Author Topic: displacement vs planing hulls...  (Read 28041 times)

noa

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displacement vs planing hulls...
« on: December 13, 2008, 04:33:13 AM »
old subject which has been discussed before, but since there are constant developments i'm wondering if there is anything new on the subject.
it's obvious that for flat water a displacement hull is the best solution. for downwinders (and depending on the conditions) it appears we have divided opinions. some go for a displacement hull where others prefer planing. what would be the reason to chose one or the other ?
my personal opinion based on relatively small experience is that a displacement hull will be faster until the wind and waves get stronger. from that point on i'm not sure if a planing hull will be faster and by how much.
besides the factor of pure speed, in a non competition setting there is the factor of feel.
with a planing hull the whole point is to catch a bump and plane and we are either planing or not, making for a very "on/off" ride. with a displacement hull you have a much more constant glide which is of course accelerated when catching a bump.
also when looking at the two boards that are the closest to us (paddleboards and OC1) we see that they are always displacement hulls with differences in rockers depending on their intended use.
would be interested in your opinions.

greatdane

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Re: displacement vs planing hulls...
« Reply #1 on: December 13, 2008, 07:19:06 AM »
My understanding (and I may be way off) is that there really are not any true displacement hull SUP boards.  To be a displacement hull, a SUP would have to be round or V shaped, which would be way too tippy for standing.  All surf and SUP's are planing hulls (flat bottomed).  People think that certain boards (Bark & Penetrator) are displacement hulls because they have a kayak like prow.  But after the first couple of feet, the hulls become planing hulls.  Just my understanding... I'm not sure I'm right though ???
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Bolt Upright

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Re: displacement vs planing hulls...
« Reply #2 on: December 13, 2008, 07:45:48 AM »
Aloha Noa,
I know very little about this subject, so I hope you don't mind if I give it a shot.
 
I  think maybe in downwind conditions, with the bumpy, choppy water, windy open ocean environment, the planning hull would  seem to have more stability. Plus, once in the glide, you can then surf your board to stay in the sweet spot to increase the time in the glide.

I've never tried a displacement hull type board...so I could totally be off base here.

In those conditions It seems to me that it maybe more difficult / unstable with a displacement hull type board. I assume that it also wouldn't surf like a planning hull board... more difficult to maneuver in the wave.
 
I mostly do Maliko to Kahului Harbor runs, where you can sometimes have head high drops into glides, it helps to be able to surf the wave...  position and reposition constantly to optimize your time in the glide. But I'm mostly using 14' boards, and basing my opinion on my limited experience of using conventional planning boards.   

In conditions that aren't as dynamic as a windy open ocean setting, maybe displacements are faster.

Plus for me, I like to surf the glides just for the shear fun factor. ;D

Am I correct in assuming displacement boards are more unstable than conventional boards in unstable conditions?  :-\

If so, then that would appear to be the key. The less you fall, the better your time in most cases. ;)

I'm sure someone could punch large holes into my theory, so forgive me if I've got it all wrong. It's a very interesting subject, and I hope someone can give an expert explanation of the matter.

In the meantime, I'm going out to catch waves!! ;D

Randy   

Velasco

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Re: displacement vs planing hulls...
« Reply #3 on: December 13, 2008, 03:19:45 PM »
Displacement hulls are not just determined by the shape of the bow -

Think "oil tanker" and you can start to see the similarities between planing and displacement.  Some of the "cutting edge" boards being produced today that are labeled displacement hulls (think Maui produced) are using these principles.

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stuey c

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Re: displacement vs planing hulls...
« Reply #4 on: December 13, 2008, 05:18:03 PM »
   First up ALL HULLS ARE DISPLACEMENT HULLS UNTIL THEY START TO PLANE !!! It's just that a hull designed for planing is very inefficient when it's not. The sharp edges particularly around the tail area are there to allow the water to break free from the hull as it skims across the top, these same edges are a hindrance when in non-planing mode. When this type of hull is off the plane water will not release cleanly, instead curling, eddying and dragging around the  crucial tail area. The nose, bow, entrance point is extremely important as well. Yes, a flat bottomed surfboard type will assist in getting you onto the plane quicker but again, when not in planing mode it simply combines with the rocker to push water and slow you down. The surfboard type rail also has a similar though not as drastic drag inducing effect when sitting low, with the water curling up and around the rail and not releasing cleanly. All these things combine to pull an awful lot of water around with you as you paddle!
   As has already been mentioned in previous posts it's physically impossible for a human being to paddle a board onto the plane. The only time a Sup will rise and skim across the ocean surface is when riding a swell. Now even on a smoking downwinder with everything in your favour this may be 20% of the time, for the remaining 80% you are paddling an inefficient hull, pushing and dragging a lot of water with you.
   A little over two years ago when I designed and built the first Penetrator I had all of the above clearly in mind. A lifetime of catching open ocean swells in sailboats, particularly, fast cats has taught me that speed is the key, that and an easily driven craft that requires as little external power as possible to maintain maximum glide. This enables you to pick up swells easier, link them together and carries you to stay on them longer. My thinking was that on a planing hull it would be harder to pick up the runs due to it's slower paddling speed when off the plane and because it requires so much more power to stay on the plane it would fall off the runs quicker. By far the fastest single man- powered ocean craft are racing skis, ava'as and oc1s, these all catch runners beautifully as well, so why not a Sup designed along similar lines? It was all a question of balance. Just how narrow and long could I build one and with the rolled and speedy bottom I had in mind would a paddler standing up be able to maintain balance without expending too much energy?
  Yes GreatDane, unlike Joe Barks boards mine are a true displacement hull, they don't just start with a kayak type bow and turn into a surfboard a few feet back but are a radically veed and rolled hull from nose to tail. The first prototype showed straight up that stability on this type of Sup would not be an issue and I was free to begin pulling in the width and finding the limits. The Penetrators combination of veed and concaved deck and rolled bottom are virtually the opposite of a modern shortboard and it runs what amounts to an upside down surfboard rail. Indeed this bottom and rail combination produced some interesting and beneficial side-effects that I hadn't initially thought of. While a flat bottom has it's maximum righting moment when in the bolt upright position the further you tip it over the less stable it becomes, my board, on the other hand works in the reverse. When in the vertical it's a little tippy but as you begin to lean over the rail volume comes into play, which when you think about it is precisely when it's required. Another benefit of this undercut rail design and it's a major one is that it pulls the width of the board way in where it contacts the water. My 18'8" model is 26 1/2" wide but that's at the top of the rail, on the waterline its width is only 23" creating an exceptionally narrow and easily driven craft thats' passage creates minimal disturbance.
   The main thinking of the design was that it would paddle quicker than it's flat bottomed equivalent between runs, pick up runs easier and stay on them longer due to it's exceptional glide. So far it's achieved all this and more, as the riders skill level increases and they become used to the board it's possible in the right conditions to easily paddle over the swell in front of the one you are riding and indeed connect up several at a time.
   Where to from here I'm not quite sure, I keep coming up with improvements but for the most part they are only minor. The steering system I devised is performing well and is very easy to operate though a bit of a pain to fit and I've been working to improve it's durability. Who knows when next that light bulb will pop up again above my head, until then I'm having a ball building and developing this design.
                       Cheers and thanks for reading,
                                                                    Stuey

stuey c

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Re: displacement vs planing hulls...
« Reply #5 on: December 14, 2008, 05:43:25 AM »
    P.S. As a footnote to my faith in the above design, Woogie Marsh just won another race on the Penetrator 572. Woogie won the 16 mile ocean race at Coffs Harbour today (unfortunately in unfavourable side winds, again) with a 3 mile lead over 2nd place. That's 6 wins from 6 starts now and I'm beginning to see a pattern........... ;D

noa

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Re: displacement vs planing hulls...
« Reply #6 on: December 14, 2008, 05:58:07 AM »
Hello Stuey,
first and foremost, thank you very much for your invaluable information. i'm always very impressed by your level of knowledge as well as your abillity and willingness to share it.
speaking of Bark boards, viewing pictures, i was under the impression that his stand up boards followed the same full displacement lines as his prone paddleboards.
once again, what you say makes perfect sense. one thing that i do wonder however is the following. speaking to some other designers such as Mark Raaphorst that makes SIC boards the planing vs non planing percentages differ to the ones you give. according to him, with good downwind conditions (i would say at least 20 knots wind) and while using one of his designs, the ratio would be around 60-70 % planing. that would make it probably turn in favor of a planning hull.
another dillema i have is, if we think of a good downwind run and regardless of how many bumps we catch, it's obvious that when NOT surfing the bumps your hull would be more efficient. it would also be more easy to catch the bump. but once on the bump and surfing the wave, would a planing hull not be faster than yours ? if it is, then it would have greater momentum due to it's higher speed thus allowinfg it to travel further and have a better ability to connect with another bump. whats your opinion on this ?
please understand that i'm not doubting your design but i would really to gain an indepth understanding on how things work.
last but not least, i'v actually talked with Joe Bark in order to buy one of his boards for downwinds.
what you explain however just sounds completely right, more so that the explanations of any other shaper regarding his design.  so i would like to ask you if and how it would be possible to buy a
Penetrator. the main problem is that i live in Greece and that shipping will most probably cost TWO arms and two legs (leaving me nothing to paddle with). but if you think we can find a solution lets talk.
i'm planning some crossings in the Greek islands this summer and i would love to showcase the Penetrator in Europe.  thanks and hope to speak soon...

ps. i think you need a Woogie in a few other parts of the world like the US, Hawaii and of course Europe...

LaPerouseBay

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Re: displacement vs planing hulls...
« Reply #7 on: December 14, 2008, 07:17:50 AM »
Hello Stuey,
first and foremost, thank you very much for your invaluable information. i'm always very impressed by your level of knowledge as well as your abillity and willingness to share it.

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stuey c

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Re: displacement vs planing hulls...
« Reply #8 on: December 14, 2008, 07:29:47 AM »
   Hi Noa,
           Thanks for your kind words, it's fairly late hear in Oz but I'll do my best to answer your queries. I've only ever seen photos of Joe Barks boards and I do like the look of them for sure, I was just going by GreatDanes comments about them being more surfboard like from a few feet back as I'm pretty sure he has one or has at least paddled one.
   In Australia we generally don't have the perfect downwind conditions available to the Hawaiians (unfortunately). Here the wind and swell are virtually never from directly behind, quite often plenty strong but coming at you from over one shoulder or the other and I was probably erring on the conservative side with my percentages in regard to planing time. However, that being said, irregardless of the time spent on them, once on a bump both hull types will travel at the same speed as the wave. The superior paddling speed of the displacement hull though will quite often allow you to catch runs that you may not be able to pick up on the planing version. As both types are only moving at wave speed when running neither (providing the two boards and riders are of similar weight) will have a momentum advantage and as the displacement hull is more easily driven, when the situation arises, a couple quick paddle strokes combined with the knife-like bow is all it takes to punch onto the preceding swell. Also because the planing hull requires more power to keep it up and moving, when the runner you are on begins to die you'll lose it whereas the additional glide of the displacement hull will carry you further. We've already seen that a well designed displacement hull will paddle faster than a similar sized planing hull and from the above we can deduce that each and every bump ridden will leave the displacement hull further and further ahead of the planing model. This is what the Penetrator is designed around.
   As far as shipping a board to Greece I will speak to my boss and get you some prices. My Dad has raced yachts on the Aegean Sea and showed me some photos with awesome downwind conditions up your way. I'll get back to you with a PM regarding freight etc.
   Finally, yes I am lucky to have Woogie not only as a friend but as such an incredibly talented test pilot for my craft and sounding board for my ideas.
   Thankyou Noa, for your interest in the Penetrator and you'll hear back from me soon.
                             Cheers, Stuey

noa

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Re: displacement vs planing hulls...
« Reply #9 on: December 15, 2008, 05:30:20 AM »
Hi Stuey,
thanks again for the rest of your info and clarification.
yes in Greece we do get some awesome downwind conditions. in my humble opinion better than Maui because we don't get their NW cross ground swell conflicting with the wind swell. so yes Greece is a spot that will get quite known in time for it's downwind conditions. plus there are so many islands with so many configurations that the playground is virtually limitless.
i used to live in Oz (Sydney) and the summer noreasters would make some ok downwind conditions on the northern beaches. although i have not been there, i think that WA would have some great downwind conditions in the summers.
anyway, waiting for your news as soon as you get a chance. speak soon...
« Last Edit: December 15, 2008, 06:11:50 AM by noa »

greatdane

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Re: displacement vs planing hulls...
« Reply #10 on: December 15, 2008, 07:34:25 AM »
Stuey: thanks for the expert input... I am always learning!  The only Bark board I have raced was a 16' "cruiser, not a specific race board.  It was very flat bottomed but was very fast based on it's over all length & little rocker I suppose.  So I can only imagine how much faster a longer and narrower hull profile would perform!!  Unfortunately, most my race board paddling is done on flat water with very few down wind runs.  Still waiting in anticipation for a GPS report on the Penetrator on flat water!  By the way, the air temp here today is 14 degrees >:(
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stuey c

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Re: displacement vs planing hulls...
« Reply #11 on: December 15, 2008, 12:57:51 PM »
    Hey GD,
             I'll see if I can get Woogie out there in the next day or so as we have some pretty still conditions at the moment. He's still recovering from the weekends race, it was a tough one!
             Cheers, Stuey

noa

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Re: displacement vs planing hulls...
« Reply #12 on: December 15, 2008, 01:19:22 PM »
now this will be VERY interesting. a gps does not lie and it's an instant hype killer. or booster, depending on the outcome...

shapeshifter

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Re: displacement vs planing hulls...
« Reply #13 on: December 15, 2008, 02:46:53 PM »
this is a very good thread going here... we all get a lot out of these conversations. i can say from experience that joe's battle boards have quite a bit of displacement especially at the tail making them a bit more difficult to handle in very rough seas. i have two examples with subtle nuances which i look forward to determining the difference between the way each handles once it warms up again in the spring.

btw, it's true that gps's do not lie... but sometimes they just don't know exactly what their telling you.
« Last Edit: December 15, 2008, 02:51:45 PM by shapeshifter »
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Shawn Michael

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Re: displacement vs planing hulls...
« Reply #14 on: December 16, 2008, 11:57:06 PM »
I would love to demo a penetrator.  If it turned a better time that my 18ft bark I would buy for sure.  I am just a bit concerned if my weight would be too much.  I can see a 19x27 double carbon custom penetrator next to my bark.  I think was is great about Barks business is that the boards are custom shaped to your bodyweight and the condition you will be paddling in. 


 


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