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Rapid Prototyped Cowling 1:72 Curtiss Hawk


dr_gn

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So the original cowling on my Curtiss Hawk didn't fit, and despite trying to mod the original, there was no way it was ever going to fit both the engine and the fuselage.

I thought why not try Rapid Prototyping a replacement. I started by scribing and filing a step in the fuselage over which the new cowl would fit:

MWT2BODO.jpg

Then, found some 3-views online:

iwe26qov.jpg

Surprising how bulged the cowl is in plan. Anyway, after scaling and measuring I drew a new cowl on proE Wildfire. Quite a simple job, only about 1/2 hour of work:

yoAw9yn8.jpg

Then 'grew' it on an RP machine. Ours uses the fused deposition moulding method, and extrudes hot ABS plastic in layers:

4rNMwtdN.jpg

The first one was slightly too thin, and cracked easily so I added 0.25mm onto the wall thickness on the CAD model, and tried again. This time it was OK, so I covered it in thin cyano to make it more durable, and sanded it back smooth:

YhK2xJTu.jpg

The resolution of the RP machine isn't good enough for surface features, so these were scribed by hand and a drill bit:

ksSlJuux.jpg

And here it is slotted onto the fuselage:

Wtpm8Z1Y.jpg

sGatdzYK.jpg

No, it's not perfect, but it will at least allow me to hopefully finish the model, plus I've learned a hell of a lot about the process. Once higher resolution RP machine become cheaply available the filling and rescribing will not be needed and the above would be the work of a couple of hours.

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That looks really good now, how does the engine fit in?

bit of work in the fuselage under the cowl flaps, and it will be a stunner

Ta,

The cowling is only about 0.3mm wall thickness so it just springs enough to get the engine in. Even so,. the rear cylinders needed chamfering, and the overall OD of the engine was already reduced very slightly during construction.

As I said it's not going to be perfect, but then again the original was't: it wasn't even symmetrical left to right.

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  • 2 weeks later...

Congratulations, great work, a lot of self satisfaction and as you say another model destined to be finished. Thanks for sharing the pics.

Colin

Thanks, but it's not all been plain sailing since the last update: The rp cowl itself was fine, but the resin gun bulges in the kit were hopeless - they weren't even the same left to right, so getting them to look right was pretty much impossible.

I have another option, which is a sls type of rp which I'll try next. The advantage of this method is that it is high resolution so I can model the gun bulges and panel lines in from the start. The disadvantage is that I'll need a sub-contract company to do it. I looked at Shapeways, but none of their resolutions appeared to be good enough. It's a shame because I was really happy with the way the original rp part was looking with the engine fitted.

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  • 4 months later...

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