Balsa Pre-Treatment?

General Discussion
21

Sabs,

Thanks for your 2 cents. Now is that 30 grams of resin before you thin it with acetone? or is the final weight of the thinned resin / acetone mixture 30 grams?

Sorry if it seems like a silly questions, but I have no experience working with wood materials of any kind. What it takes to properly seal a porous material is a mystery to me.

Which brings me to a question.

Correct me if I am wrong, but once I have sealed the balsa, my epoxy lam coat is now “bonding with the sealant” and not the balsa?

And if that is indeed the case, than what I use to seal my balsa is very important. Otherwise you could run into delam problems not due to outgassing but because of a poor “bond” between the epoxy and the sealant.

22

Do you think that it would work the same if you used alcohol instead of acetone?

23

Hi Bart Paul and Dan

Paul -I find with a single 3oz you cant dent it with your fingers,I should add that my pre seal on the outside is a very light coat and I dont increase the density of high ware areas of my own boards however it has merit if you are doing boards for others or you have an area of uour board that you know you punish

I used to use 4oz then went to 3 oz in a bid to find the breaking point

I am using balsa

Core densityif you look at the pvc core materials such as dcell you will find that the densitys vary you can get very soft right thu to unbeliviably hard ,they are all for use in sandwich construction.The softer the core the more the flex of the sandwich panel and vis versa.

Quite often it can be a trade off between thicker laminate skins vs denser core material vs thickness of core material

There are just so many variations to pick from!

Im not sure of the figures you want?

See the note below on the inside skin

no i havnt been venting though i should be venting even more so now summer is here

I think that we are very lucky here the temps are not that extreme, at xmas we are going to vist the folks in Perth so i will have to put vents in for there temps

The eps I use is the light stuff

Bart - Yes thats the total mixed and thined amount

And yes its all a chain part a connects to part b etc

Your lam is bonded to the sealer but the sealer has bonded to the balsa

It can give a better deeper bond than just a surface bond

In any construction all materials should be compatiable

Its not so important on the inside skin as the vacuum takes care of bonding issues

Beware there is a difference between sealing and saturating a porous material

Dan

I havnt looked at that I would check with your epoxy dealer they will be able to advise you about what there product can and cant be thined with

To every one beware where you use thined epoxy as thining it does affect is strength

Mike

24

Dan

I have used, cellulose thinners with success for thinning epoxy resin for sealing purposes, as long as you lam within the resins overcoating time all will be well. Cellulose evaporates more slowly than acetone, I haven’t tried, but I bet it melts eps the same though!!! care must be taken when sealing!

25

Hey All,

bringing this thread back to life!

So have any of you found a good balsa pre treatment to prevent much resin soaking into the wood? I’m curious to know because I do my skins a la DanB. I made my bottom skin using 1:1 ratio for the glass/resin but realised how much resin was being sucked into the balsa. The outcome was really light though. I then read up on an old thread by Bert saying that he prefabs his skins under high vacuum and heat letting the skins fuse into one. I interpreted that as adding more resin. So when it came down to making my deck skin I added an extra helping of resin to the fiber glass and prefabbed the skins with high vac like DanB still, but it came out WAY heavier than the bottom skin. Bottom skin was 1/16 and top was 1/8 but I don’t think the thickness added to the weight. I think the extra resin amounts soaked into the balsa and made it heavier. I’d like to do 1:1 with my cloth/resin but I’m afraid of the balsa sucking up the little resin on the cloth so I was wondering if there was any news on sealing.

I dug a bit on google and found some ideas like lacquer, hairspray, Baltek presealed balsa, etc. but I don’t know if these are good ideas. Here are some links…

Sealing balsa before Vacuuming

Sealing Balsa Core

Cheers,

Rio

PS here’s my cloth/balsa/cloth out of the bag (-25 HG was used)

26

nah bro

thats sweet

you want the resin in the wood ,its a good thing.

if you build to superlight, durability suffers

sealng and pretreatment are two different things with two different purposes

pretreatment-is for waterproofing and improving quality/durability of wood

sealing- is to prevent your balsa breathing causing cloth pinholing and its not actually 100% necessary

it sounds like you killed two birds with one stone

balsa density varies greatly

so that could have something to do with the weight difference as well

keep the dense stuff out near the rail

27

Personally, I would use a perforated release film with a layer of bleeder. But if you’re going to do it the DanB way, you really have to do it the way you did the bottom skin. Because if you put extra resin, it either has to go into the balsa, or if you if you seal the balsa, it will just make a thicker layer of resin on the surface. It has no other place to go. If anything, you want the resin to be absorbed into the balsa to improve compression strength. But in that case it would be better to use 1/16" on the deck to keep the weight down. Think of it like making the balsa a higher density, like it’s now the equivalent of oak or something.

But if you want to try sealing it, I would just use epoxy to seal the balsa. The reason being, you will be guaranteed a good bond. With lacquer, or hairspray, I wouldn’t chance it without doing some test panels. But you never know, it might work. With the epoxy, just do your best to get a very thin layer. A squeegee might work better than a brush. The Baltek balsa is end-grain, so you probably don’t want to go that route unless you’re feeling experimental. On the other hand, it might pay off to give Baltek a call and ask what they use to seal their balsa.

What did you use to hold the balsa in place — masking tape, super glue, or the “adjust in the bag” method?

28

good stuff from silly and kenz…

I’d like to do 1:1 with my cloth/resin

Ive said this before in other threads…why?

I know I know, higher strength to weight, but how valuable is that when the board gets waterlogged? The shell has to provide a good seal and that isnt going to do it.

Btw, you can get 1:1 or better using hand methods. You just gotta experiment creatively. But still, I wouldnt use it to seal the structure. Good luck on your project! Looks like your making good progress there…

Cheers

29

Your deck probably wants a bit more resin in it, adds to the durability and helps to prevent water absorption when you ding it.

I shouldn’t worry about the vacuum sucking all the resin out, it will be more prone to pin holing though.

With regard to your picture, you say it’s glass-balsa-glass? how are you sticking it to the board? have you peel plied the inside ready for sticking with resin / foaming epoxy? just curious.

30

Every time I see the skins done under high vac I’m so impressed - and yours are no exception! I think the problems many of us are running into are not from technique, but rather from lack of experience. When Bert started the bagging thread he did not expect people to go in the direction that we went. A lot of us went pretty quickly from never seeing a vac bag to making superlites - which are very close to the edge. Going this route shows the weakness in ones understanding very quickly. I agree with some of the other comments that getting some resin penitration into the balsa is a good thing, but its not that easy to do. However, I do differ with Dave in that I think going 1:1 gives a lot of benifits (cost, weight & strength to name a few) and can produce very few pinholes with a little practice and the use of the right materials. Keep up the good work!

31

have any of you guys looked at building more than one skin at a time?

We want to build a bunch of them under one pull by stacking them between sheets of 1/4" ply or something cheap.

We’d use blotter, and perf release as well as plastic as needed.

But I haven’t heard of anyone’s techinque here in bagging a bunch of skins at one time…

Been thinking long and hard of getting into the “skin trade” and just specializing in making fancy patterned wood skins for bagging. If you can find a way to build the with cloth so you can roll these up to ship in tubes I think you might have something there…

somehow I can just see that chipfish comment coming my way about this “skin trade” idea.

Oh by the way I am using a spray on styro primer sealer under and waterbased acrylic wood sealer over the wood as a test. helps in smooth sanding of the wood anyway to prep for the final glass. A clear epoxy slur would be nice to seal and coat the wood to get an absolute smooth surface prior to glassing to prevent the sand throughs some of us get. trying tot smooth the surface after skinning it. Hand steel scraping after the wood sealer is also somthing I’m trying to prevent sand throughs.

32

Hey Guys,

Thanks for all the suggestions they all make sense I guess I just need to tweak my technique a bit. Some things that I might do next time:

-I think I’m going to go a little bit more than 1:1 because my bottom skin seems to be OK and light but just a little bit more resin should make it perfect (I guess this is the “tweaking” part)

-Another option would be to put a cheater coat on the balsa before lamming the fiberglass then letting it dry to make sure the balsa has enough resin for hold while not absorbing more resin.

Ken- yeah, perforated release film would be good even peel ply would suck some of the resin out…but I’m trying to keep my costs down as much as I can. And yeah, it’s not that expensive I know but…I think I can make this work…hehehe. Oh I used CA glue to glue the balsa together. I noticed that the epoxy wasn’t bonding to areas where I used ALOT of CA glue. It was really quick & easy to glue and make whole sheets of balsa with the CA glue but the bonding issue worries me.

Craftee- I really don’t care if its 1:1 or not, I just want to get the same kind of numbers you guys have been getting. Maybe my next one, I can break the 5lb barrier.

Mark- I attach the preformed skin with Gorrila Glue (actually, the cheaper Elmer’s glue). I use a paint brush and brush it on the skin not the eps, because I read a guy tried to use GG and the eps just sucked all of it. A very thin layer of glue on the skin then back in the bag. It works quite well. I was surprised.

Once again thanks to all. Cheers,

Rio

33

Hey Oneula,

I was just thinking about how cool would it be to go to a skin store and just buy your skins. Wouldn’t that be cool?!

I think DanB had a thread where he put his balsa skin between some formica and he noticed that he got bubbles and pinholes because the formica didn’t allow for the bubbles to escape. So, if you’re going to make skins on top of another make sure to be able to let the air out?

I think you’re on to a good idea. let us know what you come up with!

Cheers,

Rio

34

I reckon you’ll need to make up some special spacer/cookie tray plates.

The top of the spacer needs to be formica/sheet-steel/whatever and gets the release agent put on it.

The bottom needs to be permeable, to let the air through.

BUT the bottom needs to be smooth and not stick to the top of balsa. Maybe you could just use peel ply to prevent sticking because only a little epoxy comes through anyway. So you could maybe use EPS, like stuff from foam boxes vegetables come in. Perhaps perforate the EPS too.

You lay one of these trays/plates, apply release agent to the top.

Then put your pre-formed skin down.

Apply peel-ply over that.

Lay your next tray/plate down.

etc.

Main point being the spacing material needs to let air through relatively easily.

Just ideas, anyway.

35

Hi Daklaw -

I read your post and answered some of my own questions.

How long do you leave the vacuum running while the GG cures?

36

Hi John,

I leave it for 4 hours. Just enough to let the glue set. I was worried that GG will permanently stick to my bagging material, but some bagging material got some GG on it and I could still peel it away no problem.

Cheers,

Rio

37
Quote:

I made my bottom skin using 1:1 ratio for the glass/resin but realised how much resin was being sucked into the balsa. I’d like to do 1:1 with my cloth/resin but I’m afraid of the balsa sucking up the little resin on the cloth so I was wondering if there was any news on sealing.

Well I did read your earlier posts Daklaw and it does seem that you do care. I dont know if I made my point. Youre in the sub 5lb cat now…the question going forward is what it will be after a few surfs. I agree with Dan we disagree. If you can get 1:1 with a good seal then alert the composite industry of the major breakthrough. Btw, 2pac pu coats counts as resin, as well as ANY added coats that get applied to the matrix…if you lam it 0.5:1 and then seal it with something else its no longer 0.5:1. As far as pu sealers…you could go that route, for obvious health reasons Im not.

38
Quote:

I agree with Dan we disagree. If you can get 1:1 with a good seal then alert the composite industry of the major breakthrough. Btw, 2pac pu coats counts as resin,

I can live with that definition :slight_smile: I’ve gotten no pinholes in the field of my light boards with no traditional fill coat, but I might not have been so happy if I hadn’t Upoled it up. All my drama has been in the rails. Things are different with the prefabed skins. The high pressure really increases the mileage you get from your resin, but it opens you up to tears-a-plenty on the rails.

39
Quote:

Doug

I reckon you’ll need to make up some special spacer/cookie tray plates.

Doug

is this the kind of thing you’re talking about

http://www.joewoodworker.com/catalog/product_info.php?cPath=44_67&products_id=2301

Quote:

Rio

One thing I learned for attaching the rails is to use a combination of GG and CA glue. I would do a zig-zag pattern with the GG on the balsa then “dot” the spaces with some CA glue and stick it on the rail that I was building up. It worked really well that I didn’t even have to use tape just hold it for a few seconds and the whole balsa plank was stuck. Amazing!

Rio

doesn’t the CA glue melt EPS?

When I used CA to glue an initial layer of 1/16" balsa it did…

I hear there’s a “no vapor” CA that won’t melt foam but your technique is very interesting and I like it since I don’t have big enough cutoff’s to clamp the rails on like others have been doing here. Rail build outs are the hardest part of doing a “Burger”

Quote:

DanB

but it opens you up to tears-a-plenty on the rails.

Dan

can you explain?

I thought reinforcing your lam with 2oz cloth would make it easier to bend with “less” breakage on the rail?

I’m looking at this new WOW (wood on wood) laminate veneer sheets that Joewoodworker is selling

http://www.joewoodworker.com/catalog/product_info.php?cPath=51_69&products_id=2800&osCsid=50ec6447bff4921d5e33049de37541dd

The lam sheets are glue perpendicular to make the venner sheet more pliable. I already have a bunch of 4’x8’ panels I ordered from these guys.

http://www.oakwoodveneer.com/

but as paperbacked veneers it isn’t that easy to work directly on EPS an too thin…

I’m gonna try this new WOW stuff of different color veneers then cut out designs and reglue them back in the holes left in the the other sheets before I apply the 2oz cloth to hold everything togethor. Looking at also applying some type of “backer” material aerovail/aeromat or even a thin layer of this spherex stuff to the back with the glass to gain a little thickness beyond the 1/42" these veneers typically comes in…

I’ll tell you one thing though…

I haven’t found anything stronger than this 1mm woven bamboo sheet to use as a deck patch reinforcement. I found the guy who supplys Gary Young with his rotary cut bamboo sheets but that stuff and the 1/8" bamboo veneer they sell from Teragren is expensive.

40

Hi Oneula,

Oops. I meant that I would attach the first rail with GG. let it set. Then attach the rest of the rail pieces with GG and CA. Check it out:

Cheers,

Rio