Vacumn forming & Sandwich construction

General Discussion
41

ready for some glass ,i ended up spraying it on the bottom only on the flat , so the cross section of bottom skin d cell is still visible and the green rails and joins will all be visible … i was going to put fabric over it, but the industrial look started growing on me , so i thought id let it all be obvious in the finished thing …

heres the deck , with finished shaped tail block (thanks halycon for the tail shape inspiration )… you guys know the rest from here…

ok thats it …

here comes some numbers and facts …

firstly the weight and statistics …

the board is 6-8 x 22 x ? ,i havent even measured it , i knew what i wanted and when it looked right that was ok for me …

the board currently weighs before glassing 1263 grams …

if it was a standard urethane blank using the lightest urethane possible , these same dimensions would be 1900 grams plus … and thats being generous …

if you glassed a urethane blank of that weight with 4oz bottom and 2x 4oz deck , youd pretty much have a disposable board youd be pushing 3 months out of …

where as the board i have here cant even be pressure dented with my thumbs in the stage its in now before glassing , when i do press it it just springs back , so what that means is , it will get glassed with 1 layer of 2oz on the bottom and 1 layer of 4 on the deck , so the finished weight in the water and surfing will be about the same as a superlight disposable urethane blank with 1 layer of 4 oz on the bottom unfinished before the deck is even glassed …

and on top of that , if it didnt handle a couple of years of constant abuse id be surprised …

here youll have a board lighter than what any current pro would be riding , lighter than any surftech or salomon , and it wont snap in a hurry because the core is soft enough to let the top and bottom move past each other in a shearing motion , where as the surftechs allow there cores to be penetrated with resin making them brittle and snappable , plus making the outer skin work harder which means small dents will still appear under the feet …

and the salomons are running a cored skin that is to thick making it stiff , and on top of that the skin material is to light so it cant support an outer glass job without folding under the front foot on any decent floater landing or solid bottom turn …

now the price …

theres less shaping work to be done than a conventional handshaped p/u ,

the blank was 150 in materials , theres less work in the bagging stage than glassing a conventional board , so if you were paying someone to bag , it would probably be the same rate as what a laminator would make ,

so you may add 100 aud to the price , but the reality is a urethane shortboard in oz can be anywhere from 400 to 700 dollars …a poorly moulded surftech fetches 795 , not custom , not made for performance … a salomon is 1400 …

a board of this nature in oz , anyone would pay 1000 , see some margins there???

plus now youve all got the upper hand over all the profile brands on the market , mainly salomon and surftech…

so after 15 years of r&d this is my legacy to the surf industry …

and the best part is if you guys have been blown away by this , you would freak big time if you knew what i build for a living , my techniques and strength to weight ratios on my current production boards …

just talking randy french for a minute …

i dont know the history of surftech , whether or not he ever tried to get it off the ground in the west through the existing industry , so there could be other reasons it ended up being made in thailand , maybe randy can fill us in …

but the reality is randy has exposed alot of people to the concept of sandwich construction …

so im grateful to randy for that because , its given me some exposure and credability for the work ive been doing all these years …all of a sudden im not branded as an eccentric anymore and given the label obtuse …

at last more people are experiencing first hand the performance differences in different materials , for me now the last few years have been a real buzz , having long time critics at last come up and say " wow so you were right for all those years "…

if you look at the real reasons why this technology has been so slow in getting to the industry , youll see a handful of players supressing technology breakthroughs and putting up there own version of anti eps epoxy propaganda …

so another bonus for me is the crew who actually made it hard for me to get access to the materials and purposely tried to belittle the advantages of this contruction through blatant propaganda , are now in a position to actually get nothing out of this construction style …

appart from guys like greg loehr , you wont need to deal with any conventional surfboard material wholesalers , theyve basically cut them selves out the market by not embracing the new ideas as they were introduced …im sorry to say , i forsee a time when a urethane blank will be considered redundant technology and grommets will say " check out the old skooler on that peice of junk"…

again , to me it shows that guys like greg were thinking ahead , in the sense of moving in the direction of wholesaling refined epoxy resins and offering alternatives …

thats me …

im off surfing , more refinement and r&d is calling me …

regards

BERT

ps , you guys at salomon , if you want some real breakthrough stuff and you reckon your reputation is worth salvaging , then you know what to do next time around …whats that movie with the french karate guy ??? wrong bet ,or something like that ???


42

Bert,

at this point you need to lay up epoxy and car paint like surftech?

is people like the grey finish, i think it looks tech…

about logos… you silkscreen direct on the board?

what about vacuum the glass job , would it be too stiff?

can you find the h 60 in grey instead of green?

43

Wow Bert, absolutely insane man…I had a hard time grasping what you had put into words first then after reading over it couple of times I now think I am visualizing the process more clearly…I hope… thanks Bert…

44

i am just wondering about the second layer glass layed on the top sheet of dcell in the photo (000_0336 edit.jpg). it doesn’t look like a normal grid weave in the dry photo or the 0wet out photo… or is it just my screen?

thanks for the hints…

45

Hey Bert,

Great stuff. Is there a composite mechanics for dummies book? 'cause I have a lot of questions. I’m interested in what I need to do to get a similar result with Core-cell? D-cell seems to sh*t on Core-cell in every mechanical property department but shear elongation. I haven’t quite got my head around what mechanical properties mean - but doesn’t better shear elongation mean more flex and memory? If I did use Core-cell what would I have to do to the glass job to accommodate different properties?. I’m guessing heavier glass on the outside with maybe s-glass or kevlar or polyester on the inside? Also in terms of design what do you need to do to the rocker and outlines to accommodate the different flex patterns of perimeter stringers? I think I read on in another thread that rail stringered boards twist while centre stringered boards bend in the middle - if that’s right, I’m guessing I should lean toward more rocker curve under the front foot and straighter rocker in the tail or more pulled in tail outline?

46
Quote:

I think I read on in another thread that rail stringered boards twist while centre stringered boards bend in the middle

Isn’t it the other way around, centre stringered boards twist more? regards, Håvard

47

my purpose for doing this thread was to show the principals of vac forming ,whats possible and how you knock off 30 to 50 % off the weight and add 5 to 10 times the life expectancy to your board …

i hear so many complaints about surfboards and how weak they are , well now its all here , the amount of information delivered in one hit , each picture and stage shows alot …

once more crew work out whats possible , and the ammount of combinations that can be achieved , then finnally crew will appreciate what else can be achieved …

because people will still be questioning how i get my current results …

the board i showed you is still heavier and weaker with less performance than what i do now …

but what i do is so far removed from current surfboard making techniques , that unless i showed some basics , everyone would continue to treat it as a novelty and put it in the to hard basket …

at least now youve got somewhere to start …

i reckon for what ive showed corecell is a better option …

the secret to performance sandwich is shear movement , something that can bend along way and not fail is the key…

polywaffle versus crunchie …

once more guys step into the playing field then well have more to talk about …

right now , just go do the ideas that your thinking …

hey bluejuice … i was wondering if you would show how you do your d cell rail wraps ??

the biggest reason i ran in the parabolic rail direction in the first place was both a performance one , and having trouble wrapping a tight surfboard rail , with either timber , other foams or purpose built sandwich skins …

surely you must have sections of sailboard rail that get as tight as a surfboard ???

another question , that core in one of your pics looked blue , or was it just the light or that blue filler they use for boats ???

im sure i was going to say something else ??itll come back to me later …

regards

BERT

48

Bert,

Maybe steaming your veneer just prior to vaccing it on.

49

Steaming in regards to tight rails.

50

its ok waaahoo , it wasnt for my benefit , i made that comment for others benifit , so everyone might get another variation on sandwich construction …i know how to bend it now , but when i first strated playing with it i didnt , thats what lead me to rail stringers , so im kinda glad that at the time i didnt work out how to wrap it , coz that opened up some new doors …

regards

BERT

51

Bert, This is just an awesome post. i’ve been planning on trying some of these techniques on some boards this sumer. Been gathering the materials. Now my nine year old boy has a project at school to predict what sports were like in the past and will be in the future. nd he’s picked surfing. We re doing a scale model of an old wooden Hawaiian style board, then a modern board using the latest materials and following your bagging instructions. He and I are both looing forward to it. I’ll post some pictures whewe get little furtheralong

Jon

52

Haavard,

I can’t find the original thread. But I thought about it and it makes sense, With a centre stringer you’ve got three beams- the stringer and the rail laminate (I’m treating the rails as a kind of beam, but a bit weaker) Shear movement of the top and bottom skins is restricted by cenre stringer so less twist. But with the perimeter stringer you’ve got four beams: rail laminates and rail stringers, less bend under the front foot, but because the top and bottom skins are anchored to beams that are further apart the skins are able to shear therefore you can get a bit of twist. If you think about trimming on a hollow wave you can feel the upward force on the inside tail rail, with a Bert type board I’m guessing that the rail might bend upward slightly which would exagerate tail rocker - so you’d compensate by having a slightly straighter tail, than you’d use with a traditional board. Does that sound right?

53

Bert yes in that board it’s the dow blue foam 28kg/m I’ve had great success with it when it’s covered with a sandwich the no 1 wa wavesailer has been using it for 3 years going for huge 15m high double forward loops he can’t believe how strong it is at 6.5 kg and it’s waterproof!

OK as for the rails towards the tail they’re very tight I don’t have any pics at the moment (I’d like to know how you put the pics into the post and not as a attachment)

Basically I place the dry div deck over the board cut out the outline put some bricks ontop to hold it in place, put on some leather gloves gently heat the div cell then use my hands to fold the div cell in place and hold it there until it cools then move on to the next section of the rail.

Before I put it in the bag I wrap a whole roll of packing tape over the whole board and very firmly around the rails. This can’t be laid onto a flat rocker bed unless a spacer 10mm thick similar to Berts contour pad is put under the board as 20mm exess div c folds under the bottom of the board.

54

ahhh , now it makes sense , when i was looking at the pictures you sent me , i thought “what the hell is the spacer for ?” but the fact your using a rocker bed as well , you need clearance for the d cell wrap…

yea i was using the dow foam at one stage under sandwich skins …

i can see the benifit for a sailboard …

the biggest problem with xtr is it has poor shear properties , but in a thicker sail board which is sandwiched it wouldnt be flexing as much so it wont fatigue like it would in a surfboard…

i found in the surfboards using xtr i couldnt get them light enough without having to reduce the thickness of the skins , they then got back to the point where the flex was then shearing the foam again , at the end of it all i was at the point where , when i was finnally happy with the structual integrity of the board , it was to heavy , and a little to stiff… i reasoned i might as well sell a guy a waterloged eps , coz it was about the same weight …

so while the end product was more problem free in xtr , it lacked the magic of a new or properly cared for eps …

i can really see the benifits with running skinned xtr in sailboards , in surfboards , needing them way thinner and flexier meant to many comprimises for me …

even tho i never did a big chunky surfboard in xtr , i reckon it would work well doing it your way in big volume surfboards , where someone isnt looking for that flex , and just wants a nice big floaty light strong wave getter …

hey pinhead , im not sure what you were thinking inregards to running perimeter stringers combined with a centre stringer , it works ok if its not a sandwich board , if you do all that stringering and a sandwich , you end up with something , that feels every bump and feels more at home in supersmall clean waves …

if you wanted clarification on the perimeter stringers versus centre stringer …

the outline stringers will allow more lengthways flex , but less rail twisting under load , also when under load will give kind of a load limiting feel where they only let your board twist so far then when you back off that load itll spring out with more force …

the centre stringer will not have as much lengthways flex , but will allow the rail to twist off further …

regards

BERT

55

Can anyone suggest a good supplier of core-cell or d-cell in the So. Cal area?

56

Have any of you vacuum bagging specialists (Bert, Michael J, Bluejuice, etc) seen this instructional video? http://www.netcomposites.com/netcommerce_features.asp?520

Tom Sullivan shows a step by step process and uses a vacuum rocker table - the vacuum bagging film is attached directly to the table and covers one side of the board only. He lays the double stick tape right to the table and presses the bagging film to that.

Obviously, edge transitions is a tricky aspect of this process. I think I can see how Bert’s use of balsa rails might help with the blending of the balsa veneer at the edges. It’s pretty obvious in the d-cell photo sequence.

Do any of you use the vacuum table approach and how does it facilitate the edge treatment?

57

John,

For those who haven’t seen this video, is this an adjustable table or permanent rocker table OR?

Could you describe this please, mi amigo?

58

Whew!! Too much info for the sandwich construction clueless like me…

59

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

60

Daddio -

It looked to me like a formica surfaced table that had been curved into a rocker profile. The ad for the video says it is adjustable but I don’t recall how easily the adjustments are made or if he even showed it being adjusted. It’s been awhile since I last viewed the tape.

I do remember that the shaping finish appeared fairly rough as compared to a finished Clark blank and that he used a lot putty and primer before painting.

Divinycell:

http://www.fiberglasssupply.com/Product_Catalog/Core_Materials/core_materials.html