*** Official Griffin Surfboards Thread ***

One-Off

Tom Curren status
Jul 28, 2005
14,123
10,244
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33.8N - 118.4W
@One-Off I did a very brief experiment when I had finished washing my wetty today. Brief because I was getting cold. I dragged a plastic spoon across the surface of the water in my washing bucket. I was holding it by the end of the handle and dragging lengthwise applying a little downward pressure. It did not dive to the bottom - it planed across the surface. There is a difference between a thin stream of water from a tap and the mass of water behind a 12 second period wave. That's why I don't believe hosepipe experiments have much value either.

Its just experience that tells me wide light single in powerful waves gives a feeling of sitting out of control on the surface - I reverse engineered the theory that the it is the lift of the concave from water exiting the rails diagonally. Wide for me starts at 19", because of this experience I only ride narrow and this stops the out of control feeling in powerful waves. You have made light single concaves - how wide and how long were they and did you get to take them out in reasonably powerful waves? What was your impression?
When the waves get serious I have a 7-4 for points and a 8-3 for my local reef. Both are flat bottoms..... :unsure:
 
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Mr J

Michael Peterson status
Aug 18, 2003
2,250
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Regional Vic, Australia
...
V bottom with concave set within the V panels on a DVS full carbon 7'4" quad fish with full rails and running GTF-1 carbon twins only.
If you want to go wide with a concave making it a double or V double is one solution. On the downstream side of the V there will be line of low pressure which helps reduce uncontrollable lift. Although @One-Off observantly noticed that the Camber surfboards underwater camera did not show flow crossing the stringer the camera was mounted on the tail of the board where the fins tend to box in the flow. I would imagine it would cross the stringer further up in certain circumstances - and a reason Greg did not like the double, V double or any V for that matter.

To quote Greg: "The flow does not have to go up and over this ridge along the rail"

pic from his photobucket. Thread link here https://forum.surfer.com/index.php?threads/rocker-and-concave.236132/#post-3545101

Ridge.png
 

One-Off

Tom Curren status
Jul 28, 2005
14,123
10,244
113
33.8N - 118.4W
If you want to go wide with a concave making it a double or V double is one solution. On the downstream side of the V there will be line of low pressure which helps reduce uncontrollable lift. Although @One-Off observantly noticed that the Camber surfboards underwater camera did not show flow crossing the stringer the camera was mounted on the tail of the board where the fins tend to box in the flow. I would imagine it would cross the stringer further up in certain circumstances - and a reason Greg did not like the double, V double or any V for that matter.

To quote Greg: "The flow does not have to go up and over this ridge along the rail"

pic from his photobucket. Thread link here https://forum.surfer.com/index.php?threads/rocker-and-concave.236132/#post-3545101

View attachment 137813
You think the fins are boxing in flow in front of the fins? I don't think so. I am now of the opinion that a straightedge placed diagonally across the bottom is misleading....unless you're side slipping.

I came back to this thread because it occurred to me that another great Griffin died in a motorcycle accident.Screen Shot 2022-09-14 at 4.54.53 PM.png
 

One-Off

Tom Curren status
Jul 28, 2005
14,123
10,244
113
33.8N - 118.4W
I'm dusting this one off and giving it a go. First time in years. Original Griffin five fin set. At that time he was very generous in advising me on fin placement, even board dims, for my second (and only balsa) compsand build.

ps new build in early stages in background.

IMG_6851.JPG
 
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JDJ

Miki Dora status
Mar 1, 2014
4,829
5,078
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The OC
Damn. Wish that I never sold the thruster Greg made me. That board paddled into everything with little effort. I always planned on getting another ….
 

ghostshaper

Phil Edwards status
Jan 22, 2005
6,243
2,866
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1134
I just realized that I still have Greg's file for my 5'6 twin/twinzer. Hit me up if you want it, and I can dig it up and send it to you.

Caveat: there's an error in it somewhere and you'll still need to hand shape the rails. My friend who cut it, said, "you should've just hand shaped this."

edit: but you might have to do something nice for need4speed to make you some fins for it
 

Mr J

Michael Peterson status
Aug 18, 2003
2,250
1,454
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Regional Vic, Australia
I just realized that I still have Greg's file for my 5'6 twin/twinzer.
...
Caveat: there's an error in it somewhere and you'll still need to hand shape the rails. My friend who cut it, said, "you should've just hand shaped this."
...
Perhaps not error, but deliberately not handing out an example of his rail intellectual property?

Greg sent me this email in 2017

Gregory Griffin wrote:
Late 60’s Mike Hynson validated the downrail , it had no tuck like the tail of modern boards
Dick brewer modified it by putting a small round contact point for control - suction -
This tucked edge design is the most efficient rail shape and can be adjusted in many ways
Flat surface before edge then tuck for suction - vary the size of tuck for how much is desired .
Then at the top of this tuck pull the rail inward to release that suction off of it
If the transition of the edge is smooth into the tuck it does not sheet water off , it climbs the tuck then releases where the rail pulls in toward the deck , if you build an edge at the bottom it does drift more .
That angle of the rail and size of it controls penetration
3 parts creating this engineered rail shape
I will draw up one


I think I understand what he is saying, although I'm still at the painting by numbers/trial and error stage when it comes to putting it into practise and making myself a rail with the desired proportion of properties.

He didn't make the diagram in case anyone is wondering.
 

000

Duke status
Feb 20, 2003
26,018
7,171
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someones sellin this on fb
1665229297707.png 350


5’7 Greg Griffin Mod Fish 5 Surfboard
$350



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  • Condition
    Used - like new
5’7 x 19 3/4 x 2 3/8 Modfish 5 - Excellent Condition