Kneeboarding At 3 G's

[red]

MTB,
Thankyou for the detailed response. Startng to get a picture of how to design/build one of these - thanks.

[Scott]

Ask requested from Man O'War: a visual of his use of tin foil over the blank to
begin forming the hull--

[MTBarrels]

umm..

MTB

you are bolder than me..

coz I won't be posting any pics of what I shaped in the mid seventies ..



hart

That's one of the few advantages of getting old.

[Man O' War]

Headwax -- We're raging against the machine!

MTB -- Looks like kneeboarding has two godfathers. You're an inspiration, especially to those of us who are not far behind. Keep up the good work!

[MTBarrels]

...<snipped>...MTB you are practising what you preach..and I for one, look forward to more
hart

Since you asked...here's the first kneeboards that I built (1968-69). Prior to this I had built two surfboards, so I managed to get the major shaping/glassing disasters out of my system (I had also never seen anyone shape or glass a surfboard) by the time I got to these.




The board farthest to the left, a foam spoon ("Goon Spoon"), is the first in the series. It was built in 1968. I had never seen a Greenough board in person, or in a picture. So I had a friend who had seen one of George's describe it to me. Clearly either he didn't describe it very well, or I botched the translation of his description, or both. In any case, I didn't like the board at all (felt slow). I tentatively attributed at least part of this characteristic to the rocker in the bottom. Nearly all the rest of my kneeboards have been flat, or nearly flat, in roughly the rear half of the board.

After that fiasco, I decided that I'd go essentially the opposite route: very flat side-to-side, virtually no rocker (2" kick in the forward 9" of the board, then flat the rest of the way back), and sheet glass everywhere except where structural stiffeners were required. This was a break-through board for me. Not only was it fast and remarkably "free", but I discovered how easy it was to duck dive waves and the board would hang around when you wiped-out so you didn't have to swim ashore (the board is kind of heavy since the glass sheet consists of chopped glass mat sandwiched between glass cloth...and it just barely floats). It's name (revised after riding it a bit) is "Glass Pearl"...not because of it's translucence, but rather by it's propensity to "pearl dive" if you didn't keep the nose up ("Down the mine shaft" to you ozzies?).

One disappointment with the Glass Pearl was that even where there was only glass sheet the flex was so small as to be virtually undetectible...and after hearing about George's boards, flex was one of the things I wanted to experiment with.

Hence my next board (third from the left) was essentially the Glass Pearl with a refined planform, thinner glass sheet (but still mat sandwiched between cloth), and more nose kick. It was also an experiment to see if a lighter--but still durable--board, could be constructed without using any foam. I liked this board a lot and decided to sell some of them through the Pacific Beach Surf Shop and Carl Ekstrom's Surf Shop (Carl shaped the plug to make the bottom mold for me as I didn't trust my ability to shape the nose "bowl" for a production item intended for sale--he did a perfect job). The fourth board from the left is one of the production ones. Two of the four molds used to build the board lie to the right of the production board (white-hull mold; black-center strip mold). All in all, I estimate that I built about 50 of these (one drum of resin plus 2 5-gal buckets). I know that at least three of the production boards still exist since a few years ago a friend of mine tried to buy one from a guy who had just bought it at a flea market, and I met another owner at the OB contest this month.

The board to the far right is the "Narrow Arrow". It was an attempt to build a board to be used with large waves with surface chop. It was hoped that the combination of a narrow hull and exceptional "V" at the nose (sort of like a flattened bow of a canoe) would cut through the chop. The first time out made it evident that with the tiny planing area that it had, it needed a good sized, steep wave to get it going fast enough to support the weight of the rider and board without mushing. I rode it a few times at Blacks and North Garbage, before I gave up on it. However, Tom Pieffer borrowed it to ride La Jolla Cove in the giant swell of December 7, 1969 and said it worked great for him.

Board Parameters (Goon Spoon, Glass Pearl, Glass Egg, Narrow Arrow):
-----------------------------------------------------------------------------------

Length: 59-1/2", 54", 55-1/2", 55-1/2"
Max Width: 20-1/4", 20-1/4", 18-7/8", 17-5/8"
Nose Width: 19", 19-1/4", 17-3/4", 14-3/8"
Tail Width: 18-1/4", 17", 15-3/4", 14-1/4"
Year built: 1968, 1968 or 69, 1969, 1969

[walt davidson]

Great photos Terry (MTB) - thanks for posting - It is nice to see someone
take a different path and try so many new ideas.

If you have photos of yourself riding any of these - POST THEM -
we'd love to see them.

Best, Walt

[hart]

MTB

The central foam 'strip' seems to certainly provide a greater cradle for your knees whilst surfing..is that the reason for its inclusion in boards 2, 3 and 4?

Or did the fact you chose a fin box rather than a glass-on fin pre-empt its necessity..and hence the different approach taken for board 6?

hart

[MTBarrels]

...<snipped>...If you have photos of yourself riding any of these - POST THEM - we'd love to see them.
Best, Walt

Thanks Walt. I am only aware of about 3 pics of me kneeboarding (all from around 1973-74).

[Aside: But that's more than of me stand-up surfing. I'm only aware of one pic of me doing that (at Blacks around 1964 or 65).]

Two of those 3 pics are by Jeff Divine and taken at Big Drakes. They can be found in Surfer Mag Vol. 14 #1, if you happen to have a copy.

[Another aside: When I was at the OB contest, RW was kind enough to give me a laminate containing the two Surfer Mag pics (along with the header on the mag and some pics of the "replica" Greenough that I built --presently on loan to RW). Thanks RW!! ]

The third pic (from Baja, by Eric Jensen, another kneeboarder) is somewhere in storage along with a bunch of my early surfing stuff, and not readily accessible.

mtb

[MTBarrels]

MTB

The central foam 'strip' seems to certainly provide a greater cradle for your knees whilst surfing..is that the reason for its inclusion in boards 2, 3 and 4?

Or did the fact you chose a fin box rather than a glass-on fin pre-empt its necessity..and hence the different approach taken for board 6?

hart

The principal reason for the 'strip' (which will take on a greater presence in my later boards with the addition of formal knee wells) was to prevent the board from developing rocker along its spine while still allowing the rear portion of the rails to curve upward under the additional loading while turning (thus temporarily developing "rail rocker" to facilitate the turn). Of course, it also made it a lot easier to incorporate a fin box (although with one exception--not a spoon--I don't think any of my later boards used a fin box). [* Oops! - Correction: I just noticed that one other spoon (later in the series) does have a box]

mtb

[Bruce Blake]

The advantage of kneeboarding seems to be the ability it gives the rider to deal with tube

rides that might require too quick of a set up to get into, but might get too tight or steep for a stand-up board surfer to deal with. It seems that kneeboarding is where the best of the skill sets unique to each of the surfing disciplines "comes together."

an online dictionary seems to have the right idea of kneelos

[MTBarrels]

The attached pics show the boards built between 1969 and 1971.




The board on the far left ("Quad") was the follow-on to the Narrow Arrow (shown in the previous post). The objectives in this board were to increase the aspect ratio (width to length) and planing area over the Narrow Arrow to improve the planing characteristics; experiment with a different nose shape and kick; and reduce the weight (due to a lesser glassing schedule). As best I recall, I didn't particularly like it.

(Aside: the brown streaks on the foam are "micro-balloons"--a phenolic precursor to Q-cell. The latter works MUCH better, as well as looking neater).

The second board from the left ("GUN") was also built in 1969. For a couple of years it was one of my favorite boards. The bottom of the nose has a modest "V". As I discovered, this required that the rider "give" the board a definite sign as to which way one wanted to bottom turn if you initially dropped in straight towards shore--otherwise it would often decide for you.

The next board ("PUGLY") was an experiment with a thick (max: 3") foam board, a bit softer rails forward, and some (but not much) bottom rocker. It was intended for small/mediocre/mushy waves. I didn't find it much fun and sold it--then bought it back a few years later to keep my collection of project boards intact. In the interim, the deck tint (yellow) and bottom tint (red) faded substantially; it acquired some serious scrapes on the bottom; and a "shout out" on the deck. Some day I will have to get around to restoring it.

The board on the far right ("Pantagruel") was built in 1971 and appeared (partially completed) in Surfer Mag. It was an experiment with: a spoon-type larger board with more planing area; "deep" kneewells; a rigid "wrap-around" handle; sheet glass "hard" rails; 60/40, non-isotropic, tight-weave cloth; and a thick (1") cross-section, foam-filled fin. As it turned out, the kneewells were placed too far forward, which inhibited turning. However, it also turned out that the combination of forward kneewells, sheet glass rails, and the "U-shaped" handle made it a superb board for riding low tide Blacks sandbar shorebreak (it was trivial to do the kneeboarding equivalent of a "standing Island" pull-out). I also discovered that it could be quite easy to break one's wrist when using a strong, well-secured handle.

Specifications (left to right):

Name: Quad, Gun, Pugly, Pantagruel
Length: 53", 57", 62-3/8", 67"
Max Width: 20-1/4", 18-3/4", 21-5/8", 21-1/4"
Nose Width: 18-1/4", 15-1/2", 18-3/8", 16-1/2"
Tail Width: 16-1/4", 14-1/2", 18-1/2", 16-1/2"
Year: 1969, 1969, 1970, 1971

mtb

[hart]

The principal reason for the 'strip' ..<snipped>.. was to prevent the board from developing rocker along its spine while still allowing the rear portion of the rails to curve upward under the additional loading while turning

mtb

and why did you choose to seperate centre-line rocker and rail-line rocker?

hart

[MTBarrels]

...and why did you choose to seperate centre-line rocker and rail-line rocker?
hart

Rocker, and especially tail kick, inhibits speed. On the other hand, it facilitates turning. Carving turns (which I like) are initiated by shifting the hydrodynamic center-of-effort forward relative to the center-of-mass of the rider and board (as well as banking the board, of course)--either by extending the wetted length of the inside rail forward, or by the rider shifting his center-of-mass aft. Rail flex doesn't significantly affect the former and facilitates the latter.

On hard (highly banked) turns, most of the aft wetted area (not counting the spray flow) lies between the stringer and the inside rail (we've all seen pics of bottom turns with a single fin board in which the fin is out of the water). That increases the load on that portion of the board--both by distribution and because banking the board and turning requires that it also generate more lift in order to support the rider and board). This additional loading causes the wetted rail area of the board to flex--essentially making the wetted area act like a board with "V" in the tail, but without the adverse affects on speed when driving across the face of a wave.

[Man O' War]

MTB -- That last set of pictures is really something. Shouldn't there be a Ferrari behind them?