Thank you to the people who replied to my query about material properties
for scuba fins. Here is a summary of replies received. Names are omitted if
the reply was sent privately. I didn't quite get the quantitative data I was
looking for, but I did get four different opinions about what scuba fins are
made of: sanoprene, natural rubber, glass-reinforced silicone rubber, and
EPDM.
A service company which prototyped fins for a previous customer said the
production units use a 95 Shore A material, possibly sanoprene.
A former toy company employee said that production fins are made from
"rubber, real rubber from trees" by a fairly involved process and that
"science hasn't found a man made compound that will compare with real
rubber."
Bill Richards at Virtual Concepts Design said the best fins are made of
glass-reinforced silicone rubber and said he'd like to try making some fins
in such material by either LENS or FDM. He went on to share his personal
experience of the possible advantages of a custom diving mask. But he also
raised the knotty problem of cost, which I will address in my article.
Nick Osborn of Swift Technologies reported on some work they have done
in making custom automotive seals by LOM of EPDM, which he said is the
material used in making both tires and scuba fins. The problems were the
stepped surface and deficient material properties.
An experienced diver from an aerospace company pointed out what I found
when I went to inspect fins at a local sporting goods store, that at least
some fins are made of two different materials. The boot part is soft for
comfort, while the flipper part is more rigid for propulsion. He also said
that the most important property for him would be buoyancy, because he keeps
losing his fins.
Justin Kidder at the U of Pittsburgh corrected my omission of FDM from
the list of fabbers that can work in flexible materials, pointing out
Stratasys' Elastomer 20 material.
Thanks for your replies folks. This does give me some interesting ideas
to work with.
Best regards,
Marshall Burns
President, Ennex Corporation
Marshall@Ennex.com
Los Angeles, USA, (310) 824-8700
www.Ennex.com
-----Original Message-----
From: Marshall Burns <Marshall@ennex.com>
To: RP-ml@bart.lpt.fi <RP-ml@bart.lpt.fi>
Date: Monday, November 08, 1999 7:12 AM
Subject: Flexible materials for scuba fin
>Hi folks,
>
> First question: Does anyone know the technical numbers that describe
the
>material properties required of a SCUBA FIN? Properties such as modulus,
>elongation, tensile and flexural strength, etc. and also surface
smoothness?
>Primarily, I see a need for a material that combines being SOFT and
>TOUGH, but I'd like to be able to express that quantitatively if I can.
>
> Second question: How close are we to being able to deliver those
>properties straight out of a fabber today? Many of you are experienced in
>using flexible materials on today's fabbers (SLA, Sinterstation, maybe some
>on LOM). How close could you come to making a scuba fin that you could put
>on your foot and go diving in?
>
> I'm not talking about a secondary process that casts in a different
>material after fabbing a mold or master on the fabber. I'm talking only
>about materials that come directly out of the machine.
>
>
> (This posting carries on with the discussion last week about direct
>manufacturing of products in fabbers. I've told you that I'm writing about
>this for an upcoming issue of the RP Report. You may have seen a TV
>commercial by UPS that shows a scuba fin being delivered from an Internet
>vendor by a fabber in the customer's home. I'll be writing about how far
>that fantasy is from becoming reality. Thanks for your help with my
research
>on it.)
>
>Best regards,
>Marshall Burns
>President, Ennex Corporation
>
>Marshall@Ennex.com
>Los Angeles, USA, (310) 824-8700
>www.Ennex.com
>
>
>
>For more information about the rp-ml, see http://ltk.hut.fi/rp-ml/
For more information about the rp-ml, see http://ltk.hut.fi/rp-ml/
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