Piercing Bows...What works and where?

[TallDude]

Thought I'd start some dialog regarding 'piercing bows'. They've been around for ages, so why doesn't everyone use them? What's good about them? How do you see using them in your design? I have one on my open water unlimited board. I been trying to understand the subtle aspects of the concept for over a year now. It's just starting to make sense to me now. I've paddled my board for almost a year. I find myself just staring at the point of the bow, watching how I enters the water in all conditions. After seeing some of the recent posts about piercing bow designs, I wanted to share some of the functions that I think are key to making it work effectively. Here is a picture of a piercing bow that I annotated. Thoughts?

[TallDude]

I wanted to add, I noticed some of the pictures of the boards posted didn't have so much of the 'Gets Wider' and 'Displaces' elements. If it doesn't displace, it dives....

[sailsport1]

I think what they really help with most is keeping the boat/board from pitching in waves. Decreased pitch is fast.

[Strand Leper]

I get my piercing bow this week... stoked!

Pics when it comes.

Tim

[createinquiry]

I'm sure this video has been viewed by many, but just in case you've missed it, its the boardworkssup video about their new yacht inspired piercing bow design.



Definitely reinforces a sentiment I have that there will not be an effective ways to mass produce these boards.

[SoCalSupper]

Infinity uses them on their race SUPS-dont distance much but theory sounds great!
Was gonna Pierce my bow too when i was younger but chickened out!!

[raf]

cool video.  I want one.  But I don't see why it would be any harder to mass produce than any other shape.

[TallDude]

Great video. It's very cool to get people of that design caliber interested our small SUP toys. Peter's knowlege of hull design is obviously vast. I hope they find some profit in this business, so we can see the evolution of their racing boards. One re-occurring aspect of the piercing bow is the issue of stability, or lack of. They are used mostly on Cat's and Tri-Hulls. The military tested a single hull boat with a piercing bow, and it wanted to roll over on high speed turns. They canned the project. I recently saw a picture of E J (Big Stick) Johnson paddling a mean looking Cat SUP. Maybe dual hulled SUP's with piercing bows are the future? I wonder how they would do on a surf in finish? Could be ugly...

[createinquiry]

My rationale about mass producing these boards comes from the amount of engineering required.

I weigh 170 and my wife 120. So I make a piercing board for myself and then put her on it. That weight difference means that a board I designed to ride somewhere close to neutral buoyancy (not too close) will now float on the surface. What was designed to ride through the waves, is now more of a traditional displacement board, with the same tendencies to pitch as any other board.

To me, these boards seem to need a bit more thought in the design. In a mass produced situation, I don't see that people will see gains from this design that would justify the production of these boards.

Please refute this if you have other feelings, great discussion.

[raf]

It seems its just those nose thats shaped different.  Drop the rocker, and put an acute angle on the front and voila, piercing hull.  The back 2/3 of the board is going to be very similar to what is already being "mass produced".

[createinquiry]

I totally see what you're saying there.

Maybe I'm overemphasizing the importance of waterline to these boards over other board types?

Rider too heavy = the board dives/pearls through chop
Rider too light = the board planes across the surface due to increased distribution of boards volume across the bottom surface of the board.

None of this is to say that these boards won't be produced on a larger scale. If the idea gains traction, and people can look at a board with this different nose shape and say, "Man, I want that!" of course it will be made.

But IF there are actual gains to this shape in any lake/sea conditions, I can't see how off the rack boards will be able to realize these gains.

Great thread, please correct my mistakes, I'm really curious about this shape and appreciate any misconceptions being corrected.

[lazymodo]

I dont think you would want neutral buoyancy in a board , would you? In scuba yes, but in boards?On an SUP, I think the design is just a way of changing the way the bow interacts with chop etc. , an added feature. On high speed cats , thats another story but i think paddleboard design needs to be approached differently, no power plant. Just muscles.

[TallDude]

Thinking of how the wind pushes my board around (and me), if the board is designed with the waterline right near the top rail, the wind may no longer be an issue (with the board). Your feet would be wet all the time, but would it still have enough glide? Being a big guy, I recently paddled a 12'6 race board that I just submerged. It still paddled and had glide. It even feel relatively stable. As opposed to riding on top of the surface. Where is the optimum waterline for a SUP?

[Strand Leper]

I dont think you would want neutral buoyancy in a board , would you? In scuba yes, but in boards?On an SUP, I think the design is just a way of changing the way the bow interacts with chop etc. , an added feature. On high speed cats , thats another story but i think paddleboard design needs to be approached differently, no power plant. Just muscles.

Spot on Lazymodo... I rode a near neutral buoyancy surf SUP a few weeks ago... 85 liters or so (me 180lbs)... 7'9" by 25 by 3.2 (ish)... I could stand... and paddle... and even caught a few waves on it... but it was tough...

First, you crouch with your knees bent and the board totally submerged... then you let the board slowly rise toward the surface... then, when the nose is near the surface... you need to paddle... with a very, very quiet upper body... once you have momentum... you are good to go and now worries...  (there is a LOT of falling down in between the board submerged and "once you have momentum" stage... ;0)...

Many lessons learned from that session... 90 liters is my limit being one of them.

Tim

[createinquiry]

A near neutral surf SUP seems like a bad idea to begin with. Surf SUPs should all be planing hull as the wave adds the needed force to get these boards onto plane. A semi/displacement hull is designed for a different purpose. So, I don't know that this is the perfect counterpoint to designing for rider specific bouyancy. This was not a board designed to be at neutral bouyancy, it's just a board that is too small.

Paying attention to the boards and the video interview below, I think that we're all stuck on making these like surfboards with fancy noses. Talldude, a question like yours about the waterline really got me thinking about the physics of all this.

Drag is proportional to wetted surface area WSA. So a fast board should minimize WSA. For a simple reference the pic at http://www.multihulldynamics.com/news_article.asp?articleID=208 is useful.

A semicircular hull gives the least WSA, but also has the least stability. The M&M boards never show the undersides of the boards, but based on their descriptions, I believe that they incorporate a flattened mid-section, but then cut away the hard edges in the tail to minimize WSA. That maintains the needed volume to float the rider who orders the board (note that they will only custom order their boards.)

Finally, a piercing bow helps with stability by further steadying the ride. As sailsport said earlier, this feature is not meant to speed  up the board, only to add stability to a board by reducing pitching. Thus allowing a paddler to put more power into their stroke, and focus less on balancing.