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Pictures and dimensions of a snowfer?
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rlemmens



Joined: 09 Feb 2008
Posts: 179

PostPosted: Mon Oct 24, 2011 3:13 am    Post subject: Reply with quote

Not sure if this is helpful, but for your metal skeg on ice if it isn't sharpened right it'll just kind of slide. If you do a little research on how they sharpen hockey skate blades you'll see they use a concave cut. A basic explanation would be you use the edges of the blade it get grip and slide and the shape radius of the blade has to do with your turning radius. Also, when you put pressure on the blade, the ice melts a little bit, turns into water which lets you glide. Hope this helps.
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MattD



Joined: 25 May 2011
Posts: 33

PostPosted: Mon Oct 24, 2011 12:01 pm    Post subject: Reply with quote

rlemmens wrote:
Not sure if this is helpful, but for your metal skeg on ice if it isn't sharpened right it'll just kind of slide.

Interesting. I would probably get the fins sharpened by a skate store. I wonder if such a store could sharpen the blade from 'nothing', i.e. from the 1/4" rectangular edge.

inf2003 wrote:
Its really just the top of a windsurf board with the bottom of a snowboard.

This is how I was thinking of making the board. I'm not 100% familiar with board fabrication so comments are welcome.

Make the rocker mold like this.
Pour urethane expanding foam on top of mold (rocker will be matched)
Cut out outline of board, shape top of foam.
Cut out holes in foam for inserts and epoxy/fiberglass them in.
Cut out p-tex, attach edges and VDS rubber (prevents delam).
Layup p-tex/fiberglass/foam/fiberglass and vacuum bag, with the bag taped to the mold.
Epoxy divinycell to top of board (is this correct?), then lay up final fiberglass & vacuum bag.

I think it would be more ergonomic to design the rocker such that top of the board is parallel to the ice when there is no snow. I imagine I will have a few different fins, so perhaps have a very low profile fin for icy conditions, and compensate with board rocker to make the top flat when using that fin. I'd really like to see your rocker once you've drawn it up.

Urethane foam is about twice as dense as EPS but weight isn't really a concern in this application. Pour foam will make matching the rocker to the mold super easy, and the foam is closed cell.

I really want to get fabrication down to a simple and cheap process so I can make boards for friends and get them out on the ice/snow with me! I wonder if sandwich construction with divinycell could be skipped by instead using thicker fiberglass? Would 18oz be enough?
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inf2003



Joined: 15 Jan 2009
Posts: 136

PostPosted: Mon Oct 24, 2011 3:10 pm    Post subject: Reply with quote

Matt, I will address some of the points you brought up just to tell you what i was thinking.

How to sharpen fin. If you look at the pictures I posted and the closeup of the fin it is clear that it is sharpened to a point and not a hollow ground like a skate. It seems to work for the manufacturer so that is how I was going to do it. If it doesnt I can always make a new fin. I dont really see how a pointed edge can slide if it is sharp and straight with rocker at the front and back like a freeskate blade. My freeskate blades are pointed and dont slide.


I like your idea with the urethane pour or spray foam. Very ingenious. like you said it will match the shape of the board.

As far as rocker. I really dont think the pirate board has any . If you look at the videos closely it looks like the board only hits just before the upturn and the fin. It looks like the bottom is just flat except for the upturned nose.

the press is a great idea if you dont have a vaccum bag but it seems like a lot of extra work if you have a vaccum press. The way i see it the mold for the vaccum press is just a flat with a flip up at the front. Easily done in foam or wood per your method if you will be pressing multiple boards. Also with the vaccum press you only have to make a one sided form with a flexible caul on the top like a sheet of plastic laminate. With the press you need two sides and you have to allow for the final thickness in between. That is much more difficult.

I was also wondering myself it you could just do a sandwich construction like a snowboard and perhaps make the core thicker or add a few more layers of glass. I think the foam is just for rigidity. From what I read on the pirate boards is they have no flex at all. I was also wondering if flex would be a good thing so that it would carve better on the snow like a snowboard. My guess is that flex would be bad as it would cause the mast base pressure to bend the nose down . Especially where you stand on the rear end of the board. Also it would be better to have a stiffer board for the ice as it would be more likely to hold an edge in the ice. Therefore I will make mine stiff. I dont know if you could just add more layers to a sandwich construction but I dont see why not. Just a thick wood core would probably do it.
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MattD



Joined: 25 May 2011
Posts: 33

PostPosted: Mon Oct 24, 2011 8:27 pm    Post subject: Reply with quote

inf2003 wrote:
As far as rocker. I really dont think the pirate board has any . If you look at the videos closely it looks like the board only hits just before the upturn and the fin. It looks like the bottom is just flat except for the upturned nose.

I guess if the board is super stiff then rocker isn't going to do anything anyway. I assume that more rocker on a snowboard will give more spring since it is more flexible.

inf2003 wrote:
the press is a great idea if you dont have a vaccum bag but it seems like a lot of extra work if you have a vaccum press.

I agree about the press, I wasn't planning on doing that. I just liked how they made their mold, and I've seen others use similar molds with a vacuum bag setup, where the bag is taped to the mold (what you are describing, I think). I conveniently have a vacuum line in my lab so I don't want to make a press (not suitable for this construction anyway, no pressure applied to the sides).

inf2003 wrote:
The way i see it the mold for the vaccum press is just a flat with a flip up at the front.

That would certainly be easier than implementing a more complicated rocker. It would be nice to have a rocker that had a lot of surface contact on ice, but I'm not sure if it is worth the effort. My worry is that with a flat rocker, only a small part of the p-tex will be touching the ice, leading to increased wear in that region.

inf2003 wrote:
I was also wondering myself it you could just do a sandwich construction like a snowboard and perhaps make the core thicker or add a few more layers of glass. I think the foam is just for rigidity. From what I read on the pirate boards is they have no flex at all. I was also wondering if flex would be a good thing so that it would carve better on the snow like a snowboard. My guess is that flex would be bad as it would cause the mast base pressure to bend the nose down . Especially where you stand on the rear end of the board. Also it would be better to have a stiffer board for the ice as it would be more likely to hold an edge in the ice. Therefore I will make mine stiff. I dont know if you could just add more layers to a sandwich construction but I dont see why not. Just a thick wood core would probably do it.

What I was proposing was fiberglass/foam/thick-fiberglass instead of fiberglass/foam/fiberglass/divinycell/fiberglass. I still think using foam would be easier than having a wood core, and would be nicer underfoot.
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inf2003



Joined: 15 Jan 2009
Posts: 136

PostPosted: Tue Oct 25, 2011 7:29 am    Post subject: Reply with quote

Matt, a little more research last night on the pirate boards answered one of your previous questions but raised another for me.


The thing that I read that concerns me a little is they explained that the strength of this board over the freeskate style is that it can go on bumpy ice and cruddy ice when it is not smooth enough for a freeskate style board. That is the condition we get most as well as partially snow covered ice.

I wonder if a rigid fin will be OK in real uneven ice conditions?


Last edited by inf2003 on Wed Oct 26, 2011 9:37 am; edited 1 time in total
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MattD



Joined: 25 May 2011
Posts: 33

PostPosted: Tue Oct 25, 2011 12:54 pm    Post subject: Reply with quote

I would be extremely surprised if they use a spring / shock absorber. I think it would be doable with some clever engineering but probably not if their asking price is 500EUR.

It is easy to reason that a single skate will handle cruddy conditions far better than 4 skates separated by a decent distance, over which the surface can change dramatically. Also, on a freeskate if a front skate catches, you're in trouble. That can't happen on a board like this.

Can you link me to the video where it shows the fin moving within the board?

Are you still thinking of including thruster fins? I really like the idea but I don't think I'll attempt it myself just yet. I want my first prototype to be as simple as possible, while still functional (& fun!).
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inf2003



Joined: 15 Jan 2009
Posts: 136

PostPosted: Tue Oct 25, 2011 2:37 pm    Post subject: Reply with quote

Matt , here is the video

http://www.youtube.com/watch?v=-4trBVToTLw&feature=related



Also I may abandon the thruster idea also. Im not sure it will work.


Last edited by inf2003 on Wed Oct 26, 2011 9:38 am; edited 1 time in total
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MattD



Joined: 25 May 2011
Posts: 33

PostPosted: Tue Oct 25, 2011 4:20 pm    Post subject: Reply with quote

If the axis is in the middle of the fin and maybe under the back foot, then I could see this working.

I wonder if the guy is just using different fins on his board, and that's why it looks like the fin is tilted? Just playing devil's advocate...

Actually, I think I've come up with a way of doing the fin box. You could have 'spring plungers' inside, and put grooves in the fin such that it is possible to slide the fin in one way and out the other way (the opposite direction to force that will be applied when you are sailing). The fin can then pivot around these plungers. If that doesn't make sense I will draw it up tomorrow when I have time. Pivoting or not, I reckon using these plungers is the way to go - if they are strong enough.
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joethewindsufa



Joined: 10 Oct 2010
Posts: 149
Location: Montréal

PostPosted: Wed Oct 26, 2011 9:13 pm    Post subject: Reply with quote

i have done winter windsurfing for a couple of seasons now
my boards are all homemade and i discuss what works and what does not on my blog
here is a photo of my ice sled which now has skis angled at 20 degrees
the brackets are made from wood and metal re-enforced.
my blog is http://joewindsurfer.com or http://joewindsurfer.blogspot.com
only the metal portion of the ski touches the ice = FAST
still working on brakes and turning
Very Happy
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MattD



Joined: 25 May 2011
Posts: 33

PostPosted: Wed Oct 26, 2011 10:34 pm    Post subject: Reply with quote

Joe, nice stuff!

What was the length of the skis you used? Did they provide enough lateral resistance to prevent side slipping? How much snow could they handle? (assuming from your blog no more than 2"?)

PS: Could you make the picture smaller? Wink
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