Latest T-Belly

What works and what doesn't. Share design ideas, references and contacts for paipo board builders.
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nomastomas
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Latest T-Belly

Unread post by nomastomas » Fri Mar 09, 2012 9:44 pm

TP48inTBellyDeck7_sm.JPG
Here’s the latest iteration of my T-Belly (more pix here http://tp4surf.blogspot.com/2012/03/t-b ... opean.html). Board is being shipped to Hamburg, Germany. While I reduced the volume of this board (both thickness and length) to better fit its intended rider (5-8, 170), I’m starting to lean more towards board volume that is similar to that of a boogie. This board has my usual concave deck, with concave in the last 12” of the bottom. The concave bottom accelerates in depth and width as it exits the tail, reminiscent of Simmons’ shapes and Rich Pavel’s Speed Dialer fishes. Its purpose is to provide an unrestricted path for water flow through the fins and off the tail. I like the center of floatation to be behind center, which is reflected in the foil of this board. But, after feedback from JW, I pushed it up a couple of inches and spread it out some, fore and aft. I think this will provide a smoother volume transition, without an abrupt tipping point. Boards dims are 48” long, 20” nose x 22-1/2” x 21-3/4” tail. Thickness is 2-1/4” at stringer and 2-3/8” at rail. Twin fins are 4” up and set with 1/8” toe-in. Nose Rocker is 2-1/2” with almost zero tail rocker. Relatively low rocker is designed to meet demands of soft, mushy Mediterranean summer time waves. I also used a sloping rail to foil out rail thickness (I started this with ClanB’s board). A thinner rail offers better wave-face penetration or “hold”. Granted, boxier rails plane quicker and have more lift, but at the same (and for the same reasons) they resist being sunk. Answer lies somewhere in between, just have to find it.

My future T-Bellys will be thinner over-all and willhave thinner, foiled-out rails (a la SoulGlider’s Pumpkin-Seed and other Hull-ish designs), but same bottom config and deck concave. Sort of a combo hull nose and Simmons tail. I still think twin or quad is the way to go, especially when you consider the width of the tail. I just haven’t found that perfect combo of fin and toe-in yet. Wave Grinders are available in 5-1/2” depth (only FCS-base), but their designer tells me that they are prone to breaking (probably too much strain where fin base meets tab) I think the science behind these fins is solid, and I’m already moving towards more upright, high-aspect templates on my personal LBs with good results.
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ClanB
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Re: Latest T-Belly

Unread post by ClanB » Sat Mar 10, 2012 12:37 am

I like it!

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Re: Latest T-Belly

Unread post by rodndtube » Sun Mar 11, 2012 2:51 pm

Looking nice. Many thanks for the thorough design discussion, Thomas.
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Re: Latest T-Belly

Unread post by bgreen » Sun Mar 11, 2012 4:42 pm

Do you use AKU shaper? I'm wondering what the volume of your boards are?

I have been am thinking of board # 3 in a series, The volume on # 1was 30.07 litres, # 2 was 20.48, # 3 I'm thinking 15 litres. Less float = easier duckdiving. I've noticed no difference in planing speed with the thinner board - max thickness is 1 7/8".

Bob

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Re: Latest T-Belly

Unread post by ClanB » Sun Mar 11, 2012 5:17 pm

My board is 32.17 liters or 90.66 beers. It will be a transition to go from plywood to this for sure. I have not had it out yet as I have the flu from hell. Duckdiving will be differnt. Im not sure you can even call it duck diving with plypos as I just swim it under water. One thing is it will be nice to sit on a board in the lineup for a change. I cant wait to get this thing in the water though, Thomas did a great job as did Ray on the glassing.

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nomastomas
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Re: Latest T-Belly

Unread post by nomastomas » Sun Mar 11, 2012 5:55 pm

I do use Aku but don't machine shape these boards (at least not yet). I use the Aku print-out as a blueprint while I'm shaping. Shaped blank is pretty close to Aku file but not exact, so volume probably varies a little from what's stated in Aku. Aku file volume on this board was 28L. By way of comparision (and for what its worth), a standard 6-2 shortboard is 27.26L while a standard 48" by 1/2" thick paipo is 4.6L!

I see paipos and belly boards as an extention of body surfing, where most of your paddle power comes from your legs. Paipos and BBs simply offer more efficent planing surface for upper-half of the body. That, and a little extra turning leverage with rail edges, and a little more turning leverage if you use fins. So I agree with Bob, in that, planing area, both shape and size is critical, and perhaps more critical than volume. Paipos are proof that you don't need a lot of volume for a decent belly slide. Volume does help the surfcraft to plane sooner and allows you to get into a wave earlier, but with no need to stand, what's the hurry? One of the things that makes BBs so enjoyable to me is being able to make the ultra-late, blind-faith take-off that you wouldn't even think of trying on a longer board. Volume does allow room for bottom and/or deck contours. Pretty difficult to put both a concave bottom and a concave deck on 1/2" piece of plywood. Oh, and yeah, it is nice to sit up in the lineup :P -tp
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Re: Latest T-Belly

Unread post by bgreen » Mon Mar 12, 2012 2:38 am

TP,

Thanks. More volume does offer the opportunity to arm paddle - handy if you want to make ground or your legs are cramping, but with every pro there is a trade-off. If a 1/2" ply paipo is 4.6L volume, 15 litres should be fine by me.

Regards

Bob

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nomastomas
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Re: Latest T-Belly

Unread post by nomastomas » Mon Mar 12, 2012 11:23 am

I'd be interested in kowing how a 1.5" thick, sandwich-construction board holds up, and what its flex characteristic are. Keep us informed....
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bgreen
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Re: Latest T-Belly

Unread post by bgreen » Mon Mar 12, 2012 4:01 pm

TP.

I've a thinner board (one of John Galera's designs but the design is completely different - see http://mypaipoboards.org/interviews/Joh ... 0922.shtml ) These boards have 2 x 12 oz glass jobs and my latest have 3 x 6 oz. The latter also has a stringer. There's some noticeable flex in choppier conditions but they don't have the whiplike feel of an alaia style board.

On a different note - is it difficult to reduce a 9' board to 4'6 in AKU shaper?

Bob

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nomastomas
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Re: Latest T-Belly

Unread post by nomastomas » Mon Mar 12, 2012 4:57 pm

Not really. You have to remove any slices that are 2'3" or less (half of the 4"6" you want to remove) from each end. Then, re-add tail and nose slices, shaping to your preference. If you want to maintain proportion of shape, rule of thumb is 1/8" of width for every 2" of length; add width if adding length, subtract width if reducing length. Keep wide point at same relative position. On model, measure distance of WP from center and calculate % of total length. Use that % to determine placement of WP. Tweak nose and tail width to match up. Not hard, right?
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Re: Latest T-Belly

Unread post by bgreen » Mon Mar 12, 2012 5:54 pm

TP,

Not hard at all???? I was hoping there was function like on photo re-sizing, where you select a % of the original and viola. I was sent a brd file of an original Simmons and was curious what it would look like as a 4'6".

Bob

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nomastomas
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Re: Latest T-Belly

Unread post by nomastomas » Mon Mar 12, 2012 10:37 pm

LOL...I've been using Aku for almost 7yr now and I'm still learning how to use it. It can be pretty over-whelming at first, especially with lack of documentation. But the more you use it the easier it gets.

I did just the opposite of what you want to do. I noticed that the template of my T-Belly resembled the mini-Sims my glasser recently shaped. I took my 4-3 TB file and blew it up to 5-8. That board is now on my "to-be-shaped" list. -tp
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Re: Latest T-Belly

Unread post by bgreen » Tue Mar 13, 2012 8:00 am

TP,

I've experimented with AKU but life is too short for me to really put the time in to learn it properly. If it was my livelihood I'm sure it would be a different story. I'll keep an eye out for the version with the re-sizer.

Bob

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Re: Latest T-Belly

Unread post by jbw4600 » Tue Mar 13, 2012 4:42 pm

I like having volume on my board. I can catch waves much earlier or deeper and you can make through slow sections when on a thinner board would slow down or stop. But I cannot duck dive it in anything but small foam or through the top of wave. But I think it is worth the drawbacks. The volume really help catching big waves. I can catch waves lmost as early as a shortboarder. I just take my time when paddling out at beach break. I was thinking about getting a board 2-3 inches longer but maintaining the same volume (31 litters?). I thought it might help with duck diving and catching big slow waves.

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Re: Latest T-Belly

Unread post by rodndtube » Tue Mar 13, 2012 5:04 pm

I asked Thomas to work up rough volume estimates of my baseline Austin and the S&S Checkered RPM (thinner). The S&S seems so much thinner and like my "short board" compared to the Orange Matter (baseline Austin) and the RPM boards are my choice in tropical/more powerful surf now and the baseline is my "East Coast/less powerful" surfing board. Rough estimates of the two boards are 25 and 30 liters, although they may be more tilted towards 24L and 31L due to through board thickness and other things. For the reasons jbw mentions, the performance-oriented board is also easier to duck dive. The basic paddleouts are not noticeably different but the wave catching on punchless surf is noticeable!

I am "parking" RPMs in Puerto Rico and Costa Rica and may eventually park a baseline board in FL.
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bgreen
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Re: Latest T-Belly

Unread post by bgreen » Wed Mar 14, 2012 8:01 am

JBW - if there is power in the water, a thin board just flies over flat sections. The wide tail is the key rather than the overall volume. They are a bit like mats - add some power to the wave and the 4th gear kicks in.

Bob

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