dr_gn Posted September 7, 2013 Share Posted September 7, 2013 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: Then, found some 3-views online: 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: Then 'grew' it on an RP machine. Ours uses the fused deposition moulding method, and extrudes hot ABS plastic in layers: 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: The resolution of the RP machine isn't good enough for surface features, so these were scribed by hand and a drill bit: And here it is slotted onto the fuselage: 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. Link to comment Share on other sites More sharing options...
Graeme H Posted September 8, 2013 Share Posted September 8, 2013 (edited) 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 Edited September 8, 2013 by Graeme H Link to comment Share on other sites More sharing options...
dr_gn Posted September 8, 2013 Author Share Posted September 8, 2013 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. Link to comment Share on other sites More sharing options...
Giorgio N Posted September 20, 2013 Share Posted September 20, 2013 Very nice job and always very interesting to see modern technologies helping the modeller Link to comment Share on other sites More sharing options...
heloman1 Posted September 20, 2013 Share Posted September 20, 2013 Congratulations, great work, a lot of self satisfaction and as you say another model destined to be finished. Thanks for sharing the pics. Colin Link to comment Share on other sites More sharing options...
dr_gn Posted September 20, 2013 Author Share Posted September 20, 2013 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. Link to comment Share on other sites More sharing options...
dr_gn Posted January 24, 2014 Author Share Posted January 24, 2014 Finished pics here: http://www.britmodeller.com/forums/index.php?/topic/234954125-special-hobby-172-curtiss-hawk/ Thanks! Link to comment Share on other sites More sharing options...
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