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early board construction methods
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superkraut



Joined: 18 Mar 2001
Posts: 203

PostPosted: Wed Dec 18, 2013 7:38 pm    Post subject: early board construction methods Reply with quote

I am writing a treatise on windsurf board construction for a club website, and - while on firm ground with Epoxy sandwich - I find I am adrift with some of the early methodologies. Asking "specialists", there are terms like "roto-molded PE" and "blow-molded" being bandied about, but nobody seems to know much about what that actually entailed.
The original windsurfer, for example: thick PE skin, no reinforcements, Urethane foam core. Roto-molded? So where does the much-cited "blow-molded" come in? is that blow-molded EPS?
HELP!
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cbknap



Joined: 03 Jun 1997
Posts: 300

PostPosted: Wed Dec 18, 2013 8:01 pm    Post subject: Reply with quote

Hi Eva--

from http://en.wikipedia.org/wiki/Rotational_molding

The rotational molding process is a high-temperature, low-pressure plastic-forming process that uses heat and biaxial rotation (i.e., angular rotation on two axes) to produce hollow, one-piece parts.[7] Critics of the process point to its long cycle times—only one or two cycles an hour can typically occur, as opposed to other processes such as injection molding, where parts can be made in a few seconds. The process does have distinct advantages. Manufacturing large, hollow parts such as oil tanks is much easier by rotational molding than any other method. Rotational molds are significantly cheaper than other types of mold. Very little material is wasted using this process, and excess material can often be re-used, making it a very economically and environmentally viable manufacturing process.
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superkraut



Joined: 18 Mar 2001
Posts: 203

PostPosted: Wed Dec 18, 2013 8:51 pm    Post subject: Reply with quote

well, yeeeees..... so was the Original Windsurfer One Design roto-molded (kind 'a looks like it, with the skins a bit thicker in the ends than on the flats), and then?? the PU poured and expanded in situ?
and was blow-molding used anywhere by any of the early manufacturers?
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shreddbob



Joined: 31 Mar 1987
Posts: 277
Location: Massachusetts

PostPosted: Thu Dec 19, 2013 1:42 am    Post subject: Reply with quote

Hi. I have an original Mistral Superlite from 1984. It has an epoxy skin and an injected eps foam core. I seem to remember this board's construction was novel for the day, being one of the first "vacuum bagged" epoxy designs, making it pretty light for its size. Light wind dominator on the race course.

Some links I dug up:

Spec's on a used one for sale today:
http://www.windpowerwindsurfing.com/shop/index.php?main_page=product_info&cPath=10_23_85&products_id=1374

this iWS thread has a lot of conflicting memories about the construction but I think Iso's explanation on this page is accurate:
http://www.iwindsurf.com/forums/viewtopic.php?p=131176&highlight=#131176

I hope this helps.
Bob
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keycocker



Joined: 10 Jul 2005
Posts: 3385

PostPosted: Thu Dec 19, 2013 12:23 pm    Post subject: Reply with quote

Thommen told me they would make the two shells in two heated molds and inject foam after joining them, then trim the edge seam.
Trimming it flat compromised the bond so a edge was left that was visisble.
It wasnt always EPS at first.
We took them apart and reused the foam to shape smaller boards in Belize in the 80s. All of those were closed cell foam which did not absorb water when you got a hole This foam added weight though.

To repair them we used a plastic hot knife and sticks of flexible plastic.

BIC pens and lighters were made of the same stuff so BIC bought Dufour in France and began making Dufour boards under the BIC name. They were thz biggest maker in those days with production figures much larger than the biggest makers today.

Even years later we left our epoxy boards at home when we travelled and took only Hifly and Bic poly boards with us/ they were so bombproof you just checked on the plane bare with no box.
they were mostly flat boards
.Thommen said they would heat them in his shop for you and bend up the nose to get some rocker. Stored in the sun they sometimes went flat again.

The mast track and fin box were glued or screwed or both into a depression in the plastic shell. Changing those items was easy. You didnt see the foam ,just a sealed depression when you changed the mast or fin boxes. so there no leaks in these areas like today.
They cost nearly a grand when that was a lot more money so modern boards actually cost less.
they didnt delam much either and needed no vents
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superkraut



Joined: 18 Mar 2001
Posts: 203

PostPosted: Thu Dec 19, 2013 12:38 pm    Post subject: Reply with quote

thanks a bunch, Keycocker and Shreddbob, that helped a lot!
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keycocker



Joined: 10 Jul 2005
Posts: 3385

PostPosted: Thu Dec 19, 2013 1:11 pm    Post subject: Reply with quote

Thanks to you milady. Your expertise that you shared on your site set the standard in board repair worldwide.
If you ever want to come to Maui send a PM; we will put you up.
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superkraut



Joined: 18 Mar 2001
Posts: 203

PostPosted: Thu Dec 19, 2013 1:25 pm    Post subject: Reply with quote

thanks, Keycocker! I may need to take you up on that, as my lake is drying to a dysfunctional puddle
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noel



Joined: 06 Aug 1998
Posts: 13

PostPosted: Thu Dec 19, 2013 4:17 pm    Post subject: Reply with quote

Lake Isabella water level better be high next year for the Speed Challenge...Already busy sanding fins day and night for this particular event! Boris better watch out Very Happy
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superkraut



Joined: 18 Mar 2001
Posts: 203

PostPosted: Thu Dec 19, 2013 5:18 pm    Post subject: Reply with quote

sand on, Noel!
with the Second Annual Lake Isabella Speed Week tentatively scheduled for May 9 through May 18, we ought to have enough water to safely sail, even though we are at only 8% full right now, and even though this winter is not shaping up to be particularly wet for us. Below view from the AuxDam, which is not at the moment called upon to hold back any water...
Stay posted!



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