Facebook posts: length: width ratios

[bgreen]

7 September, 2022
https://www.facebook.com/groups/paipobe ... 149590080/

Looking at the dimensions of kneeboard influenced bellyboards got me thinking about length:width ratios. A 60" x 24" board, which seemed wide to me, has a length 2.5 times the width. Steve Artis' board 66" x 23" board, has a length 2.9 times the width. My 52 x 21" boards are 2.6, the same ratio as the most extreme bellyboards I know of, Jeff Chamberlain's mega platter 73 x 29". I know some will throw their hands up and say shaping isn't about numbers, but it does suggest seemingly different boards might have more in common than supposed. Rider height to board length is a different matter.

Rod Rodgers
How about those ratios for alaia-style bellyboards and UK-style bellyboards?
And then there is the "perfect aspect ratio" for speed, 2:1 (Lyndsay Lord, "Naval architecture of planing hulls"):
https://mypaipoboards.org/pubs/BookSummaries.shtml...
An Annotated Bibliography of the Paipo Board
MYPAIPOBOARDS.ORG

Bob Green
John Elwell would say, as you did, go read Lindsay Lord. If I do my sums as aspect ratios - 24/60 = 0.4, 23/66 = 0.35, 21/54 = 0.39, 29/75 = 0.39 which are all pretty similar but as Keith points out lower than a body board. As for alaias, Tom Wegener made me a board which from memory would be 18/50 = 0.36. This may have been wider than most, so say 16/50 = 0.32. Taking the measurements from the Timewarp UK BB site 12/47 = 0.26. Interestingly Andy Bick's board at 20.5/47 = 0.44 is closer to a bodyboard, but not a typical UK BB, many of which seem to be ridden in whitewater.

Keith Usher
Simmons first and Godard later had "golden ratios" for what was the fastest board. But what they gain in speed they lose in turning ability. 2.5 and 2.9 are pretty far apart. A standard bodyboard is about a 2.0 ratio at 21" wide by 42" long. If you made that 2.5 and 2.9 they would be 52.5 and 60.9.

Bob Green
Don's post made me recall what Larry was seeking, which was speed, he was also into maneuverability, but said he wasn't really a tube rider. Based on Larry's boards, my initial designs were very fast because of the flat bottoms. Adding a more standard surfboard foil and concaves, they slowed down a bit but were better in tubes. As we come from different surfing backgrounds we likely differ in what we mean by maneuverability.

Keith Usher
By "turning ability" I simply mean how easy a board is to get off a straight tracking line.

Bob Green
My avatar is a photo you took of a great day, I'm sure we drew different lines. I've experienced tracking where I want to go one way and the board doesn't, I see that as a bit different as just going so fast it is hard to break from that line.

Rod Rodgers
breaking the line isn't just a function of a single design characteristic. Sometimes smaller skegs are needed, sometime more kick in the tail rocker, sometimes a different rail edge. Or, with bellyriders, a quick fin in the water in the direction you want to drive.

Bob Green
The situation I have in mind doesn't happen often and usually occurs in specific circumstances - a very long, steep wave, strongish offshore and going superfast, riding high in the wave where you are in the power spot.

Rod Rodgers
I recall it was an issue with your Bonzer Paipo. I went through a skeg trials and reduced the center fin and the large runners with small runners, and it turns on a dime in Pacific Ocean waves (other design characteristics make my Campbell Bonzer less effective turning in the USA East Coast wave and many of my Puerto Rico breaks).

Bob Green
The bonzer was different, the issue was more the first scenario and as you say, fin position and type are the solution. Jeff Quam recommended a more raked fin, with less area than the true Ames fin it came with. More recently, I have ridden it without the centre fin.


Rod Rodgers
Did you ever find a sweet spot on your Campbell Bonzer? I recall our being different in several respects.

Bob Green
It's been a couple of years since I last rode it and then that was the first time in a while. I left it down the coast to ride, but a lot of places involve a longish walk so I opt to take lighter finless boards. I've had the handle removed and some of the weight taken of it. A ride report is overdue.

Rod Rodgers
How long and wide is your board? Mine is 50" x 17-3/4" x 20-3/8" x 19" x 15-1/2" and 1-7/8" (thinner in the twin concaves), and has less rocker than yours. It weighs 7.8 lbs. with 4 runners and 6" center fin; 7.0 lbs without fins.

Bob Green
I'd have to check next time I'm down south. I think it was pretty similar to Robert's 4'6" board.


Don Boland
Hi Bob your post on dimensions/proportions is thought provoking as is Keith’s post from the bodyboarding angle.
With the aid of computers my boards are step ups. When I began surfing again I just wanted to get the same feeling as before.Pino and I having discovered a new thing (for us)are now on a path still influenced by past surfing experience but now coming from our new surfing experience.
Pino and I have boards some are epoxy.some are PU and some are stringerless .It would be good to get Keith’s views on different materials.
PS I guessin we all want Speed and Maneuverability

Rod Rodgers
I fall into that category in wanting speed, maneuverability and speed from maneuver. Of course, all of that is the ride. Equally important is paddling out to the break (those 100+ yard paddles), duck-diving and wave catching. And, tangentiating a little here, 'Socrates teaches that a man must know "how to choose the mean and avoid the extremes on either side, as far as possible." Furthermore, Plato asserts proportionality's relation to beauty and goodness. That is why our boards have curves unlike Lord's rectangular slabs.

Rod Rodgers
My average aspect ratio is 2.4. The Lyndsay Lord "perfect ratio" for speed is 2.0. An alaia example might be 4.1. The boogie-style board as Keith noted is 2.0. A longboard is in the ballpark of 5.0. Then all those other confounding design elements come into play: plan shape, rail, rocker, thickness, bottom contours, skegs...

Damian Coase
Great discussion and some other important variables may include paddling power, or lack of, duck diving ability and wave size, shape and power. I find the in depth analysis on this site so refreshing. If I post on the kneelo page I might get a nice board or cool spray comment but you guys want to know dimensions, fins or no fins, why they are where they are, and a whole lot more. So many valid and diverse opinions. Keep up the good work

Rod Rodgers
yes and it helps when we provide a context while discussing design aims and outcomes. For some riders being able to easily duck dive means everything to a fun session whereas others can have a very floaty board if there is a paddling channel or you go to the surf spot on a boat.

Bob Green
Rod's paipo forum has lots more information. It's not been very active in recent times but has included input from people who don't use FB but are knowledgeable, inventive or curious: https://mypaipoboards.org/forum3/ Besides posting stuff, we collaborated on the interviews, which are also a wealth of diverse views on riding prone. There is more to be found on the site, which contains a lot of articles (with a bit of crossover with early kneeboarding at the Wedge), which are worth delving into, as well as stuff Rod has collated.

Rod Rodgers
There are two parts on the domain mypaipoboards.org, the main site and the paipo forums. There is also a header link on most pages (but not on the forums) for searching across the main website and the forum. There is also a search capability within the forum itself.
https://mypaipoboards.org/SearchMyPaipoBds.shtml

Elijah Baley
My first plywood paipo that I rode many years was super fast. It was 40x120cm, long and narrow, completely flat bottom, no rocker. So yeah it was really fast down the line, but I have to admit that the maneuverability was kinda limited. I could turn it for sure, but not as much as my new fiberglass paipo, which is 38"x18" with a slight rocker. On this shorter paipo I rediscovered more of a bodyboard feeling, I can really turn hard and quick. But it's a trade off, as it is a bit slower. I feel like the part of a board that is bellow the waist can "disturb" the turns in a way (although it helps to go fast). It's really of matter of preference.

Another aspect of the perfect ratio is ... the look of the board, will its ratio make it a nice beautifull wall hanger or not ? It's very futile but I have to admit it is part of the equation to me. I spend way more time just looking at the board in my living room that actually riding it in the ocean, so I need to admire it .

[bgreen]

Joe Mac
26 September 2023
·
https://www.facebook.com/groups/paipobe ... 534225080/

Question for everyone.I’m seeing all different length boards on here. I’m wondering what the advantages are to a longer board that’s maybe over 4ft. Can you still kick into waves with a longer board? Just trying to get some info because I might have one made. My boog and surf mats are much shorter than 4ft.

Matt Pierce
Less ball slap on bigger waves

Joe Mac
any easier to get into small or mushy waves?

Roger Harrell
Google Australian Gutslider surfboards
I myself ride longer boards because I don't use fins & at my age I don't go out when it's big anymore

Larry O'Brien
Once upon a time, surfboating was popular in Massachusetts.

Joe Mac
I’ve never seen that but I was at Horseneck Sunday.

Larry O'Brien
Fish board at Nantucket, Massachusetts in 1932, decades before the fish board was reinvented in California in the sixties.

Stephen Newbegin
Besides the argument over what is a Paipo and Bellyboard the answer is it depends on you and what you want. You may have started surfing and cannot surf anymore. You may have been a kneeboarder focused on speed and tubes but realize knees do not last forever but addicted to the adrenaline. You may have been a body surfer or raft rider and found using a tiny board gives you more speed. Maybe your a boogie boarder and like no board fins and safety of foam but want more than production boogs. You may like crafting your own designs and wood can be both fun and beautiful. So you are a surfer who cannot stand anymore but do not like swim fins or a surfer whose shoulders are done and want float with swim fins to catch the waves. Rule of thumb depending on your body type is if you use swim fins the sweat spot for float, speed, catching waves is 4' 6" to 5'3". If your just into wave intimacy and low float catching waves inside and easy duck diving 4'5" and lower is the thing. Another big variable is what type size waves do you ride.That is what makes this group interesting because maybe you try something new or stay with what you are comfortable with.

Joe Mac
ok now we're talking. I've been a prone surfer for a while. Love my fins. Boog, mat surf and bodysurf with hand plane. I also surf on a SUP because the beach closest to me has mushy waves and its a good place for the SUP. I guess I'm looking for something new but also I'd like a board that I can catch waves on the outside and goes fast. I do go out when there are overhead waves but I'd say more often than not it's 2-3 or 2-4ft and mushy. I think it sounds like around 4'5-4'6 might be good?

Keith Usher
I have come from 20 years of bodyboarding to finless paipos, i used my fav boog as a template from my paipo, so my board ended up due to a more pointed nose 43" from using a 42" boog as the template. If you are a competent boog rider I think anything bigger is just a hinderance and not needed. I also have a CNC machine cut file for my board if you want it.

Joe Mac
interesting. I would definitely say I’m competent.

Joe Mac
do you make your own boards? Are there fins on that? The reason I’m not going wooden finless is I like the security of something that floats. I also really enjoy sitting on my board in between waves.

Keith Usher
I shaped my first board about 7 years ago with the help of a shaper friend and then he glassed it. I then tried about 4 more versions only to find out that I had got it right the first time. I then had that original board measured and made into a CNC file for future board cuts by machine , I am now riding board 2 which was cut by machine and it rides just like board 1. (board 1 got heavy use and had to be retired) Its around 26L and floats me just the same as a 42" boog. its is finless and has a single concave inside a V hull. Its is faster and holds a rail in a barrel better than any boog I have owned, works in surf from 1ft to over 10ft, I have still yet to find its limitations. In This video i'm on one of the board i did not like as much up too 4,00 then on the good board after that. https://www.youtube.com/watch?v=QO3cPlQP3Cs...
Pointbreak paipo

Stephen Newbegin
Your coming from smaller boards up. You are tall and can definitely go longer. You can get more float and still sink your fins for getting into waves early. I am shorter than you and I have prone boards up to 5'8" but my highest performance prone board is the smaller orange fiberglass board I highlighted if you click on my old discussions. Of course I am an old kneelo who gets a rush prone in high speed 3-4 foot tubes now. I have plans to have a custom board built that will look like nothing on these pages but I have no idea if it will work but that is why exploring is so much fun.

Joe Mac
Do you find you can into waves nice and early on your paipo's? Out with the longboarders and SUPs?

Stephen Newbegin
Funny you should ask. I went out for the first good size waves today at two different places and times. I took out my really great Orange one. The place is usually crowded and the surf was pumping with no crowd at all. Of the surfers there most all were clustered at the peak. They claim it was 1-3 foot swell but the normal sets were 4-5 feet. The waves were backing off for many long boards and the short boards were taking steep late takeoffs. I notice when the biggest waves that came in it was mostly overhead 6 feet and closed out at the main peak. I picked the spot north of the peak that was the only place you could take off if you were at the right place and took off like it was going to break on your head. I have really strong legs and wear duck feet. I have the float and planing surface that allows me to move like a long board but even greater ability to make late take offs. I caught five of the biggest waves that session at the break that no surfers got. When I kicked my way into the vertical drop, I have the ability with this board to immediately turn into the breaking wave without having to make a bottom turn and maintain full speed the whole wave. Most surfers would not make this and definitely not any Paipo board or boog I have seen. I just wish I had pictures you could see since the biggest waves I made needed no cutbacks until way inside. After so many flat days I am beyond stoked right now.


Stephen Newbegin
I got asked three times today if I had a kneeboard and I told them it was a Performance Paipo.

Keith Usher
I also see it this way, a stock performance stand-up shortboard is 5.10. and a performance boogie is 42". so if you go much longer than that you will be paipoing an midlength/minimal and the same performance losses will happen. I think if you want to retain performance in a paipo but catch waves weak waves its better to go wider and thicker, length will just make turning harder and put board out infront of you thats volume in the wrong place. they dont make long bobyboards for a reason.


Rod Rodgers
very well stated. There are many answers for many different riders due to their own condition, waveriding experience, wave judgement, style of riding preference.
I ride foam/fiberglass boards with skegs. I use swim fins. I have ridden a 50 inch board since 1968 (even though my weight is 80 lbs greater than my 15 year old self. Many reasons for 50 inches, but as a practical matter, this is the length I can be mounted on the board and leg paddle without clipping my knees.
Width and thickness and plan shape and skegs are varied within a small range. To catch and ride weaker Florida surf my go-to board is thicker with a full profile from stringer to rail. For tropical reef power I ride a slightly thinner board.

Steve Wall
Fascinating content in this thread Port Macquarie Surfing Museum

Bob Green
It depends on your height. Larry Goddard reckoned the ideal length was about 3/4 of your height. There will be a tipping point where you go too long that you have to move around too much to kick and the nose is pointing too far up. Arm paddlers tend to like a longer board but are more likely to have their fins further forward, if finned. Finless on a longer board, you are also more likely to lose some tail/rail connection if you are too forward.

Joe Mac
I’m 5’10. 3/4 is 52 inches I think. 4ft 4? I definitely don’t want something too long.

Bob Green
I'm the same height as you. 54" is my standard,. My first NoFin that I got from John Galera was 57" but had a rope handle, which allowed me to lie a bit further back and get leverage from it.
No photo description available.

Rod Rodgers
roughly the length up to your sternum, or bottom of the chest. Also a 5'10" and for me that is 50". Some variation depending upon one's upper body/lower body ratio.

John Morris
I've been transitioning to prone for a couple of years after nearly 60 years standing. I'm 5'10 and about 168 lbs and was never any good body surfing. Five joint replacements starting in my mid 50's. I wear flippers but my kick isn't very strong so I trade off paddling with kicking. First prone board was too big at a high volume 64 inches long. Great for arm paddling and surfing low energy waves. I've progressed to a low volume 4'11 and feel like I'm now at the low end for efficient arm paddling. No idea what the volume is in liters, but maybe comparable with what the pro tour surfers are riding(?) With all my boards I mostly kick around to get in position and do the tail dip followed by quick arm strokes to drop in. The 4'11 board needs some juice to get going and all take-offs are late. But duck diving is a breeze and pulling through the back in close-outs has never been so easy. I'd say expect to try a couple of boards before finding what works for you in the waves you've got. I generally show up with more than one board, a boogie and a mat in the rig.

Joe Mac
thanks. I think you’re right. It could take a few tries.

Bill Wurts
I believe Thomas Haugh in this group has a formula for determining needed size and volume based on rider size.

John Morris
I have notification of a response to my recent comment, but can't find it. A 'formula' is just numbers, what is it based on, do you know?

Bill Wurts
For Thomas Haugh, no. For me with flat-bottom hulls, it is the Lindsay Lord Planing Hull aspect ratio of 0.4. I use thickness with XLPE for stiffness. However, I like more buoyancy for arm paddling.

John Morris
tHere are some photos of people whose arm stroke is undoubtedly better than mine. I feel like board width over 21" starts to interfere with my stroke. I estimate that the distance between inner arms of these swimmers is even less.

John Morris
Board width vs human anatomy.
No photo description available.

One more.

Bill Wurts
I don’t find 22” width restrictive — don’t really go over that. But for paddling a board, my stroke is different than for swimming.

John Morris
Two shoulder replacements here, preceded by two shoulder repair surgeries. I never had any swim coaching or other feedback, but my paddling style felt better and resulted in less soreness with boards under 22" wide. Going with Lord's .4 ratio that means a board 22" wide needs to be 55" (4'7") long. But my shoulders are happier at 21" wide which equates to a board 52 1/2" (4' 4 1/2") long. To get enough volume for arm paddling something that short requires a pretty thick board. With a concave deck the rails would have to be even thicker.

Bill Wurts
I can see how width might your paddling.

Martin Hallen
I am 67, 6' 1" , 130Kg (285 lbs) and ride 6' 6" boards. My old kneeboards were under 6', but I need the extra length these days. use both fins and arms!


6'6" in indo - Photo : Shayne Nienaber

James Lintott
I use a 6' classic Gephart Fish, ridden prone. It works fine, and the length is an advantage on fast, steep waves. My take-off technique is centered on sticking the wide tail down deep into the water. then leaning forward, as I feel the wave start to pitch, at first, the fins are used, then pull your weight forward, the aft end of the board acts as an underwater oar, and it really helps push you over the edge. I use fins, and webbed gloves, for paddeling out through the surf, and for the take off. too, I like to go fast, and it can be done. My next board will be a 6' 10" "Long Fish", shaped by Michael Miller (San Diego). I have already rode one, and it went really high, and is a very- tube worthy design.

Tom Wolverton
Do you wear flippers?

James Lintott
I do wear flippers, and webbed gloves. Those can be used alternately, to conserve energy, while paddeling thru waves.

Bill Wurts
Thomas Haugh told me at Swaylocks, based on his design parameters, that a bellyboard for my height (5’9”-5’10”) and weight (170-180 lb) would be, ‘49" long, 21.5" wide, and 21L.‘ This was very close to what I had built for myself, except the one I built has more volume.

John Morris
He has computer programs to determine volume, but what is the basis for determining dimensions such as length and width? You don't mention thickness, which gets trickier with a concave deck. 'Length of vessel' is a factor in speed through liquid and width affects arm movement for paddling, among other things. So why not longer and narrower if it results in the same volume?

Bill Wurts
I have no idea how Thomas determines lehgth and width. If you know length and width, in general, volume should give you an estimate of thickness. Among other things, length affects spin radius. Aspect ratio is an important factor. The benefits of a Lindsay Lord 0.4 Aspect Ratio are decreased resistance, increased load capacity and reduced percent wetted surface. One primary benefit is speed.

John Morris
ep, familiar with the planing hulls L and W versus drag formula. But recall that the test conditions were very controlled and did not take into account the dimensions of a human body. One thing I can claim based on a few years trading off between mat, 42" boogie board, and paipos between 59 and 64 inches, is that the paipos allow for the sort of moves I know from my days standing. Running out onto the flat before bottom turning, floating across the top of a collapsing section are just two maneuvers the longer boards make possible.

Thomas Patrick Surfboards
Bill Wurts let me add some clarification...From longboards to cafeteria trays to handplanes, every prone rider choses his/her own vehicle with which to ride waves. Every prone-ridden shape has its own set of riding characteristics that are a function of shape and size. These characteristics interact with similar characteristics of the rider to produce the experience of prone riding. Choosing a specific shape will in many ways define the rider’s experience; choosing an inflated mat will yield a much different surfing experience than choosing a plywood paipo board. Notice I said “different” not “better”. Having spent years riding Tom Morey’s invention, the “Boogie”, I chose this shape as my preferred prone-riding basic shape when I embarked on producing prone boards. I was so familiar with the fit and performance of the boogie, but, then I was exposed to the designs of Larry Goddard. I quickly saw the advantages of foam core & fiberglass shell construction, and those FINS! I was hooked.
My first prone board was handshaped from a polyester-foam “fish” blank and using Goddard’s published dimensions and outline. After riding this board, I made another board incorporating changes I felt would improve performance. Thus began my journey of trial-and-error development which culminated 40-50 prone boards later in the T-Belly Generation 7. My basic design goals were (1) a length that would allow me to kick-paddle the board while remaining in max trim position and simultaneously able to keep my elbows on the deck and still reach the nose. I wanted to be able to go from a kicking position to a riding position with little or no movement on the deck. And, (2) I wanted the width to be just great enough that my body from hips to head and from side-to-side rode on the deck without over-hanging and causing drag. And (3) I also wanted enough volume to enhance paddling but still be easy to duck dive and I wanted the volume to be in the right place. These requirements lent themselves to being derived from the rider’s dimensions, i.e. height and weight. After determining through trial-and-error what I found to be ultimate length and volume for the shape for me, I determined numeric ratios so that I could design the most appropriate T-Belly shape for any rider’s given height and weight. Key to this process is the availability of the CAD program Aku. It allowed me to tweak volume flow and make minor adjustments to width and thickness while holding length constant, and maintaining all of the bottom and deck contours.
43 w43 weeks ago

Bill Wurts
I did not know the specifics of your calculations. But I felt they were relevant to this discussion. So far, I like the modified Lis Fish template with tail channel I use, at 3” thick — kneeboard/bodyboard hybrid.

[bgreen]

Bob Green

23 October 2023

https://www.facebook.com/groups/paipobe ... 375660080/

A long but hopefully interesting post. Below is an e-mail from Thomas Patrick Haugh. Here is an interview with him: https://mypaipoboards.org/.../PatrickTh ... 0821.shtml I was asking him about the differences in the foil of a BB and KB. Some photos from FB highlight where a KB turns/trims from and a bottom turn prone by John Galera. Thomas wrote: "I started shaping kneeboards about 5-6 years ago. A prone-board customer of mine was also an avid kneeboarder. He was constantly asking me to shape him a KB, which I declined to do, having no personal experience riding KB (as you probably know, I’m very reluctant to shape anything I don’t personally ride. It goes against my build-test-build-test shaping philosophy). I finally gave in when he proposed that I build him a KB based upon my G4 prone-board.
At the time I was also following the typical Aussie KB fin-placement, which pushes the fin cluster forward about 4 compared to a standard shortboard.. I dubbed the first KB based upon the G4 as the MPH which stands for modern planning hull , and it was essentially the G4 stretched out to 5-10 x 23-1/2 (coming from a non-Kneelo perspective, I was shocked at the time by what appeared to me as an excessive width. But who was I to argue with an experienced Kneelo?) I tweaked the outline to accommodate his requested Aussie-style fin placement, placing a wing/flyer just behind the leading fin box.
Here's what I’ve learned: Rider position on a kneeboard is very different from both surfboards and prone board (obviously!) but especially with regard to turning. Surfboard and prone boards are turned by weighing the tail and simultaneously shifting weight in the direction of the turn. It is much more difficult for a kneeling rider to shift weight far enough back to sink the tail. This was not an issue for the original Lis-style kneeboards (precursor of the fish) which had a relatively straight rail-line and were surfed in a more flowing, drawn-out turn style. As surfing style progressed and shorter-radiused turns became more in demand, kneeboards had to adapt. The adaptation was (1) increase curve in the outline and (2) move the fin array forward. The primary way to increase curve in the outline is to widen the center, hence the 23 + width of contemporary KBs. As a board is tilted over onto its rail, rail curve reduces the amount of contact that the rail has with the water.
Yaw is the term for the horizontal rotation of an airplane or ship around an axis that intersects its center-of-gravity (COG). Yaw is controlled by the rudder . Surfcraft typically don’t have moveable rudders, but their fins act as static rudders. Moving the fin array forward places the fins closer to the board’s COG, allowing for quicker changes in yaw. It also places the fin array where the kneeling rider can apply maximum pressure. In general, I find that turns on a kneeboard feel much flatter and pivot-y than turns on other surfcraft. (Not to say that full rail turns don’t happen or can’t occur.) So, I see the forward location of the fins combined with the curvy outline as a compensation for the rider’s inability to shift weight back far enough due to his static kneeling position. I find it important to also have the wide-point behind center, shortboard-esque , and the combination of fin location and WP location creates a pivot point for turns that is close to the rider’s position. You can see the same dynamic in the shape of surf skis , surf kayaks and other butt boards , where the rider has a fixed position on the deck. These adaptations are all done in service of shorter-radius turns. And, while you can kneeboard successfully on the old style parallel-rail, fins back fish-shape, the contemporary shape accommodates a wider range of surfing styles.
More volume forward of center may be helpful for paddling, but then the question becomes how much and how do you add volume? Increase width? Increase thickness? And how does the thickness flow impact the board’s performance. Less volume forward of center reduces the swing weight; it’s like swinging a baseball bat from the fat end. This distribution favors turning over paddling, although only slightly if not done in the extreme.
Attached are a couple of photos. The yellow board is my current ride 6-0 x 23 x 2-5/8 37L. The other is the board I shouldn’t have sold MPH 5-9 x 23 38L. Lastly, I use the fin setting specs from Hanalei Fin."
Assuming a finned shape, I still put as much curve in the outline as I can, and I push the wide-point even further behind center. Then I align the fin array just below the "hip". Trailing edge of quad rear fin usually lands about 6" up from tail. Twin fins a couple of inches more. All of the turning action takes place in the rear quarter. Finless requires as much rail line as possible for hold, so I keep a relatively straight rail for finless.

Rod Rodgers
Nomas Tomas also mentioned with regards to "float distribution" in the foot surfers boards in trying to keep a 25%-25%-25%-25%.

Bob Green
Further, Nels Norene directed me to David Parkes site: https://www.parkesaustralia.com/KneeBoards.htm where there are many impressive kneeboards. However, the board I liked the most was a throwback to the 70s by Peter Ware. This isn't surprising as this was around the time the influence of bellyboard design on kneeboards declined, so this board is more reflective of a BB.

[bgreen]

Thomas Haugh
29 July 2023

https://www.facebook.com/groups/paipobe ... 729475080/

Haugh29July23a.jpg (64.32 KiB) Viewed 1264 times

Haugh29July23.jpg (27.03 KiB) Viewed 1264 times

Haugh29July23b.jpg (23.05 KiB) Viewed 1264 times

There seems to be a d interest in both kneeboards and prone boards in this group, and rightly so. There is a natural common ground between the two types of craft due to the rider assuming a non-standing position in each case, and relying on arm paddling and/or kick paddling for propulsion when not riding an actual wave. What I wanted to present today was an example of how my design thinking on prone boards was successfully transferred to kneeboards. The images below are scaled photos of my 5’9” MPH (modern planning hull} kneeboard and my 49” T-Belly G5 (fifth generation). Both shapes have a similar outline, deck concave, rail shape and belly-to-flat-to-double exit concave bottom contour. Likewise, both shapes are quad-finned, although I have built twin-fin versions of both. The tail configuration differs between the two due to rider location when surfing, and width of tail (wider tails benefit from a split-tail design). Both shapes have similar performance characteristics; speed and hold on steep faces. Likewise, they are both best suited for smaller waves, in that they tend to develop too much lift in larger waves resulting in a loss of control.

Sean Catlin
Wow love them

Damian Coase
I like your thinking.

Ryan Titilah
Looks great for Emma Wood

Thomas Haugh
yes, but even better up at Pitas...

Harlan Fujioka
I am/was a kneeboarder but am using some of my kbs as I call them gun paipo. Many of my boards are 6’0” but having an issue with one of my knees I just paipo them. Some work better than others.

Tom Newton
So what changes do you suggest for larger waves. Have already ridden mine in some fairly solid peaks. Can handle getting slightly airborne. It's any amount of chop in the wave face that can bring me undone.
No photo description available.

Thomas Haugh
My shapes and most prone boards are basically planing hulls, made to generate lift. Lift increases with speed, and speed is mostly a function of gravity (of course there are other factors , e.g. surface conditions, wave shape, etc) So, sliding down a big wave generates more speed than sliding down a small wave. But the wave is also moving towards the beach and there is significant water flow up the face, so there is a vector of forces which impact speed. "Bigger" is such a relative term, but I find wave size in the "overhead+" range to be the strating point, The craft must be in contact with the water to allow control. What I do to compensate for the excess speed and accompanying lift is de-tune the shape. I go narrower, reduce volume, use bigger fins. In other words, increase form drag. I would also use a flat to slightly convex bottom; no lifting bottom concaves.

Bob Green
I think Damian Coase in another thread posted about nose vee reducing the chop effect.

Damian Coase
es both Don Boland and I have gone with a vee in the nose, in Dons case combined with an edge bottom, to help with the board chatter created by chop. For larger waves we have longer, narrower and heavier PU boards that seem to cut through the chop. Don is healthier and fitter than me and still charges 8 foot plus waves on some of the heavier reef breaks around here. This is my 5 9 edge bottom PU board.

Thomas Haugh
This is a good graphic showing what I believe are the critical design elements. This applies to both my kneeboard and my prone board. In other words, I took the prone board design and enlarged it to accommodate a kneeling rider.
No photo description available.

Haugh29July23graphic.jpg (8.03 KiB) Viewed 1264 times

Bob Green
Did you ever fine tune a finless board? I know you dabbled.

Thomas Haugh
First and only finless attempt...TBFX Eventually added fins....

Haugh29July23finless.jpg (9.87 KiB) Viewed 1264 times

...worked much better, of course

Haugh29July23finlessb.jpg (12.17 KiB) Viewed 1264 times

Bob Green
It looks like the rail wing is lower than area where the fin is, almost like an edge board. Is that correct?

Thomas Haugh
Not really...but kinda. I attempted to use a an "edge bottom" on the G5, but found that the eps beads kept pulling out, not allowing a hard edge. Using resin to build the edge would have been too labor intensive. However, the resulting rail shape helped to keep the sloped deck rail very thin for max wave face penetration, so I kept it in the design. When I did the FX, I just used the same deck and bottom contours from the G5 but added the four channels.

Ryan Titilah
Is there a way to order 1 from you? Are you building customs? Do you have any paipo T-Belly G5 available to look at. I’m in Ventura?

John Morris
With experience prone and kneeling I wonder if you’ve pondered this comparison. Both types are able to tuck into tight spots nicely I reckon. But the combination of short hull length and low vantage point seems to limit the ability of paipos to look down the line and run out into the flats when needed to get past broken sections and set up for sections down the line. Anyone else notice this?


Bob Green
I think it depends where you are. If you are high up the face, I don't think the view would be much different. There are points doing a bottom turn, where vision can be more restricted.

Thomas Haugh
I think the visibility from the kneeling position is better than from a prone position. Riding prone has some advantages though over kneeboard; more fun in smaller surf, heightened sensation of speed, easier to duck dive in larger surf. Prone boards are especially good in super fast-breaking waves; no wasting time getting to feet or knees, just drop in and go. Bottomline: I'll have fun on my prone board regardless of wave size or speed. My keeboard needs chest-high face before the fun starts, but its 39L volume makes duck diving a chore for me at head-high or above. I keep both in my car at all times.

John Morris
nmy aim is usually to trim high, but also climb and drop, come hard off the bottom and the top. I know fins dragging in the water likely slow things down at times. But I feel like I’m usually spotting opportunities a little later than I did when I was standing. Maybe anatomy/neck mobility is also an issue. Rotating the head while upright provides a wider range of movement than bending the neck while prone.