Vacumn forming & Sandwich construction

General Discussion
61

hi John!

Checked again to see what we’re looking at… To vacuum on the bottom sheet of d-cell; Tom S. simply uses double sided glazing tape to secure the perimeter of a flat sheet of standard polyethelene plastic to his rocker table; next he puts his bottom lay up on the table (just like Bert shows), and lastly he uses more glazing tape to secure a 2nd sheet of polyethelene over the top of the entire setup - and vacuums.

I haven’t tried it this way myself because it seems like the bottom-most sheet of plastic could possibly seperate from the rocker table - especially considering that EPS surfboard blanks are a lot thinner and more prone to bending out of shape than windsurf blanks. But then again, you could always just simply stack books in or whaetver you have lying around on top of the whole thing - like MrJ showed earlier in the post.

I like Bert’s rocker cut-off set up better myself… much sturdier - allowing for more vacuum ‘forming’ of the EPS blank itself to conform to different rocker profiles.

Tom shows 4 different ways to make a rocker table:

  1. Bert-style EPS cut-off - slick and easy!

  2. Plywood secured to a set of 3 - 3/4 inch stringers like a skateboard ramp (labor intensive and definitely not adjustable!)

  3. An entire bottom mold of previous board (reinforced with carbon cloth? expensive!)

  4. The one he actually uses in the video; umm, imagine an 8" square metal beam oriented horizontally with about a dozen vertically adjustable 18" lead screws that connect to the bottom of a some some reinforced formica-like sheet. This is the only adjustable one of the bunch. I’ll try to take some pictures of my TV…

I built a big sandbox that I cover with thin sheet metal but it’s just so much work! …especially when your EPS rocker cut-off is just sitting there, giving you that ‘blank’ stare. (ok, Not funny.)

In response to why his finished product looked so rough…

There were all kinds of windsurfing attachments, cut and capped into the final sandwich and since he was painting over the whole thing (like the snakes), Tom didn’t take the time to vacuum on individual pieces of the d-cell where his EPS was showing through ater cutting the d-cell to wrap around the rails, he just filled any spaces with thickened resin - you could always clean up the tail Like Bert did with extra pieces of d-cell.

The top sheet of d-cell is bent around the rails by putting a solid foam spacer underneath the blank to lift everything just a little bit off the rocker table so your vacuum bag will conform around the rails… bluejuice’s pic there, illustrates it very well.

For anybody interested, Tom Sullivan’s “Vacuum Bag Board Building” video is only $35 at fiberglasssupply.com… 80 minutes of enlightment and thick Canadian accents.

http://www.fiberglasssupply.com/Product_Catalog/BooksVideoCat/booksvideocat.html

cheers,

Brennan

62

Brennan - Thanks for the update! Like I said, it’s been awhile.

63

Bert and Haavard - looks like I got that the wrong way round. Bert - I wasn’t actually asking about three stringers, I guess my post wasn’t too clear. I’m just interested in how I would adapt a rocker designed for a PU board, to allow for different flex patterns of this sandwich construction. Have I got it right this time - the sandwich board will bend more in the middle and twist but spring back. However it’ll be stiffer overall so it’ll take more load to get that longways flex or twist ? This is going to be much trickier than PU boards - flex and buoyancy and rider weight (load) are kind of connected with trad board design - bigger guy - thicker board, more buoyancy, less flex but higher load - so everything gets equalised. With this type of board bouyancy and flex are factors that can be controled separately.

Thanks Bert for posting this - I can see a bunch of sandwich boards are going to be posted to Swaylocks in the coming months.

64
Quote:

hey skipI found this site. there is a store in Corona . but it looks like Divinycell can be mighty expensive. eek!.. not to cost affective for me… anyone know where to get this stuff at a reasonalbe price in socal…anyone?

http://www.aircraftspruce.com/catalog/cmpages/divinycellfoam.php

I also found this one but I do not know where they are located…they do have some nice end grain balsa and other cool stuff for all you vacuum bag heads

http://www.fiberglasswarehouse.com/core_foam.asp

Ben,

The supplies can be had for almost half those prices. Check with fiberglasssupply.com or call fiberglasshawaii.com for starters. For people in Southern Califorinia the Fiberglass Hawaii’s store in Santa Barbara where you could pick up directly and avoid high shipping cost for a large sheet.

Call in your order for Fiberglass Hawaii because they may need to bring in down from their store up in Santa Cruz, and they don’t have a web store. There are also major composite distributors, but you usually need to order in larger amounts.

And on the overall foam price…how about getting about Ten 8’ blanks from a $187 – 39"x49"x97" – block of 1lb EDRO EPS from Insulfoam. This should offset the cost difference just a bit. And pricing from fiberglasssupply.com; Sheet, 1/8", H-80 Divinycell Plain, 48" X 96" (32 sq. ft.) $38.40

I’m still seeing that the foam portion (eps/pvc) of a composite surfboard is a bit less than conventional blanks.

65

So…If you could use some plexi as half the bag…hmmm.

Build a big charcoal pit in the backyard, “honey - where’s the poodle?” Then make a frame for your sheet of plexi - heat until saggy over your firewalk pit - then vacuum that rascal onto your single into double concave bottom shape form and???

Just daydreaming…

390×792 50.8 KB

66

Cool…Im glad someone else was thinking as I was (can you imagine the storage reqs if you had a rocker table for each rocker!!!).

You wouldn’t need that many adjustment rods…too many would interfere with the natural curvature and make it too diff to adjust.

Not that I would do it, but to get a curve you only need three points of support…assuming you want three curves…entry, transition, exit, then that would put it at around 7 rods from front to back…in theory, the plexy would naturally give you a nice finished blend. Nice drawing btw.

PS - there’s been some talk about center vs perimeter stringer flex characteristics…all of which can be estimated using scale models…put some sticks together and test it. I would be interested in a flexy board only if it had a flex stop limit…Im sure Bert has figured this out.

67

Bert’s statement…

as an example , if you get a few sheets of veneer or paper cardboard or even playing cards , bend them into a curve , then press tightly at the ends as if youd glued them together and try to bend them the other way , for something to flex it needs some shear movement , you can glue 2 flat sheets of something together and it will still move a bit and spring back to its original shape a bit , but glue 3 sheets together and it stays that way forever …

I’m not sure if Bert was eluding to this flex stop limit when he said put three playing cards together, hold the ends and they won’t flex. Could there be more than one horizontal stringer in there? Are they glued together, or is there some foam between them and they are attached at the ends? Three thicker ones in the very center?

Course the balsa wood skin (and rails) makes everything behave differently flex wise than pvc plastic or epoxy/fiberglass…

I guess we just gots ta try it out ourselves!

ps thanks for editing my overabundance of rods.

68

I read Bert’s 3 layer part to refur to bottom skin, eps middle layer, deck skin and stringerless; not refurring to stringer layers. Off course you are getting more layers as you add glass in between the foam layers.

69

hmmm…meecrafty and I are just trying to think ahead.

Two horizontal skin layers plus one horizontal stringer equals three playing cards. The eps foam just keeps all the layers separated better than air can. Why does he still use eps when it takes on water? Probably springy and lighter than anything else, and it looks like his quest is now for the ultimate foam or? If you read between the lines he gives us many hints where he’s at now.

Follow the leader - crew?

70

hey john , ive never seen the video , but what brennan mentioned all makes sense …if you dont mind mowing excess foam , then a rocker table that is adjustable , allows you to use flat sheets of foam and just press them into shape …

youd be surprised how many different rockers you can build with a handful of beds and wedge inserts then a sheet of ply laying over the top to smoothe the curve ,

sometimes if i want to try a variation of a rocker and i want it exact , and i want to know where every mm of curve is , i just order 1 blank then i get a new rocker bed included , if the rocker was no good well i still got the blank , and the extra wastage of only getting 1 blank in a block might have cost me an extra 15 dollars …

these are cheap easy solutions to some of your questions …

also dont forget every time you get blanks you get a new bed , i have customers who may have a certain board which is a discontinued rocker , no problem coz all the rockers ive ever used are on file at the foam cutters , i just ring and say i want 1 x 8 gun v-1 fitted in with the other 4 x 8 gun v-3 flat all in the one block , make sure you put the v-1 as the bottom blank so i get the bed …

hey daddio , eps does suck water , but the fact the water has to get through glass , your sandwich then another layer of glass means your core is fairly well insulated , plus with the right procedure its easy to get water out if you should hole through all that …

performance is the biggest factor behind eps , maximun shear movement without failing …

eps allows everything to move , so you can optimise the characteristics of whatever structure your using …

glenn you posted a good link the same as the one john posted as well , some good information on that site as far as general overviews of the different processes, the net composites one …

i thought it was interesting , coz i see people quoting certain methods as the way you would do a certain technique ,

but in reality once you move into this method of construction so many other possibilities open up that you could resin transfer, infuse , then autoclave all in the one operation , or any combination of those techniques together …

or even purposely allow air to enter a resin transfer operation so the resin bubbles and becomes foamy , giving it greater bulk without the weight …

theres a whole new world in there …

which is not that out of reach for the custom board builder …

regards

BERT

71

Ok Bert I’m gonna convert to epoxyism… I’m convinced and born again. Now then, for a novice:

1 - Do you vacuum pack the hotcoat?

2 - Do you need a vent?

3 - Do you spray on to the divinycell or do art after you’ve glassed?

4 - How many points do you give to the eps cutters to cut the rocker?

so…exciting …

72
Quote:

1 - Do you vacuum pack the hotcoat?

2 - Do you need a vent?

3 - Do you spray on to the divinycell or do art after you’ve glassed?

4 - How many points do you give to the eps cutters to cut the rocker?

1 - that depends on what techniques you figure out …

2 - that depends on how much resin you allow into the core , if you saturate the core , then no , if you want maximum shear movement and good performance then yes …

3 - up to you , you can even tint and pigment … core cell is better in that regard for finish …

4 - ask them what they need …

regards

BERT

73

In looking through the various eps sites I’ve seen large scrap grinders. Is this for recycling at the large plant stage only and/or do you recycle cutoffs and etc?

We haven’t found a computer cutter business near us that will include the cut in the price of the block, so we will be making wood templates at first and can make our own bed. It seems that this step is crucial if you want to produce more than just a one or two off.

Thanks for splainin’bout the shear properties of eps.

Did he say, "foamy resin?’ …hmmmm

Hey meecrafty - what if we just hotwire off a 1" thick “record” of the rocker to write production notes on and store that? Also if you keep more rods on the rocker table you can make different lengths with the same plexi by starting the nose tip farther back towards the tail…

74

yep thats right about the large scrap grinders , the polystyrene companies recycle a percentage of munched up off cuts and put it back into new foam …

i cant remember the percentage , but there is a maximum allowable limit by law of how much recycled stuff they can legaly put back in …

ok , on your marks ,get set ,GO …

im curious to see what you guys come up with , judging by some of the emails and messages ive had , a few are jumping in the deep end and taking a leap of faith …

have fun exploring …

i was thinking a custom s core for my next thread , but with a full eps core for more support …

but if i do it , i need another hotwire cutter…unless salomon want to donate a few 10 mm sheets for the project ???

thats a fair trade in exchange for a few pointers hey guys … thats a little cheaper than plowing through 12 mill …

regards

BERT

75

bert for a few months ive been doing a sandwich style epoxy board. its not as durable as yours by any means, in fact so far its about as durable as a 4x6 pu combo. but the performance is extremly high. its been called magic by anyone thats ridden them…its totally customizable too. i have some new skin product coming that will increase my durability(fingers crossed without changing flex character too much). the vacunm bag process is used once in whole operation. it is much less labour consuming than your shown method so the cost is about $40aud more than pu… im currently setting up a whole new concept store at present in fact it opens toomorow to public… so im a little snowed under to post pics and methods. im stoked youve shown every one and got em pumped on advancing

76

stoked dave …

you took the plunge , i know we spoke like 10 years ago , back then you wanted to get into vac bagging , but i was probably somewhat elusive with my answers …

in fact for years i would give ridiculous answers to questions , just to throw people off the scent …

im sure if you had any specific questions these days , i would give you the real story and point you in the right direction …

im not really into the business keep the competitive edge situation anymore …

im into enjoying life and building a few boards to support my leisure activities …

so just give us a hoy if you need anything dave …

looks like some action going down at your place tonight , if i jumped in my car now i should get there in about 4 days , so better not wait up for me …

hey pinhead , your summary of flex versus stiffness and some of the other variables was pretty good …

with perimeter stringers you get proportionatly more flex as you get closer to the middle in comparison to a conventional stringered board , or in reverse it gets stiffer as you get closer to the nose and tail with perimeter stringers …

thats where the horisontal stringer comes in , it gives the middle a little more support under heavy load , so now you can get that snappy twang from more front foot oriented moves , especially as the boards get longer , when they would normally feel floppy …

see , 100 kg or 220 lb , standing on a rockered performance 8’ mal and it can still support my weight in the middle without hitting the floor …not bad for a board that weighs 7 lb or 3.2 kilo …and is 2 3/8 thick ,see the 1" increments drawn on the foam block …

this man is a surfboard builder , so we cant show you his face on tv …

regards

BERT


77

Hi Bert

They just keep coming heres the second this ones got a balsa skin

The green thing on the right is a radio controlled scale model of my 42 foot yacht which we sailed around the world

My wife says just how many boards do I need exactly

I guess she is hinting that I should finish the house renovation jobs off before starting the next board

I wonder just how quick I can get those jobs done !!

Oh that new board 7’1" x 18 3/4" x 2 1/16"

Mike

78

That’s impressive, OK now jump and down 10 times. :wink:

79

Hi Swaylocks crew

Ive had a request to post some pics of the construction

Bert Please take care not to hurt yourself while laughing when you see how many steps it has taken me

It was my second eps sandwich board I now feel that I can combine some of the steps with confidence first you must crawl before running

This is the blank hotwired,bottom done with a template on the profile table , deck done by sticking a template on to the foam

Now this is the perimeter stringer being attached,they are 3mm cherry

The things in the plastic bags? salt lick blocks for the cows! perfect for weights!!

Now I have added some cross grain veneer in the areas where i put my hands when standing and where my knee goes when duck diving

The last board developed some cracking here due to the for aft grain and the hard edge of the stringer

Hopefully this should remove that hard edge

That done now ive layed up a layer of glass to each side ,first i put down a seal caot with resin micro ballon mix

Next time I will miss this step and put the glass on to the veneer before bagging and not put the seal coat

down

go to the next post for the pic

80

Now I bag on the pre joined balsa skins

Note the fridge compresser vac pump ,very cheap!!

The bag is plastic sheet folded in half joined with 3m double sided tape on one end and the side the open end is sealed each time with masking tape

The vac take of is the top of a fruit juice bottle taped on this means that to remove the vac line you just undo the cap

I put one of these on each bag i use be it be small or large

Next the rails were added these are three layers of 5mm balsa

Now the rails were shaped and then the top and bottom glassed

the bottom is a single 4 ox the deck is two by 4 oz these were laid up and peel ply applied in one hit then the whole thing bagged again

After that all it required was a finish coat of epoxy which was then sanded down to 800 grit then buffed with cutting compound

go to the next post for fins