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| Home Made Boards (6188 Posts)
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Home Made Boards |
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On 10/11/2000 Glen
wrote in from
(216.102.nnn.nnn)
Here are some good Vacuum bag, composites, epoxy suppliers.
http://www.acp-composites.com/
http://www.fibreglast.com/
With a vacuum bag, you should only need one side of a mould.
The one that Chris Chaput has in the middle of his design page is probably he best way to go with one modification. Fill the squared off edges with a structural wood filler.
The vacuum bag should give you very even pressure. Your board WILL match your mould so make a good mould.
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On 10/10/2000 Nick
wrote in from
(203.96.nnn.nnn)
I posted some links to make vacuum pumps out of fridges a while back, but still haven,t gotten to try them. The local fibreglass guy has his pump running through a 44gallon drum in between the pump and the bag for extra pressure???
The water hose method can be used to make surfboard fins, which are solid fibreglass and resin, much like a 70,s skateboard.
Now that I think of it, the sites that suggested using the fridge freon compressors were making aeroplane wings,which must be of a decent size.
I,m not familar with car smog pumps, but they sound like a pretty similar type of thing to an Automobile air conditioning compressor and electric moter which is meant to be good. Beer keg coolers have freon compressors which are meant to work. Many types of hose will colapse under vacuum pressure, so this needs to be considered, as well as a release sheet with some sort of holes in it too let the trapped air escape(i,ve heard of peel ply)and some sort of breather cloth to absorb the resin squeezed out and stop it clogging up the pump.
Anyone have the suss on how long these things are meant to be left running for???
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On 10/10/2000
hugh r
wrote in from
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My vacume bagging buddy bill says that car smog pumps are the way to go... HR
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On 10/10/2000 roger
wrote in from
(198.206.nnn.nnn)
Perhaps the cheapest vacuum pump…
I was thinking about cheap pumps, and the cheapest I can come up with is a 20' length hose filled with water hanging vertically. As the water runs out the bottom a vacuum is formed at the top. In fact this is exactly how pressure/vacuum is measured (tubes filled with mercury). However it can only evacuate limited volumes of air and can not sustain operation to compensate for any leaks.
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On 10/10/2000 Nick
wrote in from
(203.96.nnn.nnn)
As far as adding composites go,s, its probably going to be too tricky trying to place back into the mould, unless the whole layup is done in one go, core and skins. An easier way would be to use a mould to press the core and then use vacuum bagging to apply the skins. For some applications an old fridge pump can be used to give adequete vacuum pressure, not sure if this would be enough for skateboard applications though, and bought pumps are expensive, especially if you only intend to use it for the odd skateboard, it would make more sence to just purchase a new quiver. Still, you can,t beat the satifaction you get speeding down a hill on somthing you,ve made yourself.
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On 10/10/2000 Nick
wrote in from
(203.96.nnn.nnn)
I hope this top mould is easy enough to lift and place on bottom mould in press. I have enough little little accidents setting up my rocker jig and its only plywood.
Might need to get someone to help with the lifting.
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On 10/10/2000 Nick
wrote in from
(203.96.nnn.nnn)
Ok, cheers Chris, I think I have it.
If I use a bending jig similar to Hugh,s with clamps and wedges to press a 12" x 50" rectangle uncut blank, with slightly more extreme curves than I need, I can smear this in vaseline and use it to cast the bottom mould in concrete.
If I then vaseline up the top side and pour in the top mould I then should have perfect moulds with a 3/4" mismatch(once I remove the ply blank.)
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On 10/10/2000
hugh r
wrote in from
(205.216.nnn.nnn)
How about a 1/8' or 1/4" peice of hard rubber on the face of each of your "close enough" mold halves. Under pressure the slight movement of the hard rubber can even up the imperfections in the mold faces... HR
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On 10/10/2000
Chris Chaput
wrote in from
(63.168.nnn.nnn)
We can all agree that force being applied directly downward on a perfectly flat mold would put uniform pressure across the deck, regardless of the deck's thickness. Whenever the deck has concave or rocker or camber or kicks or wheelwells or drops or anything that isn't flat added to it, one half (usually the top) of the mold needs to be reduced to allow for the thickness of the board to "fill the gap". The greater the angle of elevation, the greater the need for mismatched top and bottom molds. When there is only a little concave or rocker or camber or a slight kick, you don't really need the mismatch in the molds.
It is not hard theoretically to understand the "right" top mold in relation to the bottom. Let's say that your deck will be a half an inch thick. Take any point (P) on the deck. On a line that is perpendicular to the tangent of P is another point (T) that is exactly a half inch away from P. Take the collection of all such points (T) and you have your top mold. The extreme example is the case of the half sphere where the top mold would have a radius exactly one half inch less than the radius of the bottom mold (just pour the wood in ;). If you had a flat deck with a single wedged kicktail at a 45 degree angle, the top mold would merely need be shifted a quarter inch toward the nose.
The theory is the easy part. The construction is a nightmare. Anyone not privy to a CAD system and computer driven machinery will usually have to settle for "close enough" and hope for the best. None of this even addresses the issue of the top mold always coming down vertically instead of each section being driven directly toward its parallel partner.
In order to keep things simple, I suggest that you work on simple molds using angles more than curves. This way you can cut out cross sections of the perfect partner top mold and shift them in slightly to get your mismatch.
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On 10/10/2000 Nick
wrote in from
(203.96.nnn.nnn)
There must be a simple way to do this moulds thing. The sandbag, compressed with a concrete block sounds good.
Most shortboard producers seem to press 3-6 boards at a time, I assume this is for a faster production, but it would also mean more glue lines to take up any gaps in the moulds.
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On 10/10/2000 Herbn
wrote in from
(216.107.nnn.nnn)
Perhaps a good mold would be a "hydropress"where only one solid mold would be needed and different thicknesses of material could be used,The hydro-jaw would be a rubber sheet maybe .5 thick clamped to close off the "shaping jaw" then a column of water is filled and a piston pushes that water in behind the sheet of rubber, pushing it against the materials in the mold,the piston would be pushed down by a long bolt threading in the cap on the water column.I decided i was ithat interested ($)in making this mold, maybe someday.
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On 10/10/2000 Nick
wrote in from
(203.96.nnn.nnn)
Moulds...ok, this top and bottom matching thing,s got me. I,ve shaped a male out of an old surfski/paddle board centre foam, and was about to start mixing up some cement.
Now the impression I,ve gotten is that in a twin tip design the top mould needs to be relaxed somewhat, so as to pressure the centre of the board.
But...the board i,m going to make is not a twintip, but like an elongated oldschool shape,kick tail with concave. Does this mean I can get away with matching top and bottom moulds?
Nick
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On 10/10/2000
Chris Chaput
wrote in from
(63.168.nnn.nnn)
Solving the issue of perfectly matched male/female pressing is easy using my simplified mold concept. Since the mold will tend to "cork" itself vertically on the angled areas, just take a little out of the middle as shown in the following sketch http://www.chrischaput.com/design/mismatched.jpg It's not much of an issue on gentle rockers or concaves.
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On 10/9/2000
Chris Chaput
wrote in from
(63.168.nnn.nnn)
De-Evolution (Devo):
1. Solid flat
2. Solid flat with wedge kick
3. Mold for to put kick in flat deck
4. Mold for rocker/camber w/wo kick
5. Mold for concave w/o kick
Easy molds so far
6. Molds for concave with kick(s)
7. Molds for concave with kick(s) and wheel wells
Now all of a sudden we think we need high tech 3D molds for a burgeoning population of new school skaters.
8. Make a simple, inexpensive mold as in #3, and then glue on wedges as in #2. Gouge carve, grind, sand or file into a finished product while others are still reinventing the molds as in #7.
Just because we can be high tech, doesn't mean we should. I think my homemade $4.00 "mock concave" board is gonna need a telephoto rear view mirror on it to spot BMW's $400 techno snail.
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On 10/9/2000 Nick
wrote in from
(203.96.nnn.nnn)
Herbn, I just clicked what you meant about the two halves not being exact.
Perhaps the same concrete casting method can be used, but some multiple layers of something between two release sheets, be used between the two halves, so as to allow for the board gap.
I assume some shapes this would be more relevant to than others.
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On 10/9/2000 Nick
wrote in from
(203.96.nnn.nnn)
Most of the newschool sites which show their presses seem to have a pretty even top and bottom mould. This means one half can be cast from the other.
Finally found a source of rice paper. The first lot I ordered is too thin, and the ink from the printer disolves it, sticking it to the paper behind. I think next order I will try one of each sheet availible and find out what thickness works best.
Has anyone ever tried making a skateboard from European Beech??
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On 10/9/2000 roger
wrote in from
(198.206.nnn.nnn)
Now that I think about it, perfectly matching molds does not mean uniform pressure at all! Any wood chip, knot in grain, wrinkle in fabric, change in material thickness or consistency will cause pressure spots. Actually a fabric is a matrix of pressure points. Also the diagonal thickness will be different creating pressure points on surfaces at angles.
An upper mold consisting of a sandbag on a thin teflon sheet might do a better job at distributing laminating pressure.
Example strata:
steel structure
reinforced concrete lower mold stabilized at optimal temperature
release gel (or whatever you call the nonstick mess)
epoxy
kevlar
epoxy
carbon
ep oxy
core material (wood, etc)
epoxy
kevlar
epoxy
teflon upper mold (very thin sheet)
sand bag (temperature stabilized)
concrete block
steel structure
hydraulic presses
steel structure
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On 10/9/2000 Herbn
wrote in from
(216.107.nnn.nnn)
Re;roger and anyone with this idea.....if you did that you would have two matching pieces but as soon as you put any material in between you develope tight spots and the mold doesn't work ,what needs to be done is ,an even layup of fiberglass or plaster(?)that should be the exact thickness of the board you want to press,then pour the other half of the mold.So i've been told,it makes sense but i've never gotten that involved;yet.
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On 10/9/2000 roger
wrote in from
(198.206.nnn.nnn)
It seems to me that the easiest way to make a perfectly fitting mold is to construct only one half (top or bottom) and use it as a mold to cast the second half with concrete.
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On 10/9/2000
hugh r
wrote in from
(205.216.nnn.nnn)
Finished up version two of the top-o-deck rail mount truck system. We used a big ol'peice of oak for the deck and this one seems to be much closer to indestructable.
The Randal-II's work very well with a lowered deck. I have some more pix on my site... HR
PS You will also notice that I have added some "fancy" hardware on the bottom of the deck... mostly for looks...
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On 10/9/2000
Chris Chaput
wrote in from
(63.168.nnn.nnn)
Hey guys, I came up with an awesome production method for a dropped CG speedboard with concave. Make a mold from several pieces of plywood cut identically to one another, that will go flat, angled down, flat, angled up, flat. Don't attempt to put the concave in the mold, add the concave by using the wedged rail system described 6 posts down from here. This way you make PERFECTLY fitting male/female (top and bottom) molds add apply the pressure evenly and without gaps for a strong deck. The "mock" concave exceeded my expectations up at Barrett Junction this weekend and will definitely be a winner. Underneath the beefy rails can easily be routed to create "handles" without sacrificing strength. Some of the Landyachtz guys were racing (very well) at Barrett Junction and seemed to like the idea too. I'm also thinking that cutting the wedged strips on the bandsaw instead of the table saw could give me strips more than 4 inches wide. Expect some very cool boards to be popping up soon!
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On 10/7/2000 Nick
wrote in from
(203.96.nnn.nnn)
Chris, driving the car up to press the boards sure highlights the old saying "more than one way to skin a cat"
I,d imagine it,ll work well though.
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On 10/7/2000 Nick
wrote in from
(203.96.nnn.nnn)
Drypressing parts first sounds interesting. I have not tried ironing the cloth, but if you use a hairdryer to lightly heat up epoxy, it thins it out making for easy spreading and saturating cloth,allowing you to use much less resin, just make sure its in a wide flat container like an icecream tub, otherwise it,ll set on ya.
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On 10/6/2000 Herbn
wrote in from
(216.107.nnn.nnn)
Well my press is mostly done,should have brought home my second drill,drilling pilot holes and driving screws with the same drill is SLOW especially with out a a magnetic drive with screw driving and drilling attachments(left them at my store).I'm drypressing all the parts,kind of like ironing the fiberglass before soaking,hey! that might work ,heat does make resin flow/soak better.Like i said i think i'll practice on my thin half inch birch boards before risking my vertical laminations.So many projects so little time,foam glass,carbon stingered/glassed ply board,simple single layer vertical laminations,barrel cut concave vertical lamination, i have my own low c.g designs also(hush,hush),camberd/rocker mold,big stable strokers,ect,ect and those are only skateboard related projects.
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On 10/6/2000
Chris Chaput
wrote in from
(63.168.nnn.nnn)
Nick, I haven't yet completed the molds. I have this interesting idea about putting the mold between two of those ramps that you drive your front tires onto and letting the weight of the car supply the necessary pressure to warp the laminates into shape.
BTW, I used to put a slot in the tail of deck and would then slide a wedge into it (instead of on top of the deck) to make the kicktails in my solid maple decks (1975-1978). Very smooth transition.
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