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Undecided about Paulownia or foam? Ideas?

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downunder
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Re: Undecided about Paulownia or foam? Ideas?

Postby downunder » Mon Apr 07, 2014 3:03 am

Something to think about since a new Brokite video showing 725g epoxy per board, and a guy says pretty much 50/50 resin ratios...

D.

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Re: Undecided about Paulownia or foam? Ideas?

Postby chrislandy » Mon Apr 07, 2014 9:56 am

Yes but look how flexible they are (not that is alwasya good or a bad thing) and you've said before on the previous videos the boards are more flexible than any board you have built.

Looking at the layup on the new board it's got less carbon than their last boards but they are using almost pure HM UD rather than HM plain woven, they also use a 1/4in foam core (6mm) so they are going to be inherently flexible anyway

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Re: Undecided about Paulownia or foam? Ideas?

Postby downunder » Wed Apr 23, 2014 2:32 am

I think I need to build something like this:

Image

Using a belt sander is not easy but possible. Finishing with a orbit sander is a go.

Finishing my Paulownia top layer which will be scarf jointed with a bamboo core.

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Re: Undecided about Paulownia or foam? Ideas?

Postby Bigdog » Wed Apr 23, 2014 3:24 am

Hello Chrislandy
A 6mm core with carbon can be VERY stiff. Actually can be too stiff. Been there done that got the tshirt LOL.

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Re: Undecided about Paulownia or foam? Ideas?

Postby BWD » Wed Apr 23, 2014 3:57 am

downunder I would recommend a hand held power plane over the router sled. And a DIY caliper.
Makes an hour job take 15 minutes. Plus you can shape surfboards with it.
I used to always use a router.
Slow and loud.
And the router takes a lot of set up, adjust, reset of the sled jig, repeat, etc., it can lead to errors.
Planer is loud too, but not for long.
Used the router for fins and inserts too, but a spade bit is fast and quieter, no jigs required, just a dot on center -if you don't mind the insert going all the way through the core.
With veneers or top sheets the drill holes can disappear. Last core I shaped I switched to the drill bit, 20 pukas in 5-10minutes - fast, uniform and no tear out (start the hole, once the center punches through, flip it and finish from other side).
That's my take.

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Re: Undecided about Paulownia or foam? Ideas?

Postby downunder » Wed Apr 23, 2014 5:19 am

^^
Ok thx,
can you somehow add a photo here? Or a hand drawing for this jig?

I did try a planner tho with not so good results. At the end sanded everything with a belt sander :angryfire:

This is what I do:

- I got 45 mm wide P.wood strips belt sanded on top both sides
- than I glue this strips with epoxy, clamps and weight
- orbital sander than to flatten all
- cutting in shape

Long process...

PS
The above jig I was planning to make with a vacuum to keep my piece flat. Than I wouldn't need any drilled holes like you said?

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Re: Undecided about Paulownia or foam? Ideas?

Postby chrislandy » Wed Apr 23, 2014 9:42 am

Bigdog wrote:Hello Chrislandy
A 6mm core with carbon can be VERY stiff. Actually can be too stiff. Been there done that got the tshirt LOL.


Hi Bigdog,
it is quite stiff but also uber strong, i'm more of a wakeboarder than kiteboarder so the loads are slightly different. I designed mine to be ultra stiff in longitudinal bending and torsion between the bindings and getting more flexible towards the tip by reducing the layup in the tips.

This is Ross Phillips, one of the British wakeboard team riding it a couple of weeks ago:
Image

Then his brother Rich took it down the cable park last Sunday to give it a bashing on the sliders, the marks on the base are the SLIDER not scratches on the board! There's barely a scratch to the rails or the base into the resin.

Image

I was thinking of removing the core in the tips so it's pure carbon (maybe with a layer of amarid or diolen down the neutral axis) to make the tips a little more flexible and reducing the likelihood of delam with fatigue.

What do you reckon then? The core has to be minimum 6mm thick at the insert positions to allow for the thread on the inserts I'm using and the go through the board so you won't get base pop if you overtighten or use long bolts, plus you can ensure the bolt is fully engaged

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Re: Undecided about Paulownia or foam? Ideas?

Postby tkettlepoint » Wed Apr 23, 2014 11:36 am

DU
i'll take one tonight for you of ours which Jim built a while back with vacuum table.

terrie

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Re: Undecided about Paulownia or foam? Ideas?

Postby Bigdog » Wed Apr 23, 2014 1:50 pm

Hey Chrislandy

Ya try thin tips for sure. I have a lot of happy boards that have only glass for 10cm on the tip flared out to include he fin positions as well. If you want it a little stiffer the snowboard tip fill material works well.

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Re: Undecided about Paulownia or foam? Ideas?

Postby BWD » Wed Apr 23, 2014 3:46 pm

downunder sorry I may have been a little unclear.
I sort of changed subjects while on the topic of saving time, from planer vs. router to drill bits.
I just use the drill for insert and fin holes, that's all I meant about the drill bits.
With the planer, the key is how you work it.
Set the blade to take a little bite (maybe 0.5-1mm?), and work the planer at a diagonal across the blank tip so the planer is following its nose, with the back part or body hanging free.
This establishes a "Step" at the tip of the board that is about 1/3 or so of the width of the planer.
Advance the planer and repeat, but this time the body of the planer can rest on the step you just created, so the planer should be more stable and easy to control. After this pass the step will be twice its former width. Repeat until you have done enough.
Go back to the tip and start over to create a second "step", repeating passes to advance the second step as far as your planned taper requires.
After roughing out the taper this way, forming several steps, it's time to smooth off the steps into a smooth taper. This can be done by taking lengthwise strokes with the planer from the middle of the blank to the tips, but it's easy to introduce longitudinal ridges this way. You could instead run the planer sideways across the core, so the blade knocks down the projecting steps, but this too can cause issues, depending on your planer, its settings, your technique, etc.
You may prefer to use a disk or RO sander, sanding block or plane to knock down the steps instead.
Anyway, once you have established a taper, you can use the planer to thin it out uniformly with longitudinal and diagonal strokes.
That's how I do it. If the router works better for you nothing wrong with it.
For the router you may not need a full jig, basically just a plate or sled to carry the router.
You can use all sorts of blocks or props to run the sled across, in case you want to change the angle of the taper. Just make sure they are secured and oriented correctly before cutting! Or maybe you prefer a jig.

Also, I start with a blank with no taper, usually.
You could of course choose to taper each strip before glue-up. Never done that myself.
One more idea, if a vac table sounds like a pain, double sided carpet tape will also hold down a core pretty well, if you are careful removing it.
picture of how I do planer tapering:
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