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Flex in Board Design

here you can exchange your experience and datas about your home build boards


SweetDoug
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Flex in Board Design

Postby SweetDoug » Mon Aug 23, 2010 3:52 pm

What function does flex in a board?

Do you need flex in a large light wind board with small waves?

Do you want flex if you're riding in chop? How about bigger waves?

Of course, you would need it for jumping and tricks to help the landing.

How much flex? How do you rate it or can you? (If the board breaks, there's too much!)

Do you want flex in just the tips or all across the board or just in the middle third? Can you build that in the middle if it's needed?

SweetDoug

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Re: Flex in Board Design

Postby zob » Mon Aug 23, 2010 5:27 pm

Hi Herkimer!

Glad to have you on board. The kiteboard building communiti is growing.

I see you have a lot of questions. It would be easier if you would decide what kind of construction are you capable of building and than search the forum, read about builds with similar construction and than, if something is stil unclear all of us will be more than happy to help you.
A lot of your questions are answered in the last couple of threads.
You technically want to know everything and more about boards and board building. There is no simple FAQ.
I sugest, you do the same way I did. Read this whole forum, every link in the threads, and other forums, which are taged in the threads and you will probably know al there is about this.


p.s.: Also reply's to your previous post

SweetDoug
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Re: Flex in Board Design

Postby SweetDoug » Mon Aug 23, 2010 10:18 pm

Yes, lots of questions. I've read a lot of the forum here and other places. What I'm seeing is a lot of "I've done this..." and no feedback or general knowledge base being developed or best practices as a guideline. (I'm a professional carpenter, heavy construction, but I know my way around fine woodworking. Lot's of thought before you cut. So I'd like to skip a lot of trial and error.) I'm seeing lots of trials but no real centralizing of the errors, which I'd like to not repeat if possible.

I just spent an hour down at Noah's Marine in Toronto. www.noahsboatbuilding.com that is mentioned many times here and other forums and it was a wealth of information.

I'm still undecided as to what type of board, ply or ply/composite w/foam and fibreglass, or just a foam composite w/fibreglass. Now that I'm sorting through the chaff, it's getting a lot clearer and a lot easier.

SweetDoug

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Re: Flex in Board Design

Postby BWD » Mon Aug 23, 2010 11:07 pm

If I were you I would consider making a cedar or poplar strip board,
with a max thickness of 3/8" to 5/8" under/between feet, tapering to 1/8" to 3/16" at the tips.
Only a single layer of light glass over the wood is needed, 4 to 8 ounces.
Get blind inserts from a snowboard place, they look better, and are cheaper than stainless tee nuts from box stores (I used boardcrafter.com).
The thickness profile should give you a good flex.
If too much flex, hit it with a sander then add another layer of glass.

This is similar to a lot of production boards, and should work while saving you the cost, consumables and learning curve of foams and vacuum bagging.
You still need a rocker table though if you want control and/or repeatability.
Of course you could vac bag it, but no need if you are careful and keep the resin:cloth ratio right.
Plywood IMHO is probably a waste of time to a guy that has the skill and tools to make a wood strip board that would be lighter and perform better.
I guess the pitfalls of beginners depend on the individual, but some basic ones are:

1. oops, used too much resin, resulting in heavy board.
2. oops, took board off rocker table too soon, all the rocker disappeared.
3. oops, mixed epoxy in wrong ratio, did not cure.
4. oops, forgot to account for 20-40% springback (with wood) after gluing up/laminating on rocker table, not enough rocker (see #2 also...).
5. oops, spent all weekend making a board instead of riding! :lol:

I have done ply boards in the past and am working on a strip one now.
I only had 1/4" strips though, so I effectively doubled my work, having to shape 2 core halves before glue-up. Oh well, it's fun and the strips were "free," leftover from something else....

Best luck, with your background you can probably make something sweet, but most people find the first board is more of a "learning experience."
If that happens, don't despair, the first one teaches you what NOT to do on the 2nd!
Attachments
cedar cores sm.JPG
cedar cores sm.JPG (37.72 KiB) Viewed 2213 times

SweetDoug
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Re: Flex in Board Design

Postby SweetDoug » Wed Aug 25, 2010 12:58 am

Love the info! Here’s some outloud thinking on your comments, which I’ll be glad to hear your response.

Had to think about your words for a bit, with regards to what I’m able to to do. I don’t have a wood shop, but I’ve got a lot tools and bench. I had planned on a laminate plywood design with 1/4” as the hull, and deck of 1/4“, 164x50, spleene door knock off with a ”slight“ rocker. I wasn’t going to glass it, just varnish. But now you’ve got me thinking.

BUT! Here’s where I sit from a manufacturing point: I’m 225. A couple of extra pounds on the board isn’t going to kill me. Spleene 164 Door is 17lbs shipping weight. Some of that must be packing, but that’ll still be a good 12-14lbs.


Rough weight of plywood is 1/4” (4x8’) is 25 lbs. 1/2“ is 50lbs The board will be 5.5ft^2. ( 164cmx50=5.5ft^2 so 5.5/32x25=4.3lbs) So I’m up to about 10 lbs with 1/2” and glass. At least.

What’s the weight difference with a similar cedar build, with fibre glass? I’ll be using about 2yd^2 of glass so about 12 ozs of fg + epoxy wieght.

I could use 1/8 x 3 sheets and glass it, and that would be quick and strong. Or just go with the 1/4 & 1/4 with no glass?


Cedar Problems---------------------------------------------------------------------------------------------------------

Noah’s Marine in Toronto has 7/8’x18“ cedar strips for $10 so 2 strips should do cheaply. But I’ve got to saw it down to atleast 1/4 thickness or 2 @ 3/8ths.

Glue-up of the cedar, as I’ll have to get a few clamps (I always like buying more tools...) then planing the surface. (I’ve got several nice planes and love using them so maybe I can do that, as I'll only be knocking off epoxy.)

I think I’m gong to have to pick up a router, as it’ll make cutting the shapes and rounding rails much quicker.

I’ll check the blind inserts. I’m up in Toronto Canada so lots of places to find’em. Any brand or are they fairly generic? BTW how many am I going to need? I guess that depends upon the foot pads, extra placement, and fins. I think I’m going finless on this one.

Managed to find a nice 2d picture of the Spleene 164 so I’ve got a nice template done up in illustrator if anyone’s interested.

Kind of rambly, it’s the thoughts that are running through the melon, and until I settle on something, I’m kind of fibrillating.

Thanks for the info!

Doug


Are you interested in joining a collaborative group on kitebuilding to iron out the above details on building a board?

---------------------------------------------------------------------------------------------------------



Spent a couple of hours at Noah’s Marine in Toronto and they gave me a bunch of great info.

Some stuff I’ll through out that I learned.

Use expoxy instead of fibreglass resin, way stronger and doesn’t go opaque in the sun, but still needs a marine varnish w/UV protection.

Better to use marine plywood as it has no voids and potential weaknesses.

Just work the resin into the glass on your board, wood or styrofoam, with a flat spatula, you don’t really need a vacuum set up. That's for volume.

The fellow recommended using 6 oz/yd Fg with epoxy instead of 12 oz/yd carbon fibre. Or use 2x the fg, as it’ll be stronger than one piece of cfg.

ONE
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Re: Flex in Board Design

Postby ONE » Wed Aug 25, 2010 2:20 am

Doug

check this out...

viewtopic.php?f=107&t=2365401

I'm 2 hours away from you if you want to see some of my boards?

ONE

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Re: Flex in Board Design

Postby BWD » Wed Aug 25, 2010 3:02 am

Sounds like you want to do like ONE did, with a door....
If so, go for it, his boards look pretty darn successful!

re: weight, cedar is 20-24lbs/ft^3, birch ply ~40 or so, poplar sprice, and fir fall in between.
My 2 layer cedar core (with epoxy edge) weighs about 5 lbs right now, it will lose a few ounces with further shaping and gain it back with glue. After laminating, should total 2.6-3kg when finished, ~3.5 kg with fins and straps.

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Re: Flex in Board Design

Postby SweetDoug » Wed Aug 25, 2010 3:06 am

Long we have heard that the "One" would come.

Damn, I thought I'd be that guy!

I am stunned. Those boards are just elegant in their simple design and function. Wood always looks so beautiful just left alone.

How big are you? I'm going with the 1/4x1/4 ply. With some fg.

And isn't that crazy how the simple front works better than the high tech eye-candy. And I can't believe the roughed bottom! That's my idea! I've been a huge fan of golf-balling things all my life! (Like why don't we do that on racing boats/sailing/aircraft et cetera, ad nauseum.)

Did you dimple it, or just rough it? That's fantastic!

I'm buying my wood and 'poxy tew-morrow!

I just spent the last day dicking around with illustrator to get an exact copy of the Spleene! Doh!

You ever get up to Oli?

I'll be there this weekend.

SweetDoug (More to come, I've got to read that page again. And again.)

YOU are the ONE.

SweetDoug
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Re: Flex in Board Design

Postby SweetDoug » Wed Aug 25, 2010 3:13 am

Did you bother putting in a rocker or just leave it flat?

SweetDoug

SweetDoug
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Re: Flex in Board Design

Postby SweetDoug » Wed Aug 25, 2010 3:15 am

BWD,

Do you have finished pictures of your board(s)? I like that cedar idea. A fellow up north made a nice ceadar plank and flys on it in light winds.

SweetDoug


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