Quad Concave Body Board Study

What works and what doesn't. Share design ideas, references and contacts for paipo board builders.
PhillyViking
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Quad Concave Body Board Study

Unread post by PhillyViking » Wed Jul 29, 2020 3:27 pm

I am getting ready to build a fin-less board. I have been looking at the trend in Body Boards to use quad concaves. The shallower inner set is for turning and taking a high line and the outer set to move water out the back fast and to further help with turning when sunk. Most of the BB makers have at least one in their line up. Its interesting to read how they relate design variations to riding objectives. Its good food for thought if nothing else.

I like what krusher and others have done to make boards perform without fins. I do know the case for fins .. I built a Bonzer Paipo for those purposes. But mine (at least) needs a lot of wave energy to earn its keep. I do not expect to get Bonzer performance fin-less but who knows. In the mean time I plan to take the Bonzer on my Central American trips. But my next board is for other purposes.

I just built a 48x19x1" fin-less using the profile of my Xylem board but the bottom concave and rails like a Tom Wegener Tuna. I actually have a tuna but do not like all that length in front of me. My build's EPS core has a epoxied basalt/innegra weave bottom so it can take a beating and it duck dives endless short period waves so easily. It has a cork deck adhered directly to the EPS core like Wegener. The cork handles compression forces and I was going for some flex or at least some shape shifting like my beloved mats. It turns better than expected but does require a late take off. Now its time to try some more float by going both a bit wider and thicker (say 48x21x2.25"). However, I might shorten it with a blunt BB type nose while retaining most of the planing area and float. Short lets you pivot with just weighting changes.

I was ready to use the same bottom and rail design as the beater when I noticed a trend in which quad concaves are used in high end BBs. In a related trend they are starting to use mesh layers to control flex. This is not your old flat bottom sponge. I actually rode a Morey Mach 7-7 for some time after my long board phase. I am thinking of making my new board using the basic BB approach with quad concaves.

My next paipo will also be stringer-less and use high density EPS foam as well as being fin-less. All the flex will be controlled from the bottom layer like Wegener is doing. But with epoxy/fabric rather than wood. I might need two layers of the basalt/innegra weave on this one since it will not have a stringer. I will try one and add if necessary .. but I want some flex. I just do not want it to break. I had some trouble getting the 8 oz Basalt/Innegra to make sharp corners so will just make my rails with cork like Wegener. That makes the overall build easier for me . A board that would feel like my mat but turn hard, duck dive and have a tether would be perfect.

As a baseline, I am thinking <= 3/8" for the outer channels and even less for the inner channels. I am not sure how to take the outer concave to the bottom of the rail .. some of the BBs transition the concave right to the rail and others have a narrow flat section in between. I do note that Wegener found that if the bottom transitions were to sharp that water released rather than wrap so the turning effect can be lost. So, smooth like the Tuna in any case. There are variations in the BB quad concave designs but generally most stop before the midpoint. Its like fins, whats the conditions and rider style?

I am not a hot shot like the pro riders you see in BB promotions. I do not aspire to 360s or aerials. I just want tot be able to get into the groove of the wave perhaps starting with a bottom turn, being able to take a high line and do some cut backs as needed. If I can get through some slow sections and/or take off in smaller conditions a bit earlier than my 1" thick board then great.

If you are not on top of the trend you can find lots of commercial product and hype with a quick google search. I found the following DIY reference useful: https://www.reddit.com/r/bodyboarding/c ... l_old_eps/
of course I will actually use EPS. He links to these shots where he shows measurements of a quad concave: https://imgur.com/a/0QDL4 Here is a build in progress: https://imgur.com/a/umI73

Any thoughts in adapting BB quad concave designs to paipo boards? Actually BBs are Paipos in my thinking. Distinctions other than soft rather than harder cores seem to be more cultural than anything else. Has anyone build a quad concave along these lines or is thinking of doing so?

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Re: Quad Concave Body Board Study

Unread post by bgreen » Wed Jul 29, 2020 9:12 pm

Phil,

You may have seen the concave on my boards. I've ridden the green board finless at all sorts of places including JBay and Cloudbreak. The orange wings were retro-fitted to the red board below. While a lot of fun, the red board didn't hold an edge in a tube. Adding the wings made it grip like glue in barrels. This was a great before and after test for the wings.
MM9_bottom.jpg
MM7-TailViewb.jpg[/attachment [attachment=1]MM7-foil.jpg

Wings_finished.jpg
]
wings3.jpg
Attachments
MM7-foil.jpg
MM7-TailViewb.jpg

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Re: Quad Concave Body Board Study

Unread post by PhillyViking » Wed Jul 29, 2020 11:22 pm

B,

Thanks for the reply. I would love to build a finless that turned and stuck steep faces as well as my Bonzer. I have seen your prior comments with great interest.

Thats a great shot of the green board from the rear. What happens to the concaves forward? Is it a single to double concave like the Bonzer? How deep are the concaves at the tail? The quad concave BBs I am looking at have another set in the center .. maybe they are not needed.

I can't see the finer points of the red board. It looks like your "wings" are concaves. Is that another set of inner concaves between the wings and the center fin box? If so that is like the BBs I am seeing. Do you have a shot from the rear like the green board.

How would you contrast the ride of theses boards by reference to their design differences?

P

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Re: Quad Concave Body Board Study

Unread post by bgreen » Wed Jul 29, 2020 11:47 pm

On the green board, if I put a spirit level on the bottom, from one rail to the other rail, by 20" from the tail the spirit level is flat on the bottom. By 25" from the tail, the wings are completely gone and the spirit shows a small gap around the rails.

Double concave to rolled through the nose. The wings are like an extension of the concave. I'll see if I can get a better photo

Here is the red board without the wings and with a single fin. The green board has more volume through the nose and does a cleaner bottom turn. It is generally a smoother ride.

SingleFin.jpg
H2_foil.jpg

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Re: Quad Concave Body Board Study

Unread post by bgreen » Thu Jul 30, 2020 12:12 am

This may or not help. It is hard to photo the curve of the wings - they gradually fade out after being more accentuated at the tail. The blue/gray board photo has the level at about 12" from the tail.
Concave1.jpg
Bottom.jpg
12InchfromTail.jpg

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Re: Quad Concave Body Board Study

Unread post by PhillyViking » Thu Jul 30, 2020 6:56 am

B,

I just reread your Aug 2018 Finless Observations comments. My take home is that the finless board was faster and more natural feeling down the line but you did better when you mounted the 2" fins at a break that required more emphasis on turning, Or, were you simply saying that you decided to use the fins and that setup worked. Would that or other finless setups in your quiver have worked as well?

A few years back I was mostly riding mats. There is nothing like a (finless) mat ride when it all comes together. However, at a heavy break I surf I often could not get around the white water to the face after a big drop. Maybe a more skilled mat rider could. The finned Bonzer I built does that with ease. However, in other conditions the drag of the fins is objectionable.,

So that scenario of needing to get around white water to the wave face you described in your 2018 comments is exactly what I am trying to address in an optimized finless design. In effect, bottom contours can become fins with the advantage of not creating the same amount of drag as conventional fins. Well, that's the objective. At my heavy break case I had trouble making power turns on my mat but could get through slow sections to enjoy long rides on two wave reforms. The Bonzer could make the power turns in the first break but dogged out after that. I want it all.

Its interesting that your green board has a convex center and e.g. krusher74 has concave centers in his designs. Both of you report good turning ability in a finless. They both work for different reasons. Likewise, my Xylem has a rolled (convex) bottom that works to a point and my recent beater board worked to a point with a single concave.

Do you think you have refined your finless design to the point where it performs as well as conventional finned boards when turning, getting around white water and taking a high line are paramount concerns? If so, how would you describe that optimal design? Is it the green board? I have no doubt that we can make finless work .. its a question of refinement for me.

I just saw the additional pics you just posted ..thx. I will comment on them later.

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Re: Quad Concave Body Board Study

Unread post by PhillyViking » Thu Jul 30, 2020 7:01 am

B,

I just reread your Aug 2018 Finless Observations comments. My take home is that the finless board was faster and more natural feeling down the line but you did better when you mounted the 2" fins at a break that required more emphasis on turning, Or, were you simply saying that you decided to use the fins and that setup worked. Would that or other finless setups in your quiver have worked as well?

A few years back I was mostly riding mats. There is nothing like a (finless) mat ride when it all comes together. However, at a heavy break I surf I often could not get around the white water to the face after a big drop. Maybe a more skilled mat rider could. The finned Bonzer I built does that with ease. However, in other conditions the drag of the fins is objectionable.,

So that scenario of needing to get around white water to the wave face you described in your 2018 comments is exactly what I am trying to address in an optimized finless design. In effect, bottom contours can become fins with the advantage of not creating the same amount of drag as conventional fins. Well, that's the objective. At my heavy break case I had trouble making power turns on my mat but could get through slow sections to enjoy long rides on two wave reforms. The Bonzer could make the power turns in the first break but dogged out after that. I want it all.

Its interesting that your green board has a convex center and e.g. krusher74 has concave centers in his designs. Both of you report good turning ability in a finless. They both work for different reasons. Likewise, my Xylem has a rolled (convex) bottom that works to a point and my recent beater board worked to a point with a single concave.

Do you think you have refined your finless design to the point where it performs as well as conventional finned boards when turning, getting around white water and taking a high line are paramount concerns? If so, how would you describe that optimal design? Is it the green board? I have no doubt that we can make finless work .. its a question of refinement for me.

I just saw the additional pics you just posted ..thx. I will comment on them later.

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Re: Quad Concave Body Board Study

Unread post by PhillyViking » Thu Jul 30, 2020 8:26 am

B,

Thanks for the additional pics. I have a completely different view of the red board now.

Here is the 48x19x1" single concave I recently built for shore breaks:
IMG_20200514_145721130.jpg
Here is my Bonzer:
IMG_20200305_101156820.jpg
Here is an example of a typical BB with a quad concave:
quadconcave.png


I am thinking about trying the contour of the BB example. I am thinking 48x21.5 x 2.25" but might go shorter to be more like a shorter body board that can take off more dramatically and respond to more simple weighting shifts.

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Re: Quad Concave Body Board Study

Unread post by bgreen » Thu Jul 30, 2020 5:04 pm

The green board is the best I've ridden. I tried fins at Cloudbreak but was happier without fins. I think part of the problem with fins was the wings and where the fins were located. I'll take a photo.

Two bottom turns, admittedly very different waves.

I think the top photo is finless and it shows trying to muscle around whitewater. The second photo is a smaller wave, the board has a handle and twin fins. Lots of leverage there.
namatou.jpg
tilted turn 3.JPG
tilted turn 3.JPG (30.18 KiB) Viewed 527 times
Personally I think you may get more hold with a concave + wing than quads.

Here is a board I was loaned. I didn't find it had the hold I wanted.
Garrett5.jpg
Garrett2.jpg
Overall, with your particular type of wave, it may be the case that a finned board works better. I tend to surf lots of different waves.

You could also do what I did, get your finless board and add some wings and see what happens. My wings were foam & resin, you could try something less permanent, that you could sand off easily.

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Re: Quad Concave Body Board Study

Unread post by bgreen » Thu Jul 30, 2020 7:42 pm

The top photo gives you an idea of fins in relation to the wings. Photo 2 a better perspective on the concaves and wings.
GB1.jpg
GB2.jpg

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Re: Quad Concave Body Board Study

Unread post by PhillyViking » Fri Jul 31, 2020 11:06 am

B,

Thanks for the Pics and comments!

If I am seeing your preferred green board correctly then it could be described as two concaves with outsides swept up to the rail edge more sharply then the sweep to the center. That sharp sweep creates the "wing". The peak of the center is close if not on the same plane as the peak of the wings. I am I seeing it correctly? Is there a single forward concave of what I am seeing as a double (i.e. single to double or flat to double) ? Bonzers have a single to double as do others. However a classic Bonzer would have a flat area between the doubles and the rails .. thats where the fins are set. However, the Bonzer is optimized for fins and your wings optimized for finless.

Are you riding the green board in the two pics you used to illustrate finless and finned turning. It seems you were making the case for fins and that does not seem like your overall message. In any case, are you saying that you can turn as well on your green finless concave + wings as a comparable board with fins in all or just some conditions?

The loaner does not reflect what I see in the BB quads. It might reflect what I understand to be a common misconception that thin rails turn. Thin rails release water so there is no wrap around water flow to create hold. I also understand that if the rails are two thick and buoyant they can not be planted into the wave. So there is balance required. Maybe the loaner would work if those thin rails were whacked off? I also noticed that compared to the BB quad concave boards I am reviewing that the concave depths are opposite. The loaner has deeper inner concaves and less deep ones outer. The loaner concaves might be too deep and abrupt as well. I keep thinking about Wegener's comments that if contours are too sharp that water releases rather than grabbing as it flows across the tail. So quad is still on the table but very different than your loaner.

You have me thinking about wings but I am still up in the air for this next build. I wish I had more build and surf time to try all the approaches. I thought I would be building this "next" board now. Instead I have been redirected to house projects. Likewise, Covid resulted in two Central American trip cancellations so far. I was hoping to travel this fall but I will plan to stay on the US East Coast. Consequently I am thinking more of a next step beach break board than reef/point break suitable designs.

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Re: Quad Concave Body Board Study

Unread post by bgreen » Fri Jul 31, 2020 4:54 pm

No worries.

The board that is really on edge is number 4 in a series. The green board is number 7. Number 4 had a flat bottom and foil more like the original design by Larry Goddard. The handle is a nod to handle aficionados (Robert Moynier and Jeff Quam, as well as early pioneer Wally Froiseth).

It is a really good all round board and is the board in the finned video, John Kovar filmed.
MM4_deck.jpg
MM4_deck.jpg (84.94 KiB) Viewed 507 times
MM4_bottom.jpg
MM4_bottom.jpg (85.46 KiB) Viewed 507 times
I agree about the removing the thin rail from the multichanneled board. It is an experiment from a talented shaper (who made the above board) and an extension of other designs:
CGarrett4_finless.png
CGarrett4_finless.png (270.8 KiB) Viewed 507 times
Regarding the green board. The concaves fade out to flat, at 2' from the tail. Yes the wing is an extension of the concave. I'll send a couple of photos later, if I can find some US coins.

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Re: Quad Concave Body Board Study

Unread post by bgreen » Fri Jul 31, 2020 7:29 pm

I couldn't find any US coins, but I did find some Canadian ones - if that is of any use:

6" from tail has a concave at the deepest of 1 x 2 dollar + 1 x 1 dollar + 3 x 25 cents + 1 x 1 x cent
1' from tail had a concave of 1 x 1 dollar + 2 x 25 cents
2' from tail has space for a 1 dollar at the rail
3' from the tail had space for a 2 dollar and 25 cents at the rail

All a bit approximate but it gives a rough idea.
SixInchesfromTail.jpg
OneFootFromTail.jpg
TwoFootFromTail.jpg
ThreeFootFromTail.jpg

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Re: Quad Concave Body Board Study

Unread post by PhillyViking » Sat Aug 01, 2020 7:30 pm

B,

Your comments and pics clear up my confusion. Canadian currency does "exchange" to US currency:

US Coins Dimensions:
https://www.usmint.gov/learn/coin-and-m ... ifications

Canadian Coin Dimensions:
http://www.saskatooncoinclub.ca/article ... specs.html

Will do the actual "exchanges" later and comment.

Thanks

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Re: Quad Concave Body Board Study

Unread post by bgreen » Sat Aug 01, 2020 9:03 pm

I look forward to see what you come up with and how it rides.

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Re: Quad Concave Body Board Study

Unread post by CHRISPI » Sun Aug 02, 2020 2:19 pm

Thanks for a very interesting post here is an extreme version of wing rails, but think of them as pectoral fins this board paddles amazingly well. You can feel lift at very low speed it will outpace most long boards on the smallest waves. On steep faces with one tip in the face it is mind blowing fast, but you have to move around on the board to stay on top of the rapidly moving centres off lift, Avery easy board to ride in mush but needs good board grip and body positioning in pitching stuff. It’s made with two layers of 5 mm airx foam board and 3 layers of 6 oz cloth, rocker is press formed. Covered with polyethylene foam for volume, you can change the density and thickness of the foam to get desired buoyancy
282020.jpg
182020.jpg

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Re: Quad Concave Body Board Study

Unread post by bgreen » Sun Aug 02, 2020 4:40 pm

Chrispi, can you send a tail view looking toward the nose. Sounds like you are getting a bit of time in the water.

How far do the side bits extend out?

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Re: Quad Concave Body Board Study

Unread post by PhillyViking » Mon Aug 03, 2020 2:03 pm

C,

Wow! now that is interesting! I would love to see the view of tail from the rear on the same plane as the board as well.

I like your approach: build composite for flex control / basic rocker shape and then add PE for buoyancy and shape refinements. That's opposite of convention but makes sense to me. Do you use a mechanical press or vacuum? I used a similar approach with a cork and linen project but did not manage the amount of epoxy that got infused to cork and used the wrong linen as well as too much vacuum. It got too heavy. You inspire me to circle back to get that all right,

My next cork core composite attempt:
* use non woven linen fabric or other material that would take less epoxy (I have developed interest in Basalt for its strength, damping and relative eco footprint and Basalt/innegra hybrid for tough skins
* prime cork so it does not absorb so much epoxy
* Try 6-8 Hg rather than excessive 21 Hg vacuum for cork - I need to adhere it not infuse it

Is your thinking that you get the same strength with less weight and bulk by alternating airex (two layers) with fiberglass (three layers). That's composite fundamentals. Glad to discuss this further.

Your approach lends itself to Bob's suggestion to use a skin material that could be refined in shape by adding or subtracting after the initial build. All the fiberglass can remain intact within the inside. I love the adobe houses in Mexico .. they are never done. They are living creatures,

How did you adhere PE to your composite?

Did the airex need to be scored or heated to bend in the form or was 5 mm thin enough? Am I looking at the right stuff: https://www.3accorematerials.com/en/products Looks similar to divinycell etc.

What brought you to this composite approach and radical wings?

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Re: Quad Concave Body Board Study

Unread post by CHRISPI » Mon Aug 03, 2020 3:14 pm

I have survived the tropical Indian ocean to North Sea transition .I am now a Cayton bay local ,my first experiences was in 9c water without a hood and got my first duck dive ice-cream headache , but the stoke is back .Getting out off a winter wetsuit after a 3 hour surf is somewhat difficult. We are going through a summer wave drought. The fins are at the back around the hips area the boards are bottom up in the picture; they have an amazing gliding feel when paddling. Tips stick out 160 mm, 700 mm between tips, the board is 1150mm long, and 55mm thick .The airex is two layers of 5mm with a layer off 6oz cloth between layers and one top and bottom and extra over the fine tips for strength. The rocker and fin angel is set with batons and cured in a homemade Utube design oven. I have tried hex core foam but it is very resin rich and a bit heavy

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Re: Quad Concave Body Board Study

Unread post by CHRISPI » Mon Aug 03, 2020 3:36 pm

Nature uses pectoral fins in all her best in water muscle powered designs, a delta shape for sustained lift at high angles of attack, sharp tips for roll and drag reduction

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