Vacuum bagging benefits.

[stoneaxe]

I'm considering having a 16' x 29" x 5" custom made for distance and racing. It's biggest focus will be for the CCBC (no more getting in the boat for me). I have a pretty good idea about what I want for shape but glassing is something i know nothing about. How much stronger, lighter, etc.. can I expect a board to be that is bagged versus not?
It doesn't have to be a super lightweight but i don't want a behemoth either.
I'm interested in durability as well.

[Dwight (DW)]

Complicated answer. You planning to build it yourself?

Weight reduction comes from less resin. The closer you get to pre-preg cloth to resin ratios, the better. There are two ways to get there and I've tried both.

1st way-
Resin removal using a porous breather fabric during the vacuum bagging process. It wicks excess resin out.

2nd way-
Remove the excess resin by wetting your cloth on a table. The flat table (versus wetting on the board) allows for greater efficiency and precision in removing excess resin. Plus, rolling the wet cloth up from the table, leaves behind even more excess resin. Rolling it up, pulls out resin.

The 2nd way removes more weight than the 1st way. Sounds crazy, but true.

You can do both methods, but you quickly learn if the 2nd way is done well, the 1st way doesn't remove any more weight. If fact, once you get the 2nd way perfected, you can save money and use simple plastic sheeting in lieu of expensive breather fabric when bagging. This method was given to me by Pat LeMehaute http://www.lmshape.com/about.html . The man who once ran Berky Composite windsurf boards and was tech editor for windsurfing magazine.

The easy way, is to wet the cloth on a table. Get your resin to cloth ratio low. Use a full carbon. Don't vacuum bag. You'll get a light durable board.

I don't bother bagging anymore. Except when I do a board that will be windsurfed. On those I want max toughness, so I bag.

[kayadogg]

Stoney, are you gonna have Vec shape it?  He's working on a 14' for me right now, similar shape to the guy in the crossing (apologize didn't catch his name) with the orange/white 12'6 Vec.  Mix between full displacement and planing.  Hopefully it's done soon, put the order in almost 2 months ago but I know he waits to shape his SUP blanks all at once.  I didn't talk glassing with him other than we agreed that making it heavier would be better than too light, as you can keep the momentum traveling easier with a board that is weighted better for the person paddling.  He said he was in the front of the group for the first CCBC on a 10'10" mainly because his board's weight was a good match for him and he was able to find the right rhythm. 

[stoneaxe]

Great info DW. Just what I was looking for. I'd love to do it myself (been very jealous following your builds) but time is not something I have much of these days.

I have talked to Shawn about it but I'm going to need to save my pennies for this one so I'm not sure when I'll be able to pull the trigger. Keith Natti at Twin Lights up in Gloucester does most of his glassing so I know it will be sweet but I wasn't sure if bagging was needed. Haven't had a chance to talk to Keith yet.

[Ucycle]

Since im using carbon on my board, i wet out the cf on a table then vacuum bag it w/o any porous fabric.  The vacuum flatten out the weave so i can skip the fill coat.  i follow the vid posted by DW on Nelson sailboard factory, work like a charm if you follow the vid.

[PonoBill]

I had Nelson do my Kalama board. Went with carbon rails, bamboo veneer and lots of glass, vacuum bagged between each layup. Should be very strong, very tough, and pretty light, but it was expensive.

I've done the layup on a table thing for smaller race car stuff. Used a big sheet of glass from a place that recycles single pane windows--it was cheap. Used a rubber roller to squeegee the epoxy. It made the layers light but the weave was pretty visible. No dry spots though, the squeegee against the hard glass gets the epoxy deep into the weave. When the epoxy is gelled you scrape it off the glass with a big wallpaper scraper.

Never tried it for surfboards, but it makes sense.

I've also used regular ripstop nylon for breather fabric, backed up with oil absorber material. Much cheaper and worked fine. The ripstop is actually semi-reusable, you can roll it and the epoxy flakes off.

I've seen a roller system making prepreg. I figured out a possible way to do something similar using a potter's clay roller for making tile. These rollers use canvas to back the clay. My plan was to sandwich the epoxy-saturated carbon between plastic and then the canvas and run it through the rollers. I already have the clay roller left over from one of Diane's creative spurts. The rollers squeeze down as hard as you like.

[blackeye]

I don't bother bagging anymore. Except when I do a board that will be windsurfed. On those I want max toughness, so I bag.

DW, big appreciation of your experience from me. 

Sorry, don't follow.  How does vac-bagging make for max toughness where pre-pregging doesn't?  Don't we always want toughness or is there a trade-off?  The trade-off must be time or consumables cost as it isn't weight or looks.

With the minimally wet pre-preg method, do you not risk more bubbles and voids? 

[Celeste]

I don't bother bagging anymore. Except when I do a board that will be windsurfed. On those I want max toughness, so I bag.

DW, big appreciation of your experience from me. 

Sorry, don't follow.  How does vac-bagging make for max toughness where pre-pregging doesn't?  Don't we always want toughness or is there a trade-off?  The trade-off must be time or consumables cost as it isn't weight or looks.

With the minimally wet pre-preg method, do you not risk more bubbles and voids? 

Bagging consolidates the layers better then you can do without it.  That consolation makes for a stronger panel for a given thickness because there is less resin making up that thickness, and resin does not give you strength or ruggedness, all it does, and should be asked to do is to stick the fibers together.

Prepreg has so little resin in it, that if you use multiple layers, you pretty have to bag it.  Pregreg is the "gold standard" because of its low resin:fiber ratio and the quality of the resin that can not be achieved with room temperature catalyzing resins.  (actually prepreg does partially catalyze at room temperature but it takes months).  One of the rules of thumb with epoxy is the longer it takes to set the stronger it is.  Prepreg's resin is so slow, you have to heat it to like 150C to get it to set in less then a few months.   

[blackeye]

I don't bother bagging anymore. Except when I do a board that will be windsurfed. On those I want max toughness, so I bag.

DW, big appreciation of your experience from me. 

Sorry, don't follow.  How does vac-bagging make for max toughness where pre-pregging doesn't?  Don't we always want toughness or is there a trade-off?  The trade-off must be time or consumables cost as it isn't weight or looks.

With the minimally wet pre-preg method, do you not risk more bubbles and voids? 

Bagging consolidates the layers better then you can do without it.  That consolation makes for a stronger panel for a given thickness because there is less resin making up that thickness, and resin does not give you strength or ruggedness, all it does, and should be asked to do is to stick the fibers together.

Prepreg has so little resin in it, that if you use multiple layers, you pretty have to bag it.  Pregreg is the "gold standard" because of its low resin:fiber ratio and the quality of the resin that can not be achieved with room temperature catalyzing resins.  (actually prepreg does partially catalyze at room temperature but it takes months).  One of the rules of thumb with epoxy is the longer it takes to set the stronger it is.  Prepreg's resin is so slow, you have to heat it to like 150C to get it to set in less then a few months.   

Oops, sorta made a leap by labeling DW's "2nd way" as "pre-preg".   It sounds like a basic form of the pre-preg method.  I see his goal is to reduce weight economically.  If I can presume to extend his windsurfing-max-toughness line using your post, bagging would consolidate the fibres even more, although at a price he can't justify for a SUP but can for a sailboard. 

[willi]

Lots of great input from very knowledgable folks --
Here is my take on bagging --- I would never glass a board without baggin it -- some guys say they can glass a board and get lots of resin out of it with a squeegie -- let me say--- my boards have no voids even around the tight bow or stern corners -- a tighter  layup translates to a stronger laminate and a lighter board. There is very little strength in the resin -- so less in this arena is --mo betta
A 16 foot board is gonna  use a pile of resin -- I would bag it and --would definately use the right materials to bag it. The peel ply needs to have holes / bleeder holes --I use green peel ply with larger holes, for better transfer of excess resin to the blanket, and a thicker  (1/4'') blanket.
Be cautious in using home depot plastic for the bag. --it may have holes in it and if you can't pull a vacuum when the time comes - ie the resin is getting hot -- the project is in jeopardy. (it happened to me.)
You can buy a vacuum machine at Harbor Freight for 100 bucks -- the rest of the stuff / peel ply / blanket & bag -- google on line and you will find folks that sell materiel by the yard. If you are careful the peel ply can be reused it---and I turn the blanket over and use it again. The bag is good for many boards -- but be careful and make sure you don't have any holes in the bag --blow it uplike a baloon after you tape it together to make sure it has no leaks -I use perminate duck tape (hd) to tape the bag together to form the bag, and put wide stucky foam (home depot) on the inside of the mouth of the bag -- then use smooth light sticks with clamps to seal the opening when I am ready to vac the board.
I pull about 10 atmospheres -that -is about all 1.5 lb eps foam can stand before it starts to crush a bit and all you need to get a good layup. I do 2 layers of 6.5 at a time.
I could get into more detail but for the sake of space will stop here --anyone interested in more --can email me with questions --i will try to answer
once you do it once-- you will never go back --just make sure you have extra hands to help work quickly and with good planning --slow hardner !!!!

aloha you all
willi
paddle hard live easy ;]