did some casting late last night so the first panel lined fuselage came out of the mould this morning. The landing gear filler and the new set of wheels were also cast.

 

 

Other than the landing gear which will be brass strip and the wing struts which may be brass, aluminium or styrene, then this is a full kit of parts. The small clear part to the lower left is the first clear landing light casting.

 

Edited October 23, 2020 by Army_Air_Force

[Army_Air_Force]

Here's a close up of the landing light casting. There's probably enough for three landing light glazings. This will allow for mistakes when cutting and fitting, or would allow a larger piece to be let into the wing to fill and blend the join, then just masking the piece that needs to be clear. Making it over size was easier than thinking about shrinkage.

 

 

It's difficult to catch the fine panel detail, but here's the new fuselage casting.

 

Edited October 23, 2020 by Army_Air_Force

[Army_Air_Force]

Going back to the cockpit glazing, I cast a new one last night with the polished resin core prepared earlier yesterday. I was hoping the solid core would prevent the shrinkage and the polished rounded corners would help to keep the block invisible in the new casting.

 

It was released from the mould today and left to cure a while longer, then out came the vernier calipers to check the dimensions. It would appear that I won the battle and both the fuselage and cockpit widths matched!

 

 

For much of today, I've been trying to finalise the decal artwork, shown here larger than model size. The two registration black crosses at the top of the image should be 2 inches apart for the image to be the correct scale.

 

Edited October 23, 2020 by Army_Air_Force

[Army_Air_Force]

While casting the main airframe parts is a moderately quick process, casting the clear pieces is much slower. Too much catalyst in the clear resin to try and speed up the cure, causes heat build up, distorsion and discolouration. There's no quick way. Also, once the resin is cured enough to be removed from the mould, it still isn't fully cured, and takes several more days in the airing cupboard to fully harden.

 

I need the canopy core completely hard so that it can be fine wet sanded and polished before going into the cockpit detail mould. The three moulds below show the final cockpit mould on the left, the clear core cockpit infill in the centre and landing light glazing on the right.

 

 

Between working on the castings, I've also been working on instructions. This has involved setting up the model in various positions, with different sections of airframe positioned together. The different poses are then photographed and a line drawing produced from the photo on a new transparent layer.

 

Edited October 23, 2020 by Army_Air_Force

[Army_Air_Force]

Each different line drawing could then be transferred to a step by step instruction sheet. Of course, instructions are just a suggested order of assembly and we all know that some stages get moved around depending on paint colours, schemes and order of painting.

 

 

I'm waiting for clear casting numbers to catch up to the cream castings, but this as already mentioned is slow going. I'm also waiting for the postman to bring some brass strip and aluminium tube for the kits. Half an hour ago, I popped out to the rather cold workshop and set up the six kits cast so far. Two of these are the pair I was originally commissioned to build which started this whole project off.

 

Edited October 23, 2020 by Army_Air_Force

[Army_Air_Force]

Casting continues with the kit count at eight now, but the cockpits are a few behind. There's two moulds for wheels for an N scale GMC 2.5 ton truck in this shot. Mixing the correct  quantity for the moulds is getting better, but still difficult to estimate, so I have a few other moulds so any excess resin doesn't go to waste.

 

 

Here's number seven out of the moulds first thing this morning.

 

Edited October 23, 2020 by Army_Air_Force

[Army_Air_Force]

The postman brought a package with brass strip and aluminium tube. The brass is for the landing gear. I need to experiment with the round section aluminium tube as I want it an elliptical section. I may need to anneal it, but the plan is to squeeze it in a vice with a piece of 1.2mm material also in the vice to limit the travel. This should crush the tube to the required section and thickness, without going too far and squashing it flat. Each strut is only about 43mm long.

 

 

The final draft of the decal graphics was finished and test printed onto paper today, before emailing the files to the printers. I was told I should have the finished decals back tomorrow!

 

Edited October 23, 2020 by Army_Air_Force

[Jamie @ Sovereign Hobbies]

This is fun to watch come along

[Army_Air_Force]

A few of the paper decals cut to size and placed on the master patterns. The 5-ML fuselage code is printed in black on the model, as the white ( with black outline ) of the colour test print was too faint to see to cut out. 

 

 

The destructions are pretty much complete, bar any tweeks as a result of the build. With the decals sorted, and that took some effort to find someone who could print them, they way is clear to get on with building the first two commissioned models. I'll get at least one airframe glued together before releasing the others for sale. After all, I'm still cockpit moulding as fast as the resin will let me!

 

Edited October 23, 2020 by Army_Air_Force

[heloman1]

Regarding the shrinkage and what seems to be an over complicated solution to the clear parts. Poly ester resin has always had it's shortcomings! Have you not thought of vac-forming the glazing into a  female mould. You can get get very good results for far less effort. Or have I missed something.

 

Colin

[Army_Air_Force]

I didn't want a vac form to support the wing, especially as the commissioned builds may be posted and need to be sturdy to survive the post.

[Army_Air_Force]

The decals arrived this morning. They look excellent. I ordered them from http://www.precisionlabels.com after preparing my own artwork. I'd tried a number of different companies and didn't get anywhere with the others. I refined my artwork after several emails between myself and John who runs the company. I was very impressed with the assistance and service and his printing system can print white and metallics onto waterslide decal paper. Well worth contacting if you are looking for custom decals. If you aren't up to doing the artwork yourself, they can do that too.

Some of the details are tiny and yet the serial on the tail, which is only a millimetre or so tall, is still readable. Here's the set of nine, followed by a close up of one set.

 

 

The tiny shields under the roundels is only about 4 x 3mm in size. The aircraft serial number is the bottom set of black numbers on the rudder and "No 255" is still clear, even at such a small size. I'll start assembling the first aircraft after the weekend as I'm down at Breighton airfield tomorrow. 

 

Edited October 23, 2020 by Army_Air_Force

[stevehnz]

Those decals look quite superb, I'm very impressed by how this has come together.

Steve.

[Army_Air_Force]

7 hours ago, stevehnz said:

.....I'm very impressed by how this has come together.......

Me too!!! 😉

[Army_Air_Force]

And So It Begins!

 

A year after my initial research trip, but after a delay due to needing to shipping another framed model, I finally got to starting the first Broussard model. Step one was to cut out the landing gear mount with a razor saw, scalpel and needle files.

 

 

Once the slot got close, I used the landing gear brass strip to check and fine tune the width.

 

Edited October 23, 2020 by Army_Air_Force

[Army_Air_Force]

The original photo of the first fuselage was blurred, so I had to take this one of the second fuselage, using the shrunken first glazing for a picture of this stage. On the first fuselage, the flat seat on the fuselage was lightly sanded. The bottom of the cockpit was dry and then wet sanded until it sat down for enough that the top of the rear fuselage blended. It was then painted black before being dry positioned on the fuselage. It was aligned with the door joint on the main fuselage to ensure the correct fore and aft position. Thin cyano was then run into all the joints to secure it.

 

 

While the fit was pretty good and that was a bit of a surprise, there was still a slight join line that needed filling. One coat of filler was applied and later wet sanded, then a second layer applied and left overnight to fully harden.

 

Edited October 23, 2020 by Army_Air_Force

[Army_Air_Force]

After a day out with the family yesterday, I got back to the Broussard today. The filler around the cockpit joint was wet sanded. On the port side, the bottom door runner got in the way, so was sanded off and will need to be replaced with a little strip of styrene.

 

 

The centre wing section was added next. It was carefully aligned and attached with thin cyano. The wing overhang was ever so slightly over the thickness of my 6 inch steel rule. So the rule was placed against the side of the fuselage and the wing roots given a slight sand flush with the rule.

 

Edited October 23, 2020 by Army_Air_Force

[Army_Air_Force]

The 1.5mm styrene extension for the oil cooler was added next. Because the rear face of the cowl was the pouring face during casting, it gets sanded flat. To make up the full length of the oil cooler, the styrene is added to the rear after the cowl is sanded to the correct length. It was glued in place, trimmed close with a scalpel and then wet sanded.

 

 

Attaching the cowl was tricky freehand. The front of the fuselage and rear of the cowl were quite smooth after sanding and kept slipping around. In order to line up the intake and oil cooler with the fuselage centreline top and bottom, I gently clamped the fuselage and cowl in a G-Clamp. This allowed me to check the top and bottom alignment before applying some cyano.

 

Edited October 23, 2020 by Army_Air_Force

[Army_Air_Force]

I made a little jig to attach the tailplane and keep it parallel to the centre wing section and square to the centre line. 

 

 

Cyano was run into the joint and that was the tail attached.

 

Edited October 23, 2020 by Army_Air_Force

[Army_Air_Force]

The landing light was cut out of the leading edge of the port wing, sanded and painted black.

 

 

The top of the fuselage was filled over the wing centre section joint and the tailplane fairing. There were a few pin holes along the spine in this first fuselage as I think I was a bit over active mixing the first batch of resin. The wings are now balanced in place for a feel good photo!

 

Edited October 23, 2020 by Army_Air_Force

[Army_Air_Force]

The start of the landing gear. The basic brass strip and the formed gear. The jig is a template to check the shape of the formed gear, rather than a former to bend around.

 

 

I slotted the landing gear into the second fuselage and balanced the wings and cowl on top, just to make sure the very thin 1/32 x 3/32 inch brass would support the weight. It did.

 

Edited October 23, 2020 by Army_Air_Force

[Army_Air_Force]

The flat centre portion of the gear had the surface keyed and was then drilled to help with gluing. Now the next bit is optional I guess. The legs are tapered from top to bottom, and after a quick file, the taper was finished off with a wet sand  on some wet and dry paper taped onto a flat bench.

You could just epoxy glue the wheels onto the brass, but I wanted to give it a little more support. So after the brass was trimmed to length, a small 'V' was filed into the ends. This was then opened up slightly with a round file. A piece of copper wire was then placed across the width of the gear and soldered in place.

 

 

The centre piece of copper was snipped out with some cutters and would be saved for the exhausts. The excess on the inside was then filed flush. The axles would be trimmed to length later. Other than that, I finished off the last of the casting resin with one more airframe. That was the end of another day, but the first model was finally looking like a Broussard!

 

Edited October 23, 2020 by Army_Air_Force