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 Post subject: Introducing the Hoff - a transparent acrylic board
PostPosted: Sun Mar 02, 2014 7:01 pm 
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Joined: Wed Sep 11, 2013 3:51 pm
Posts: 32
This was my first board build, and I think it turned out excellently.

The idea is simple - support a flexible sheet with rigid spars.

In practice there are some complications to overcome, i.e.
    Shaping the spars to include a rocker component
    Placement/shaping of the spars to support the sheet edges and leave room for boots/pads
    Bonding the spars to the sheet

I consider this build a prototype, and therefore wasn't too critical about the material used. I sourced the following from my local Builders Express:
    Perspex (acrylic - PMMA) sheet: 1400 x 450 x 4 (mm)
    Aluminium sheet (I assume 1200 0 alloy): 1400 x 50 x 2 (mm)
    Aluminium blind rivets: 4 x 10 (mm)

The next version will probably use 5083 alloy and polycarbonate sheet, and I'm considering methacrylte adhesive instead of rivets to bond the pieces, depending on whether the rivets cause notching/cracking.

Anyhow, for the board shape I simply traced the outline of my LF Harley wakeboard, and cut it with a hand held jigsaw.

For the aluminium spars I traced the rocker outline, cut it with a jig saw, and bent it into shape with a vice and a hammer.

Polished all the edges and drilled 4.2mm holes 50mm apart to join the spars to the acrylic sheet with the rivets.

Attached my LF Vantage boots with bolts directly to 7mm holes drilled through the acrylic sheet.

Total build time was about 10 hours.

Board specs: 1400 x 450, 8cm continuous rocker. Deck weighs 2.9kg.

For comparison, my LF Harley Grind deck is 3.7kg, and my carbon split kiteboard deck (128 x 40) is 2.8kg.

So how does it ride?

Well I took it for a spin at the local cable park today and am pretty stoked about it! The ride is really smooth and stable and it edges really well. It's more flexible than any of my other boards so it doesn't pop much but it seems to handle chop quite nicely.
I've done a few raley launches off the dock and a couple of ollies and it seems pretty robust. Haven't done any kickers or sliders yet but have gone down hard after catching an edge - so far nothing bent, broken, ripped out or cracked.

Only bummer is swimming in with the board requires you to keep hold of it. It does not float!

I'll post some more detailed pics of the build if there's interest..

First dry run in my back yard
https://vimeo.com/87932915

First wet run at the cable park
https://vimeo.com/87995258


Attachments:
Hoff prototype bottom.JPG
Hoff prototype bottom.JPG [ 162.27 KIB | Viewed 1519 times ]
Hoff prototype top.JPG
Hoff prototype top.JPG [ 208.53 KIB | Viewed 1519 times ]
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 Post subject: Re: Introducing the Hoff - a transparent acrylic board
PostPosted: Sun Mar 02, 2014 8:21 pm 
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Joined: Mon Sep 23, 2002 1:00 am
Posts: 1801
Location: Cape Cod, MA USA
Nice job. Is your water clear enough to enjoy the view? Are you going to add any fins?

To bad the density of lexan is so high. Maybe an OR goJoe would keep it afloat?

Ed


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 Post subject: Re: Introducing the Hoff - a transparent acrylic board
PostPosted: Mon Mar 03, 2014 6:51 pm 
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Joined: Thu Dec 04, 2008 1:50 am
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Really cool to see the actual wetted area on a board as it planes.....

There's some super interesting stuff going on there for sure.
I'll have to watch it a few more times but there's a lot to be learned simply by watching that vid.

Be really interested to see the water dynamics of a few hard load and pops.


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 Post subject: Re: Introducing the Hoff - a transparent acrylic board
PostPosted: Mon Mar 03, 2014 8:57 pm 
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Joined: Sun Sep 04, 2011 5:37 pm
Posts: 1732
Can't wait to see this loaded up under kite power, with a rail dug in !!

Bille


Last edited by Bille on Tue Mar 04, 2014 10:08 pm, edited 1 time in total.

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 Post subject: Re: Introducing the Hoff - a transparent acrylic board
PostPosted: Mon Mar 03, 2014 9:49 pm 
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Joined: Mon Mar 14, 2005 4:05 pm
Posts: 1101
Location: Islamorada, Florida Keys
Nice board! I have a similar board made from Lexan. (I think) It is heavy but floats. Kind of heavy too. I will try to post a pic of it. You really can't see much as your riding because there is always a little air under the board. Sits in the corner as a talking piece more than a riding piece.


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 Post subject: Re: Introducing the Hoff - a transparent acrylic board
PostPosted: Tue Mar 04, 2014 3:57 pm 
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Joined: Fri Oct 30, 2009 9:13 pm
Posts: 941
I never take my board off when I fall until I get to the shore any ways. My thoughts are it probably will give out at the boots before anywhere else. Looks sick anyways.


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 Post subject: Re: Introducing the Hoff - a transparent acrylic board
PostPosted: Wed Mar 05, 2014 4:21 pm 
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Joined: Wed Sep 11, 2013 3:51 pm
Posts: 32
The water at my local spot is not clear enough to give any kind of view below the water, although I can imagine riding this over a reef at an idyllic island spot would look spectacular.

I generally ride without fins so haven't considered putting any on, but it would be a fairly simple matter to drill the holes and mount fins.
You could probably even heat-bend some tabs down at the edges to create fins as part of the board shape.

As TheJoe mentioned, if you ride boots then the fact that it doesn't float is immaterial. Something like a GoJoe would probably help but would totally kill the coolness factor :-)

If you ride straps then both the sinking as well as trying to find a transparent board in the surf would be problematic. Then it may be better to consider other non-transparent plastics like polypropylene which have a lower density and you may end up with a non-sinking, visible board. These materials are also more durable than acrylic or polycarbonate.

I'll be stress testing the board a bit more in the near future to see what breaks.

Some pictures below:
    Spar attached to sheet with rivets.
    Bending the spars with a hammer and vise.
    Cutting the board shape.


Attachments:
curvature.JPG
curvature.JPG [ 152.35 KIB | Viewed 1045 times ]
spar shaping.JPG
spar shaping.JPG [ 158.18 KIB | Viewed 1045 times ]
board shape.JPG
board shape.JPG [ 119.9 KIB | Viewed 1045 times ]
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 Post subject: Re: Introducing the Hoff - a transparent acrylic board
PostPosted: Thu Mar 06, 2014 4:40 am 
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Joined: Thu Feb 12, 2009 9:50 pm
Posts: 358
that is amazing!


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 Post subject: Re: Introducing the Hoff - a transparent acrylic board
PostPosted: Thu Mar 06, 2014 3:43 pm 
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Joined: Mon Jul 01, 2013 7:16 am
Posts: 283
Location: Perth, Australia
Nice,

how is it riding, looks a bit slippery with no fins and concave?

Perspex board was introduced a few years back:

http://extreme.com/kite/1009040/plexiglass-kiteboard


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 Post subject: Re: Introducing the Hoff - a transparent acrylic board
PostPosted: Wed Mar 12, 2014 10:51 am 
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Joined: Wed Jan 15, 2014 2:37 pm
Posts: 11
Location: Windy!
any movie edit will be available?


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