Best way to build???
A true concrete shape master would start with a solid rectangular block of concrete, and just chip away anything that doesn’t look like a longboard, using tiny tiny cuts and only custom-made tools (or really old ones like a Skill model 000 diamond-blade circular saw).
The “hollow masters” would of course work on a hollow concrete longboard by building it from the inside out, first laying up the framework of rebar, then plastering it from inside with a custom concrete mix (color optional) much like the Sistene Chapel.
The “pop out” school would build a big mold out of foam and fiberglass, then fill it with concrete. Of course this may result in a board that is too light for some people.
The “machine” guys would spend 7 or 8 years on the software needed to program a mixer to dump its contents into a wheelbarrow at precisely the right instant. All that’s left at that point is some minor hand-finishing by a ghost “creter”…
A “crete mat” is also an option, but it’s tough because the concrete has to stay semi-fluid inside the mat confines in order to allow the rider to properly squeeze the rails. Only a few folks know how to build these!
Hope that helps, Mr. Clean… as always, just one guy’s opinion, and your mileage may vary.
here’s some good ones if it’s longskates you’re after… i’ve had best results with making them with two wood layers sandwhiched around an EPOXY and fibreglass core. they are pretty easy. altogether about 4-5 hours per board including laying up and finishing…
I remember gene mentioning something about one.
There are concrete canoes. Probably use that method.
Concrete longboard…well, you have definitely stumped the panel there.
But a quick look through http://www.cae.wisc.edu/~canoe/ and especially http://www.cae.wisc.edu/~canoe/Design%20Papers/Design_Papers.htm yields up some very interesting possibilities. Though carbon fiber concrete is prolly a little nuts… but the latex and other additives for flexibility seem like a necessity.
A vibrating plate arrangement for compacting the stuff could be made up from a not-very-good half-sheet sander and mebbe a plastic bag ( or, whaddya know, they make one : http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=90304 ) , shotcrete sprayer from a modified cheapo gravity-type mini-sandblaster ( such as http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=45998 ) , small batch relatively precision mixing with a 5 gal bucket and one of those mixing paddles the sheetrock guys use on a half-inch drill ( http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=41015 for example) plus a kitchen scale.
Are you thinking in terms of a hollow structure or something laid up over a foam core with a mesh overlay?
This oughtta be interesting…
OK, taking a cue from some fellow Northern New Jerseyites who specialize in concrete watercraft (principally shoes) first make sure the “surfer” is either dead or knocked out so they can’t move around and wreck the setting concrete. Then you get a form or mold which is open on top so that you can attach the “leash” or “leashes” to make sure the board does not get away. Then pour the concrete and let it set enough to position the surfer and get good adhesion. At this point it is OK to allow the surfer to wake up if applicable and examine the fine lines of his new stick. Then you’re ready to have them hit the surf, which in this case usually takes place at night. The surfer will need help in getting out to the lineup. Don’t expect to see a long ride, as the flotation on these boards tends to be lousy. In fact, one ride is all that can be expected with these types of boards. I think Jimmy Hoffa was one of the more famous riders to use this design.
Nah…I was talking about making big old heavy concrete boards to go outside on the patio of a resort.They would be indestructo table tops.Mike Manzi got me thinking though…build a concrete board and do something to polish it up so it looks real.Leave it on the each and do a candid camera thing when people try to check it out (or rip it off)…oughta get a laugh.
Ah, okay, table tops or benches or bar tops, etc… now I get it. Light dawns over Marblehead.
Make your mold ( quick and dirty from an old longboard ) with some glass mat and cheapo resin formed around the deck and rails. Leave the thing straight from the wide point of the rails to the level of the bottom so it’ll come out of the mold okay. I’d do a hotcoat and sand job on the inside of the mold for good release. Might want to use some small wood blocks in the mold to keep the mesh from showing at the top, you can fill them later.
Coat your mold with some of the oil the concrete form guys use, sorry I don’t know the name of it. One of the local concrete guys will probably give you all you’ll ever need for a sixpack.
Lay in lots of mesh, some rebar tied to it with the soft iron wire the concrete guys use, then some more mesh. run a stick along your mold edges to check that no mesh or rebar is sticking up too high. As this is gonna be a relatively thin concrete structure ( unless you build up the sides of the mold, may be a good idea) then it’s gonna need reinforcement.
Mix your mud kinda soupy, use pretty much the same mix as the guys who spray pools use. It’s too much to do in a wheelbarrow, so you may want to buy, borrow or rent a mixer. One of the guys I do small jobs with just got one of the $150 or so Harbor Freight electric mixers and likes it for the small jobs like Sonotube columns under decks and sheds - if you do several of these it might be a good buy, it doesn’t take up much room. Some of the new additives they have to make concrete more rugged could be a Real Good Idea too.
Pour it, vibrate it with one of those rigs that looks like Steely Dan and for that rounded bottom edge, one of the seam tools the sidewalk guys use could be run around the edge of the mold to do that when it’s gone off a little. This is similar to how they do site-fabricated concrete floor beams in Central America, it’ll be fairly rugged. When it’s well-cured, roll the mold over ( carefully ) onto a couple of old mattresses and thump it a bit with a rubber mallet to release the thing. Building some long levers into your mold support framework would sure help with this.
I’d patch any pockmarks and such ( like the holes the wooden blocks left) with epoxy-based goo or Marine-tex or maybe even Sakrete, grind protrusions and edges with a small grinder and a masonry wheel, give it a coat or two of some of the epoxy paint they sell for concrete floors. Might take a few coats to build up a nice finish but that’d be a whole lot easier than grinding concrete smooth.
At least, that’s how I’d tackle it. That help any?
so kool! now i want o make one!----"hey! comin’ down! that image in awesum!-----actually, making one as a real lawn tingie would be really neat…sure would show that THIS is a surfers house…but i think my wife would kill me…
Hell cleanlines why make it out of concrete? I just got one of your old longboards in for repair. (The guy rear-ended a school bus! The last foot of the board is 90 degrees straight up.) The thing weights a ton…just make your benches out of clark foam and use the same glass job as this one.
Bitchin. finally something i can comment on. o.k. check this out. have you ever heard of GFRC? Glass Fiber Reinforced Concrete. you could actually make a concrete surfboard. i know it isn’t exactly what you are talking about, but it is an interesting thought nonetheless. it would have to be made in a two pc. mold. because of the glass fibers you can lay it up as thin as 1/2". if you were to lay up the top and bottom halves and then foam fill the hollow core you might be able to get away with 1/4" skin. an acid wash on the concrete would give a sweet look like you wouldn’t beleive. if any one really wants to try it i will explain how to do it. i actually think you could make one and surf it. it’d probably weigh 60-80+lbs.
I have seen pictures of Acid Washed concrete and some of that stuff is incredible to look at.Has anyone ever done it???I saw floors in a Modern design magazine that looked like cooperfish acid splashes.As for my situation with the concrete board (resort outdoor dining table) we are checking with comany that does precast concrete.The tables need to be heavy and they will never be ridden plus the fact that they need 60 of them by July 4.Thanks for all the input. R.B.
if any one really wants to try it i will explain how to do it..
I’m interested in how it’s done.
to build a concrete surfboard i would do the following; first select a board design that i like. in choosing i would keep a couple of things in mind. first and foremost that i want it to be particularly thick. (this is so there is a large cavity area that can be filled with foam for buoyancy.) next a mold would have to be made. the mold would be two pcs. split at the rails and make a minimum of 3" flange. (if you decide to do this and don’t know how to make a mold i will explain that in detail later) after the mold is made you are basically ready to cast your board. there are special concretes and additives and things you must use. but at the minimum you will need concrete, glass fibers, and water. there are varying grades of concrete you could use. some require a plastilene type liquid additive used in place of water to create a water proof concrete. the fin box could be cast right in. the concrete and fibers are mixed into a slurry. the slurry is placed in the mold and around the fin box. you would carefully apply it kinda like mom greases a cake pan with shortening. build it up thick (3/4-1")around the fin box.the mold surface has been prepped with a release agent before hand. the concrete would be built up to the desired thickness. use a tooth pick or something like it to dip into the concrete layer and determine average thickness. screed concrete to mold flange so there is no concrete sticking above the flange. let concrete “cure”. once the concrete is hardenedand basically moisture free you can cap the two pcs. together. have lots of clamps and freinds around for this part. you will need them to help you put the deck pc. on and apply c-clamps as quickly as possible. seperate into two groups. one will be applying foam to top pc. and other to the bottom. the group applying foam to the top will simply be brushing it on the exposed concrete surface. the “bottom” group will be brushing it on as well as pouring the bulk of the foam into thr bottom. the foam is an A/B urethane foam mix. once the foam is mixed you have about 3-5 minutes to get the top pc. set on the bottom. mold registration on the flange and a dry run test fit before hand will help greatly. after the mold pcs. are together put the clamps on as quikly as possible. i mean quickly!! let it sit over night and wax it up in the morning. if you decide to do it i will give you much greater details. think about it. it would be cool and history.
rent the mold from walker or clark?
I hear their molds are concrete and extreeeeeeeemly heavy. They use heavy machinery just to lift the deck lid. They are also for forming blanks, which as you know are unshaped surfboards. Your mold will give you an exact duplication of itself. In other words you would get a concrete “blank” if you used one of their molds. You would most certainly have to fabricate a mold for the specific purpose. The mold should be a minimum of 3/8" thick with “egg crating” on the out side surfaces. I’d make the “egg crating” out of 3/4" plywood.