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[SURFFOILS]

 Hi guys, Im looking at doing a CS with a difference or two.
First, Id like to see if I can make it hollow, heres my plan...

Put down 3 layers of different foam and materials for the hull and rails.
10 mm for the hull, 25mm for the rail blocks and balsa / ply for the top level.

 Cross section pic.







The idea is that I can vac the three together with some glass and the 10 mm foam on the bottom will form with a contour mat on a rocker table.



The 25mm foam should give enough thickness and bouyancy similar to a standard construction and the balsa becomes the springer / perimeter stringer/ deck layer.
 Ive chosen materials that are a little heavier than usual because of the altered construction, so that with the foam and ply being just a collar or donut they would normally be very light and flimsy but the increased density should balance that.

With the open technique I can vac the bottom skin and rails in one go and then vac again to add internal support and then vac again to put a deck level on.

 Theres still some internal and deck components to come but Im going with a minimal approach to construction and shaping.



 

[tomway]

I like it!
So, if I understand this will have a 'parallel' profile, albeit a thin one? Or will the internal deck support allow for thinning out the nose and the tail?

Looks like a very clean approach so far 

[SURFFOILS]

Thanks for the comments Tomway,

 I had thought of doing the 'parallel profile'  thing but I think aesthetically that thinning the ends will be more pleasing.
Theres always the opportunity to go wacko and do something bizarre but I think I'll do a few subtle construction tweaks and see how it turns out.

 The internal supports are only guesses at the moment as well as  how to vac something hollow without crushing it.
 
 This is a first attempt and its all still falling into place so any help is most appreciated.

[SURFFOILS]

Tapering starting from 12 in out at either end.






Done on a flat board, its very easy to shape.





Nose and tail on rocker board.














I'll give both ends a little extra rocker lift at the finish.
 I bought a new pump from eBay today so Im going to do it with all new equipment.

[tomway]

Worked out how to vac the top one yet?
I can't see how you can really 

I guess you could vac the core together and then clamp the deck skin like the hws builders do?

[tomway]

...or fill it with 3/4# eps 

[SURFFOILS]

  I think that the overall contact area



 between top and bottom isnt too large so theres not a lot of economising of resin to be gained. I might have to preform the deck to fit but I guess that with the right internal reinforcements and a bit of subtle vacuum regulation    it will all come together without imploding.

 Im thinking that I might be able to do some kind of 'strip or ring vaccing' where I just vac along or around the entire rails without covering the centre.....
 Or clamp it like you said.

[SURFFOILS]

 Heres the deck piece...
  25mm XPS



 Ive tapered both ends so it blends a bit better.





And then it sits, (later to be vac and glassed) in a centralised position on the deck ply. Overlap of 50 mm.



Before tapering it was a max of 65 mm thick, or 2.5 "





And Im going to keep the max thickness thru the middle.

 Ive yet to roll the deck so yes it looks blocky.





So in the end there will be 4 levels, 10mm foam hull, 25mm foam donut, ply donut and then the 25mm deck piece. And a few layers of 2 and 4 oz later on. And internal supports.

 So far its taken about 2 hours of easy cutting and flat sanding to put together.
 No weight measures yet.

[SURFFOILS]

Finally got my pump delivered from eBay, as its my 1st rocker table attempt, I tried a test vac.
Simple setup...
 Just a polyethylene garbage bag cut down the sides so its doubled in length. Maybe 20 c per bag. And a green pot scourer over the end of the vac tube.









Taped the bag over the board and found the sides of the bag pulled away from the table when the vac started.



So I untaped the bag, kept the vac on and after it had formed over the board, I retaped the edges of the bag. The thin bag really forms well and didnt rip so Im going to stay with the garbage bags.







 Im going to make a few board with the same dims so I taped a pe sheet under the board as well.





 Thats the dry run out of the way.

[lemat]

Let's go ! 

[tomway]

2nded

Really want to see what happens next. Good to see some new things happening here 

[SURFFOILS]

Its sucking as we speak ! I had 1/2 and hour to get it running before I did dinner, it took 1 1/2 hrs, but its on the table, all the layers are in place and its sucking big time.
 Is it normal for the pump to spit oil out the exhaust ? Not a lot but there  are spots on the floor. The pump is rated for constant running but its scaring me a bit with the light oil cloud thats emanating from it !!!
 Apart from that and the 100 yards of tape I used..... its holding together well.
 Ive got the 10mm XPS (sanded to remove external skin)
then a whole layer of 4 oz,
 then the 25 mm XPS donut,(sanded)
4oz donut,
 then the 3 ply donut,
and a polyethylene sheet,
 and then the garbage vacbag over the lot. No internal support or the deck cap yet.
I still dont know if I should do just a central stringer of 20 mm wide XPS or maybe 2 thinner ones ?
 Its been on the vac for 3 hours, might take it off before bedtime as I dont trust a smoky pump.
 Photos later, its been a busy day.
 Thanks for the support guys !!!!
 Cheers !

[SURFFOILS]

Ok heres the pics...

$150 spitting pump...



$20 eBay gauge....



Sucking its little heart out !





 Btter turn the pump off rather than burn my sons house down.
Cant wait to see if all the layers hold and what sort of weight and flex it has, esp with the 'donut' components.

[tomway]

Ha, funny - I'm just about to by EXACTLY the same pump that you have pictured... but it sounds like it smokes and spits just as much as my air conditioner pump so maybe I won't bother! Is it quiet?

Do your 'garbage bags' come on a roll? Are they a tube?

I use cheap plastic that's already a tube, looks like what you've got. I started by cutting and taping and gluing and sealing with silicone as detailed on various forums, but in the end came up with a much simpler solution. I'll see if I can post some pics, but in short I just tie a knot in the closed end of the bag to seal that. On the vac end I put the tube into the bag, bunch the bag up around the tube and then wrap some string round a couple of turns to close the bag to the tube. I do a shoe-lace knot so you can open the bag up real quick if needed.

I never get leaks and it take about 30 secs to prepare. You have to be careful though as the bags do puncture easily if you've got sharp edges. With thicker/tougher skins I've also wondered if the bags stretch too much to get as tight a curve as possible. Mostly they're great though.

[SURFFOILS]

I didnt know they spat oil at all ! The last one I had was like a household vacuum cleaner and it obviously had no oil. This one puts out a fine cloud of airborne oil and spits bigger drops out the exhaust on top. On the good side its really, really, quiet, but it appears to be going thru the oil at a great rate.
 Where do I get replacement oil ? Can I get it offa eBay ? The manual that came with it said, in shithouse Engrish, that it needs FVR  32 oil...?
  The garbage bags I got at Bunnings Hardware, theyre the bin liners for the 240L OTTO bins, HDPE, approx 1.2 m long. Slit the sides and its 2.4, easily enough for my 6'2".
 I loosely push it against the board then turn on the vac and then tape it from the top dowm. With a second PE sheet over the board it was enough to avoid any pinholes.
I'll use a new one for the next vac.
 Im busy for the next 2 days so Im going to leave the board sitting on the rocker table and I'll unveil it later.
 Any tips on where to get the pump oil would be greately appreciated !!!!