I know I’ve seen recommendations for how much vac pressure to use when bagging 1 lb eps, but after extensive searching I couldn’t find any posts that talked about how much is too much. I pulled about 21 hg’s when I bagged my balsa bottom to my 1 lb eps core, and it totally crushed the eps. I’m gonna remove the crushed eps from the balsa and try again, how many hg’s should I pull?
Yea, I did that the first time I tried my new vacuum pump…You need to pull about 7-9 Hg, no more then that.
Most of these girls can’t handle more than about 12".
And lighter EPS handles less than that before becoming a tastless, crunchy pancake.
The vac switch is a bit inexact. I dial mine in to shut off at 13 and it kicks back in around 9 after some pressure bleeds off. It cycles (and bleeds) less & less often as your epoxy sets up.
Some pics would be fun to see.
" Most of these girls can’t handle more than about 12".
your nose is growing [to 12"]
About 8 for 1#
15-18 for 1.5
20+ for 2
2.5 all the way
This varies depending on a number of aspects. Foam is different depending on where you get it. Be careful …
your nose is growing [to 12"]
LOL! Well it’s true. Even VH Grade (at 32kg/m2) starts to deform and break down when you go past 12 inches of mercury.
That’s from memory, mind you. So my thumb-in-the-air is to sit around 10".
Satori
Don’t get down, I just spent 8 hours yesterday on my first vac pull with less than complete success. The vac went well but that was about it. I tried to vac the bottom balsa on with top and bottom layers of pre wet out 4oz. Two monkey trying to have sex with a football came to mind. It was my first wetout and my first vac pull. While trying to put on the outer lam I pulled all my balsa up and spread it out over the board. After putting the puzzle back together and with about 5 minutes of working time left I was able to roll the wetout cloth on a cardboard tube and reroll it onto about 90% of the board. I got it into the bag with no time to spare. With bubbles the size of small nations everywhere the vac smoothed most of it out and it looks to be salvagable. I was using #2 eps at 15hg and cycling back on at 10. Pull number two in two hours yee ha.
christian
I have to write myself notes & staple them to the wall…
Edit: don’t move #13 up the list. Results, then, not so good.
I can’t say that I agree with not moving #13 up. If it doesn’t improve the actual quality of your work then at least it will improve the preceived quality it the short term!
Benny,
When I went to take off the tape my balsa it did not stay in place. That was my oh s#*t moment. I should have bagged it right then and gone to #13 instead of trying to put on the outer lam. How do you deal with keeping your balsa in place after the tape is removed ? I put the bottom lam on the board and then placed balsa on top of that. that probably is the difference.
christian
Yeah, I’m sure that was the difference.
I lay out the balsa on the workbench & tape it all together. Then flip the balsa sheet. Lay glass on the balsa, not on the blank. Pour resin & squeegee around just like I’m laminating a board, but its on the balsa. Any resin that drains will soak into the wood, not the foam, where its actually beneficial.
Then I flip the blank down onto the wet glass/balsa, grab it by the rails, and flip the whole thing back over. Smooth out the balsa sheet (glass now invisible between balsa & foam) and pull the tape. Wet out the outer glass, back on the plastic-covered workbench where I did the glass+ balsa already. Roll it up, move it to the board, roll it out.
Took a few before I had the motions efficient… 
Thanks
its all in the details. this is what it looks like so far
Cj3, your board looks like its turning out great. I’ll post a pic of my crushed board tonight for those of you who wanted to see it.
Oh, and thanks for all the advice and tips, guys!
Hey Benny,
What about superglue (cyano acrylate)? I thought that was what people were using? do you still need to tape even after using superglue? Any downsides to superglue?
Rio
I tried superglue. It took two bottles to do one side of a longboard, which is a little expensive. It stuck to my gloves & tore holes in the fingertips so I got it all over myself. And it made my eyes burn pretty bad.
So I might use it again…but probably not.
The board skin came out fine. No problems there. Just not user-friendly, for me.
Thank Benny for the tips. The top went on with no drama just like you said. I didn’t wet them out though I just hand lam them and used roughly the same amount of epoxy. 5oz of 4oz e cloth and 5 fluid oz of RR epoxy for each side of balsa.
Its like Christmas when you get to open the bag.Time will tell if I have been good or bad.
christian
Satori, cj3,
Haven’t done my first “live” vac pull yet Know what I have been doing while I get everything ready? Doing test runs on scraps. I think I have learnt a fair bit from this and that it’s helped me avoid some nasty mistakes. I learnt that I need to set my vac switch to mid-range for the EPS I am using to prevent crushing it, for example. But I only lost some scrap offcuts in the process. Not a whole board’s worth of 2lb EPS. So I highly recommend taking that approach with anything you aren’t sure of.
The other thing I have been doing is dry running the minor things I have tried. Because I am going with preformed skins I have been playing with laying the whole thing up and pulling vac on it WITHOUT the epoxy. I’ve figured a couple of things form this too. Process planning is important (like Benny’s plan), laying enerything out vbefore I start helps me, getting component/section properly laid out helps me get what looks like being more even. Of course, the proof is in the pudding so I won’t know until I do it with epoxy. But that should be fairly soon.
All,
With my pre-formed skin I am only going to do the outer glass. Here’s my plan:
-
Clean cookie tray and apply two layers of carnumba wax.
-
Use blue tape to lay out balsa strips.
-
Put any writing, etc on balsa.
-
Mix epoxy.
-
Pre-wet glass.
-
Lay wetted glass onto cookie tray.
-
Lay logos, etc on glass.
-
Lay balsa onto glass.
-
Put it in the bag.
-
Position shadecloth between balsa and vac hose.
-
Seal bag.
-
Set vac switch to 15"hg.
-
Switch vac setup on.
-
Monitor bag until all air evacuated and flat.
-
Clean up.
-
Check the whole thing.
-
Have a beer.
-
Go to 16
Appreciate any thoughts on this since I am about to have my first live shot at it.
Maybe Dan??
Thanks all!
doug
maybe some peel ply between glass and bag. Also you may be able to pull more hgs with no foam in the bag. One thing I have seen done by a very knowlegeable bagger is to add heat ie. electric blanket while pulling vac. I think those are a few of the advantages to preforming the skins. light strong and flexable almost fusing the glass and epoxy into the balsa. Other wise the way benny does it makes more sense with less steps.
let us know how it goes.
christian