Natural Fiber Reinforced Compsand (glass-free)

General Discussion
1

I am soliciting advice on the above referenced project. I am currently working on a sandwich board using eps, balsa, hemp, and maybe some other stuff.

At this point I’m vacuuming on my bottom skin (in case any one was wondering if this was one of those theoretical mind shaping posts which never come to fruition.) If you want to check my progress and method thus far, I am doing a step-by-step here. I figured there was little need to cover this ground over again with sway band width.

I remember Bert saying in a post that he’d always meant to do a board with no glass but hadn’t gotten around to it. Glass free seemed like a great idea to me because I always worry about the little glass particles I see when cutting, grinding, sand, etc.

My primary question in this post involves alternative laminating fabrics for the exterior lamination. I have enough hemp to do the insides of the skins and so that’s what I’m planning on doing. I was wondering if anyone had suggestions for the exterior lamination.

I’ve considered the following:

-more hemp (it’s so expensive though and heavy)

-cotton sheets–percale per an old Greg Loehr discussion

-that stretchy bamboo cloth advertised and sold by the greenlight surf company in the resources (not cheap)

-something else?

I’d like it to be a natural fiber and it would be preferable for it to be pretty transparent when laminated to show the wood.

If I used cotton sheets, does anyone have thoughts on the number of layers needed?

Oh, I am also in touch with the idea that I’ll probably need to vac bag the exterior laminate and that’s cool.

Anybody?

2

While I’m at it I suppose I’ll toss my rocker numbers out there for folks to chew on and give me some thoughts. It would be sick if experienced compsanders would drop some knowledge on the boys!

Rocker plan:

(from nose)

N: 5 3/4

N6: 2 7/8

N12: 1 3/4

N18: 7/8

N24: 3/8

Basically flat beginning at N36 and continuing 4.5’’

(from tail)

T: 1 3/4

T12: 3/4

T24: 1/4

Nose rocker is taken from one of my favorite boards–a wrv thruster made mid–nineties

Tail rocker comes off of the 6’5’'P clark blank

Foil–that’s a tough one. Obviously max thickness will be a little over 2’’ accounting for skins. I don’t have any numbers for that yet. I was planning on eyeballing it I guess. I remember some discussion about sort of reversing the foil in a compsand build.

My thought is that I want max thickness about a foot or so either side of my front foot since thickness should translate to less flex in that area. I’m thinking along the lines of yoshio’s mushy hemp board and Bert’s proposed fix. I’m not sure how thin to go in the tail area, but I’m thinking that is where I want the most flex and return based on the following comment from craftee’s comsand stiffitus thread–“back foot flex is for fine control deep in the pocket , powering out of any hard back foot turn , fitting into tight spots with the back foot , hanging in the lip longer if you wish and helps with old skool type boosts to kick the tail on the launch” (thanks for such insights Bert!–I hope I’m not taking things out of context).

3

I would go with silk over cotton. More expensive, but much better mechanical properties. I did an experiment while reglassing a broken board where I used an silk inkjet media to do a graphic on the silk. It didn’t go clear, just a bit milky, but much better than hemp.

4

Thanks t-meat. I’ll check it out.

Oh, I forgot to call dibs on my tradename for this construction: SMOKEROPE

Get it?–Firewire…compsand…hemp…smokerope…hehe. I am not a hippie.

hunter

5

Thats an awesome project, i’ll definitely be following this one closely!

Good stuff.

It’ll be really interesting to see how it rides, the durability, weight etc.

Yet another example of how a backyarder can take the tech and do something bloody cool!

Pu/pe just doesn’t let you play around will stuff like this…

Kit

6

WOO HOO!

i just love a good “theboys” thread!

=)

7

Okay, so you’re vacuuming the skins on but are you going to seal it with anything? If so, what?

8

Natural bamboo fabric is the way to go. It’s nature’s solution to building anything “Green”.

Hemp fibers do not sand and the hemp fabric is extremely difficult to wrap around the rails.

In most cases, the price of glassing a surfboard with bamboo fabric is the same, if not less expensive than using 6 oz fiberglass.

You can get bamboo laminating fabric at

www.greenlightsurfsupply.com

Greenlight’s bamboo fabric stretches approx. 25% so you use less fabric to glass a board

“Bamboo is nature’s version of titanium and carbon fiber rolled up into one replenishable form”

9

I’d LOVE to try that fabric…

Any thoughts of shipping internationally?

I don’t think i’d find a similar product here in New Zealand.

Some questions, if I may -

What weight per yard is it, I couldn’t find a figure on the website. The weight per yard changes when you stretch it I realise.

Does it wet out clear, or semi clear, or is it totally opaque?

I’d use it over wood, just wondering what it’d look like.

How do it’s mechanical properties compare to normal cloth?

I’m guessing it’s pretty tough, bamboo is crazy strong stuff!

Nice product, would be great to get my hands on some.

thanks,

Kit

10

I just checked out the website too, and have a question to add to KKSurf’s:

I saw that you’re recommending Resin Research epoxy. Which modulus? I used 2020 with hemp on Greg Loehr’s recomendation; the hemp stretches more than glass and needs the extra give in the epoxy to prevent resin cracking. With something that stretches as much as that bamboo cloth, are you using 2040? Is having a board that flexes too much a problem? It looks like a great product, and if the price on your site is per yard, then it’s much more affordable than hemp. Would love to have more stats.

Pat

11
Quote:

Would love to have more stats.

Yes, like actual field results would be nice.

12

Hey greenlight, how do I get some of this cloth in the UK? would love to give it a try.

I second Kits questions about clarity etc?

Answers please.

13

Yeah, I’d definitely been considering the bamboo fabric. I’ve checked the site and read your materials. I’ve gotten a bit of advice on the subject and will chew on it for a while.

For the sake of clarity and in response to monkstar, I’m building this board using what I understand to be the ‘regular’ compsand method… cloth inside and out with perimeter stringers with the only difference being that I’m not using fiberglass cloth in the laminations.

Any thoughts on my rocker and foil? I’m going to build my ‘rail templates’ this evening, I think.

14

Sorry everyone, I know this isn’t surf industry politics related, but thought I’d post it anyway.

The use of a profile template for templating balsa or Dcell rails has always bugged me a little bit. I know that it works fine, but still… the coming up short part and the difference in rocker made me hesitant to do things the easy way. Plus, in my case I didn’t have any profile templates to start with, so I created some specialized rail line rocker templates which attempt to account for the length of the planshape curve rather than the centerline curve.

My plan will be to use these templates as ‘spines’ in the bag when I vacuum on my rails. I don’t know, but widowmaker said it worked. If it doesn’t, I have a general idea of where he lives and works. We also have occasion to go boating and surfing from time to time… alone. Accidents happen, you know.

Behold my methods here. There is some pretty basic crap being discussed there and I’m sorry. The discussion on that particular forum is more tailored towards my friends and newbies in my geographic area. hohar is not for everyone!

Hopefully you old schoolers out there will be pumped at the lack of computer technology employed in plotting the template… Ah good, I managed to bring this back into the realm of relavant discussion. hehe.

15

Nice skills with the plotting!

Sorry for the hijack about the bamboo stuff earlier, it just caught my eye.

Yeah, on this site there sometimes seems to be more people bitching about building boards than actually building them! :slight_smile:

When I do my rails, I cut the rails off square at the stage you have it now, then trace around it onto the rail wood.

I scarf joint the pieces so you don’t waste as much wood.

Then I cut everything 1/16 to 1/8 oversize for peace of mind, length too.

Cut them all in one go, a big stack of them, with the jig saw. Tape them together to do it. Makes it easy to flush them up to each other when you put them on if they are all identical.

What thickness rail pieces are you using?

Using more than 1/4 inch thick pieces to build out the rails strip by strip will cause you problems. (thats with balsa, cedar or paulownia, etc are way more springy)

A lot of guys use as small as 1/8", and just do many layers.

It’s slower, but fighting 1/4" thick balsa can lead to errors.

Get a nice join around those rail pieces and it’ll look so good!

I’m really interested to hear about how the hemp handles, eg. ease of wetting out, drapability, clarity when wet, cloth weights etc.

Bloody good project man, keep it coming!

Kit

16

Kit:

Your method was something I’d actually planned on doing. However, I don’t have my finished rocker in the blank so I figured I’d go ahead and knock it out all at once… hopfully.

I’m using 3/16 pieces for the rails. I did a perimeter stringer board with this thickness and it bent well with tape–compromise between 1/8 and 1/4. I’ve got my strips laid out-- 3’’ x 2’ sections and am going to scarf them when my templates are done.

Thanks on the plot, I was stoked at how it came out. It was hell fun to do too. I’m pretty excited about this rocker. I wish more folks had something to say about it but at least I know the two ‘halves’ of it are relatively proven to work for me. I bet craftee thinks I’ve got too much nose rocker, eh? Of course, 50% of it is in the front 6 inches and most of the rest is in the front 12 inches, so I’m thinking alot of that is a cosmetic type flip. I was really intrigued with the ‘sweet spot’ on the ‘parent’ coinciding with the flat section in the rocker. I’m pretty sure the board I pulled most of the numbers from would be described as having a ‘staged’ rather than continuous rocker curve.

No worries on the bamboo cloth stuff… I’m interested in that as well. If I don’t use it on this board, I will definitely use it on the next.

The hemp is not that bad to work with. It’s cool in this application because there are no concerns about unraveling. Superfatpat broke the technique down to me… wet it and wring it. I used about 8 oz of material to wet out the inside layer of 7.5 oz cloth. I just got it damp and the vac took care of the rest. I’m not so sure about the exterior lam though. I’m trying to work up some techniques for that in my head… maybe something like the greenlight ‘stretch and tape’ method (its on their site) combined with vac bagging it.

My main concern right now involves the board being to flexy–I’m thinking right now about a top hat sort of deal ala sabs under my front foot area. Yoshio’s mush board had 2 layers of 7.5 oz hemp top and bottom along with 10mm rails–basically what I’ll have except I’ve got the 1/16 balsa sandwich skins in the mix. I’m thinking I’ll probably still need a stiffener under the front foot ala bert’s suggestion in that thread.

I’ve also been told by some folks that the tensile strength of hemp, or lack thereof, will compromise this board and that fiberglass is structurally necessary in this application. Does anyone have data on tensile strength of hemp fibers in an epoxy matrix? Everyone concurs that hemp has great impact strength characteristics. What about tensile strength. I’m still going to go through with it anyway, but I’d like to know.

I keep wishing Bert or some of the other guys will lay some knowledge on me in this thread… but at the same time, sometimes its best to figure things out your dang self.

Sorry about the snippy OT thing, but I couldn’t help it.

17

in my experience, panel stiffness has alot more to do with board flex than the amount of glass used. For instance, I could lam my skins 6oz in and 6oz out with a 1/16 core. If that panel is more flexible than a comparable panel, say at 1/8" thick, but glassed with 2oz in and out, the thinner panel will still make a more flexible board. The board should also be more able to handle loads as there is more glass. The thicker panel, with light glassing, may be lighter than the flexier, thinner one, but will give a stiffer board and when the stresses eventually overcome the tensile/compressive strength of the wood, there’s less glass to support the matrix and board breaks.

trade-offs, right? You want light, with snappy flex, then it’s thicker cores with lighter cloth, but the board will eventually snap when it encounters a large enough load. You want resilient flex that won’t have as much wood “snap”, but will give you a really durable product? Thinner skins, heavier glass. You have to design the board and laminate schedule with intended use in mind. Small, slopey, junky waves? build it light, light, light. Surfing somewhere hollow with repercusions regardless of size? Beef it up and maybe thin the wood a bit if you want the flex.

Don’t know that you’re going to have alot of luck finding tensile strengths for bamboo cloth; hasn’t been commonly used by engineers in the applications you’re thinking, so the testing may not have been done…

my bet says that you won’t need a “top hat” or other kind of stiffener either with the laminate schedule you’re thinking about, unless your board is really, REALLY thin, or you’re really REALLY heavy.

hth

g

p.s. meant to add; hemp has been used in ropes for a long, LONG, long time; I bet it’s tensile strength is pretty kick ass, if you can find the numbers…probably greater elongation than glass fiber, but I bet that it’s one of the best natural fibers out there…(guessing only…who wants to wager?)

18

Cool, thanks g.

I know you have some experience with hemp lams so that’s encouraging. I suppose I could always retro-stiffen as necessary.

The surf here sucks, but this is as much a materials experiment as a performance experiment.

19

no experience with hemp “lams” here, but I’ve seen some pretty big hemp “rope”; I do live in Vancouver ;).

speaking from glass experience, but the theory still holds.

and yes; much easier to make a board that is too flexible stiffer after the fact than to make a stiff board more flexible after the fact. a very good approach if you’re not adverse to “redoing” your outer lams.

interested to see how this all works out for you.

20

Hope this helps:

Table 5: Comparative Mechanical/Physical Properties of Bast and Wood Materials: FIBROUS MATERIAL DENSITY (g/cm3) LENGTH (mm) DIAMETER (um) L/D RATIO TENSILE STRENGTHS (psi) FIBER BUNDLE RANGE AVG RANGE AVG FLAX 1.51 1.2 10 - 65 32 10 - 25 18 1,778 51,000 KENAF (bast) - 1.2 1.4 - 5 2.6 14 - 23 21 124 58,000 KENAF (core) 0.31 - 0.4 - 1.1 0.6 18 - 37 30 20 - HEMP 1.48 1.2 7 - 55 25 13 - 30 18 1,087 118,000 S.Y. PINE 0.51 - 2.7 - 4.6 3.7 32 - 43 38 97 11,600 D. FIR 0.48 - 2.7 - 4.6 3.7 32 - 43 38 97 15,600 ASPEN 0.39 - 0.7 - 1.6 1.2 20 - 30 25 48 7,400 Sources: Wood Handbook; Danforth International; W.S.U., WMEL; Columbus, 1996, Institute of Natural Fibers, U.S.D.A., A.R.S.; The BioComposite Center.

EDIT: looks like the table didn’t cut and paste too well. Just go to the link, scroll down to the table labeled “table 5.” It’s not actually the 5th table, but near the end. Tensile strength for hemp with their stats is 118,000 psi.

I got it off of this site:

http://hempology.org/CURRENT%20HISTORY/1996%20HEMP%20COMPOSITES.html

The thing about hemp, or any other natural fiber, is that the numbers you get depend to some extent on how it was grown, etc. Even more than that, how it was processed and turned into cloth makes a huge difference. I’ve handled some raw hemp fibers, straight from rubbing them out of the stalk. The fibers were as long and the stalk was, say 2-3 feet. Impossible to break by hand, those things were strong! But unravel a bit of your hemp cloth, and you can tease apart the fibers that make up the strands; they’re much shorter and pull apart easily. I don’t know any of the technical stuff about textile production, but it got me thinking back when my hemp project was happening.

Pat