Tag Archives: Mack Models

‘Miss Severn’ 1922 Gold Cup Racer – Mack Models 1:8 (Part 7)

Having finished the engine diversion it was time to get back onto actually building the Miss Severn model. Not surprisingly these activities have focused around the engine bay and installing the new engine model in there.

In order to try out ideas and plan the installation of components, without the need to constantly handle the engine, I reverse engineered a CAD model of the boat’s hull and installed the virtual engine within it. That allowed me to quickly try different layouts of equipment.

One of the first activities was to manufacture an oil tank for the bay. I’ve no idea what size the Hispano engine requires, but I do know that the Hawker Hurricane with the Rolls-Royce Merlin had a 7 gallon tank. If it was good enough for Sydney Camm and Rolls-Royce, it’s good enough for me.

A quick box tank design was sketched out with the requisite scale volume (~2.2 fl oz since you ask) and some brass sheet cut and bent into to two C sections to form it. These were then soldered together, which was not the easiest thing as I’m no coppersmith.

A small frame was made from plasticard to support the tank.

The new oil tank in its intended location toward the bows.

The filler cap was left off while I waited for some suitable sized brass tube to be delivered. Once that had arrived a simple cap was soldered up.

The whole affair was then ‘aged’ in another ammonia vapour bath. It was in there rather longer than I intended due to the distraction of our cat. Not a complete disaster though.

There’s not much room between it and the end of the engine. Fitting the oil pipes might be fun later.

That brings me on to the engine mount. Up to now I’ve been using a gash item made from balsa, because it’s easy to work. I wanted to turn that into something more substantial for the final model, so reached for the birch ply.

The inner parts of the mount will be completely hidden in the finished model so are more structural than scaled. It was quite an involved task to get the right shape, despite having built the balsa prototype. There was a lot of trial fitting and fettling before I got the shape I wanted.  Particular attention was paid to getting the mount parallel to the main deck.

The whole affair was then given a quick coat of epoxy resin, and when that had cured, a sand smooth followed by a coat of matt light grey to match the rest of the bay.

The cockpit bulkhead in the engine bay was a bit of a mess as a result of hacking it about to make a hole for the gearbox to fit into. In order to restore order I’ve cut out some 1/64″ ply to act as a veneer and cover up the previous sins.

Having done that I wanted to make sure that it was actually possible to get the engine and gearbox combination into the bay while fitted to the engine  mount. Trying to bolt the engine onto the mount once the latter is in the boat doesn’t bear thinking about.

The fit is exceptionally tight indeed, and requires more force than I’m strictly happy with to get it to snap into position, but it will go. Just. It amuses me to think that when I first set out designing the engine I was concerned it might look a bit lonely in the model’s engine bay.

As you can see from the picture above, having actually got the engine in place, I finished off the exhaust installation.

I’d always imagined that there would be a flexible section between the engine and hull mounted parts. When I was working as an aircraft designer I recall seeing a number of braided high temp pipes when vibration isolation and a degree of flexibility was required, so decided to try and replicate something similar. My design is based on some braided oil hose from a turbo installation left over from my kitcar building days.

 

While the hose might be flexible in real life it certainly didn’t want to go in the curves I wanted it to and was much too stiff for the model. The forces required to get it to lie ‘naturally’ were too much and something was going to break. In the end I resorted to putting in another supporting armature, made from 1/4″ copper brakepipe, to force it into the shape I wanted. The whole affair was then filled with epoxy resin, so it’s anything but flexible now.

As you can see from the above picture, I’ve also made some top-hat ferrules to support the pipe at the cockpit bulkhead end. They are made from brass pipe and sheet, soldered together, then bright nickel plated. They are designed so that the flexible section isn’t hyper-critical on length too. I’ll have a little leeway at both ends when it comes to final assembly.

Next up was a battery.

I’m doing the model to look like a vintage machine might appear today. I’m already committed to that path actually, as the ignition wiring on the engine is modern style. No Gutta Percha insulation there.

Again I went down the 3D printing route because I’m much better at CAD than I am carving! A modern style battery was knocked up in CAD, printed, then used to make a mould for resin casting.

I also scoured the net for some pictures to make decals from. In this case an Exide marine battery of 100Ah capacity. I’ve gone for 12V too, as that is the norm for boats under 40′ apparently.

A quick coat of matt black followed by the decals and an overcoat of satin lacquer resulted in…

I had planned on a fairly detailed battery box for the engine bay, made from photoetched brass sheet, but some research revealed that most of them are simple wooden box affairs. Hence, that’s what I went for in the end.

The planned location for the battery box in the engine bay. The location is determined by the need to keep the positive feed to the starter motor as short as possible. That minimises the voltage drop along the cable during the very high current draw of engine cranking.

I’ve also finalised the installation of the main cooling water feed. In the picture some trial duckboards are installed, but they won’t make it into the final  model.

The latest activities have been centred around making the engine bay door hinges and frames. I decided to photoetch them (as I did on the Chris Craft model) because that avoids any distortion of the thin brass sheet.

Masking up the brass sheet prior to etching. Both sides of the hinge are masked together. So at least if it is slightly out, both sides are out together.
After etching and some fettling to sharpen up the edges and corners. The assembly at the rear shows two halves of the hinge inter leaved. Once the hinge pivot rod is placed in the base of the right angle the individual tabs can be bent around it to form the hinge.

Things aren’t going so well at the moment though, as the first hinge is malformed! One side must’ve moved in the jig during the bending of the tabs, so there is a distinct taper to one wing. If I can’t get it apart I’ll have to start from scratch again which is a couple of days work down the pan.

Yours, 

Not happy of Worcestershire.

Yeah, where the sauce comes from. Lessons on how to pronounce it are available at reasonable rates…

Alternatively just say Wuss-ter-sheer.

Next month, how to pronounce Leominster, Gloucester and Shrewsbury.

‘Miss Severn’ 1922 Gold Cup Racer – Mack Models 1:8 (PART 2)

Well hopes of the next post in this series coming along sooner than the last weren’t realised. It’s been quite a long time since the last post on the Miss Severn build. However, progress has been going on in the background albeit slowly, despite illness and such.

In order to make some progress while I wasn’t at my best I polished up some of the fittings that come with the kit. The improvement in them is quite marked. Hard work without being able to use power tools though.

Having completed the basic hull, the next step was to plank it with the mahogany strip provided in the kit. The operation is pretty standard stuff. the planks were fixed with medium grade (as opposed to thin or thick) super glue. It’s a messy job as the glue seeps through the pores in the mahogany so it is almost impossible to stop it getting on your fingers at some point.

Having completed the bottom of the hull the chine line was redrawn and the planks cut back to it.

Chine line

With the chine line re-established planking of the sides commenced.

When the first few layers had been completed the boat was finally freed from the baseboard. It was at this point that I realised I’d messed up a little.

I’d stuck the doublers LS3 and RS3 on the wrong side of deck. Obviously they should be on the underside of it to allow it to be planked on top. It’s not specified in the instructions, probably because it should be obvious, but not having built many boats before it wasn’t to me. Ho-hum. They weren’t that hard to remove anyway with a chisel.

Having cleaned the deck up it was possible to get on with the assembly of it and the associated hatches. This was all done as per the instructions.

I took the opportunity to coat the inside of the hull with some expoy resin prior to completimg the decking. It was finished in a coat of mid grey paint.

Completed hatches
Hatches installed with spacers to allow for the hinges later.

The decking was completed which in turn allowed the remainder of the side planking to be finished and sanded flush with it.

Looking more like a Gold Cup Racer now.

At this stage I decided to get on with making some of the cockpit internals for a bit of light relief from all of the sanding, which I struggle with.

First up was the gearbox cover.

The wood in the kit wasn’t especially attractive to be honest, and the fixing tabs were very visible, so I decided to cover the entire assembly, and the rest of the cockpit items, with some mahogany veneer I had to hand. The improvement in the appearance between the veneer and kit parts is shown below.

Kit ‘mahogany’ on the right. Mahogany veneer on the left.
Finished gearbox cover with mahogany veneer applied.

The model I’m building has the optional lighting kit included. In order to hide the switch I decided to adapt the gear lever by installing it on a small rotary switch. The switch I opted for was a 24V, 0.5A Lorlin MTL-21-10 part, which I actually got from Farnell (Order code 2797234). The switch is an 8 position rotary one so each throw is 45°.

The whole assembly was then stained and varnished.

Modified gear lever, adapted to switch the lights on and off.

Next up were the seats which went through the same process.

And the cockpit ceilings and sideboards.

The sideboards, as supplied, had some annoying voids in them which thankfully would be hidden by the veneer.
After a bit of staining and varnishing. Oh, and a new cutting mat.

It was onto the seat squabs and backs next. The squabs were quite straight forward. A little bit of sculpting to make them look like they had been sat on in real life and some piping added around the edges, made from 0.5mm solder wire secured with super glue, and they were ready for sealing and painting. The seat backs were a different story.

The kit parts come fully marked up and just require some careful cutting, carving and sculpting to achieve the desired shape. However, sculpting and carving are not my strong suits, and the final results of my efforts did not make the grade. At all.

So I decided to make them again in a different way. I made some half round balsa strips of the right diameter and glued these to a thin piece of plywood backing as shown below. That at least gave me a nice even shape to seat backs which were then coated with resin, which was allowed to pool a little in the valleys so that they became rounded at the bottom.

Patent tooling for the making of half round balsa strip. Take your oversize square piece and hammer it through the nut and splitter to get two half round strips.

The final result was much more even than I could carve.

The instrument panel was my next project. I started with the instruments themselves. You have to cut the ‘glass’ yourself from clear acetate. I cut out some circles as a guide in masking tape using my sharpened compass. Then stuck them to the acetate, chopped off the corners and then sanded it circular.

The kit tells you to fix the pictures of the instrument faces supplied directly to the acetate with super glue. This was not an unqualified success for me as my glue disolved the print.

Luckily I’d already scanned in the pictures in case I needed extra copies. Bitter experience has taught me to always do this. So I was able to remake them. The second time around I mounted the pictures on some white plasticard and glued that into the bezel, behind the clear acetate glass.

The whole project then took a bit of a lurch to the left…

I was mocking up the dashboard to get a feel for how it would look. In particular I was trying to come up with a more in scale switch assembly than the one supplied in the kit. I ended up with a stainless steel pin in a small eyelet which looked OK. You can see it below next to one of the machined switches supplied in the kit.

The one thing that does leap out at you is that the grain on the instrument panel is very out of scale itself.

The real instrument panel in Miss Severn.

I decided to try a few other woods to see which looked best.

Oh, and I ought to warn you at this point that the kit dash has a hole in it which isn’t used and shouldn’t be there. It’s at about 2 O’clock from the steering column hole.

The drawing of the instrument panel vs the pre-cut kit part. The latter had an extra unwanted hole in my kit.

Having made the samples the decision was made to go with the pear option. Then commenced the job of actually buying enough pear to remake all the parts I’d just finished in mahogany!

While quite a few people advertise that they sell pear veneer and structural veneer, I discovered that most seem to only buy it in when someone orders it, and they can get it. It took me quite some time to actually locate some satisfactory supplies. A couple of months in the end.

The gearbox housing remade in pear is shown below next to the original mahogany one below. The improvement in the scale of the grain is obvious.

A lot of work went into the picture below. Honest!

Cockpit components remade in pear wood.
SS316L 2mm stainless steel strip used as capping for the sideboards. The screws are from US Microscrew P/N M06-30-M-SST PAN. They also sell on Amazon. They are M0.6 x 3.

The cockpit floor was also covered with pear veneer. Simulated brass screws were made using 0.8mm brass rod sanded flush, then scored with a knife blade to simulate a slotted head.

The floor was airbrushed with mahogany stain.

Mocked up in the model prior to the airbrushed stain being removed from the brass screwheads with acetone.

After it had dried the stain was removed from the screw heads with acetone on a fine brush. Be careful if you try this. A slight excess of acetone on the brush and it will pool and strip the stain from the wood around the brass too. Go careful.

CAREFULLY removing the stain with acetone.

And here it is again after the stain has been removed.

The next question was what finish to do the cockpit in? I had assumed that it would be gloss, but the satin looked so good. The problem was how to manage the transition from a satin cockpit to the high gloss hull outer. The latter has to be gloss as it is such a key characteristic of these boats.

In order to help make the decision I’ve decided to make a mock up in both satin and gloss just to see how they compare.

Mock-up in satin to determine the best finish in the cockpit.

I’ll let you know how it goes…

‘Miss Severn’ 1922 Gold Cup Racer – Mack Models 1:8 (Part 3)

‘Miss Severn’ 1922 Gold Cup Racer – Mack Models 1:8 (PART 1)

Having shelved the Chris Craft build for the time being until I can locate some acceptable fittings, or am well enough to make my own, I decided to move on to another boat build.

The model chosen was another 1/8th scale model. This time of a 1922 Gold Cup race boat derived design called Miss Severn. The kit is produced by Mack Products, and mine included the add-on lighting set. As the model will be built for static display, none of the radio control elements  will be fitted.

Continue reading ‘Miss Severn’ 1922 Gold Cup Racer – Mack Models 1:8 (PART 1)