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 Post subject: Strenght and flexibility
PostPosted: Thu Oct 11, 2012 10:25 pm 
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Joined: Thu Jun 28, 2012 10:14 pm
Posts: 5
Hi,

I'm reading this forum already for some months because I want to make some boards. I found a lot of information on several topics but there is one thing I don't find information. That's why I registered to be able to launch a question.

So here it is: What is the desirable strenght and flexibility in a kiteboard? And how can I measure it?

Thanks in advance,

Blup

P.S. I'm a very bad kitesurfer, my sons are doing pretty well, but I'm more drinking seawater instead of catching wind. But building something, that's my thing.


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 Post subject: Re: Strenght and flexibility
PostPosted: Thu Oct 11, 2012 10:51 pm 
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Joined: Sat Aug 29, 2009 11:25 pm
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Location: The Naki
for a strong flexible board you want to choose a thin core and use more reincforcement. eg fibreglas


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 Post subject: Re: Strenght and flexibility
PostPosted: Thu Oct 11, 2012 10:56 pm 
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That's what I want, but how flexible it should be? Does it need to be stiff in the middle and flexible on both ends, or does it need to be flexible all the way through the board?
And how flexible it should be?

If I put some weight on it, how far should it bend? and where should it bend?

Greetings,

Blup


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 Post subject: Re: Strenght and flexibility
PostPosted: Fri Oct 12, 2012 2:23 am 
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Joined: Fri Jul 16, 2010 6:27 am
Posts: 2382
Location: Ford Lake, Michigan
if you put your hand on top of the board and step in the middle with all your weight, the board should bow by about 1 or 2 feet, if it bows an inch or two, it's way too stiff and will spank your knees, if it bends all the way in half, it's too flexible and will eat up all your speed.

untreated marine grade 1/2 inch plywood has almost exactly the right flex. The more fiberglass and epoxy you use, the smaller you will have to make the wood core so the flex is right.

disclaimer, this is all my personal opinion, everyone has different opinions on the perfect board.

ideally you want the board to flex the same throughout the entire board so you dont have a weak point on the board that breaks easily. Again just my own opinion, others have different ones.


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 Post subject: Re: Strenght and flexibility
PostPosted: Fri Oct 12, 2012 12:27 pm 
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I would suggest measuring some boards that you like. Rocker and shape have a lot of effect on how flexy a board should be. Personal preference all so will dictate what you want in a board. Start by trying to copy something you know you like and then tweak it to suit you better.


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 Post subject: Re: Strenght and flexibility
PostPosted: Fri Feb 15, 2013 4:48 am 
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Location: scott klandl burlington, VT
Rocker has nothing to do with flex characteristics but means something when talking about overall design.

I like foam, lighter than wood by a lot and easier to build to your desired specs. Ie no spring back.

My suggestions
12-15mm foam in middle taper from inner insert pack to tip 2.5 mm
20 oz triad
Good place to start


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 Post subject: Re: Strenght and flexibility
PostPosted: Fri Feb 15, 2013 10:34 am 
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Location: The Naki
rocker will have an affect on flex. concave a greater effect.


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 Post subject: Re: Strenght and flexibility
PostPosted: Fri Feb 15, 2013 10:55 am 
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Joined: Sat Sep 11, 2010 9:12 am
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And channels even greater effect. BTW in order to control flex in terms of board shape - check liquid force DLX 2011 - it has channels on the top :lol: - just to make it stiffer in the mid section. So shape does matter.


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 Post subject: Re: Strenght and flexibility
PostPosted: Fri Feb 15, 2013 12:24 pm 
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Location: scott klandl burlington, VT
And how does rocker affect flex?


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 Post subject: Re: Strenght and flexibility
PostPosted: Fri Feb 15, 2013 3:10 pm 
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Location: The Naki
Changing the properties of the board by adding rocker will change its flexi characteristic. At the very least rocker allows the board to spill more water and that in turn will affect flex. with a wood core board the pretension between glass layers and the core will adjust flex.

Lastly. grab any peice of paper. hold it at each and flat and flat it about. yourl notice its very flexi. now set a rocker into your paper by holding it in an arc. now flap... notice the increased stiffness.

I believe more rocker = more stiffness.


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