Swaylock’s™ Surfboard Design Forum

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CONTENTS: Hanging Vacuum Hoses; Shaping Room Hints; Glassing Room Tips; Lights For UV-Cure Resin; Grit Drums on Planers; Learning To Sand Boards; Sanding Pads and SandPaper Tips; Using the Right Grit of Paper; Cutting Sandpaper Discs; Sanded Finishes on Boards; Polishing and Rubbing Out Gloss Coats; Compounding; Surfboard Design – Concaves and Vee; Types of Surfboard Blanks; Types and Weights of Fiberglass Cloth

HOW DO YOU HANG VACUUM HOSES SO THEY DON'T GET IN YOUR WAY WHEN PLANING UP AND DOWN THE BOARD?

[Tom] I have my vacuum hose attached to an overhead cable with a pulley that goes up and down the board with me as I shape. I leave just enough hose hanging down so the hose isn't laying on the board. There's a bungee cord from the overhead pulley that hooks on to the hose about 3 feet off the board to pick up any slack. I only use the vacuum when I'm doing production shaping. The vacuum hose moves up and down the board as you walk up and back via the pulley attached to the cable.
[Old Longboarder ] Just a thought, how about an eye bolt over the top of the work area, and a pulley close to workroom wall with a light weight nylon rope/cord attatched to maybe a 3 pound fishing weight to act as a counter balance?? The eye bolt would allow the rope/cord the ability to just slide through without binding where a pulley above the work area would bind the rope/cord up.
HOW BIG OF A SHAPING BAY SHOULD I BUILD?

[Rob Brown] I've had 8’ x 17’ and 7'6 x 15’ but now I built a 10 x 10 x 20 the perfect bay. I used a wider bay once and it didn't trap the light right. It could of had a better light box for the lights I guess.. I had Paul Jensen build me 12' long by 12" deep light boxes. Plus if you’re going to run a vacuum hose you need to get it up at 9' overhead to get the hose to travel the 12 feet...

[Herb] 12' X 20', is better,or 12' X 16’, 10’ X 16'

OTHER TIPS FOR A GOOD SHAPING ROOM?
[Herb] Sound proofing can be done in several ways. If you can get a hold of some egg crate mattresses, they work great! Or just cut the bottom out of a sh*t load of used egg cartons and staple or glue them to your walls. Or use foam padding, something that absorbs.
Keep the side lights about 4" above blank height, that's when you have a blank on your racks the lights should be 4" above that.
As far as the distance between/apart for your racks, that would depend on the length of your blanks/boards, enough to keep the board stable, and from tipping off when you work/get towards the ends.
Rack height depends on how tall you are. Keep in mind that the rack height is in relation to your height, and the blank thickness on the racks. You don't want the racks so low that you stoop over and kill your back, and you don't want it so high that you lose your vision when doing rails, and have to reach up and over the blank.
Wall color varies from flat black to blues and greens, here's a tip, use flat finish paints, no gloss or semi gloss paints, you want the walls to absorb light, not reflect it. This makes a big difference in controlling your shadows. I only have some small areas at the ends of my racks(on the walls) that are painted black with horizontal lines on it to check for even levels, the rest is pictures and junk.
[Cleanlines] My racks adjust up and lengthwise. Mine are 40 inches and will stretch to 64. Normally I keep the height so that the board surface is as high as my navel. I change them for different applications (your choice). Lights should be say 4 to 6 inches above the blank surface but I keep mine higher because I sometimes raise it up for certain things. Walls are black but I think I will go to blue or green. No soundproofing because I'm half deaf anyway(that should tell you something). Put up some wall racks above head level for storing blanks.
[Paul Jensen] Yesterday I helped set up a new shaping room... I made the light boxes 12' long-3 twin tube 4'ers... 11" shelves above and below the fixtures - 5" between the shelves... Nothing fancy... Here's the cool part... I attached the light boxes to the wall with 12" ACCURIDE 100# FULL EXTENTION DRAWER GUIDES... This allows the lights to be adjusted in height for anyone from 5'4" to 6'4"... I put sliding barrel bolts on to hold position.
[Jim Phillips] I have a big room, 9'3" wide by 20' long, the ceiling are only 8', I would have liked it to have been 10 foot. My front and back walls are black. I had the walls flat black, but the flat paint collected too much dust and made the walls too light a color. I put a coat of gloss black over that and it was much better. I like my room a dungeon, dark as possible walls and shelves, etc. I want as much contrast as possible between work and walls. My racks are at about 38 ", hip high and my lights are at 53", just above the deck of the board. I see many shapers with the deck really over shadowed with the lights down low, but I like to see the scratches and chatter in the foam really clearly. My side lights are a combo of an 8’&4’ fixtures butted together, same with my overhead lights. I tried to get a stronger bulb wattage, but believe it or not, 60 watts is the max by LAW, new conservation rules for fluorescent bulbs.
HOW ABOUT A GLASSING ROOM? WHAT’S BEST?
[Mike D.] In my humble opinion, you can have too much light. It seems to be a fine balance. I had a booth at my last place with poor lighting. I got a little carried away trying to light it up. With a white blank, clear resin, and silane cloth (it kicks clear) it was very difficult to see the air bubbles and the nuances of the lap lines with too much light. All I could see was white. I had to kick back the lighting a bit. Every space will be different, especially with a high ceiling you will find a range of light you will be comfortable with. Put sand on the floor of your glassing area. I have tried cardboard, carpet, containers for the resin to drip into, etc. For me the easiest thing is sand (like a playground sand, not too coarse). When your resin run off kicks you can pick it right up off the floor and dispose of it. This is way easier to deal with compared to a mound of hardened resin that forms on the floor after a few months. The easier it is to take care of quickly the more likely you are to do it (at least for me). When I had carpet and cardboard down, I kept putting it off. When I had to move I had about a 10" thick slab to deal with. I had to do relief cuts with a circular saw, then break it up with a sledge hammer and haul it away. What a pain.
[Crabie] If cost is not a problem, I prefer metal halide lights, 10000k is the best choice. Remember to choose anti-ultraviolet bulbs and glass, otherwise it hurts your skin.

WHAT ABOUT LIGHTS FOR GLASSING WITH ULTRAVIOLET RESINS?
SAFETY NOTE: USE CAUTION, protect your eyes, skin, and lungs!
UV light is electromagnetic radiation in the part of the spectrum between visible light and X-rays. These wavelengths of light (100-400 nm, which includes UVA, UVB and UVC) cannot be seen by the human eye BUT are very bad for your eyes. Cataracts are no joke! Don't risk your vision.
Don’t risk your skin either: Direct and indirect exposure to UV, especially in the UVB and UVC range, include sunburn, aging, and carcinogenic changes. UV output can burn skin in minutes.
Wear UV protective clothing, skin creams, and UV protective eyewear to work with artificial UV light sources (which includes incandescent, gas discharge, low pressure mercury, medium pressure mercury metal halide, and xenon lamps).
Another hazard associated with the use of longwave UVA bulbs (above 350 nm) is that they can also cause lung damage from the ozone generated.
[Noodle] Suncure resin kicks in 5 minutes in full sunlight. You won't find another UV source stronger than the sun. Artificial cures will range from 5 minutes upward. For best curing efficiency, you want tanning, or blacklight UV. But Suncure will kick less efficiently in wavelengths close to tanning lights. I've cured Suncure in 20 minutes using cool white fluorescent tubes, mounted less than a foot from the resin surface. Using handheld lights is pretty tricky. From my experience with street lights, I can recommend bare (not color corrected) Mercury Vapor, with no intervening glass. Look for the clear bulbs. A 175W guard light would provide sufficient UV for reasonably quick portable cures. The guard light should cost less than $30 U.S. I would cover the inside of the clear plastic chimney with aluminum foil. A couple of 400W Mercury Vapor street lights would cook a whole board in short order. Most street lights cast an oval light pattern. Try putting a 175W guard light on an extension cord and see how you like it. Mercury Vapor emits just over half as much light per watt as fluorescent tubes. But Mercury Vapor costs less to buy, and the fixtures are more compact.
[Tom Sterne] Noodle is right on with the Mercury Vapor lighting. I tested an old outdoor security light I had and is does emit a huge pattern of usable UV-cure. UV system cures from the inside out and the light must be able to penetrate and bath the particles with light. Tints will work but opaques will not, fin box/plugs no good either. For a quick ding repair light I use "Black Light" bulbs, not perfect source of light but good enough for dings, lam patches etc. These are not bead curtain and lava light type black light lamps, what I use are a bulb that is installed in many types of bug attractant type fixtures. Insects are attracted to these same types of wavelengths. Mine is a double tube 24" fluorescent fixture with 2 fluorescent "BL" tubes. Start looking at a True-Value hardware or lighting supply. Works like a champ for ding repair.

WHAT’S THE FUNCTION OF A GRIT DRUM (INSTEAD OF REGULAR BLADES )ON A PLANER?
[Jim Phillips] I have one Hitachi with the grit drum on it, it is great for extremely fine cuts, but can't remove the material fast enough for deep cuts. I use it to thin the tips of noses on short boards where there is a chance of blowing the stringer apart. It is also good for coming back over the main bands for the tune up work. I equate it to a belt sander that you actually have control over.
HOW CAN I LEARN TO SAND BOARDS?
[Herb] Here's a beginner's tip, get an old stick at a garage sale, don't pay more than 10 bucks for it, and use it as a sanding practice board. Also good for learning to do fin boxes, etc.
OK, I GOT A ELECTRIC SANDER AND GOT WILD. HOW DO I FIX ALL THE QUARTER MOON DIVOTS I HAVE PUT ALL OVER THE NOSE AND TAIL?
Fill them with hotcoat resin and redo it.(unless you hit foam -- if so patch with glass).....
WHAT’S THE RIGHT WAY TO SAND BOARDS?
Use a Power Pad to sand with and hold your sander flat. When sanding and learning how to hold the sander, you should be able to float the pad on the flats. I mean with one hand and a slight twist of the wrist change direction. Using the spinning pad to guild you and your wrist to change direction. Always sand the opposite side of the board as it will keep your arms and wrist square. Put the machine in front of you not under you
WHAT SANDING PAD SHOULD I USE, AND WITH WHAT GRIT PAPER?
[Rob Brown] Always use a hard pad to make things flat. Soft pads float over bumps. The trick is to make things flat again. Soft pads are only for fine sanding.. They bend around rails... Hard pad = 80 grit Medium pad = 120, 180, ( 220, 320, 400 Polish ) Soft Pad = 220 sand and 600 wet dry but never wet always sand gloss dry in one direction...
[Cleanlines] I go 80 grit with medium pad just to get the big bumps...100 grit with the soft to get most of the shinies...next I put the same piece of 100 grit on the super soft Ferro pad.....finally its 150 grit with the super soft pad. This is great for pinlines and gloss. Some guys gloss at 80 or 100 grit but I don’t for two reasons. I do resin pins and the gloss drags out better at 120 or 150. If you go finer the gloss may separate. I use a variable speed Milwaukee sander (0 to 6000 rpms). Just take your time, as we all said sanding is a very difficult thing...don’t try to mimic the pros. I think that a lot of guys have seen the J.C. glassing video and try to do it like the sander in the film...he is friggin unreal but probably has done a million or so.
[Rob Brown] Remember you’re just removing scratches with the 120 and finer grits. The 80 grit does most all the work. Just a quick once over with the 120 and 180 to smooth out any 80 grit swirls... you need to go to 120 before glossing but no need to go any more. Why waste time to sand any more than 120 for a gloss...

SHOULD I USE PRECUT SANDPAPER OR CUT MY OWN?
Pre cut paper sucks.. Cut stock 80 grit 3M but cut it with points. That is, cut straight then cut straight again leaving little feathering tips on the paper. When sanding glass on fins you can shape your base easy - try it with a pre cut after you'll see. You will never see swirls again... NEVER CUT PAPER ROUND.... you’re asking for swirls. When polishing it works even better.... cut wet /dry paper the same way.. I've cut my paper that way for over 30 years...
Not square but let’s say 10 sided - think of a pentagon but more sides.. Leave tips so as the machine is spinning it has these tips that will bend up allowing you to feather and blend without leaving swirls.. I just lay a old pad on a few sheets of paper and outline then cut little straight lines. It also allows you to line up the paper on the pad so as not to be lopsided... Making for a true spin. Hence no swirls.. Like I said it makes foiling fins and working around wings heaven...
HOW ABOUT TRICKS FOR SANDED FINISHES?
[Paul Gross] A neat way to complete a sanded finish is by taking it all down to 320 Wet/Dry, then turning over your last sheet of 320 and going over the board by hand with the paper side and water. It knocks off the micro-ridges of the 320 work without removing the scratches. A great surface slipping through the water.
ANY POLISH/RUB OUT HINTS?
[Kokua] I see some rub outs where the texture of the weave is visible when finished and that means it got to hot when using the shurlustre and that reverses the curing process so the board has to recure for another 2 weeks or so.
One tip, when rubbing out the nose and tail rail areas I never use the flat area of the bonnet, instead I use the strands on the outer edge of the bonnet since these are the areas that are easiest to rub thru to the weave and nobody wants that.
WHAT TIPS DO YOU HAVE FOR THOSE OF US TRYING TO MASTER THE POLISHED GLOSS?
(Cleanlines has already beat it into my head that a good quality glossing resin is a place to start).
[Rob Brown] It starts with a good sand job. I grind (plugs and laps) with a 6000 rpm Makita grinder. Then I come back and sand with a hard Power Pad with 80 grit and the 6000 rpm all flats (deck and bottom). Then I come back with the same used 80 grit paper on a medium Pad and my polisher speed at 3000 rpms and fine tune the flats. After I hit all the flats I slow the machine down to about 1500 rpms and sand my rails with a light touch from nose to tail walking the rail. After I have finished removing all the gloss from the hot coat I hit all flats with 120 grit at a slow speed maybe about 2000 rpms. After doing my hand sanding I hit the edges again with the 120 to remove any hand sanding scratches. Now if I'm glossing I'm done sanding. (If I’m doing a sanded finish I will hit the board with 220 and 400 grit).
Gloss - Now that I have a good sand to 120 grit only, I apply a mix of gloss and sanding resin ( 249a and SA ) it helps flow better and it sands and polishes better. Take your time when taping off to make for a clean tape line. You'll see why when to buzz the rail bead.
Polish - Dry sand with 400 and a Medium Power Pad (use a good one!) bottom and deck. With the same paper buzz the bead of the rail - don't burn and hit cloth. When using 400 grit hit the edge on the tail to remove the build up on the hard edge area. When you get done make a pass slap the pad to remove any extra gloss off the pad. Then I come back and hit with 600 with a soft Pad and roll it down the rail (less hand sanding ) to remove any tits. Don't worry about scratches on the rail. Rails polish so easy I only use 400 on my hand sand.
The one trick is pull your paper (sand) in one direction NEVER CROSS SCRATCH or as little as you can and in those areas just polish a little more.
You can fix a real bad gloss - start with 120 or 220 then follow with 400 and 600 but always use a medium or even a hard Pad to remove and sand out splits and tits. Remember when fixing a bad gloss never sand to much with 120 or 220 just remove any bad sections. Finish with 400 and 600. Then use any good polish. and a yellow 3M pad the finish up with lambs wool pad. I hope that covers it. Make it shine!

POLISHING AND COMPOUNDING

[Cleanlines] For polishing I recently started using 320 grit with the soft pad to cut zits and dull wax. Use 500 grit with the super soft pad. Polish with sure luster and wool pad. The pro that clued me in gave me a couple of good tips...use slow rpms. The 320 and 500 grits are kind of odd but trust me, 500 cuts better than 600. Sure luster compound will buff it on out. I polish with a wool pad at around 3 to 4,000 rpm with a Milwaukee Variable speed sander. For the rails, I do the old razorblade scrape and hand wetsand.
How to use sure luster compound: Apply about a half-handful with a brush any where on the board. At a slow rpm start working it until the compound loads into the pad. Start working it while increasing the speed…you will see it starting to shine. I use a windex sprayer with water to spray a mist on every once in a while. This rejuvenates the compound in the pad. Just play around and it will become obvious. The biggest mistake people make is to use too much compound...just take your time and let it do its thing.......

[Rob Brown] Empty shampoo bottles and squirt art as you polish - you can control how much you use. One empty 32 oz cheap shampoo bottle best kine... They come with a flip top so you can close and wipe it off at the end of the day..... Load up and go as the pads gets a little feeling reach over and grab a little compound and work out any swirls left from not cutting your paper right!!! A good thing to think about is keeping the board wet by keeping the pad wet. Work the nose and tail with a clean pad then blend the middle to the polished ends.. The hard thin edge in the nose and tail heats up fast so move that pad all the time never let it sit long. As Cleanlines said sure luster is the best but any good compond works fine. Think auto body and they have it all. 3M comes in a 32oz bottle and a flip top ($10 to 15) does 4 boards with left over...A little squirt will do ya!!!!!

WHAT IS A GOOD BRAND OF EPOXY?
[Sluggo] Do yourself a favor and stay with System III SB112. Fiberglass Supply sells it on the internet, see attached link. http://www.fiberglasssupply.com/Product_Catalog/Epoxy/epoxy.html
Epoxy typically takes 7 days at 77 degrees Farenheit to cure out fully. It goes into a "B" stage that can either be brittle or flexible while it is curing. You want brittle so it is easy to sand (but will spider crack easy). Also the SB112 is clear, has UV additives to help prevent (not stop) yellowing and cures without any blush.
To speed up cure apply heat. Cure time will be cut in half with every 18 degrees Farenheit you go up in temperature.
Also, make sure you measure correctly (by weight if scale is available) and mix the crap out of the material.
[Dave] Fiberlay.com also sells system three SB-112, you can also go to systemthree.com and download info and ask the company reps questions they are helpful and full of answers. I have glassed boards using SB-112 and it works great, but it is expensive.

SURFBOARD DESIGN - HOW DO CONCAVES AND VEE WORK TOGETHER?
[Rob Brown]
1. If you add concave you create lift.
2. Vee allows release.
3. Double concaves help direct flow thru the rear third of the board, by splitting water coming out of your single concave.
4. Fins channel energy creating drive from water flowing past your fins.. hence everytime you pump rail to rail your board accelerates.
Now that we covered the basics. I shape a lot of shortboards and ride them too.
Most all my shortboards run a basic configuration.. Lets say I shape a 6'2 x 18 1/4 x 2 1/8. I weigh 165 (add 15 lbs for a wet 6/5/4 winter suit). So, I need a bit of lift to compensate for weight on such a shortboard. I want the board to turn square off the top not slide so I don't want a lot of lift in the tail behind the side fins. I want to be able to add more drive ( punch ) without having a wide ass tail. (The wider the tail is, the harder to sink it off the bottom and the top).
Now I need to design a board that would fit me. The board would run a low rocker throughout the board, with a light single concave beginning just front of the wide point blending double concave between my stance (or say half way between the wide point and the front edge of my back fin). Because of foil in the bottom as the double concave blends off between the back fin, I add a bit of lite vee into the tail that runs between the back edge (vee is only in the last 11" inches, not the last third ) of the side fins and to the flat off the tails end.
So in a nut shell, single concave to double concave to vee to flat works good. That bit of vee behind the side fins allows me to control the little bit of release I want to sink the tail off the top, pushing through turns without the worry of spinning out or tail-sliding off the top to much.. Moving your fins in and out (toe) will make a change in the bottom release to. The more straight the fins are, the more drive - better in beach break waves. More toe will allow the board to turn tighter but the more toe, the more slow.
There is much more to all this but remember a few things: the more lift you create, the more release you need to create in the right place. Lite vee behind fins, soft rails, less width in your tail all allow release of water flowing off your tail.
Another thing to remember, the longer you go in shortboard design (say to a mini gun 6'9”) the less lift you need. My 6'9” has a flat to light double concave to vee to single concave and very lite vee off the tail. When waves get over head who needs lift??

WHAT’S WITH GREEN AND BLUE BLANKS? THEY LOOK WHITE TO ME!
Clark Foam sells blanks in various densities, which affects their strength (heavier foam is stronger, lighter foam is weaker). Although they are all “white” when you buy them they are marked on the tip with colored paint, e.g. a “supergreen” blank has a green tip.
SUPERGREEN, the heaviest/strongest of the four stock weights.
SUPERBLUE, approximately 5% lighter than Supergreen.
NEW SUPERLIGHT, approximately 9.5% lighter than Supergreen.
ULTRALIGHT, approximately 12% lighter than Supergreen.
You can also custom order three older high density formulations:
CLASSIC (formerly Superlight), approximately 8.5% heavier than Supergreen.
LIGHT, approximately 22.5% heavier than Supergreen.
REGULAR, approximately 38.5% heavier than Supergreen.



WHAT KINDS AND WEIGHTS OF FIBERGLASS CLOTH SHOULD I USE? VOLAN, E CLOTH, S CLOTH? 4 OZ., 6 OZ, OR HEAVIER? IN WHAT COMBINATIONS?
[Rob Brown] Hey I've used it all. Volan, being green, is old school and it's stronger (they say). I've only used 7.5oz or 8oz Volan - I use it on long boards with 2 1/2" rail cuts. The wider the better I say.
As for 4 oz. S cloth, 4 oz. E cloth, and 4 oz. Volan, I see it like this: 4 oz. E is clean, clear and strong enough for short boards as long as you wrap it wide and tight. 4 oz. S is very strong for its weight; it holds more resin because of the weave. It's not as clear or clean (brown spots show after you pour the resin ) and that much more for the cost and stiff feel. I hate sanding it. So when I use S cloth I only use it on the bottom and as a deck patch then I cover it with E cloth. 4 oz. Volan is green and you have to cut laps, no thanks! I charge $30 ( $15 a side ) more for cut laps of Volan.
As far as mixing it can get tricky when you layer 6 oz. and 4 oz., it slides easy (don't bump your prep, and do the thinner cloth first. Never lay thin over thick...
I prefer using 4 oz. E cloth on blue foam on short boards. It’s more than strong enough. On long boards a 4.5 oz. S cloth bottom and 4 oz. E cloth deck patch with 6 oz. E cloth over the top makes for a strong but lighter high performance long board.
7.5 oz. Volan on the tankers is way strong and cool school....

[Sluggo] Actually, Volan is the sizing (coating) that is covering the e-glass. The sizing on your 4 oz glass is called Silane. It is designed to make a very clear laminate. Both of these coatings are compatible with polyester and epoxies. Whether the coating has a better bond to the other is debatable, however 4 oz Volan is not readily available. Both of these products are made from E-Glass.
S-glass has a slightly different chemical makeup in its raw material. Yes, it has higher strength properties.
You can also order what is called "direct sized" glass in both E and S that have higher physicals since it is not heat cleaned. Fibers are stiffer and harder to work with. Hexcel's e-glass version is marketed as "Real White Glass" or RWG.
You can also buy a flat weave S glass. Since there is no twist in the fibers, you will get a thinner laminate with less resin. The draw back is boards made with a flat weave S glass gets compression dings easier.
Overall if you want the best strength for your money, you will learn how to use Direct Sized E-glass. S-glass is very expensive.
[Paul Gross] One thing about the debate between Volan and Silene coatings is that Volan is much more difficult and expensive to make, in part because of environmental restrictions, yet it is still being manufactured. The retro-surfboard market can't be large enough to justify this, so there must be something to Volan beyond cool looking cut laps for us old timers. My own experience with Volan is that it isn't objectively stronger, but it is more durable over time. My 3 year old Volan boards are still going strong, whereas my Silene boards with the same glass schedule turn to junk in a few months, and land fill within a year.
[Matthew]
A quick primer on glasses, E-glass is short for electrical glass and is in relation to how the individual filaments are produced from raw materials. S-2 glass is the commercial version of S glass which uses a different manufacturing process to make the individual yarns. After the yarns are made they have to be spun and woven into fabrics. Styles 1522(3.7 oz), 7533(5.6 oz), 1521(3.7 warp), & 7580(6oz warp) are E-glasses that are woven with a twisted yarn the additional handling and twisting of the yarn makes it weaker. Styles 372 & 3733, 5.2oz(K-glass, which is an e-glass) and 5.6oz respectively are flat weaves, which means that the yarns are not twisted. This improves the tensile strength but also makes them harder to laminate.
Volan is typically used where clarity is not an issue. It was used in early boards because that is what was commercially available. Silane finish has been developed for clear laminations, specifically for surfboards. 4oz Volan is readily available, however you would either have to buy 60" widths and split it or by a whole roll of 60" and get it split by the supplier. The finish is what allows the resin to adhere to the glass, it used to be that volan was a better finish. However it is pretty much a toss up now.
Both Burlington (BGF) and Hexcel have direct sized E-glasses. The RWG, which stands for Really White Glass is Hexcel's, and Burlington offers the Aeralite A218 finish in a direct size which is denoted by an "N" following the style number. RWG was not a big hit when it came out, however the BGF fabric seems to be a well accepted fabric. RWG is available in rolls in style 7533 from Fiberglass Supply and BGF's direct sized glass is available from them in 1522N and 7533N in roll quantity. Direct sizing means that the yarns are sized before weaving and that cloth does not have to be washed and sized after being woven. This is possible due to the use of newer, cleaner looms that don't get the cloth dirty as it is being made.
As to durability you have to step back and look at the whole picture, substrate, glass, resin, and application. Where are your failure areas? Is your glass failing or your resin? Typically the problems that I see are not related to the tensile strength of the glass but the breakdown of the resin on the deck from being compressed. There are two ways to combat that, use more glass on the deck, and use a better resin system.
[Herb] If I want the weight of a six oz. bottom with a double six deck, but I'm trying to grab as much strength as possible,and money is no object. (all in E type glass) ........Double 4oz bottom. .......a double 4oz deck with a full layer of 6oz between the two layers of 4oz. .......SUPER TOUGH,and lighter in weight than the latter, if done correctly.
[Rich] My favorite boards are mid length. I've found that the difference in weight in a real light glass job just isn't worth it. If you wrap the whole board with double 4oz. and work a 6oz patch from a little ways up the tail to about the middle of the board the amount of weight gained on say an 8'0" board over a single layer 6oz glass job is very minor. I don't think the weight increase a glass job like this can be much more that 15 percent. It may be less. I'll tell you one thing for sure. The slightly heavier board will hold up so much better than the lighter one it's amazing! As far as I'm concerned I wouldn't do it any other way.