Edgeboard KB/Greenough inspired

MIdwifed by Dale Solomonson! Tons of generous info and ideas over hours on the phone and email correspondance. Mnay thanks!!!

Board is 4’10" X 18 X 20 1/2 X 18 pod is 13. 4 inches nose rocker starting from dead flat at wide point which is approx 3 inches up from center. 2 inch hull depth. At widest point, planning area is 13 1/2 inches wide, chines 3 inches at about 25 degree angle. Chines cut wider then after glassing, backfilled w/ micro balloons/resin mix to make strakes. Balsa runners epoxied on at end. Pictures follow.

1st is pretty much all the tools I used to shape the blank. long and short surform, 1 inch block plane, 2X4 for sanding block…

Couple views of start of shaping and finished shape w/ poorman’s mold release applied. First tried covering blank w/ alum. foil but when first layer glass applied it pulled up in large areas and seemed a mess. So, pulled it off and covered w/ resin resistant masking tape then Turtle Wax car wax (carnuba) and PVA mold release. Spoon bottom popped off when done easily enough but took on impression of all the littled overlap lines of the tape. A major butt pain to properly sand out. Live and learn.

Glassing bottom. All poly resin and 4 oz e-glass. Next time will use epoxy for sure but haven’t done much glassing at all and none for about 25 years so wanted fewer variables. And I have worked w/ poly and e-glass.

Due to triplane bottom, center was super flexy and rails ridgid so added some uni-directional fibers down center to stiffen and also at knee contact area to strengthen against breakage later.

Soon as the film gets back from drug store (yes I have no digital camera…I am a luddite) I’ll post pics of building on the strakes and the fin and the finsihed board.

How many layers of glass?

Is the blank sacrificial or reusable?

I love unusual projects. Thanks for taking the photos :slight_smile:

Looks like nice work. I was out on the flexspoon site yesterday looking at details for one of these and have a couple of questions about the construction process. Not necessarily directed at you DrStrange would like feed back from everyone that has an interest.

Why use a form for the hull pull it off and then use two part expanding foam? Isn’t that stuff open celled and if you perforate the glass it takes on water (not a good reason eps, pu have the same problem)? Also seems like a lot of work to create the form for the foam etc.

I read on the site and a couple of threads here that folks are using a combination of e-glass, s-glass and/or carbon fiber, which would make for a very stiff composite when you are done. Why when you are trying to make a water craft that flexes. Have you heard of/tried this product? Polyester Fabric

Polyester fabric is primarily used as a cheaper substitute for Kevlar® to impart toughness to a laminate but it does not provide as much stiffness as does Kevlar. Style 29019 is a 20x19, 1000 denier, 5 oz plain weave, previously available only in 60" width but the most recent shipment was 47".


I use it in kayaks to add toughness. Instead of being stiff it adds flex (it almost a contaminant). One other added bonus is that it is a synthetic like Kevlar and is very difficult to break in a composite. I have taken cut-off edges form a finished composite to fold into the trash and I can break the glass, but the poly fibers fold, flex, but will not break unless I get the tin snips out. The poly fibers hold up even when the rest of the composite is broken. It takes very sharp scissors or tin snips to cut as it is. I have one set of scissors for synthetics and one for glass.

Here’s my plan for this toy. Any and all insight/direction welcome.

I plan to use EPS and epoxy.

  1. Form your bottom shape and rails.

  2. Tape off the area to be removed in the center with clear packing tape.

  3. Glass the hull using the following schedule g/p/g/p/g g=glass, p=poly

  4. Trim and flip it over. Remove the center area where it has been taped. The tape lines will be less of a problem. Just rough up the smooth areas. Shape the EPS for the deck side.

  5. Glass the deck using the following schedule g/p/g. Taper the fabric back from the nose to maintain flex 4” between glass layers. Keep the poly covered. It fuzzes when it is sanded. Maybe add a layer of glass over the foam rails for added protection. Add color if desired.

  6. Make and attach the fin. Need two for a river board.

What do you think?


glass 9 layers of 4 oz on each side outer 5 staggered on each side. Using other materials the considerations are strenght, lightness and flex characteristics. Need snappy flex not soft mushy flex–this is key! so don’t know if the poly fabric would work or not. Depends. W/ s-glass etc can use less and get lighter board same strenght w/ same flex more or less. Maybe. Also, GG using carbon had very little flex except in tail end of edge boards.

blank is reusable to make copy or modified copy. The pour foam is 8 pound and I think a normal blank is about 1 1/2 pound (per cubic foot) so much stronger is pour foam. Under flexing, surf foam breaks down much more quickly than the heavier pour foam. Plus, w/ the pour stuff you get the blank back.

More pics soon

If Dr. S doesn’t mind me chiming in with an answer here while he’s off at the photomat - 'cos I do have an interest…

The reason for using a form, rather than sanding away everything, is so you can make more than one if it’s successful and cheaply/easily adapt the beast if you want to play with the shape some. It’s a male mold.

Glass cloth is not only cheap, but it’s not terribly flexible when glassed with polyester resin. That’s a good thing, as it lets you grind away some to tune the flex of the beast. 'Cos no way will it be right, right out of the box. You need to be able to play with it.

A few other things -

Epoxy is not only at least twice the price of polyester, it varies a lot in inherent flexibility - and thank you Patrick for making those test pieces. Patrick found that System Three SB112 epoxy was- what, lets say 2-3 times as stiff as RAKA epoxy, all other things being identical. Polyester is as stiff or stiffer than the SB112, though it tends to crack and fail when flexed beyond a certain point while the epoxy stands up to that degree of flex and returns.

Foams- again, polyurethane foam can be shaped easily and is compatible with polyester resin. Polystyrene foam isn’t, so that if you are glassing with polyester or making a male mold - especially a more permanent male mold with a glassed skin - it’s gonna be problematic.

For foam in the board itself, the sprayable or 2-part foams are useful. If you can get hold of them, sections of polyurethane foam sheet might be even better, laminated on. I am given to understand ( Via Dale Solomonsen) that sign foams are good for this, as well as some marine foam sheets which may be higher density. Nice thing about that is the stuff is more homogeneous than the poured/sprayed foams, so you will have less worries about odd points in the flex/stiffness of the foam.

And even better ( thanks MTB) are the foams sold for aircraft homebuilding, notably Divinycell - see http://www.aircraftspruce.com/menus/cm/foam.html for more. Also http://www.fiberglasssupply.com/Product_Catalog/Core_Materials/core_materials.html which has a good deal of Divinycell info which is applicable to other foams in some degree.

I have played with the idea of using balsa-core, myself, just 'cos I am kind of a wood freak, but question it’s use with regard to long-term adhesion in a highly flexed structure, besides the density of the stuff vs necessary buoyancy vs stiffness vs thickness. I don’t know that I would necessarily trust a flexible structure made with a significant amount of balsa-core.

Dr. S. has done a very clever thing with the masking tape and wax: ‘poor man’s mold release’ indeed, I’d call it clever man’s mold release. Nice thing about that is the foam is relatively accessible for modification, rather than having to rip off a layer or two of glass. .

If I may make a small suggestion, for the next one you might want to try brushing on a relatively thick layer of plain home canning/jelly making type paraffin- shades of hot-waxing back in the day- to deal with the tape edges. Deal with any brush marks with a hair dryer or heat gun…'course, you prolly already thought of this one…

hope that’s of use


Awesome stuff guys. I was hoping more people would get into this. I understand the need for wanting to make more than one. I used the same poor mans release on a male EPS mold for a kayak and toboggans for X-country skiing. Only difference is I used really cheap clear packing tape. Works great and lets me refine the shape as needed with out starting over. Never have seen the sense in making a mold for small time one-off projects.

As for the use of poly. It has good spring back. I found this out first hand when I was bending a cut out from a cockpit. 6 layers of alternating glass poly. It left a hell of a mark across my chest when it slipped out of one hand. I was lucky I kept my chine back. It doesn’t make the composite mushy at all just less brittle than straight glass or mixes with CF. You can adjust it some also by using more or less in the lay-up. Its also nice because it works well anywhere in the lay-up (works good in tension and compression), so you can hide it and not worry about sanding issues. Polyester cloth is also very cheap. If you look at the link its about the same as glass for the same weight( it only comes in 6 oz.).

Doc, I’m a wood freak also. The first 3 boats I made are wood strippers. One thing I did learn about polyester resin is that it does not wet out wood as well as epoxies. In fact the one time I tried to use it floated on top of the wood and did not penetrate at all. I’ve never used it since. You may find that a spoon with a balsa core would work/live longer if it was put together with epoxy. Constant flex may also create a shear between the wood and the glass, and cause a delam. Maybe the divinycell, would work better, but if you’re worried about the cost of epoxy that stuff would cost way to much. I have a couple of pieces for a kite board and as I recall it was very pricey.

Dr.S I’m not being critical of your project. I’m just trying to learn more. I find the more I learn the less I know.

Thanks for the input. And the pictures. Are you going to put up some notes after the first ride?


Dr S

Nice photos, thanks for posting them I have been following MOW’s threads on KSUSA, glad to see you have found some time to build your spoon, keep us posted on how she rides, how much grinding you do/do not need to do to tune the flex

Hi Mark -

First off, and off topic- composite toboggans for X-C skiing? Wish I had thought of that, but now that you’ve brought it up, I may have to play with the idea some. 'Cos i am expecting snow here like we had last year…

But, back to it, in no particular order…

Agree completely with the problems of wood, particularly balsa, and polyester resin. I’ve seen far too many balsa and other lightweight woods used as stringers fail in shear with the glass/resin laminate. The foam right next to 'em had flex characteristics more like those of the laminate and they seemed to stick together just fine.

Also with balsa, I suspect the shear between laminate and impregnated surface layer of the wood would be okay, but the shear between that impregnated wood and the rest of the wood could be a weak point.

Similar problems might arise in very thin glass-foam-glass laminates - though I note that http://www.johnrsweet.com also carries an interesting sheet foam, nylon peel-ply and even knee pad neoprene! Let alone iron-on tape and wetsuit neoprene…

This could be dangerous…

doc… hell, I already have the stuff to sew the neoprene…

This starts to get interesting

Dr. S. has done a very clever thing with the masking tape and wax”

Credit where due–got the idea from Dale Solomonson. The man is chock full o’ crafty ideas and techniques…

got the 8 pound pour foam from www.shopmaninc.com for about $17 plus shipping.

fascinating stuff , [both] Doctors and Dale !!

The waves you are riding , Dr.Strange …

I take it they are hollow and powerful , and you have a god pair of flippers ??

I wish I lived there , I would LOVE to watch , and photograph you surfing this board !! [and josh on HIS , when he is in Angourie !!

I guess you’ve probably seen the Greenough article ?? …but for those who haven’t , photos and words from THE MAN himself !! [this is from The Australian Surfers Journal , volume 2 no.2 , used without permission]

cheers !


A rare siight indeed - 3 recently constructed flexspoons. DrStrange board is on far right.

NO waves really at this point. Had it out once in Big Sur but 10 inch deep fin and bull kelp thick as your arm and dense as a rug just don’t mix. Can you say face plant, boys and girls?

Any way, it floats, barely and does catch waves well enough. The edge board with strakes and runners was later invention of GG to hopefully work in wider range of conditions. Have yet to test it out myself. Just got a 2 mil vest to put on under my 4/3 full suit as I nearly expired of hypothermia after about 1/2 hour in the 53 degree Big Sur water.

Here come the rest of the pics…

-Dam of cheap ($2.50 for 8 feet at Home Depot) molding hotglued on after coating w/ PVA release.

-filled w/ microballoons and resin at putty consistency

-then ground down and I put a layer of 4 oz over it though likely not a necessary step

-nose view showing finished strakes

-foiling lines on the deck

-whole fin set up–ordinary panel w/ holes drilled and tapped (8/32) in base. Drill thru board and attach fin over wax paper and lay up rope base. Remove and foil base. Retangular piece is about 9 layers of glass to act as lock washer on deck

-fin attachment from deck side

-fin attached, very solid feel…like glass on

-runners made from same molding as strake dam and epoxied on

top and bottom template shots. Riding report when I get some waves on it.


intelectual bliss

may the maiden voyage meet with

hot waves and amicable cohorts