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Sponson Stress Testing

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LohringMiller

Well-Known Member
Joined
Jan 25, 2017
Messages
477
Well, my last set of 3D printed sponsons failed the stress testing. I did hit a buoy during tune up testing, but everything looked OK. I couldn't understand why the boat stopped turning during the first heat. When I brought it in it was obvious.

I decided that printing with the layer lines along the long axis would help since the tensile strength across the layers is around half of the strength along the layers. Below is the new design. I divided the sponsons into quarters, giving a central bulkhead for even more strength. I used 4 perimeters and upper layers with a low infill percentake. see below.

Lohring Miller

P1010517.JPGP1010515.JPGP1010516.JPG
 

ALLAN YUEN

Well-Known Member
Joined
Jan 14, 2005
Messages
5,614
Wow no more wood so replace Bullet Plastic . I wonder that Is it float or sink down?
 

Buoyhunter

Well-Known Member
Joined
Nov 10, 2002
Messages
378
Prints will absorb moisture after being in the water for a while. That can be remedied with a little clear coat. It seals the possible gaps between layers of the plastic.

I have several sets of sponsons drawn and printed. Right from Geraghtys JAE plans. Not as fancy as yours Lohring. I'm on version 3 and have not driven on any of them yet... they are super strong and lighter than the foam filled ones that you build from the kit. Pretty happy with the latest version. This pic is of version 2. I was looking to epoxy a plywood bottom on the print but after seeing the final product opted to skip the bonding step.
 

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LohringMiller

Well-Known Member
Joined
Jan 25, 2017
Messages
477
My sponsons haven't lasted long enough to worry about waterproofing. I haven't noticed significant leaking, though. Race boats shouldn't spend long times in the water.

Lohring Miller
 

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