Vacumn forming & Sandwich construction

General Discussion
81

The fins are balsa core with a carbon spar section

First glue together the balsa and carbon (carbon layup unidirectionals )

Then shape now lay out a sheet of plastic sized to cover three fins twice

Wet out two layers of 4 oz glass on the peel ply and plastic now lay the three balsa carbon fins on to it .Wet out another two layers and lay this over the top ,cover with peel ply now fold the plastic over

Put this in a small vac bag and leave overnight

Now cut around the fins with sissors and sand smooth then top coat

These fins are so light and stiff you wont belive it to alter the stiffness play with the glass lay up

The sockets and plugs that they fit in to are

plugs good quality ply (10 to 12 veneers) covered with balsa and glass for looks the sockets are just mouldings of the sockets

These are dead easy to make ,in two nights after work you can have a complete fin system

The board now has a do it your self system which gives you for and aft fin tuning and toe in adjustment

The total weight of the board with fins is 2.75kgs Im happy with that and looking forward to the next one

Mike

82

Wow sabs - looks amazing — a coupla questions:

1 - what kind of balsa sheets did you use?

2 - did you lay them out , laminate one side and cut to shape?

3 - Did you simply epoxy your stringers to the blank … (why didn’t you bag this stage?..problems ?)

Cheers…

83

sabs !!! that looks hot … and the weight is good …

i can guarantee , that not 1 pro would have a 7’ board that light made out of pe/pu …

what youve done there , was show just how real and how achievable doing a vac formed board can be …

im impressed …

you did well with the fins …

for a second board , that was hot …

man keep em coming like that and ill be trying to talk you into putting sunova stickers on them and reping in N Z …

i think youll turn a few heads , showing that you can build something like that in your first few attempts …

once again well done sabs …

regards

BERT

hey sabs , how did you finish your tail off ???

if this helps , i make a large laminated block , then i cut sections out of it and stick it to the tails ,and noses on longboards then i can just shape the wood …

the tails get alot of punishment , so it helps with the knocks with an eps core …

84

I just gotta say that this thread is awesome. I can remember coming to this site for the first time about a year back and not even knowing the difference between a gloss coat and a lam coat. I’m loving the descriptions of the whole process, and want to try Vac bagging next. I’ve gotta finish a couple of other projects first, and then I’m allowed to build another board.

A few quick questions though. First, is it possible to over-vacuum a board? I might be able to get an old vaccuum pump from a milking parlour, but these things can put out phenomenal amount of suction, and I don’t want to suck the epoxy right out of the bag. But because I’m a cheap Dutch farmboy and I can get it for free, I’d like to use it. I don’t know any sort of ratings for the pump yet, but it has a 5 horse motor.

Another question here. How does the bag not stick to the epoxy. Because it’s plastic does that mean that it won’t bond to the epoxy? Or do you spray the bag with non-stick cooking spray or something? Could I use building poly-wrap?

I’m guessing that this method removes a lot of the gassing problems from using eps/xps because of the vacuum, but have you ever gotten those problems? Espescially on a bigger board, like a mal or something. I’m in Canada, and so the sun don’t get to hot, and the waves in my area(well, 1.5 hrs away minimum) are pretty small and mushy. So I want a nice easy riding board, but built using easily available parts. I’ve already done a hollow wood, but I want something a whole lot lighter. Thanks a lot man, I’m loving this thread and soaking it all in for now…

85

Hi Bert

hay thanks for the comments

The tail, i just dug out some of the eps then inserted a bit of vertical grain balsa,that should help with compression when it gets knocks

If it gets too damaged over time I will just cut it back and put a tail block on

The other reson I did it this way was now you can see the perimeter stringers which makes it easier to explain when people ask me!!

The fins and boxs are great and real easy to do Ill do a bunch of pics when I make my next set then post it

Mike

86

Wow Sabs - looks great! Just like a bought one. How did you do the rails? Did you do them with several lengths butted end on end? I’m guessing you didn’t use three single lengths on each rail.

87

Red! I totally agree with your sentiments… whenever I finish a board I put a little asterisk by my signature for swaylocks.

My first vacuum pump was something I ripped of an old fridgerator… when glassing the inbetween layers between your core and the sandwhich material you using it’s difficult to pull too much vacuum and suck out epoxy but if you’re using a real light density EPS core than it is possible to crush your core if you squeeze too much. Many industrial vacuums like the one you describe don’t pull much more than the average top vacuum of 28-30 inches of mercury (in Hg) BUT they just really pull air fast, in other words high rate of flow, cubic feet per min. (CFM). Is the one you descibed for milking cows? cool. I think if it pulled much more than 28" Hg than you would hurt the cow so you should be OK.

There are a couple low tech ways to solve the problem of pulling too much vacuum… 1)put pinholes in your bag 2)install a release valve in your vacuum line - to make a release valve all you need is a bolt threaded into a T connection in your vacuum line that you can loosen to allow air in.

A higher tech way of doing it is connecting your vacuum line to a reservoir tank and wiring a vacuum contoller to the on/off switch of your vacuum pump. I’ve posted this before, but check out veneersupplies.com for a tutorial on how to test and set-up your vacuum pump - the owner, Joe, is a great guy and is super helpful - thats where I bought my vacuum controller. But don’t worry about this yet if you don’t want to… all you need to start is a vacuum pump and you got one. http://www.veneersupplies.com

In reply to your other question… Plastic just doesn’t stick… next time you do a ding repair stick a piece of plastic over it - your repair will come out smooth and the plastic just peels off! I’m sure there’s some chemical explanation for why this works… building poly wrap should work jsut fine, sounds like it’s probably poletheylene - used it before, works fine - it looks like what Bert was using in his pics.

XPS vs EPS - XPS has boding issues… it’s too much like plastic IMHO. EPS will bond, you just have to decide how thick you want the epoxy to absorb into the EPS. Stick with EPS and when you’re done, vent the board. EPS core has a lot of air in it because it’s a lot less dense than PU. Extreme heating without a vent and the board will inflate like a ballon and delam. The basic windsurfer style vent is available at fiberglasssupply.com but only allows for manual venting but there are other systems out there that you can make yourself that have some sort of membrane… gortex, or rubber… that will give and vent the board when it gets hot.

As for available sandwich material - you could order divinycell from fiberglasssupply or try to find some locally available veneers, or start growing balsa. You’re in Canada right? You could use even use hemp instead of fiberglass! we all know what goes on up there.

cheers! Brennan

88

Hi pinhead

Yes these are cut out of 1 meter long sheets from the local hobby shop, i just put a little scaff join on each one and made sure that all the joins were not on top of each other .

Mike

89

Hey Bert. A mate of mine makes his own sail boards using the vacuum bagging principle. Seeing his rig first hand gave me food for thought. His set up consists of a fridge pump, varous bits of retic valves, tubing and oil resevoir for the vacuum and a rocker bed made out of an MDF sheet.

He gets a chunk of eps from the likes of Clarke rubber 3" thick and shapes the rails only. He then forms the rockers by vacuuming the rectangle of eps onto the rocker table, he therefore avoids the need to hotwire the blank to get the rocker shape.

He then goes through the same process to what you describe in this post, except he substitutes glass for carbon in the top and bottom sandwich layers.

His last board has seen a full season of wave abuse at Lano and doesnt have any sign of wear and tear.

My interest is in the way he creates the rocker, have you tried this method of creating the rocker by sucking the blank onto the rocker table? I wonder if it creates any weakness and what the pros / cons are of this method.

cheers

Gray

90

Thanks Sabs - look foward to a report on the first ride.

91

yea thats no problem gray , i think i even mentioned it further up the thread or it could have been on another one???

if you have a good bed , a flat blank will work fine , ive used that same system with sheets of xtr before …

having the blanks cut to size , means you get a new bed with every new rocker you design , plus you wont have to mow as much foam …

if your doing it for a living , the time you save offsets the few extra dollars …

that will all work fine , you may get a little spring back with one side formed on , but once both skins are vacumned on it wont spring back at all …

regards

BERT

92

Bert,

You do glass all that up for a final shell, correct?

Do you recommend going very light (4oz, number of layers, etc?) to retain flex?

93

hey guys another update on the vac board …

its glassed and been waiting for fins for like a week and a half …

i wanted superlight fins , was thinking about using my fin system , but that would be almost 20% of the weight of this board , plus the wood fins and boxes would look out of place on this board …

so i got some 12mm d cell foiled some nice full small wave fins , then glassed with tooling urethane …

check out the weights …

on the scales are one 7mm thick red x fin at 122 grams …

then 3 foam cored urethane fins at 12mm plus weighing 119 grams …

im going to do glass ons … my goal is keep the board under 5.5 lbs , ive only got 250 grams left up my sleeve , i blew it , coz the board was so wide i didnt have any 4 oz big enough to wrap when laminating the deck , so i used 6 oz , i reckon i lost 200 grams plus just doing that …

post finished weight and dimensions eventually …

when i get some work done , instead of letting the kids talk me into sandboarding …

regards

BERT

hey sabs looking forward to the fins …

im working on something at the moment , no screws or pins , just clip in and out …

screws and threads are a hassle , plus it means you can clip out your fins to paddle over shallow reef , just put em down your wet suit …


94

Hey Bert -

When you put balsa stringers on your eps - do you put a layer of glass in between the wood and the foam or do you just apply epoxy direct to the balsa?

getting things moving…just have to get my head around CAD - what’s the best package to get for board design?

95

Hey Bert, think about a tiny leash for the fins.

I made myself some clip-ins, left a small cavity between the base of the fin and the box, enough room to tuck in the leash. One board I even ran the leash through the deck, it was short and thin and didn’t affect my feet or grip at all.

Many times I would knock a fin out paddling over shallow reef and not once did I lose one. Once in safe water, flip over, click, ready to go.

In the water I once had a guy suddenly appear in front of me, paddling up the face of the wave of the tube I was in. I could do nothing but mount him, ran straight over the top of him. We came up, we both seemed okay, he looked at the bottom of my board and saw no fins, and couldn’t stop apologising.

He must have thought I was a bit weird cause I just said don’t worry about it, and paddled back out. I then flipped my board, clipped in the fins, and went out and caught more waves. I loved it.

And they weren’t forcful to put in, just a firm click. It’s surprising how little force water imparts on the actual leading edge of the fin, and a lot of that depends on the efficiency of the foil. Of course the box has to support the fin vertically like all fins, but the force pushing the fin backwards is much less.

Sometimes my fins were even a bit rattly, but I never had a fin come out under normal surfing conditions, normal being from overhead fast reef waves to punchy beachbreaks.

I highly recommend clip in fins. Even though there are no good ones on the market, there should be and will be eventually.

Go to it Bert and everyone, you won’t regret it.

96

Anybody got ideas on how the home builder could make something similar to the contour mat Bert shows in his process here. What other options are there for the home builder to mold in concave , vee, or both combined during the bagging process?

Bert, I don’t know if this “contour mat” is a secret of sorts. Are you at liberty to explain it more?

Is it something I as a home builder could replicate?

For me, the less cost the better. What materials are out there which could be formed without too much effort to give a bottom contour during the bagging process? I’m assuming the contour mat that Bert is using is flexible and transferable to be used with different rockers. I’m thinking it is some sort of silicone or plastic even.

I was thinking maybe shaping a sheet of d-cell for the bottom contour you want if I use a blasa skin for the bottom.

This seems to me one of the aspect of composite board building that make it not as finely tuned as you can get with a polyurethane blank, or is it?

With a PVC skin on the bottom I guess you could shape it after it is bagged to the bottom of the EPS. What about Balsa?

Mike, are your two boards just flat bottoms? Do you have any ideas on this?

97

FYI, Brian Hinde from Open Ocean sailboards www.openocean.com has been building boards both out of stryro and Clark blanks for years using sandwich technology. Currently he is working down at Fiberglass Supply as the surfboard guru, if you have any questions and would like to speak with him you can contact him there at 509.493.3464.

Quick Divinycell primer: H-60 is 4lb density, H-80 is 5lb, H-100 is 6lb per cubic ft. 1/8" is not always easy to find. Currently Fiberglass Supply is out of 1/8" H-80 and the manufacturer has 16 week lead time on new material. H-100 is available and if you ask nicely we will sell it at the same price per square ft as H-80 grade. Weight-wise you will actually come out pretty close to the same as the cell structure on H-100 is smaller and “soaks” up less resin. We also have a complete line of vacuum bagging supplies and a small book that covers the basics.

I have also in the past just done the deck as a sandwich over Clark Ultralight, using Vinyl-Ester resin. It makes a bullet proof deck and is not as involved as doing the whole board. I just mention that as an option to ease into building the whole board from scratch. Once you begin to learn more about the different materials out there, the options begin to become mind boggling…

Matthew

98
Quote:
.....With a PVC skin on the bottom I guess you could shape it after it is bagged to the bottom of the EPS. What about Balsa?

my sandwich boards all have complex countours on the underneath, none of them duplicated although all on the same rocker/basic outline - hull contours is the variable i’m tweaking.

So for me shaping the concaves, rolls and chines into the eps then putting the entire board in the bag WITHOUT putting the rocker table in the bag will allow pvc to conform without a mould mat. Pic shows corcel in a double concave. Herex is on my recent board and that conforms even more easily.

I stack heavy books on top of the board to maintain rocker coz I am not sucking it to the table like Bert.

i would guess the disadvantage with what you are suggesting is that shaping contours into the skin would thin and weaken the sandwich structure, also would be limited to just 1/8" (the thickness of the hull skin.)

cheers,

Mike J

99

GLENN

The shorter board is flat the longer has a concave mid to tiny v at the back

Its easy to shape in any thing you want

To make a contour mat I think you would have to get an existing bottom you like polish it then laminate 5 or 6 layers or maybe 1 glass layer coremat then another glass layer,if you polished it well it will release no problems.

I think that you can fine tune shape just as well as a standard blank

Its just that the methods and tools are different ,after doing a couple I think it is a better constructon method to achieve what you want compared to normal board building

And much much cleaner,I hate blank dust!!

Mike

100
Quote:

i would guess the disadvantage with what you are suggesting is that shaping contours into the skin would thin and weaken the sandwich structure, also would be limited to just 1/8" (the thickness of the hull skin.)

cheers, Mike J

Yeah what you say is definately somthing I was thinking; that you’d affect the properties of the [/url]foam core sandwich (http://boatdesign.net/articles/foam-core/[/url]) of the skin if you shaped into the PVC. Making the areas that were thinner pvc more flexible, less rigid.

Sabs, you replied at the same time. Is everyone here named Mike! :wink: I guess with putting the balsa/cherry perimeter stringers on and using a rocker table while doing it that when you actually bag the balsa skin on the bottom your not using the rocker table at this point so the contour you shape into the EPS itself is not affected during the bagging process? So you did not get any twist during the bagging process with the perimeter stringer on?