Making 3-bladed props

I think it would be very hard to cast props in resin without a professional set-up. A pressure pot and a vacuum set up would be virtually required to keep the bubbles out of something as long and thin as a prop blade. I've only done open mold resin casting of small parts and have had a lot of trouble with bubbles.

 That's why I scratch built the last time I needed props for the old Revell 1/115 scale P-3. I made a master template out of brass for one blade and used it to cut all 16 that I needed from card stock. I stuck the template to the card using double sided tape. I carved around the template and got 16 pretty uniform blades.

I shaped them all, one at a time by eye. Once you get the rythm of it, they end up pretty close. Probably not perfect, but I try to loosen up my perfectionist streak a little so as to not go crazy and so I can actually finish a model now and then.

The P-3 props have spinners that I made by modifying the kit spinner (longer and more steeply conical) and then cast in resin (with lots of bubbles) in an open mold.

The weapons are scratch built as well, not too much available in 1/115 scale in the marketplace!

I've cast parts in resin and have found that there is a lot of variation in different makes of resins, and also it does not age well in the containers.  I think moisture is the culprit.  I've had pretty good luck with resins from TAP Plastics, that's a chain store in California.  Resins that go off too quick are a problem because they seem to build up more heat, that has caused bubble problems for me.  I pour the resin into the mold very slowly, in a thin stream, so less air gets trapped in the mold.  I've made some pretty thin parts, and I've had my share of failures.  I make my molds with silicone mold making material, and that does require vacuum, which I used to get by plumbing to the intake side of my air compressor.  Worked fine, got down to 27 inches of vacuum.

I've got a similar prop problem on the horizon - I'll need to update Revell's 1/144 E2-C Hawkeye to the new 8-bladed prop configuration. If there's an aftermarket source out there, I haven't found it yet.

I do like the idea of a brass template for the master - much more practical than the thicker plastic I was contemplating. I THINK I can use the existing hubs, but at that small scale ... how would you attach the blades with any hope of having them staying on? 

 

mfsob wrote:

... how would you attach the blades with any hope of having them staying on?

I used a #80 drill and some 12thou brass beading wire. They aren't at all rigidly fixed and I have to re-bend them in place every time I touch the thing but none have fallen off. ...yet...

Hey Dave, John and mfsob

Thanks for the tips, advice (both positive and negative) and sympathy.  I agree, the brass template idea sounds like a winner.  I knew there'd be help here.

I've never considered a scale smaller than 1/72, and the idea of doing 16 scimitar-shaped blades makes me shudder.  Dave, your P-3 effort is inspiring to me.  I believe now I can do it!  BTW, are those torps two different models?  The lengths look different to me.

Thanks again

Dick

rlawson wrote:

BTW, are those torps two different models?  The lengths look different to me.

 Thanks for the comment!

Well, there are both Mk-46 torps and AGM-84 Harpoons in the picture, the Harpoons are a lot longer. If you mean just the torpedoes, there are six of them arranged in two piles of three in an inverted "V" with a gap between the two stacks. So, I think it may be just perspective that makes the back three look shorter. It might be affected by the macro setting on the camera, too; they are all the same length.

 

 

Dave

After a second look, I see what you're saying.  Thanks.

Dick