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Old     (surfdad)      Join Date: Sep 2004       11-16-2009, 7:36 PM Reply   
Some "shooling" for those following along. Fabric has a warp and fill direction. The fill direction is widthwise and is perpendicular to the warp or lengthwise direction.

Composite fabrics have a breaking strength value, normally expressed in pounds per inch. The first number will be the breaking strength in the warp direction. The second will be the fill direction. Most fabrics are stronger in the warp than the fill because higher tension is placed on the warp fiber keeping it straighter during the weaving process. Rare exceptions occur when a larger, therefore stronger thread is used in the fill direction than the warp direction. Fabrics are generally considered ”balanced” if the breaking strength is within 15% warp to fill. “Unbalanced” fabrics are excellent when a greater load is required one direction and a lesser load in the perpendicular direction. Unidirectional Carbon runs mostly in the warp direction, with a few in the fill direction to hold it all together.

Carbon is great in tension, not so much in compression. The compressive forces are on the top of the board, the tension on the the BEST use of carbon is on the bottom of a board or the bottom of the sections of a sandwich. For our purposes, we have more forces applied to the board through it's length than through the width (hence lengthwise stringers), but there are some widthwise forces.

Based upon that, I intend to run some uni carbon lengthwise in the tension side of the components in this build.

That said, Carbon is super stiff in a laminate, 1# density foam isn't. Further 1# EPS is mostly air or blowing agent. Typically 1# eps is sealed to prevent outgassing, but another good reason is to create a uniform surface/uniform dispersion of resin in the attached laminate (reduces absorption from the laminate).

This is a close up picture of some shaped 1# EPS you can see the pukas or craters in the foam.

Old     (surfdad)      Join Date: Sep 2004       11-16-2009, 7:41 PM Reply   
EPS is sealed with all sorts of stuff - even elmers glue. The most commonly used product is an ultra light spackling compound. Easy to apply and sand and being white has aesthetics. However, it's got no stiffness or strength. Another option is epoxy with microballons. The micro's aid with sanding and help reduce the weight of the mixture. The epoxy will make the seal stiff and provide a good surface to bond too.

When applying an epoxy seal coat, I tape the rails off to avoid having to sand or pick off any drips/runs.

Old     (surfdad)      Join Date: Sep 2004       11-16-2009, 7:43 PM Reply   
My slurry mixture.

Old     (surfdad)      Join Date: Sep 2004       11-16-2009, 7:44 PM Reply   
It's a little hard to see, but I have a unifrom surface after the seal coat.

Old     (surfdad)      Join Date: Sep 2004       11-16-2009, 7:47 PM Reply   
I have found that the best way to remove extra mixture and still leave a good seal is to spread the mixture all around, then one pass lengthwise, not to remove, but to spread it uniformly and then I drag the excess off widthwise and scrape it off the squeqee onto the edge of the bucket.

Old     (brewkettle)      Join Date: Jan 2009       11-17-2009, 4:42 AM Reply   
i like when fast and final gets kinda old and dried out , its easier to spread because its thicker
Old     (surfdad)      Join Date: Sep 2004       11-17-2009, 5:27 AM Reply   
I have a hard time find F&F in my locale, so I use the ACE Hardware version. After a month that stuff starts to get chalky and requires the addition of water.
Old     (masonwakerider)      Join Date: May 2003       11-18-2009, 11:52 AM Reply   
have you looked into stitched fabrics, that are not woven but layered then stitched to stay together. I don't know if they make them in the light weights that you are using but they are the standard in large structure build such as wind turbine blades. I was doing a repair to my snowboard and i appears thats what they were using. Snowboards use around a 22oz triax.
Old     (surfdad)      Join Date: Sep 2004       11-18-2009, 1:38 PM Reply   
Hey WAlove, thanks for following along. CST sales has tons of different UNI with different binders - the stitched like you mention and I think just a film that glues the tow together.

I've only been messing with the uni for a little bit now. I love the properties and lower cost, but don't have enough practical experience with them to know what's good or bad yet. :-) I'm sure I'll discover the bad stuff quickly. :-)
Old     (surfdad)      Join Date: Sep 2004       11-18-2009, 7:34 PM Reply   
It's hard to see, but the fill direction is "white" it's fiberglass holding the carbon in the warp direction.

Old     (surfdad)      Join Date: Sep 2004       11-18-2009, 7:36 PM Reply   
A layer of 3 oz eglass

Old     (surfdad)      Join Date: Sep 2004       11-18-2009, 7:40 PM Reply   
Here is the first application of the UNI - it's on the tension side of the board, about 6" wide and 3 foot long.

Old     (surfdad)      Join Date: Sep 2004       11-18-2009, 7:41 PM Reply   
Skinned, bagged and in the autoclave. :-)

Old     (surfdad)      Join Date: Sep 2004       11-19-2009, 5:21 AM Reply   
Out of the bag and ready for shaping the deck and rails.

Old     (masonwakerider)      Join Date: May 2003       11-19-2009, 6:57 AM Reply   
i got a job this fall working in the composites lab at school. We test resins and glasses that are used in wind turbine blades. I had never seen stitched fabrics. All the fabrics we use are not uni but 0/90's, +-45's, random mat/45 and its is all stitched. The deflection of the glass fibers when woven really decrease the strength in both directions. (fibers are no strait and laying flat) A stitch fabric should have the same weight as woven, but have more strength.

(Message edited by masonwakerider on November 19, 2009)
Old     (brewkettle)      Join Date: Jan 2009       11-19-2009, 7:19 AM Reply   
i also use the heated blanket ,
Old     (surfdad)      Join Date: Sep 2004       11-19-2009, 7:39 AM Reply   
@ WAlove - I'm not sure I understand - 0/90 stiched and not a weave? So two layers one going warp, the second fill and they are stitched with a binder? That's an interesting concept. Typically folks use uni's on a bias 0/90 anyway, so that would be cool and like you say, increases the strength of the resultant composite.

@ jim beam - my ghetto autoclave. :-) I was looking at some molding shop and they had heating elements built into the mold itself. It wasn't to keep it at room temperature like we're doing, instead to heat pre-preg's. I think the mold itself required some construction that would diffuse or spread the heat across the surface evenly. Interesting concept, I wish I knew more about it.
Old     (masonwakerider)      Join Date: May 2003       11-19-2009, 5:13 PM Reply   
you got it multiple uni layers stitched together to create one fabric. glass fibers lay flat and strait in all directions to increase strength.

we use heated pads on our molds, they are made by omega products somewhere around $800 for a 3'x4' pad with controler box, and run on 220 power. The pad will do 200f+ we are at 100f or so. That is just for the precure, then they are in the oven at 350f for 24 hrs post cure. It all depends on the resin being used. I know production snowboard presses use heat pads at around 180f for only 20 min or so.

we also have a mold built on top of a heat exchanger, that we run hot tap water through. that can get up to 140f but is hard to dial in specific temps so we mainly use the electric pads.
Old     (surfdad)      Join Date: Sep 2004       11-19-2009, 7:34 PM Reply   
$800 for the pad?! Holy crap! I'm guessing I'll be using my electric blanket for awhile. :-)

Marking the deck height and the after picture.

Old     (surfdad)      Join Date: Sep 2004       11-19-2009, 7:40 PM Reply   
I'm sealing the deck with the epoxy and microballoons mixture, also. I found that laying a sheet of PE drop cloth on my rocker bed allows me to seal the rails and then I just throw the PE away.

Old     (surfdad)      Join Date: Sep 2004       11-20-2009, 8:09 PM Reply   
A little carried away with carbon. :-) I've found that I can build them super light and stiff, but an optimal weight (subjective) is about a pound heavier than I've been making. I don't really know where the best place is to add that weight, so I decided to spread it out along the rails and between the feet.

The uni is a 6 oz and the tape along the rails is an 8 oz, under all of that is 3 oz eglass.

Old     (surfdad)      Join Date: Sep 2004       11-20-2009, 8:11 PM Reply   
Skin attached and rails wrapped.

Old     (surfdad)      Join Date: Sep 2004       11-20-2009, 8:12 PM Reply   
In the bag cooking.

Old     (surfdad)      Join Date: Sep 2004       11-21-2009, 6:53 AM Reply   
Disaster struck sometime last night. The circuit breaker to the shop tripped and so my vacuum and heating pad were non-operational over night. I've reset everything, but I'm not sure how the epoxy will do after being mixed and left in sub 40 degree temps for 8 hours. Keeping my fingers crossed!
Old     (brewkettle)      Join Date: Jan 2009       11-21-2009, 7:01 AM Reply   
if you mixed the epoxy at 50/50 then(fast/slow) , it takes 3 hours when i can turn the vac off.
Old     (surfdad)      Join Date: Sep 2004       11-21-2009, 7:11 AM Reply   
I used a medium hardener - 5 to 5.5 hours to cure, but from what I can tell, it's been sitting mixed and uncured at around 38 degrees for 7 hours. I'm expeting the worst.
Old    mobster            11-21-2009, 10:11 AM Reply number 4
Old     (masonwakerider)      Join Date: May 2003       11-21-2009, 12:55 PM Reply   
from my understanding you should be ok once the epoxy gets enough heat energy to finish the chemical hardening process the results should be the same. I know the time between the precure and post cure has no effect on the finished strength. We keep our prepreg in the freezer to maximize its life, since once its mixed the chemical process starts and can't be stoped just slowed. Their are many variables in epoxy though. I have access to lots of knowledge though, working with two post dr. in composite research.

What brand do you use?
Old     (surfdad)      Join Date: Sep 2004       11-21-2009, 5:44 PM Reply   
My own ghetto pre-preg! The only thing that seems to have happened is a shifting of the skin as I was wrestling everything back into place, and also the tape up at the nose bunched. The other thing that happened is that I was laminating pretty light, so as the tape shifted, I must have scrubed some of the epoxy off and two areas didn't stick.

Disaster averted! :-) It'll need some work fairing everything back in, but at least it's not junk.

Old     (surfdad)      Join Date: Sep 2004       11-22-2009, 7:20 PM Reply   
.014" Mylar. The RC plane folks use Mylar to impart a gloss finish on curved surfaces like wings.

I wax it with Partall #2 to aid release. Normally when glossing a board, there are three layers of resin and of course three separate instances of the application of that resin.

1) Lamination
2) Hot or Fill Coat
3) Gloss Coat

My hope is to achive the gloss with slightly less resin than the three separate applications and with just the labor/time involved with the lamination.

Old     (surfdad)      Join Date: Sep 2004       11-23-2009, 8:22 PM Reply   
Normally when I laminate this size deck with this fabric, I use about 5 oz of resin. Hotcoat is about 2 to maybe 3 oz and a gloss or polish coat is maybe another 2 to 3 oz. For a total of about 9 to 11 oz and several hours of application and Epoxy just doesn't gloss well.

I'm hoping that I'll get a decent gloss, total labor time to apply the deck fabric and mylar was about an hour. I've used a total of 7 oz of resin for a net savings of 2 to 4 oz of resin and the associated weight.

We'll see what it looks like in the morning! Checking the breakers NOW! :-)
Old     (surfdad)      Join Date: Sep 2004       11-24-2009, 5:22 AM Reply   
It's a little hard to see, but it's a perfect gloss - as if someone spent all day sanding through the grits.

Less overall weight than required for a gloss and it took me an hour, so possibly a savings of 5 to 6 hours on this side...and the gloss is with Epoxy (crappy epoxy at that). :-)

The yellowish bars in the pictures are the reflection from the overhead lights.

Old     (fuller313)      Join Date: Oct 2006       11-24-2009, 1:37 PM Reply   
Looking Good!
Old     (surfdad)      Join Date: Sep 2004       11-24-2009, 8:11 PM Reply   
Thanks Jeff - btw, nice name. :-)

Board in the bag, bag in the autoclave...attaching the bottom lamination.

Old     (surfdad)      Join Date: Sep 2004       11-25-2009, 7:10 PM Reply   
Bottom is laminated, over the long weekend, I hope to scavange some fin boxes and traction and then this board will be done.

Old     (surfdad)      Join Date: Sep 2004       11-28-2009, 4:39 PM Reply   
I scavenged some traction and fin boxes. Ready to ride, with fins and traction it's a fraction of an ounce over 5 pounds.

Old     (notsobueno)      Join Date: Dec 2004       11-30-2009, 6:17 PM Reply   
I like. I want to try this one pls. How can we make this happen?
Old     (surfdad)      Join Date: Sep 2004       11-30-2009, 6:33 PM Reply   
You'll need to pay billion, gagillion, fafillion, shabolubalu million-illion yillion...yen. :-)

Just give me a chance to ride the little devil first and then we'll figure out how to get it down to you. My boat's in the shop (again!), hopefully I'll get it back before this weekend. After that, you can knock yourself out.


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