Vac bagging - lessons learned & more questions

General Discussion
1

So, I’ve now bagged on top & bottom balsa skins on my 6’0" fish project (photos in a few days, hopefully). I left the rails alone for now, going to build them up from thin balsa strips glued on again. These boards are sort of a Bert B-start, Paul J-finish build method.

So I learned a couple cool things while bagging. First off, I read carefully where CMPHawaii & Bert were saying they didn’t like sanding off the blue tape from the outside of the balsa when it comes out of the bag. Bert’s a little mysterious about how he does it, but CMP said he now uses the cheap paper masking tape on the inside and assumes the epoxy is penetrating it to stick to the wood. I like that idea, but I’m suspicious that any masking tape is designed as a moisture barrier, either in the substrate or the adhesive.

So I used cotton athletic tape on the inside of my balsa skins. I tested it first on a 1’ square piece of foam 1" thick with 3 pieces of balsa laid side by side, taped, and stuck on with epoxy & 6oz. It also let me test the bagging process on a throwaway piece. I could not break the joints with my hands. Finally, I got the foam to break by leaning an elbow on it between 2 bricks, but even then the balsa & glass bent 180 degrees in about a 1/2" radius rather than break. With balsa & glass on the other side, I can only imagine how strong this construction is. With the real board, the tape on the inside seems to have worked - the balsa pieces didn’t gap apart and the epoxy didn’t squeeze out between the cracks and make thick spots that would have to be sanded.

The other cool thing I found is that the bagging on of skins helps a lot with the shaping. I shaped the bottom - hot wire & then planer & then 2’ wide block - and bagged on the skin before shaping the top or even cutting it to thickness. This solves the problem of shaping a light, floppy, stringerless piece of 1# EPS. Once the skin was on the bottom, I hotwired the deck, planed, and block sanded. Then bag on the deck skin.

And here’s the cool part - I pulled about 4 in/HG into the bag for the deck, shut down the pump, and then made final adjustments to the rocker. That’s enough pressure to hold the board when you push it & pull it, but with the long open time of the epoxy and the friction between the balsa, glass, and foam, you can actually tweak it before pulling final vacuum and letting it set. Specifically, I was able to even up the tail tips which had developed a bit of a twist when I bagged on the bottom. Now, they’re perfectly straight. So once I had it set the way I wanted it, I turned the pump back on and let it go up to 13 in/HG. My auto vac switch is set to stop pumping at 13 and then it clicks back on if the vacuum drops below 10. It ended up cycling for about 30 seconds, every 7:40 minutes. I let it run all night & the next day as its a bit cold in my garage. The pump never got hot and the cycle time didn’t deteriorate.

This is a totally amazing & satisfying process. I almost can’t imagine building boards differently anymore.

So…outside glass lamination with the vac bag? I assume you just laminate by hand, put on a layer of peel ply and a layer of breather and it all goes in the bag? Do you overlap these things over the glass & tape them on? Freelaps, obviously?

It just sounds so freaking messy compared to sandwiching the glass between the nice dry foam and the nice dry wood. And since you don’t really need clamping pressure to do a lamination, is the gain really only in sucking some excess resin out through the peel ply for slight gains in strength & weight reduction? Is is really worth the trouble and the disposable (eventually, even if you get a few uses from peel ply, breather, and bag) materials? Or should I just go ahead & laminate by hand like usual? Any hints here or big gains I’m not seeing? Bert? Mr J? CMP?

Thanks so much, all you guys who let the cat out of the bag, so to speak. This process is really fun for me and is occupying my brain in ways my work can’t touch these days…many, many thanks!

Ben

2

stoked …

no more hints from me tho …

i think i once said , that once more people tune in to this technique then youll really start asking how the hell does bert do it …

mr cameron is the closest one ive seen yet …

now im just watching cats run around the yard …

regards

BERT

3

Benny1

Don’t use peel ply or breather, do a test and you will see why! I have just done a test using perforated release film (bread wrap, v cheap) and paper towel to act as breather and absorb resin that comes through the bread wrap. make sure that you tailor the disposables so they dont wrinkle up, and start by doing one side at a time, I am planning to do the deck first (tape off bottom) and trim laminate over tape, then overlap the bottom laminate over the rails. Lay your breather/ bubble wrap on the bottom of the board, if you keep the resin to a minimum, you should be able to reuse these as no resin will travel in to them. Pull the bag nice and tight, otherwise the cloth may wrinkle into the bag folds. Before you bag your board, do test out any ideas that you have, I would also recommend a dry run with your disposables and no resin!! you will soon find the best way to go. Hope this helps.

Cheers

Mark

4

Agreed marky… Benny, the advantage of bagging the outside glass is less weight! Weigh up your glass, measure out your resin to match closely and just get your glass soaked, squeeze out the excess, throw it on the board and the vac bag will compress the glass to fill in all the little squares and hopefully give you a smooth finish, depending on what else, if anything, you throw on top of the board before sliding it in the bag… as long as you can clean out and reuse your bag, you’re good to go… expensive peel plys are for the people that have money to burn and/or don’t have time to calibrate their resin usage before throwing it all in the bag… or they just have trouble soaking everything out at a close to 1:1 glass:resin ratio.

meow! thanks Bert.

Brennan

5

Congrats Benny!

Can’t wait to see the finished product…

I’m also totally blown away with how simple and fast this new process can be to create a light, strong, and beautiful board. Like you I’ll never go back to the 6 month wait for a “custom” from a handshaper backyarder or brand namer. Just ask for a shaped blank and do the rest myself if I want one of those name brand boards again.

A couple of secrets you’ve just revealed is that:

  1. you don’t have to completely finish off the foam shape just do it on the wood lam but plan for the concave and bottom depth. The wood smooths everything out and gives you something to finish shape that’s alot more manageable.

  2. Put the bottom on and then shape the top… The bottom lam stiffens everything up.

Definitely suggest cheap paper masking tape on the inside and no if little blue on the top with a glass layer in between. Anyone who’s spent hours peeling and picking out blue tape chunks with a razor and tweezers and then sanding down epoxy build up from leaks on soft wood will understand. I could sand 5 boards in the same time of doing one the old way…

My next one will be another CNC shaped clark blank from CMP that I just have to hand sand finish in a couple of weeks.

In the meantime I’m glueing up balsa rails on a 7x18.5 Hawaiian gun EPS blank that CMP and I can try a wood sandwich (4oz glass under/over) over wood rails ala Kahuna Bert. I’m also glueing up 1/64" matched walnut, mahogany and maple veneer over 1/8" and 1/16" balsa ala Marke (glued on 1/8" Luan ply) for my next project’s skin…

As far as glassing, unless you really need to go super light, I’d just do a light 4oz epoxy glass over the top like normal. Expecially if you’ve already vacuumed a layer under your wood lam. keeps things easy.

Thanks to Kahuna/Sensei Bert… Yup and I don’t use the term lightly.

Perfect example of pointing the student to a direction without revealing all the details so the student learns the craft through experience through apprenticeship meaning that the knowledge gained will be everlasting.

And CMP/Greg have been just unbelievable with what they’re willing to do/share to help out us newbies.

There’s alot to learn from a few significant posts laying around here and in the archives…

“think it… feel it… do it…” - rasta’s dad

6

Maybe it’s just cause I’m from Canada, but reading your post got me thinking of using Hockey tape for the tape on the inside. I don’t know what “cotton athletic tape” is, but it sounds pretty similar to good ol’ hockey tape. How tight is the weave on the cotton tape? I’m guessing fairly tight because no epoxy squezzed through? anyways, I’ll be trying that soon hopefully. I just got my milking machine vacuum pump, and hotwired my blank…

7

Benny1,

I think you should do a light hand laid glass job with polyester or epoxy resin. Since you didn’t mention what fin system you intend to use you might not have a choice. I have made boards the surftech way with all the fiberblass between the foam and wood and the outercoat with just resin and no fiberglass. The fin boxes where put in the foam first and then carefully cut the wood around boxes and did the vacuum layup. I stopped routinely vacuum bagging the outer glass in 2001. At times I am an army of one at work and I couldn’t control the wrinkles and it added time in sanding. A extra set of hands is nice to get my release film wrinkle free and taunt on the glass. Also it would tie up your vacuum tables for that process and slowing down other lams.

The athletic tape is a good idea. Isn’t that heavy though. Oneula and I have 40 lams with the $1.69 per roll 1" cheap masking tape. I am convienced it is better for time savings alone. Now I am using 1/16" balsa lam because the fear of sanding through the wood trying to get the tape off is out the door.

If I recall from my Tom Sullivan tape which I viewed in 1998, He had a known weight goal for his final product and was weighing it during many of the steps to see if He needed to sand weight off. Something to consider but hard to apply for wood lamination.

8

I don’t think the athletic tape (not as thick as hockey tape - its the tape trainers use for taping ankles, wrists, etc. and you get it at the drugstore…) is very heavy, but it is more expensive than tan masking tape. If the masking is working fine, I could easily convince myself to go to that. CP, have you done any tests on breaking foam with wood & your tape on it to see where it separates?

I did layer 6 oz glass (probably overkill, but its what I had) under both the top & bottom balsa and plan to do 6 oz over as well. I think I will just lay it up by hand. I’m a much better laminator than a shaper and I’m not afraid of resin usage. I would worry that if I bagged my outside lamination, too much resin would soak into the balsa land leave dry spots on the glass. I don’t want to seal the wood first, because that would seem to negate the weight savings of bagging…

Marky & Brennan - thanks for answering my questions about laminating with the bag. Maybe one day I’ll give it a try, but I’m too comfortable with hand laminating to bother for now.

Oneula & CP - the next one looks like it’ll have a wood stringer again and fully shaped foam rails, then wrap everything with veneer like you guys do. Very inspiring, and I’m quickly getting bored with building up the rails, one 3/16" thick piece at a time :slight_smile: Especially now that I fully understand how the power of the bag and the adhesion of the epoxy can conspire to bend but not split thin wood…

My balsa is a fat 1/16th" this time too, CP.

Fins will be glassons - I like tails of small boards too thin for boxes.

CP, I noticed your update website. It says you’re now putting glass under the veneer too - is that a recent change? It sounded before like you skipped that in favor of thicker wood and heavier foam. Is the shaping machine doing such a good job with EPS that you don’t need any clark blanks anymore?

Lastly (sorry to run on like this), tell me about the board in your ‘sold’ list - the 12’+ crowd control model. I think that’s the next project - one I can take my boys out on with me. How thick? What stringer schedule under the veneer? Glassing? Final weight? I saved the rocker & thickness numbers that Paul J posted for his 12’ and I got a tracing of the nose & tail of a friend’s Phil Edwards 10’0" that I think will stretch nicely…so its in the planning stages…Thanks much

Ben

9

Benny,

I have not done any load testing on my boards. They are stronger than a regular foam board, I also have no knowledge of a wood lam board of mine that has ever snapped or buckled while surfing. So real life load testing seems acceptable. With this new technique of inside taping the cut off tail section of the boards getting tail blocks have perfect adhesion. Also I never seal the wood because it gets sealed from the inside out with the resin and the vacuum pull. To be honest with you I never made my boards to be the lightest thing going. They had similar to maybe 10% lighter weight of a polyester surfboard. Regarding durability there is no comparison, mine are stronger and will hold up longer because of the epoxy. I just did the wood mainly because it looked very cool. The customers who give me feedback tell me they are conversation pieces on the beach and in the break. People are curious about them. The curiousity usually stops when they see the price though.

Regarding the glass under the foam. Tow boards and kite boards I will put glass under the wood routinely. Surfboards I will upon request. My website reference is probably from 1999 info. I sometimes update the for sale page when I can make boards beyond what’s ordered. I am going to start putting 2-40z under the foam on regular boards routinely though, and lighter glass on the outside. Oneula and his brother are going to make some that method and hopefully we can figure out the effective method to get the total package of cool looks, light weight and strong board and not do it any slower than we can make a board presently.

The 12 foot crowd control was an eps blank. I don’t recall the specific dims but it was 24" wide and 4" thick and weighed aroung 18 pounds. 6oz bottom and 6/4 top. A board collector from honolulu bought it off the rack. I glassed it in my driveway because it was too long for my glassing room.

I have started using bennet blanks from AU and eps from a local manufacturer here. The foam type of eps or conventional is customer driven. I have plenty of both in stock. Cutting foam is a chore so I plan ahead and cut 2 times per year instead of each individual order.

Can’t wait to see your board when it’s finished

10

Cool, CMP, thanks very much.

I agree with you about EPS cutting.

I’ve also run 5" EPS blanks through the bandsaw to rip to 6" wide, then turned them on their sides and used a single rocker/thickness template to draw the profile, then cut them again on the bandsaw. Its much faster than wire cutting, and if you’re putting in stringers anyway, it works out…

I can glass up to a 10’6" inside, so I’m with you on the driveway. :slight_smile: Be nice to have Mike Eaton’s shop, wouldn’t it…

11
Quote:

So…outside glass lamination with the vac bag? I assume you just laminate by hand, put on a layer of peel ply and a layer of breather and it all goes in the bag?

It just sounds so freaking messy compared to sandwiching the glass between the nice dry foam and the nice dry wood…

Ben

hello Benny1, i don’t think you’ve missed anything regarding the pros and cons of bagging the outer lam. the exciting thing about this method of construction is that its still being developed and there is no established conventions layed down yet. So do what you feel suits you - economy of construction or experiment with more bagging.

i stand by the reasons i give on my ASH thread for bagging the outside:

  1. The bleeder and peel sucks out excess resin and keeps things lightweight.

  2. The bag can do a much better job than me single handed with a squeegee of lapping and squeezing out the airbubbles. Its a bit like having a magic hand go over my work.

  3. I get to play with my cool technology again

i’ve added a bit more explanation to the peel and bleeder process on that thread too.

PS i don’t think its messy - just more expensive and elaborate, wetout table keeps mess down.

the resources available to the fantastic factories of Sunova, Cobra and Kinetic sport exceed what is possible at home. But as a home builder i take advantage of being free from the need to make a profit, and this opens up the possibilities

i look forward to seeing some pics of your project

12

While we are on this vac bagging topic, I just came across something kinda neat in an old issue of “B&H Wood” (Dec '02, #146)

I was flipping thru, and this one article caught my eye because it was all about this one guy on Deleware uses veneers to make curved trays and stuff. What really caught my eye was that he was using a vacuum bagging system to lay up his surfacing veneers onto flat ply stock. 33psi. Nothing new in all of that there, but what got me was the bags that he used.

He didn’t use plastic bags or poly or anything like that. What he had was old sheets of industrial rubber roofing. You know, the stuff that looks like a giant sheet of ‘inner tube’(maybe you call those something different in Australia, but I have no clue…) It makes sense to me. The stuff is strong, doesn’t wrinkle very easily, and bag seams can be made with rubber cement. Cheap cheap too. I’ve worked on site where they have used that stuff before, and pieces large enough to bag boards with were regularily thrown onto the garbage pile. I wish I had grabbed some. As far as clean up, I’d assume it would likely pull off sort of like plastic. Definitely hold more, but if you stretch it as you pull it out, it should come clean. Downside to it is that you can’t see inside your bag. But I’ll likely try it out sometime.

Anyone else tried this stuff? Or got 2c to throw in on this idea?

13

I’ve have a silicone rubber sheet vacuum bagging system. It’s expensive, but you can see through it. It works great. I haven’t used it for a surfboard yet, only snowboards. I’ve been wanting to try doing it with a surfboard because I think that the stretch would smooth out the wrinkles. Here is where I got my silicone rubber sheet:

http://www.bondlineproducts.com/

I’ve also looked into latex sheet which is available translucent, and much lower in price.

14

theres some pretty stretchy clear plastics around …with a proper bag holding system , your only crinkle should be at the rail apex …

who let the dogs out ??

regards

BERT

15

OK - I admit, I’ve stayed up nights trying to figure some of this out. A couple of things continue to puzzle. I’ll just toss them out and see what you guys think in regards to some stuff that’s already been presented but not completely explained…

  1. What the heck is going on in the photo of scooped out core in the tail of one of Bert’s boards? Does he fill it with something or leave it hollow?

  2. If he leaves it hollow, how is he bridging the gap, attaching fin boxes, etc?

  3. Does the “Contour Mat” he shows offer any clues? Maybe a molded rigid shell that covers the scooped out core?

  4. If he fills it in, is he using some sort of flexible material like EVA foam?

  5. He mentions Mr Cameron as being close and Mr Cameron’s process involves heat… post cure heat apparently strengthens epoxy and is used to cure pre-preg fabrics. Too much heat will melt or distort the foam so maybe Bert’s shell is molded, heat cured and vacuumed to core?

  6. Balsa stands up to higher temperatures, right?

  7. If you inserted internal stringers that were glued in the front and center of a blank but slid into slots or channels (unglued) in the tail, would this allow greater tail flex without breakage?

Bert - you can stop laughing now at my feeble guessing.

16

There’s also a new silicone sheet that has a grain pattern on the inside that allows you to go without a breather. Also, since silicone doesn’t stick to anything, you don’t need a release sheet. I think that this would work great for wood skinned sandwich construction or a precured skins sandwich. For a wet skinned construction I’m a little skeptical if it would work.

17

Heres my “Bert’s Way” guess. He starts with lite eps. He routes in a groove to place a horizontal stringer. The stringer is not glued in so that you will still have flex but gain some support. The groove is then filled with more eps. At this point the balsa rails are attached and the board is shaped. At this point he probably needs to selectively seal the eps. In places he wants to keep it lite and flexable gets some type of sealer. Places that need extra strength and toughness are not sealed and probably get extra resin during lamination so that more soaks in. Now the top and bottom are prepared. I bet the reason Bert doesn’t need to worry about peeling tape is because he doesn’t use any. I think that the balsa is layed out on some type of form and is held together with pre wetted glass from the wetout table. The skins are then cooked in an autoclave. This way he does not need to worry about crushing the foam. He can use as much pressure as possible. I don’t think that the skins could be all the way cured because there wouldn’t be enough flex to fit correctly on the blank when it is applied. The autoclaved skins are attached to the blank with a layer of glass in between the eps and the skin. The rails and other high stress areas would need extra glass to hold the whole thing together.

I’m probably amusingly off base, but it is the only way that I can piece together all the bits and pieces that Bert has given us.

18

Like CMP I’m not a big fan of vacuuming the outside. It’s usually just one layer and the weight savings are relativly small, less than 1/2 lb. But if you really want to here’s a couple methods to try.

  1. Try spray gluing the cloth to the blank. Then slowly wet the cloth with a 3" chip brush using just enough resin to wet the fabric, no resin going into the foam. This is done by dipping the brush into a cup of resin and then lightly brushing the cloth. After the fabric is wet, put the board into the bag and pull to about 7-10 in. No bleeder or breather are required because the right amount of resin is in the glass. The bag will pull the cloth tightly to the foam and enough resin will be transmitted to the foam for good bond. A seal of microballoons and epoxy may be required after this step to make the laminate water tight and to allow finishing without pin holes.

  2. Use a wet out table to saturate your fabric. Get everything nice and saturated on a peice of plastic with no excess resin and when that is done flip the whole thing onto the blank, smooth and lap, and then bag. Again, you should have the right amount of resin in the glass so no bleeder or breather is nessasary. You can leave the wet out plastic on which makes it easier to get into the bag.

I actually like the #1 better than the #2. Less wasted resin, not as messy and actually easier and I always got better results with #1.

For those so inclined, as stated above, once the blank is covered with divinycel the board can then be glassed with polyester. It will come out about a pound heavier though, with the same glass schedule. Seems a waste to put in the effort just to add dead weight to the outside.

19

Is the spray glue the 3M type of glue?

20

Can’t find Mr Camerons post. Could you put up the link please? thx