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Molded 40mm FAI Airframes

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TheAviator

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A couple of months ago, a member of the US Spacemodeling team showed me a 40mm model he bought from a Russian manufacturer. It had an immaculate surface finish indicative of a internally molded process. I recently came by some scrap 1" thick acrylic stock, so I am taking a pass at making my own 40mm airframe molds.

These are two halves of a complete mold machined on a ShopBot type router. They're hot off the presses today, and the next step is to polish the molds with increasingly fine grit sandpaper. First, I need to polish the mold cavity and resin channel, then knock down the extra material around the cavity and polish the parting plane. More info as more work is done! Time for some elbow grease...

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watheyak

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Super cool.

For a long time I've wanted to make airfoiled fins in a two part mold. A ShopBot was discussed, but with MDF mold material. The acrylic is a really cool idea.

Subscribed!
 

James Duffy

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Very impressive, Brian! Please keep us updated as you progress with this project.

James
 

watheyak

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Super cool!

Can you explain a bit about the molds? We're they made made by you or by a third party?

My recent bladder mold was a ton of work and probably not much cheaper than an aluminum one.
 

kkooch

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Super cool!

Can you explain a bit about the molds? We're they made made by you or by a third party?

My recent bladder mold was a ton of work and probably not much cheaper than an aluminum one.
Scott- 2nd party and an FAI team member. I provided the coords and general mold parameters and he turned it out. With CNC aluminum molds, polishing of the mold surface is required after receipt. 500 grit sandpaper to start and then working up to 0.25 micron diamond polish is mandatory for a mirror like finish on the mold and then on your finished model.
 

shockie

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A couple of months ago, a member of the US Spacemodeling team showed me a 40mm model he bought from a Russian manufacturer. It had an immaculate surface finish indicative of a internally molded process. I recently came by some scrap 1" thick acrylic stock, so I am taking a pass at making my own 40mm airframe molds.

These are two halves of a complete mold machined on a ShopBot type router. They're hot off the presses today, and the next step is to polish the molds with increasingly fine grit sandpaper. First, I need to polish the mold cavity and resin channel, then knock down the extra material around the cavity and polish the parting plane. More info as more work is done! Time for some elbow grease...

View attachment 295456

View attachment 295457
Fantastic. Good Luck!
 

kkooch

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Super cool.

For a long time I've wanted to make airfoiled fins in a two part mold. A ShopBot was discussed, but with MDF mold material. The acrylic is a really cool idea.

Subscribed!
I've had aluminum molds made for thin fins via a UK Fai modeler. With small thickness fins and a razor sharp TE, when removing from the mold, they can distort, slightly and unfortunately. This will cause squirrely trajectories! Composite, tiny thickness fins that have a good molded airfoil is something to endeavor.

Best so far is true C-grain balsa, contest grade with Japanese tissue on top and vac'd down. Flat, and can be attached to the body using a jig. With flat fins and attached accurately, there is minimal spin on boost. Though I have been imparting a very small angle so that the model does spin slightly on boost and because of head winds aloft. So a tiny spin on boost is desirable - 2-3 rotations before apogee.

Kooch
 

kkooch

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are these molded for 10 or 13mm motors? Will they be available to the general public to purchase?
Shockie- Show up for a contest using and I can supply you with models! They are molded 10mm, but a simple cut at the aft and you can add on a 13mm tube. I have no desire to get into the rocketry kit biz, unfortunately, if you are thinking. Too much going on with my career.
 

shockie

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Shockie- Show up for a contest using and I can supply you with models! They are molded 10mm, but a simple cut at the aft and you can add on a 13mm tube. I have no desire to get into the rocketry kit biz, unfortunately, if you are thinking. Too much going on with my career.
What does this mean?

Show up for a contest using and I can supply you with models!
 

GuyNoir

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ched to the body using a jig. With flat fins and attached accurately, there is minimal spin on boost. Though I have been imparting a very small angle so that the model does spin slightly on boost and because of head winds aloft. So a tiny spin on boost is desirable - 2-3 rotations before apogee
What method do you use to make that happen? I would think that imparting that little spin would take a precision that my N years old (N = large positive integer) eyes can no longer support, even with glasses. . . .
 
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