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[huie]

good stuff  rickeds.
                                  now keep   posting more  off your thouights.

        boatbuilders know all about boards

[Kit Sidwell]

You are right Rikds, that sounds spot on to me, and I know that you know your stuff!
Though I also think that Geoff (StrangeBrew) wasn't actually worrying about compression in the axial sense of the word!
He was just talking about heal or knee dents, which kevlar won't really protect much better against, unless you convert the forces on it to axial tensile forces, as you say.
Stiffness of the laminate/skin is what stops dents, so carbon, sandwich panels, or just heavier glass are the ways to go.
Obviously using kevlar on the inside of a sandwich puts it into tension when someone is jumping up and down on the panel, so thats a perfectly good use.
If there was such thing as 2oz kevlar for a reasonable price, i'd use it for that! Solves the UV problem too!

[rikds]

Hi Kit,

Surely there is no such thing as an "advanced" fibre at a reasonable price! My son is making a hollow carbon board for his A level project, thing's only 6ft and the carbon alone cost £120.

The stuff is a beautiful 2x2 twill. Terrific until you cut it and then it refuses to hold any shape at all, distorts horribly on the bias. We had a hell of a battle before we were satisfied and got the bag on. Wanted to put 2 skins and some H80 (6mm) foam into the mould in one go. Ran out of time and have had to do 2 bags.

Exciting stuff!

I cannot even buy 200gm S glass at the moment.....

[Kit Sidwell]

Aaaargh, carbon twill is the bane of my life!
I've been using it for yacht hatches that I infuse, and I agree it's a b**** to lay up. Almost like its got no binder in it, as you say it just distorts like crazy.
It looks awesome on large panels though eh, which is good because thats the only application I can get it to go down undistorted!

I'm keen to hear about the carbon board you guys are doing, do you feel like starting a thread on it?

[rikds]

Will happily do a thread on it. The Boy has a mass of pix and is doing the write up as he goes along. Will probably complete the beast and then post the whole process in one go. It's not ground breaking stuff and we have had to make a few changes to the original plan as we encountered unforeseen developments (like how bloody thin the original board is in the nose!).

The original is a PU blank glassed in the usual way but apparently goes like stink. Will be interesting to see how the carbon one goes by comparison. The nice thing will be building a few boards from the mould using different lay ups and comparing them....

[Kiterider]

Yeah,,, I'm also looking forward to seeing  your hollow carbon board...

You're right about Kevlar;      It has fantastic tensile strength,, thus should be placed on the bottom of the board as this area see's the most tension.

 While carbon has a very respectable tensile strength it's real strengths are realized on the deck as it fairs better under compression than  Kevlar...

  In simple terms:    Hardened carbon deck areas act like a stiff load spreading "plate" when used as a deck laminate.....
For example if you were to put carbon " epoxy/plates"   under a E or S deck laminate, they'd spread the heel denting compression load out to a larger diameter surface area..

 It kind of acts like patch of a bamboo veneer would in the same application..

Kevlar's main advantage is it's ding resistance or sharp impact resistance...
 If you were to hit a reef or some rocks, the Kevlar bottomed board stands a far better chance of staying water tight than standard glass,, and even more-so than brittle carbon...

 High impact water craft  benefit from the use of Kevlar,, unlike carbon,, it doesn't explode if struck hard (point loaded impact)..
 Another excellent trait of Kevlar is it's ability to dampen shock and vibration.
It works well for me on twin-tip kite-boards intended for use in heavy chop conditions....
 Kevlar on the rails of a board would be another ideal ding resistant application...

Cheers Kiterider...

[ric_vidal]

Kevlar's main advantage is it's ding resistance or sharp impact resistance...

But how do you cut the bloody stuff, and sand it for that matter without it just being a fluffy mess?

[ric_vidal]

Question for you learned folk... just doing a PU with stringer board, Surfblanks green foam - team weight, so light and definitely open to destruction. Deck is reasonably firm, bottom is soft as, but glassing with epoxy. Have already done the laminates, 6oz bottom, 4 oz deck with a view to...

Here’s the question bit... been thinking of vac’ing on a skin of high density foamed PVC then perhaps glass over it. Anyone tried such a comb? This stuff going to conform to the shape, fall off, be as stiff as... ?

Any thoughts would be appreciated.

[huie]

hey ric    you got my e mail  you can talk anytime

 1. 6oz on the bottom of midgets green should be ok i would sand & finish.
if it is glassed in epoxy make sure it is well &truly post cured
if the lam is done it is to late to put skins on for any gain.
next time e mail me & i will give you an easy guide to wat you are seeking.

[ric_vidal]

hey ric    you got my e mail  you can talk anytime

 1. 6oz on the bottom of midgets green should be ok i would sand & finish.
if it is glassed in epoxy make sure it is well &truly post cured
if the lam is done it is to late to put skins on for any gain.
next time e mail me & i will give you an easy guide to wat you are seeking.

Something weird happening here between our computers Huie, on-screen it says 'vic' when I quote it says 'ric', have had the same thing with your e-mails for some reason.

Anyway, moving on, have sent you an e-mail with a couple of questions. Remember this is me, it doesn't have to be an orthodox approach or a tried and true compsand. Just dabbling with another way of reinforcing a deck.

[huie]

ye yea  i got your emails   ring me up nights
 i got afew ideas

[Kiterider]

Kevlar's main advantage is it's ding resistance or sharp impact resistance...

But how do you cut the bloody stuff, and sand it for that matter without it just being a fluffy mess?

Some cheap scissors will cut Kevlar...   But I spent the $25 t0 $35 Can.,   for real dedicated Kevlar shears..
I have one set I use to cut only dry/ non epoxied kevlar.. And another pair that I use to trim "wet" kevlar...
 If you're serious about using this cloth you need the right scissors,,, right epoxy,,,,and a vacuum bag/peel-ply setup to cut,,,,, laminate,,,, and reduce resin absorption/press ,,, respectively.....

A lot of builders say Kevlar is  not worth the effort or money, but it has   sharp- impact,,,, flexibility vibration dampening,,, and shear resistant qualities that are unmatched.....
 It's simply harder to work with, has to be applied under sand-able cloth, and needs the right tools as well as  positioning on the hull locations of the board to make it a great alternative.........
 It's not for everyone, but with the right gear, it's a cake-walk..........
 Some say "It soaks up epoxy like a sponge" Yes it does ,,if you don't vac. bag properly...
Kevlar is actually quite a bit lighter  than glass and carbon before adding epoxy.. You have to draw out the excess resin under vacuum to realize the weight saving...

Cheers Kiterider...")

P.S. The vibration absorption , impact resistance , are 2 traits that I swear by from years of  "practical"Kevlar use,,,, for what my opinion's worth..lol..
B.tw.  I've never broken a board with Kevlar in the laminate, and I weigh over 200 lbs

[bobmarley]

Anyone here using a realease film over there laminate to get a perfectly smooth/flat laminate? one of my problems has always been getting a smooth lam from pooling resin or something and ending up with sand throughs etc..

I was planning to bag the lam with just a realease film nothing to soak up resin, and thought about also possibling sealing the wood first with brushed on resin to make sure theres no dry spots

[surfdad]

I just messed with some mylar like the RC plane folks use to create a gloss finish.  It's a little hard to see, but in the top half of the picture, I've laminated the carbon/kevlar fabric on the deck.  The yellow'ish line of the reflection of the overhead lights in the gloss.  That is straight out of the bag.  No pinholes, etc.  It honestly looks like I polished it all day long.  The bottom of that picture is a matte finish.  I hate to sand, so I just laid some blue nylon release ply over the fabric and then the perforated peel play so that I would have the equivalent of a sanded finish on the bottom, without the work.

The process for the mylar on the deck, I used, was to wet the fabric on a wet out table, lay it on the board, place the mylar on top of the wet fabric and then a perforated peel play all over that.  I taped the perforated peel play down, so as to pull all of it down somewhat tight and then slipped it in the bag.  As I was pulling the vacuum, I just kept pulling the bag taut along the rails and bottom of the lap.

As mentioned above (by kiterider?) this took a considerable amount of time, so I wasn't rushing the process and I didn't wind up with any pinholes.