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 Post subject: Cedar strip board No. 2
PostPosted: Tue Aug 02, 2011 10:11 pm 
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Posts: 2409
After making a big 137x43 cedar strip board with lots of rocker last fall, I decided to make a smaller flatter one with channels for when conditions are stronger. Why channels? Why not?
Seriously, the challenge of shaping and glassing channels was interesting, plus I wanted a different feel.
So I started this board in March hoping to finish it for an April Hatteras trip.
There were some bumps along the way. Mistakes were made ...
It had a bad batch of epoxy :angryfire: on the deck and so after Hatteras I came home and had at it with heat gun, alcohol (careful :!: ) and scrapers, sanders, etc.
Then the rocker wouldn't come right, and it was too bendy.
Finally after reworking, shaping, extra laminations, etc., it's done. (?)
Unfortunately the extra work did not allow for as good a finish as I hoped, but i left it clear anyway.
Some details:

Western Red Cedar blank 1/2" strips glued up with epoxy.
Attachment:
PICT0007s.JPG
PICT0007s.JPG [ 76.72 KIB | Viewed 1940 times ]

The center section between the channels was glued up first and the V-hull form shaped into the tips by hand with saw, plane and sanding blocks. Then the outer strips were added to the blank and the outline was cut with a router and epoxy rail poured.
Attachment:
DSC02338s.JPG
DSC02338s.JPG [ 24.5 KIB | Viewed 1940 times ]

The core was freed from the blank and the deck contour was shaped by routering ramps into the tips to create a taper roughly following the channel/hull shape beneath. The deck shape was smoothed out with RO sander, scrapers, plane etc. until somewhat fair and symmetrical.
Attachment:
DSC02339s.JPG
DSC02339s.JPG [ 30.37 KIB | Viewed 1940 times ]

Inserts and filled epoxy fin blocking were cut in with the router and filled.
The core was cleaned up and sanded, then glassed, which was where the problems occured.
Eventually it ended up like this though:
Top
Deck stringers (added after to adjust rocker and flex):
6 oz e + 4 oz e glass x 3" wide strip capping uni carbon
6.7 oz,1.75" wide unidirectional carbon fiber
6.7 oz 1" wide uni carbon fiber
Deck:
6oz e glass patch beween straps
6 oz e glass
7/16" (11mm) cedar core
6oz e glass
4oz e glass
4 oz e glass patch between straps
Bottom
That sounds like a lot of glass, but I don't think the board will be too stiff, keeping in mind a significant part of the glass is "remedial," laid over the first layer, which was sanded and so loses some of its stiffness.
I had hoped the weight would be about 2.7-2.8kg, but it's about 3kg instead. Not bad considering the extra laminations I guess.
For what it's worth, I tried vac bagging and spray glue for glassing the channels.
Spray glue works at least as well. :thumb:
I used carbon because the board was too wiggly and I didn't want to add another layer of glass over the whole deck. I'll see how it does, feels ok on land...
Dimensions:
132cmx40.5cm
22mm rocker (I wanted it to be 25 to 30 :( )
Channels 3mm at tips to zero 30cm in from tips.
Concave 3mm center, zero at tips.
Attachment:
DSC02458s.JPG
DSC02458s.JPG [ 52.48 KIB | Viewed 1940 times ]

Attachment:
DSC02459s.JPG
DSC02459s.JPG [ 47.78 KIB | Viewed 1940 times ]

Attachment:
DSC02455s.JPG
DSC02455s.JPG [ 32.11 KIB | Viewed 1940 times ]

Attachment:
DSC02456s.JPG
DSC02456s.JPG [ 17.48 KIB | Viewed 1940 times ]

Were the channels worth it?
Will the flex be good?
Will it ride ok with only 22mm rocker?
Is it good to change lots of variables in your design at once? ( :lol: )
I'll let you know....


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 Post subject: Re: Cedar strip board No. 2
PostPosted: Thu Aug 04, 2011 11:12 am 
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Joined: Tue Feb 24, 2009 1:43 pm
Posts: 340
Location: Iv.G.-Slovenia
Hi!

It's encouraging to see even so experienced board builders (as I think you are) encounter problems in such a degree, that make you rethink and fix things during the build. And in the end you get a board, that's OK, but not GREAT or SUPER, not like you expected it to be.
So you take it for a test, but not with such excitement if it would be perfect, because you have in you conscience, that you will have to do another board where you are going to fix your flex, make the rocker stand where you want it to be, lower the weight,... only than you will go for a reall test where you're going to be focused on details to implement in the 3rd board (or in rework of the 1st).
It is happening to me all the time, but I think that is normal, since I didn't come to a construction which I would stick to yet and I make such big changes I can easilly miscalculate.

Respect for doing channeled board. I am trying to do less complicated board and channels wouldn't help on this road.

Hey, tell us how did you do the pured epoxy rails aspecially on the channel area.


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 Post subject: Re: Cedar strip board No. 2
PostPosted: Thu Aug 04, 2011 3:24 pm 
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Joined: Thu Jun 05, 2003 3:37 am
Posts: 2409
Thanks for the encouragement.
There are stories like this behind many boards i think, but the stories don't always get told.
The board will be a little stiffer and flatter than planned, but I think it will still be good.
It would be nice if the bottom lamination was totally clear and beautiful, but the point of this board was to use new techniques and a new shape, not to go into production, so it's ok, although there were some moments during the build I was not really happy about it.
I guess I could have just put graphics on the bottom and said it was my "hardcrore pkra freestyle" board with low rocker, and not said anything about the process.

I used modeling clay to make a little dam to hold back the epoxy from spilling out of the rail groove into the channels. After the epoxy hardened, the clay peeled off the wood easily. I dont think this would work as well with a foam core, unless you sealed it first. Even with wood it left a slight residue that had to be scraped off. Next time I would seal the channel surface with a coat of epoxy first. 8)


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 Post subject: Re: Cedar strip board No. 2
PostPosted: Mon Aug 08, 2011 6:21 pm 
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Posts: 2409
1st Ride:
80kg, 11m C kite, 17-20kts, 0.5m-1m chop from 2 directions, & some 30cm "waves"
Channels felt nice, straight tracking but easy to break loose and less squirrely when loose compared to a smooth bottom of same size, imho at least.
Flatter rocker and shorter took a little getting used to, had to remember to hold the nose up coming over the back of waves/chops -been a while since I rode a medium to small board (or one with low rocker).
Carved nicely in spite of low rocker -I like the outline, flex and tail width. :thumb:
Good upwind but a narrow groove to avoid throwing up spray from the tip, due to length and channels wanting a "straight" path through water. Just needs another session or two to get dialed in I think.
Seems to pop nicely also, but didn't jump much b/c weird chop made timing hard.
Still kinda wish it had about 5mm more rocker, but this board will be good for riding in lagoons/flat, and seems like it would like to do tricks I can't begin to pull off. Glad I stuck with it.

Ideas for next board:
1-2cm longer, maybe 5mm more rocker.
Maybe toe-in channels a hair to make it easier to keep nose a bit higher (not sure yet)


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 Post subject: Re: Cedar strip board No. 2
PostPosted: Wed Aug 10, 2011 11:06 am 
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Location: Iv.G.-Slovenia
Did you do the channel edges parallel or does it get wider thoward the tips?
What do you think would be the difference between this two options or maybee even a channel that is getting wider, but not in straight line but in slight radious?
Do you have a feelling the board tracks enough to loose the fins?


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 Post subject: Re: Cedar strip board No. 2
PostPosted: Wed Aug 10, 2011 4:22 pm 
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The channels are parallel.
Once my board is edging on its rail, the range of angles at which channels, fins, and rail feel like they are working most efficiently seems pretty narrow.
Angling the channels to be wider at the tips could reduce drag when edging the board under some conditions, this might be good.
But I think it could make the board too loose when ridden flat, unless it had plenty of rocker (or big fins). Angling the channels could also decrease the flat rail area outside the channels at the tips, which might be bad.
Angled or radiused channels would affect the feel of how the channels break loose and generate drag when sliding/carving/landing. Again, could be good, could be bad.
So, to those questions I can only say "it depends" I guess :naughty:
Or, "Don't know, haven't tried it" :wink:
But either way, I think it might be a good idea to make the walls of the channel at a 50 to 75 degree angle, rather than as vertical as you can, to get a little more AOA range to work with (also easier to glass)...

I think the board I made could easily be ridden without fins, at least in smooth water.
It was choppy and gusty conditions when I rode it, so I didn't want to try that for the first ride.
In fact the fins I had were pretty big, like 50mm. I would like to try this board with little fins next time.
And without fins.

UPDATE: got out for another session Sunday in flat water, 15-20kts with 11m kite, very nice getting it a little more dialed, fun to pop and felt easier to time with sent jumps compared to some previous boards.
Landings felt great, partly because the timing was easy making for good form, maybe the channels helped too... hard to say but the result is satisfactory!
Also felt really fast :) with the low rocker.
Still riding with big fins, hope to try with 25mm ones sometime soon......


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