TBG5

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Re: TBG5

Unread postby nomastomas » Tue Feb 20, 2018 2:00 pm

(1) "...typically hanging [on] for the ride." EXACTLY!!

(2) and, yes "More on-rail surfing" would definitely help, but see (1) above.

More on-rail surfing is definitely the correct tactic here. This thought crossed my mind earlier in the thread, but for some reason I didn't give it enough attention. Now considered, it makes total sense. Turing almost always results in a de-acceleration. Learning to sense when my acceleration reaches lift-off speed and knowing when to start to roll over onto rail will take some practice. I just need to anticipate the speed and be prepared to take action when the situation arises.
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Re: TBG5

Unread postby rodndtube » Tue Feb 20, 2018 2:12 pm

Going on-rail is nice but often times isn't practical, e.g., making a late drop on a sizeable wave out in the ocean and with wind rushing up the face -- riding on-rail turns the board into a sail, and you go rocketing back over the lip (or experience that sailing up to the lip and then smack down by the lip! Now that is a jarring experience!). So, in the bottom turn or coming out of the bottom turn at speed, that is the challenge of skipping skimming like a flying saucer over the surface chop or slight cross swell on the face of the wave. On a stand-up board one can mitigate some of this by positioning on the board and also having the knees serve as shock absorbers.
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Re: TBG5

Unread postby nomastomas » Tue Feb 20, 2018 2:26 pm

Can't argue there...sometimes the lift happens immediately on the drop. Or rather, on the bounce! Late take-off to air-drop to bounce-air-bounce-etc. Sometimes on big, steep waves it helps to take off on an angle. There is still the air-drop but landing just below and parallel to the lip helps reduce the immediate acceleration that typically follows going down the face. Fins really help to "stick" the landing, but you need to be wary of getting sucked up into the pitching lip. That rarely ends well...
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Re: TBG5

Unread postby bgreen » Tue Feb 20, 2018 3:35 pm

No strategy will necessarily always work, but there are the rudiments of an approach here.

Nomas suggested awareness - one question is, as you start to feel bounce will an adjustment to reduce board bottom to wave face, make a difference. If so, how much rail needs to be dug? There may also be a speed & chop threshold - something may work up to a certain speed or level of chop. Rod added in the variable of strong winds.

A design where this seems less of an issue, but is a different dimension, is the foil. One thing I liked about the design was Surffoils description of being able to ride through chop/white water.
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Re: TBG5

Unread postby rodndtube » Tue Feb 20, 2018 8:24 pm

bgreen wrote:<snip, snip>
A design where this seems less of an issue, but is a different dimension, is the foil. One thing I liked about the design was Surffoils description of being able to ride through chop/white water.


I can't imagine being out at my specific break with a lethal foil weapon! That would be very, very scary. Reminds me of Terry Hendricks's initial hydrofoil paipos which had a push button mechanism to deploy the foil (but that was mostly to easy paddling out in shallow and weedy waters). Maybe a foil such as Gilbert Lum's would be manageable (less deadly).
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Re: TBG5

Unread postby jbw4600 » Thu Feb 22, 2018 1:31 pm

All my boards have point forward of the midline. But I ride my boards all the way forward. My elbows are 13 inches from the nose. So I drive the forward edge. This a better purchase on the water. One of my boards has a more of a bodyboard outine. I can pretty much ride anything on that board. I skip on waves, when there is chop.
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Re: TBG5

Unread postby bgreen » Fri Feb 23, 2018 8:14 am

I asked John Elwell about this - excerpts from two e-mails:

"The skipping stone is a good example about planning and LIFT. It was probably the first example that early humans saw of planning on the water. No one could explain it except flat oval rocks the right size can actually skip and fly. Most rocks can't skip and sink.

Bernouilli's equation explains some of it. The stone has momentum when thrown, It hits the water at an angle with force and it's weight....the leading edge, a hydreon deflects the water producing kinetic energy increasing it's momentum each time it's skips. It finally loses momentum, and sinks.

When Simmons came along and speeds increased some riders experienced a violent sensation after hitting chop and being propelled with such force when they hit the water they hit the water bounced and painfully with impact they were "skipping like a stone".

Lindsay Lord sheds more light on this with planning hulls. Planning hulls don't do well in rough water, especially boats which become dangerous, with bows plunging. Speedboats hit chop skip and somersault and crash.

With surfboards the same thing happens. Simmons made a board so light that it flew and went out of control. He increased weight and turned up the nose that had camber or belly.

Lord worked out a number of problems for the Navy as the PT boats in WWII were breaking the bows off and yawing. The problem was redesigning the bow so it would lift go over the wave and re enter gradually with out pounding. Simmons understood this. He spliced a 3 foot section on the bow, he called a scoop or 'spoon'.

The uplift and camber pushes the water to each rail for earlier lift. If the bow comes in contact with the water on steep take off or encounters chop, it lifts. While we surf he said the bow is out of the water. Lord said flat noses work in calm water but when they come down at higher speed and slap it like putting on the brakes!

What we are experiencing is resistance from the bow or nose that had to be dealt with if possible. Planning hulls skip and bounce in rough water to the point of great instability from resistance.

We must remember we are dealing with "dynamic forces". On a surfboard we get thrown off and body board we feel those forces in our arms and on our body. We may be able to improve it by redesigning the nose to lessen the impact and correct itself depending how ...antagonistic the sea is.

Pat Curren came up with a heavy balsa and redwood board with a cambered nose that of 45 lbs, that was hard to get into waves but if you took off late, the board was stable and momentum and went through the chop. Pat learned how to ride it. Others could not equal his style of hair raising late take offs.

Simmons also recommended two coats glass which provided 4 layers on the rails. His big wave boards were also 45 or so pounds, for stability and momentum. You can try and increase weight and improving the nose and see if that works".

"In rough water we usually reduce speed, in aircraft when we hit turbulence we try and avoid it but usually pilots will reduce speed and altitude.

One way to reduce speed in turbulence is to change the angle of attack by bringing up the nose to stall and let the tail drag to get through the resistance. We do put more pressure on the board in down angle for acceleration. The equation works on pressure "P" squared that squares the velocity "V". We control the throttle by controlling the pressure and angle of attack. We can trim through some of these things.

His noses on all of his boards were cambered like a "spoon" and dished out on top for lightness. Concave may also help as it may cushion the slam into the chop. This is something you can play around with on experimental boards:.
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Re: TBG5

Unread postby nomastomas » Fri Feb 23, 2018 2:02 pm

Thanks! Some interesting stuff..
"Skipping stone" stuff - yes, especially the notion that that there is actually an acceleration as a result of the skip. I've definitely experienced that.
"Nose scoop" - yes, I've slowing been increasing the nose rocker on the TBGs. Current nose rocker is 3". More rocker throughout might also hlp to slow things down a bit, and to improve on-rail performance. All the TBGs have "belly" in the nose as well. Maybe steeper "V" panels would help cleave through the chop?
Tail pressure - Lord found that, as speed increased and a planing craft lifted, there was an increase in pressure in the rear third of the bottom, which created drag. This was true for the rider-less sleds he used in his experiments. The addition of a rider would only increase that pressure. Simmons took this idea and placed an open end concave in the tail of his shapes to help relieve the pressure , reduce drag and thereby increase speed. I adapted this idea by splitting the single concave into two, parallel concaves. Campbell Bros Bonzers have a similar design feature. Perhaps this feature is not only unnecessary but detrimental in larger waves? Too much speed generating too much lift.
Concave - assuming a "contained" concave (not open at one end), adding concave increases lift, complicating the issue.
I still like the notion of reducing planing surface by being on rail more often, but I think there are also some design features that can be manipulated to create a "better tool for the job".
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Re: TBG5

Unread postby rodndtube » Fri Feb 23, 2018 3:22 pm

Weight is certainly a mitigating tool when dealing with stone skipping phenomena especially in light surface shop and some mild cross swell effects. One reason that I have my boards made with a heavy fiberglass cloth regimen (two coats, top and bottom, and not just the 4 oz cloth). Riding rail, when that is possible, is most useful in glassy, low wind conditions. I haven't observed riding rail as mitigating much in choppier/cross swell conditions nor in high wind situation. I'd like to see what the heavy nose "V" could do to mitigate stone skipping.
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Re: TBG5

Unread postby nomastomas » Fri Feb 23, 2018 3:37 pm

I'm not a believer in the effect of board weight. Different story if boards surfed without riders. In my case, the total "load" would be 5lbs for the G5 and 190lb for the rider = 195lbs. The G5 is only about 3% of the total load. Doubling the weight of the G5 would only add 5lbs to the total load, or another 3%. Heavier objects accelerate slower than lighter object, but I don't think I would notice a 3% increase/decrease in mass one way or the other while riding. Walking back up the beach is another matter:-)
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