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PostPosted: Mon Oct 30, 2006 11:25 pm 
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Joined: Mon Dec 05, 2005 4:44 pm
Posts: 158
You can do it all in one hit if you have all your cloths cut first and everything ready .4 mm thick for a rocker table face is not thick enough .It will distort under vacuum . CONTI BOARD is best for a rocker table face . Butyl tape for vacuum tape .Cover the board completely on top with breather, and double for where the vacuum connector is on the bag. You should not get trapped air in a vacuum bag using a rocker table .Are you using the right vacuum hose? Hydraulic hose will work and doesnt collapse.DO not use MDF . Use white CONTI BOARD.

Keep at it Tom


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PostPosted: Tue Oct 31, 2006 6:46 pm 
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Joined: Wed Oct 05, 2005 6:43 pm
Posts: 665
Location: Sweden
Crabman and Bill,

Really, thanks for your help and encouragment.

Yes, i can see that the 4mm MDF will deform. I´ve made a rocker table 60x180cm that has 18mm of concave over a 34cm width and a 25mm rocker over 135cm length. This is a lot of compound curve on the MDF, so anything thicker is not going to take that shape, i have tried 10mm but its too stiff.

I´ll try to source Conti board, but i´m in Sweden and some materials are hard to get, others easy...

I may have to go back to making a glassed foam rocker form that i put into a full bag. What i did before was mill a 40x 140 block of foam, putting a convex form on block thick enough to take it and have some thickness left over. Then i glassed it all around in a full bag and pressed it down on a simple curved longitudinal rocker with weights. Sanded and finished the rocker form to give it a good surface.

Then it was easy to put my whole board onto the rocker form and the whole kit into a full bag...

TW


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PostPosted: Tue Oct 31, 2006 8:56 pm 
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Joined: Mon Dec 05, 2005 4:44 pm
Posts: 158
Tom
You can get Conti board from any good builders .I use standard 14mm thick on all our boards for rocker tables .If you need say ,upturned tips ,what you can do is route or saw the back of the Conti across the width of the table where you need more bend in the rocker table . One half bag ,one table , all in one hit with any shape. Simple . :thumb:


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PostPosted: Tue Oct 31, 2006 10:26 pm 
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Joined: Wed Nov 20, 2002 1:00 am
Posts: 894
Location: rhode island
also.
if you like your current rocker table dimensions.
you can laminate another 4mm sheet of suitable material to the existing top. epoxy or even construction adhesive should work fine .
doubling the thickness will increase stiffness 4X .

if the mdf fails a vacuum check there are lots of smooth non-porous surfaces at most home centers.
formica, pvc, aluminum etc. a good car wax would probably do the trick.

if all else fails, you can put the whole thing in the bag :)

no worries.
-bill


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PostPosted: Wed Nov 01, 2006 11:47 pm 
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Joined: Sat Mar 18, 2006 2:09 pm
Posts: 26
Location: camber sands
bond two sheetstogether as the fella says above then you can coat it or cover it ,an easy method is to get some spray adhesive (temp tacky kind so you can renew the layer easyer) and cover the whole surface of the rocker table then stick a layer of vac bagging plastic over that ,works a treat and enables you to have an air tight seal every time.ive had adjustable rocker tables with metal on but i didnt like the lack of adjustability even though i could just cover in release agent and away i went,with wood you can fine tune sooooo easilly , lengthening / shortening, concaves/rockerlines etc with ease. i tried many different methods but found it to be a good system as mdf is really great for forming into shape.there really isnt a right way or wrong way, all youre aiming for is acheiving a good end result. so dont be afraid to do a few experiments

with regards to layup i laminate the bottom to the core with all i need then flip it over holding it by the ends,and on to the table which is premarked so i can centralise the board. then i layup top as norm or whatever layup you use. then you vac it ,job done. if youre using certain weight fabrics they wont screw up on you when you move em(8-12 oz cloths). i have no probs with wrinkles and i can acheive perfectly flat surface laminates everytime. my boards are just a one shot proceadure and after they have been trimmed/drilled i hotcoat the deck and rails (masking of the bottom off) and then polish to perfection. i make complex shape boards and found that pre laying up laminates and using them cured/semi cured wasnt working , i think pressing under heat is a better option for that . i prefer vaccing for its ease though so im sticking with that.

mylast bit of advice would be get the best materials you can and be spot on with mixing your epoxy , these factors will make a stronger lighter board. pressed pop outs are good but you will never beat a true custom ,made to measure ,kiteboard, and when you built it its even better!! :thumb:
hope all gos well for ya!


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 Post subject:
PostPosted: Sun Nov 05, 2006 9:01 pm 
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Joined: Wed Oct 05, 2005 6:43 pm
Posts: 665
Location: Sweden
I bought another 4mm mdf to put over the first one, but it was way too much work to get both down.

With 18mm concave over a 34cm width (table is 60cm) and a 25mm longitudinal rocker over 135cm, the 4mm mdf is really "tight"- stretched like a drum.

I suppose i could do it in 2 steps with wider wood stringers underneath, but that would mean rebuiiding everything from scratch...

so, i covered the 4mm mdf in a layer of 155g glass and then coated with epoxy to get a smooth layer. Turned out good.

Test bagged it tonight and it held a vacuum. had a 15mm (not tapered to 5mm at edges, like the blank) foam piece on the table, couldn´t see any table distortions.

Must have been the untreated mdf is not airtight....

Still worried about the recommendations on distortions...I just cant see where the MDF is gonna distort. The MDF is screwed down to two fixed rails along the edge, screws at 10cm centers. The center of the MDF is pushed up by a stringer that is about 40mm higher than the edge rails. Both the center and edge rails have a longitudinal rocker of 25mm over the board length of 135cm. So the mdf is really "tortured".

TW


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 Post subject:
PostPosted: Mon Nov 06, 2006 10:21 am 
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Joined: Thu Nov 02, 2006 5:12 pm
Posts: 76
TomW wrote:
Crabman and Bill,

Really, thanks for your help and encouragment.

Yes, i can see that the 4mm MDF will deform. I´ve made a rocker table 60x180cm that has 18mm of concave over a 34cm width and a 25mm rocker over 135cm length. This is a lot of compound curve on the MDF, so anything thicker is not going to take that shape, i have tried 10mm but its too stiff.

I´ll try to source Conti board, but i´m in Sweden and some materials are hard to get, others easy...

I may have to go back to making a glassed foam rocker form that i put into a full bag. What i did before was mill a 40x 140 block of foam, putting a convex form on block thick enough to take it and have some thickness left over. Then i glassed it all around in a full bag and pressed it down on a simple curved longitudinal rocker with weights. Sanded and finished the rocker form to give it a good surface.

Then it was easy to put my whole board onto the rocker form and the whole kit into a full bag...

TW


I have a rocker table built with 9mm MDF and a 6mm Plexiglass surface.

The plexi allows me to Push 8mm concave without any problem at all with anywhere from 30-40 mm of rocker.

regarding deflection, non than I can measure.

Image


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 Post subject:
PostPosted: Mon Nov 06, 2006 4:07 pm 
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Joined: Wed Nov 20, 2002 1:00 am
Posts: 894
Location: rhode island
hi tom.
you'll be fine.
i'm sorry you went to the extra work of glassing your table but that should stiffen it considerably.

since you did a test run, dont worry about any of our conserns.
you cant argue with results.

besides, in the end, everything works.

have fun,
-bill


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