Adjustable rocker table

General Discussion
1

Wondering whether any of you eps balsa guys have bothered to build a rocker table yet, I notice that Sabs used one on his earlier boards, I am fed up with using the offcuts (too much wasted eps for one) and think it’s time to invest in a table. I have seen one in the archives using stud bar and nuts to adjust the rocker, just hoping that someone, DanB, Benny1, Silly etc has developed something else???

The board that I am working on at the moment has an extreme concave deck and I think I need the stability of a table to keep the bottom flat when I vac the deck on. Any suggestions will be grarefully accepted.

2

Hola Mark!

Maybe planning to build a sailboard?

Me too.

Daddio was planning to build this thing last year. I don’t know if he went trough.

http://www.swaylocks.com/forum/gforum.cgi?post=184491;search_string=plexi%20rocker%20table;#184491

390×792 50.8 KB

3

I don’t know, but isn’t it harder to seal with all that tape running around the entire board?

I’ve seen this before

Not adjustable, but same principle for the vacuum/sealing. So it works, I’m just not sure how consistant.

regards,

Håvard

4

I’ve been thinking the same thing you have. For the past couple weeks I’ve been thinking of how to make the best adjustable rocker table. Every time that I come up with a good idea it fails. For examble, the one with the bolts I think would have stability problems with a large rocker and you would need rather large oval holes in the plexiglas because the plexiglas kind of change lengths as it raises and lowers. I’ve realized that you would probably need 2 tables in order to make any size board (for example, one for 8’ to 10’ boards and one for 6’ to 8’ boards). I plan to start it next week so I’ll post pictures if it turns out to be useful.

5

I’ve thought of it too. Dan, you wouldnt’ need oval holes if you set the heads of the bolts (carriage bolts) in track so they could slide. The two rails that hold all the bolts & sit on your workbench, right? Just slide in all the carriage bolts. Once the nuts above & below the plastic are tight, the bolts wouuld stay in place.

But for me, I just can’t see dedicating that much time, material, and space to it. I’ve been perfectly happy shaping my bottom rocker & contour while the blank is still square & bagging on the bottom skin & under glass as a square. Then thin from the top, cut the template from the bottom, add rail pieces, turn the rails, and add the top skin. No stability problems in shaping or bagging at all.

6

You folks did see Tom’s table in his Sailboard Vacuum Forming video right?

One bar one set of bolts right down the middle.

Looked like plywood to me attcahed to some channel bar

7

I have been in the thinking phase of a table similar to the one in daddio’s sketch. The problem with that design is twist. if the two bolts directly across from eachother are not set exactly the same the table will have twist. This could open up a whole new realm of controlled asymetrical boards. Likely though we will be striving for lack of twist in the beginning.

I can only see this being overcome in one of two ways:

  • attach the rocker control bolts to a rod that passes through a tube running side to side attached to the rocker table. The tube would be set at exactly 90 deg. to the intended stringer line. This would also remove the need for slots or holes in the table itself.
  • Attach the bolts the centerline of the table, with lateral stabalizers running at 90 deg to the stringer, only requires one set of bolts along the stringer axis.

As for the table material I was thinking of using thin aluminum plate with a slick formica type surface skin. The formica when combened with a mold release should be easy to maintain, and cheep to replace if neded.

Rob

8

Benny

I have been happy this way too, up til now, but with the deep concave deck, I imagine that the force required to bend the balsa sheet into the concave and over the hump onto the rail wood will result in a concaved bottom (from flat), so I want to vac the lot onto a rocker bed to keep the bottom flat.

Neira

I am thinking along those lines, but using melamine faced ply or mdf, (much cheaper than plexiglass), I do like the track idea though, I have some old genoa track somewhere, can put it to some use.

Anyone else out there have any ideas??

9

I really wanted to make the bolt idea work, but problems keep arising. For instance, the middle of the rocker table is completely unsupported. Without this support It would be very easy for the melamine to form a concave or a vee.

I’ve got a question everybody. I have been looking at a lot pictures of boards that I had put into aps3000 and blanks from the clark blank catalog. What I’ve noticed is that the middle on most boards ( I’ve looked primary from the 8’ to 10’ range) there is a 1/4" curve in the rocker for the 2 feet behind center and about 1/4" of rocker in the foot in front of center. Does this sound fairly reasonable? The reson why I ask is because I thought that it might be a good idea to machine this into a section of 2x4 (like a smile) in the middle 3 feet of the rocker table. You could then glue an screw the melamine onto the 2x4’s. This way the middle of the rocker table would be completely stable (no twist or flex) . On either end you could cut out of 2x8 the minimum rocker your boards would have. Now you go with daddios bolt idea (except spread the spacing out to every 8" or so). This way no bolt would be longer than a couple of inches (this would minimize stress) . To span the distance from the bolts you could take a heave duty metal washer (the type that goes with concrete anchors) and weld it to something like rebar. This would really stabalize the middle.

Benny - I’ve made all of my boards so far without any rocker table at all (foam or otherwise). I don’t like having all the waste of the foam rocker table and my current technique deforms the rocker too much. I am also looking into the idea of using conture mats so I need the table.

By the way, I thought that I would add that a lot of shaping can be accomplished through the use of wedges. For instance, you don’t need the table to be able to handle a tail kick if you use a wedge.

There’s nothing like a group brain to work through problems!

10

Dan

I like the idea of setting up the framework with the min rocker to save bolt length. if you connected each pair of bolts underneath the melamine with angle or 2x1 then this should support the middle of the sheet, which does only need to be about 26" wide.

I also hate the waste and have managed to squeeze 2 more boards from my offcuts (No eps recycling facilities in my county at present), so have no rocker beds left!!!

11

If you went with the 1x2s you could put a strip of velcro across the strip then another couple strips on the melamine going perpendicular to the 1x2s so that it would hold the melamine snuggly to the 1x2s. If you rigged up some sort of pin coming off the bolts you could have the 1x2s swivel so that you had maximum contact with the melemine. I think that I would make mine 30 inches wide because I mostly do longboards and a lot of the “BertBoards” are 24+ inches wide.

12

I make kiteboards and use a adjustable rocker table.

There are really easy to make.

This one is 6mm MDF glued to 25mmx25mm cross-table batterns.

Each end of the batterns has an eyelet fitted. The eyelet allows even clamping without distorting the table surface.

If you want to put concaves into your boards then a piece of Plexiglass is fitted above the table.

This is my one.

I hope this helps.

Simon

13

Morning Si, your workshops looking tidy in that photo. How’s that latest board looking? Maye some photos would be good don’t see too many kiteboards on here.

I’ll be round with my blanks later.

14

thats a very nice solution there simon…nice and easy too…

the studs would be a problem if one wanted to vac the entire blank/table…but…how nice and useful it would be to place your foam beds on top of your table w/o studs…

15

That looks really nice! It looks like a lot of my fears were unfounded. Do you bag you kiteboards, and if so how do you go about it?

16

hey mark

i honestly cant see the point in building a rocker table

it seem like a lot of effort and money to me

id rather spend the money on other stuff…

if you have a large block of foam and just slice off what you need it works out pretty economical.(ill use the the deck slice to make fishes)

i have been using the same bag since i started this trip and it easy to just slide the foam table in to the bag before i go to work .i think all the off cuts will be eventually used for something else(glued together for lost foam tecniques,maybe a sea kayak).and the rockertables should last indeffinately . u can use little foam wedges at the end to slightly alter rocker…

do you have a sheet of masonite on top of it when you bag a board??? (that keeps every thing nice and flat. have a few guide lines and tape in place you can even put down a sheet of plastic if your worried about things sticking).

I hear what you are saying about waste

it bugs me as well . im trying to keep it minimal.

foam dust bugs the crap out of me and used tape…

but i love my foam rocker tables(i can move them around etc)

i even shape my rails on them

17

Gents

Thanks for the nice remarks, regarding my table.

The table was built originally for the making kiteboards, but I can see synergies and crossovers in other board construction too.

The table in the original picture I posted did not have a mould surface attached which is used to form the concave by pushing the core and laminate over it until set. This results in a fantastic concave and accurate rocker profile.

The method I use is as follows:-

1 - Create a wooden stringer, this is used under the mould surface to cause the concave bump.

The placement of the concave on the board is determined by this stringer. This means I can place concave anywhere I want it. For kiteboards this is usually only in the middle section with no concave in the tips.

2 – screw the mould surface down over the stringer and attach to the table edges.

2.5 Clean the mould surface.

2.6 Place bagging tape around the outer edge of the mould surface ensuring a good seal all the way around.

3 – Wax the hell out of the mould surface.

4 – pour resin onto the mould surface, then lay the laminates as in surfboard construction, wetting each layer as you go.

5 – Place the core onto a glassing rack and do the top laminates, again wetting wet out every thing.

6 – Wet the underside of the rails with resin.

7 – take the core, with its top laminates already wetted out and place on top of the wetted out bottom laminate already on the table.

8 – Next lay out a sheet of peel ply over the board

9 – Remove air bubbles.

10 – Release film, then breather cloth, and finish with the bagging film, this is just one sheet and it attaches to the bagging tape, thus sealing the whole thing. The bag does not need to go around the table, just on top.

11 – Attach vac piping, one at each end of the table and seal into the bag.

12 – Attach vac pump, and turn on.

13 – 5 hours later, remove the board, it pops right off.

14 – Sort out any flashing and finish.

I may have gone into a bit too much detail here, but I just love building like this.

The bottom comes out fantastically and the top just needs a quick sand and hot coating.

There you have it… Easy ehh!

The rocker table can easy be altered and reused. There is no reason why you could not form a non symentrical rocker into this type of table.

It was easy to build, you dont need steel like I have used.

You could try a 4x2 inch frame then use bolts through that, then the table top.

18

I like the look of simons table, looks pretty simple to me, thanks. Silly, up to now I haven’t needed or seen the need for a rocker table, when I do the bottom balsa, I put the foam deck offcut in the bag and vac the lot, when I do the decks I have been just putting the board in the bag and laying this on the deck offcut and weighting it to stop it twisting etc.

I have now got in a position where I have a board with the bottom and rails vacced on, deck shaped and the deck balsa fabricated ready to vac on.

I could just go ahead and do it or do a dry run, but this board has way more deck concave than any I have done previously and is much thinner partic in the tail, it has also curled up a little longitudinally giving more rocker than I want.

The last board I did, I made a temporary table to vac to, only took an hour to build, but thought that if I keep having to do this, may as well make a permanent one. I also have no bottom offcut to use as a bed because it was so thin and I skipped it.

Once you have one, I think that more options open up, it seems that all the kite and windsurf guys use them.

19

I was going to use the deck offcut as a rocker table (you can see it on the bench at the left) but I decided I wanted a little more nose rocker at the front 18". So I just put the board in the bag, on glassing stands to vac on the deck skin w/glass under. Pile a few bricks up near the nose, & the weight & stands fix the rocker…

I’ve also found that its a very good idea if you’re using a bag to pull to about 6lb/Hg and shut down the pump. At that pressure, you can fix twists & rocker issues and pull wrinkles off the rails. The bag is loose enough that you can manipulate it, but firm enough that it’ll hold whatever you do to it. Once everything’s happy & smooth, I start back up to my normal 11-15 lb/Hg that my vac switch holds.

20

The more I look at that table the more I like it! Thanks for the writeup, the detail really help visualize how it works. I agree with markyv, I think having a rocker table would open up many new opportunities. I really think that there is something to the use of contour mats and they seem like they would need a rocker table. Another use would be using infussion to make the skins. I you put a curve (concave) in the 2x2 slats you could have the balsa closer to the shape of the boards deck. You could even up in a bump where the deck concaves so that it would be easier to fit the board to the deck.