venturi effect?

I know this has been discussed. Is anyone else following this rabbit hole? I’ve been chasing it for almost 10 years now and have a twin-hull catamaran type design that is fun to ride. I have 4 of these things and they work well in FL for me. I proved the 4’ 8" in the joaquin swell last year in well OH surf. They don’t use fins. The reason I went this way is because I’ve had a lot of spinal injuries/surgeries and my neck is fully fused with no disks remaining and my low back has a triple fusion because it was broken a couple times when I was younger. So, I needed a board that didn’t give me instant neck spasms and could create it’s own speed.

 I create speed by dropping in, heavy on my front foot and this makes the board essentially “finless” as the hulls are mostly out of the face. When it’s time to begin setting the bottom turn I shift back and the rear gains traction. I can do cutbacks, hacks, gouges everything I can do on a finned board.  I try to ride these things in high-tide beach break, which isn’t huge; but can be fun here in FL. My favorite is Balsa Bills reef, it has some hard ledges, and it’s right at his shop. I started with fishes and simmons and kept making my keels with lower rake to reduce drag and deeper slots through the middle to move more water. So, I remember when fins were made out of foam and matched to each board. It wasn’t long before the fins blended with the side of the slot/concave/channel and after experimenting for years I have something that is fun to ride. I find the RNF template with single wing swallow seems to help with the water flow off the tail and is less drag when paddling Shifting weight from front to back creates speed, but it can be pumped rail to rail for speed. It’s very hard for me to do that with the fusion, because I lost the drive and flexion with my hips.

 So, now I’m just fine tuning the design. The black/white is an anti shark measure. It also helps to hide my less than perfect craftmanship. 

Cool boards and back story (unintentional pun!), sorry to hear about the spinal issues, but awesome that you have found a workaround.  The pic makes it hard to see the exact contours, or maybe its the b/w graphics, would be nice to see pics of the unpainted blanks after shaping.  Are you gluing the foam “fins” on?  BTW, venturi has been disproven as a valid surfboard design, water can be channeled but it can’t be compressed across an open contour.  The bonzer brothers have long since dropped that explanation, but their design is still very popular and functional.

BTW, give the man some upvote points everyone, he needs 10 points to respond.

Point given.

This might be of interest

https://www.instagram.com/p/BJH0sUljdY3/?taken-by=garymcneillconcepts

 

Cool!

Cool stuff. Reminiscent of a Belly Bogger bottom.

+1 to see a shot of an unpainted one.

I’m also curious how you handle paddling with your neck issues?

I switched to prone riding completely some years ago because of neck problems effect on my paddling ability…

Point given.  As wtih several others who joined years ago, the new forum format has robbed another member of points to post.

Come on folks.  Give the man some points.

Interesting designs CrazyTom.

I have always been partial to this Mike Daniel creation found in the Less Fins thread.

 

 

 

 

 

 

It’s interestig to consider that just about the fastest shape you can ride on a wave is a skimboard. Dead flat. To me it’s planing that’s the key to speed.

Huck- The foam is offcuts from when I cut the outline. I brush resin under it and use a couple toothpicks to hold them in place. Venturi seems to be the term people use. I call them “keel-hulls”, personally. I have tried to use catamaran and double hull racing boat influence. I think it was Woody Brown who first put a fin on a board and invented the catamaran sailboat. I just always thought that was interesting.

 Some of the older boards like unclegrumpy and stoneburner pictured have definately helped give me some ideas. There were some hawaiians that rode similar designs on the north shore years ago. I even drew inspiration from an old pic of a hawaiian, with diamond head in the background and he has an alaia with a definate slot on one rail and that also gave me a direction to experiment torwards.

Unclegrumpy- I can usually only have a 2 hour session and the spasms get bad. I try to flex my neck as little as possible. Like if I’m swimming laps, with my head down paddling and looking up only occasionally. I put ice on my neck and back as soon as I get in my truck heading home, and then I use heat on my neck at home. An inversion table has really helped my low back, but you can only hang upside down for so long and then it gets to your feet and ankles.

spuddups- I agree, the skimboard is the fastest. But I’m an old cripple and can’t handle that slipping and spinning at top speed. I built some facets into these things and when I’m more on the nose, (like a cheater five) the majoity of flow is under because the tops of the hulls are flat. It’s just the last 4 inches that has a bevel or cant like a keel fin. 

I just started my 5th one. I use a US blank 5’10" RP stock fish blank. I have only cut the outline so far. It will take a little bit for me to shape, because I do have my bad days. Anyway, I’ll try to put a step by step posting of pics. Hopefully I can answer questions as I go or at least be mildly entertaining.

 Thank you everyone for your interest.

​Have you seen the double-hotcurl boards of Roger Hall? Do a google search, pretty interesting.

 

CT, this is the link to thread where Daniel’s photos came from.  Some interesting finless designs there.  Still, there is something about that  Daniel’s creation…

http://www.swaylocks.com/forums/less-fins

I have sacroilliac issues from an old injury that flare up occasionally.  Also, I push my back muscles too far from time-to-time.  My sister gave me one of these decades ago. With your condition, I don’t know if would be safe.  For me, it is magic. I have picked up several of the originals on eBay – made of “rock maple.”

Original Ma Roller by Ma &/or Matrix International (both out of business now):

Image result for original ma roller matrix international

Image result for original ma roller matrix international

The old/original instructions and claims that came with the rollers are unusual/ineresting.  Regardless of that text, it works magic for me.

I guess the reason why not SUP is the wind. Don’t mean to offend, just curious

I would love to see pics of the build and video of somebody riding these. Sounds cool. 

This is cool, I’m giving it a bump. Been thinking about trying a finless board.