How To Build A Spoon

[flexspoon]

DrStrange - yes that's much more of an all-around board. Less frustration - more FUN in a wider range of conditions.

[DrStrange]

Less frustration - more FUN in a wider range of conditions.

Eggzactly what I'm after. Would love some specs i.e.:

inches of rocker and depth of hull and depthandbase of fin and how far up widepoint...


Have found 8 pound pour foam but the next one is 16 pounds. Just for fun would like to get 12 pound (will settle for 8 if need be). Anyone have any contacts for mail order foam???

I think kthe hardest part is going to be cleaning the garage first to clear a space

[AM_Glass]

The hardest part will be cleaning the garage AFTERWARDS. Foam and glass dust goes everywhere.

I'm at the same stage as DrS, I'm trying to clear out a workspace knowing I'll be spending a good about of time there.

As a note, here in Santa Cruz we have a blank distributor (Fiberglass Hawaii) that offers foam sheets in varying weights. I was in there asking when I was thinking about a thin foam paipo but since the guy didn't know what I meant I said skimboard. He showed me the catalog with light to very dense foam sheets in varying sizes and thicknesses. Anyone have 2 cents on laying out a foam rectangle, adding another layer or two where the rails would be and gluing it all together as a spoon blank?

[Man O' War]

Glass -- I don't know about that one, but I do have a very important note for you and Dr. S and any other spoonmakers: when you start glassing your hull, do your first layer with a greater weight cloth than the rest.

I glassed with 4 oz all the way through EXCEPT my very first lamination. I had some 7.5 oz laying around that I wanted to get rid of, and it looked strong, so I used it first. Little did I know.

Today, as I was grinding the tail and deck for the last time, putting more flex into everything, I had some anxiety. You don't really know how deep you're going except by feel, and if you go too deep, you might as well slit your wrists. So I'm grinding down very very carefully and suddenly I see this larger weave appearing before my eyes. It dawns on me: this is that spare layer of 7.5 oz I threw on their first. Oh, happy day! I have ten layers beneath me, and I can gauge all my grinding.

To be honest with you, ten layers was way thin enough for me. Using the larger weave as my guide, I was able to do all the rest of the grinding with what I consider no risk.

Needless to say, I recommend you do the same thing for your own peace of mind and for the safety of your precious board.

I edited this epiphany into the spoon-building steps above: the Materials List, Make The Hull, and Grind The Deck.

[flexspoon]

DrStrange - I found that picture/site yesterday - just an example.

As for the foam mix 8lb and 16lb equally until you get 12lb?? Just kidding.
http://shopmaninc.com/foam.html some info.

This is Velo.



And check the original Greek spoon - this is what I copied when I made one.
http://www.romanoskykneeboards.com/html ... poons.html



Eggzactly - egg shaped rails - a couple of my friends bought spoons from Greek after I got mine, which was like the one on Ron's site. Theirs were all downrailers and didn't work well. One was a 5'6" giant downrail monster. My friend wound up cutting off the tail to make it 5' long. 5' length for a spoon seems right.



And remember - I'm just a guy who made and rode plywood kneeboards, then rode spoons and has an opinion about what I like based on what I have ridden. And I know NOTHING about "regular" foam and glass kneeboards.

So what are the standard measurements that people use when discussing boards?

This from doc at Swaylocks: Same doc?

[DrStrange]

MOW good epiphany!!! Could also tint that layer I guess.

Thanks for that Flex. 5 inch rocker for all around board? Just a bit less hull depth than original Velo?

My plan for garage is make a big box with PVC pipe (irrigation stuff) and tape up some light weight plastic sheets. Pretty cheap all in all and should contain the dust. I figure most of the dust I'll carry out embedded in my skin.

[doc]

Same doc - like the proverbial bad penny, I turn up all sorts of places.

Now, if I may, let me suggest some kinda evolved dimensions:
(from viewtopic.php?t=1222&postdays=0&postorder=asc&start=45 )

Vintage: 1994
Length: 68 inches
Max width: 24 inches
Nose: 20.25 inches
Tail: 21 inches (twin fin, flex rail)
Rocker:
.... dead flat rear 30 inches;
.... 5/16 inch @ 48 inches;
.... 4-5/8 inches @ nose
Bottom:
.... Flat side to side at tail;
.... 3/8 inch bowl (actually more like slightly rounded/angled chines) at midpoint
.... 1/2 inch bowl 12 inches back from nose
Moderately hard rails all the way around (1/8 inch radius bottom to vertical, 1/4 inch radius vertical to deck rails forward; harder aft)

Intended Usage: Small wave board. Typically used to 1.0X to 1.5X ovrhd (also depends on hollowness)

Note that this isn't a lot of convex in the nose compared to many if not all of the 'greenough-type' boards. 'Displacement hull' is, of course, a misnomer - round-bottomed is considerably closer.

My own thinking is that too much convexity in the nose might tend to make a board which would tend to yaw a little much. As Terry notes from experiment, the water pressures forward are higher than those aft. Something to consider is that those pressures are gonna be normal ( at 90° or perpendicular ) to the bottom surfaces of the board and the more 'belly' there is in it, the more the pressures will have a horizontal yaw-inducing component ( x) and not just a lift component (y).



This could tend towards unintended torsions on the board, not necessarily a bad thing in a flex board, but also some interesting effects on angle of attack, etc, etc. Plus, of course, drag, especially way forward where the horizontal component was opposed to the direction of motion.

Something to consider, anyhow. The yaw would tend to create drag - when you think about it, a long, skinny fin with relatively little rake and a good deal of flex, especially towards the trailing edge and tip, would be a Good Thing, to minimise drag in the tail.

Though a relatively small set of twin fins might have the same stabilising effect with considerably less drag penalty. Or a cutaway base ( presumably quite flexible) quad setup like shown on viewtopic.php?t=1222&postdays=0&postorder=asc&start=30

Something that's kinda interesting too is the possibility that part of the board forward might be verging on stall conditions while the flat sections aft were still planing.

Greater convexity in the bottom should, theorteticly, be more 'chop friendly'- though the height of the chop would be less than the depth of the convex section for this to be of great use.

My own thinking is that something which offered as little resistance as possible is the way to go, combined with a relatively simple bottom contour. We shall see, I guess......

doc....

[Man O' War]

Doc,
Since you're talking board specs, have you seen Hart's sketch over on "New Beginnings"? What do you think? He's getting some commitments out of the way, then diving in.

Good luck with your board.

PS. I passed you up in no. of posts. Better get on it.

[DrStrange]

One thing I've read re bottom contour is that the convex hull part tends to pull the board up the face (would that be the yaw) and the fin tend to force board back down face and the interaction of those two forces is partly what gives the board its pocket hugging speed. That may all be irrelavent in smallish low powered waves and what you want there is maximize planing. If that's true, maybe ideal for small wave "spoon" would be a fish type bottom rails and rocker dished out for flex.

Personally have ridden lot of hullish foot boards and really like the thru the water feel they have. The deeper hulls are definitely slow in weak waves though all my footies had rocker in back except one and that was more a triplane (wide middel plane, narrow ones at sides) and that was dang fast in most anything over 3 feet or so.

Today's fantasy is about 4 inches nose rocker, flat in back, wp about 2 inches up and moderate hull i.e. maybe about an inch to 1 1/2 inches deep at widepoint

[flexspoon]

What is the advantage (or perceived advantage) of width in

1. a foam kneeboard?

2. a spoon?

I'm asking because I really don't know

and

I never considered having a spoon over 20.5" wide until I got
the Project Velo board, which is 22" wide. And I never considered
or have owned a spoon over 5' long. That's for a 5'11" rider
between 180-200lbs. Just something to think about.

Kneeling on a 19.5" wide board

[hart]

Hey flexspoon

good pic..

but there is a lot of you that I can't see?

I can't imagine what is happening behind your knees when you are surfing..

other than grab

hart

Is your body (or parts of it) in, or out of, the water?

because it sure looks like it would be..

wet

[doc]

ah.... maybe three or four forums I work/futz with, and they all have some subtle differences in how they work....... and tackling several answers at once isn't gonna help. Ah well, bear with me...

Lets see- Hart's sketch I haven't seen - 'new beginnings' I'm not quite familiar with..... could you give me someplace to aim at with that?

Something I should do a little search for is some info on Terry Hendricks' 'home made shaping machine' as he described it in the '3Gs ' thread - also some similar on Swaylocks - as I trust my ability to cut/make templates and guides a whole lot more than I trust my ability to shape relatively featureless foam to good tolerances.

Couple things I was thinking about after that last post;

First is this, and pardon the lead-in I am about to give

See, back at school, one of my professors and I were standing around thinking about helicopter design. Yes, they had helicopters then.

Consider a helicopter - the rotor tilts, the blade pitch can be changed and so on. The lift of the rotating wings is thus a variable which can be adjusted.

Okay, but consider it as it moves forward. As the blades of the rotor go around and around, the one going towards the tail of the 'copter is producing less lift ( it is going slower relative to the 'copter) and the one going towards the nose is producing more ( 'cos it is going faster) . How do you design it so they get tweaked and produce equal lift instead of slowly leaning over and falling out of the sky like a drunken bat?

Tricky engineering problem. Forward speed is a non-constant, so how do you account for that. We played with the idea for a while, came up with no satisfactory solution. And then later that day I was still thinking about it and came up with this -

You don't build that compensation into the rotor design. You have a pilot and he compensates for the asymmetric lift. Prolly without even thinking about it.

major 'duuuh' on my part.

Similarly, you hear somebody say 'so and so could ride an ironing board' and do well with it. Well, yeah. They can futz with their balance, etc, to compensate for the oddities of the thing.

Now- let me put forth the proposition that no board on a wave is travelling in a perfect straight line that is paralell with the centerline of the board. There is always some yaw, something going on. But there is kind of a dynamic ( and quite likely unconscious) control going on, or compensation, so that the board and rider are on a straight path.

Now- thinking about a spoon-nosed board - and being too lazy to do a 3D drawing, I'll try to fake it -



For a board travelling along, you have resistances. They vary with the shape of the board that is presented to the water at that given point - the water hits the surface at angle 'a' at that point. We can deconstruct that force into vectors, as shown above. R being the force vector operating in the direction of travel, L being that part of the overall force generating lift and what for lack of a better term I have called H, a force vector acting perpendicular to the direction of travel and causing yaw - that is, the drag that would cause the board to pivot.

Now, this is an oversimplification, of course. And there are a zillion different points like the one noted, each with their own set of resistance vectors. The sum of them all gives you the total forces acting on the board.

This H vector, by the way, is precisely what Dr Strange is describing - a tendancy for the board or at least the nose and other convex parts of the board to be pulled up the wave face. The center of mass ( which gravity is acting on, making the board go ) is not lined up with the center of resistance.

And the faster the board goes, the more lift is generated and the less of the convex part of the planing hull is in the water. As Terry confirmed by testing, water pressures are higher there and so this part will get lifted first.

( another major 'duuuh' on my part, as the ramifications of his test results sink in. I get there, but awfully slowly. 'Glacial' comes to mind.)

As an aside, in a board with just rocker, no spoon to it, the H quantity falls away to zero.

Ok, what is the result of all this?

Well- lets go back to the analogy of the helicopter pilot -he is happily bebopping along in his Sikorsky, compensating for the asymmmetric lift of his rotor while the helicopter is moving forward, and doing it without thinking about it.

Similarly, lets take somebody going along a wave and going in what we'll call a 'straight line'. The doodle below is a horrible oversimplification but it'll do...and I really have run out of drawing ability.



Okay, the center of mass which is driving the board is lined up with the center of resistance, and that line connecting the two is paralell with the direction the board is going. You've seen boards going along a wave, and the immersed section of the board is never a nice slice paralell to the centerline, it's always angled. It varies with every board, every wave, indeed to compute it would take One Hell of a Computer, like the modelling they have used for America's Cup boats and large naval vessels.

Also - the force exerted by gravity on that mass isn't as nice and simple as I have doodled here.

Things that can probably be ignored include the flippers in the water - their blades are gonna be paralell to the water surface and so the force acting on them will be more lift than anything else, little or no force acting to slew the board around or slow it down unless they are very, very hard rubber and at quite an angle to the horizontal.

Anyhow- that's about as much as I want to think about this just now - need more coffee, I think... just to lubricate the mental bearings, as it were.....

doc...

[DrStrange]

Don't know enuf design to really make intelligent comment on Hart's proposed.

I definitely am hull/convex bottom positive. Flat across middle for most of board essentally a triplane, egg rails. Up front the roll under the rail essentially is contiguous w/ belly. The roll gets gradually shorter (across width of board) and less as go toward tail. Back 1/3 or 1/4 of board there is little to no roll under rail with smooth transition to 60/40 and gradually bring in a VERY tucked under edge. Makes for a very forgiving and smooth riding board. I am not a high proformance surfer, bit of a kook actually, and like my sticks to forgive my sins.

My impression from all that's been here before is that Velo original had 5" nose rocker and 2 inch or so deep hull? Good for juice waves starting to work at shoulder to head high and really waking up in overhead lined up powerful surf and good to 15+ foot faces even inside Sunset. I'm hoping for something that will work in NorCal good waves but have a bit less range on the top end and more on the lower end. SOOO, keep rocker near 5" and make less deep/extreme hull? Or also reduce rocker? Don't know enough about what makes these boards tick to know. My thought would be to reduce rocker a bit too but don't want to be flailing when the surf gets pumping. Will be riding conventional fish in small surf most likely for at least awhile... Any takers on giving cheap advice? This will definitely be a hull, egg rails etc. The lower railed approach will be for future expericments. Like maybe a traditional fish dished out to full spoonishness some day.

[Flexman]

.

[surfhorn]

Dr. Strange - when you build your sheet plastic shaping room there are a couple things to think about. You may want to tack on a little room where you can change out of the shaping clothing. Once you open the spaping bay door, foam/glass dust goes EVERYWHERE. Overlap your plastic doors -a lot- not just cut to fit; you have to contain the dust.

Check out a shaper when they walk outside into the sunlight. There is a trail of 'pixie dust" floating behind him.

Make sure you wear long sleeves and tape up sleeves and all opening with masking tape so the dust doesn't intrude. Same goes for your head....hat or some type of covering. And a mask - don't scrimp; buy one with good, changable filters.

I've been around fiberglass manufacturing all my life (1950's with boats and then surfboards starting in the 60's) and its a nasty business.

But good luck and have fun!!