Thanks again for a response, I think it's great that you're engaging with your viewers. It's interesting to think with extreme examples. They can make obvious the problems with considering only one measure of a board. For instance, we imagine a board which is constructed typically, with the addition of a single very long foam spike penetrating the water. As the length of the spike increases the volume of the board continues to increase, yet little vertical dynamic lift would be generated by this spike if it were to move through the water. We might find this strange board meets the typical volume requirements for our weight, calculated by manufacturers, yet this board would likely be unsurfable in a typical orientation. I think volume in conjunction with board shape gives a much more complete picture of whether the board size is suitable for us. On the question I asked, it's been a while since I asked it. Since then, I have read more and I think the term "planing area" is not typically used, and "wetted area" is the more correct term for this measure. In terms of my surfing progress, you and your team's engaging content has helped me in at least one way. After reading the web article about how a surfboard works, and after some reasoning and arguing with myself about the content, I came to the idea that boards can travel faster than the movement of the breaking point of a wave, even without the rider pumping (which seems so obvious now). For any boards where this is the case, a rider will inevitably outrun the steep section of the wave and slow to a halt. Now, for me to stay close to the steepest section of the wave on a fast board, I must do one of the following: stall the board and wait for the wave to once again pick me up, increase my drag and travel at the same speed as it, or perform a cutback after surfing away. The necessity of cutbacks has never been this obvious to me. Before I saw them as something I would eventually learn just for more control or style, now I see them as necessary to increase the speed of my surfing, and I've since learnt to perform them adequately, and I'm having a blast. Looking forward to more content, Phill.

Epic video Harry, loved the second question, it's so obvious when explained this way.

At the end you said it's really hard to compare the surface areas of 2 different boards. However, if you see someone surfing a board and wondered what size that board should be for someone of your own weight, what you can do is divide the weight of one surfer by the other, take the square root of the answer and use this number as a factor to adjust the dimensions of the board. For example if you weigh 80kg and ride a board 6ft long (72 inches) x 19 inches wide, and I weigh 100 kg, 100/80 = 1.25. The square root of 1.25 = 1.118. Hence the length of the board I would need to ride to be the equivalent of yours would be 72" x 1.118 = 80.4" (ie 6ft '8ins) and the width would be 19" x 1.118 = 21.25". This would give me almost exactly the same surface area as you have. It's also the reason why virtually no larger people successfully surf small boards, and in my experience hardly any shapers appreciate just how much bigger they should be making their boards to suit bigger surfers. Incidentally, if you want to get the same volume for your weight, you'd need to take the cube root, which makes the differences slightly less.

Great video, quite surprised about the buoyancy difference between Eps and PU, having ridden same volume boards in both I can (an am not the only one) say EPS paddle noticeably better.

Pretty please go into more physics detail about hard rails. I’m a wake surfer and most of your content translates wonderfully. The episode about rails understandably focuses more on soft rails. I’m a skim style wakesurfer so my rails are usually hard all the way around depending on the board. I love what you guys are doing!

Good job Harry. Someone is definitely going to pick on your “smaller area generates more lift” at 9:35, when it’s clear than you meant that as the speed increases, the area necessary to generate the same lift reduces, as lift is proportional to the speed squared ))

I was just thinking about this the other day surface area vs volume, great video, thanks!!

Such a nice content, thanks for all. I was wonder if you can talk about paddling for a tube and tube position. I always had a huge problem for paddling to fast and shallow waves. thanks again.

Very interesting videos man! I've learned a lot :) If I may give some videography advice which could help the production quality by a lot. If you use an extra microphone, turn sensitivity a little bit up (the volume now is a little low, even on max on my system at least) and if you don't have one, Getting a simple shotgun mic from Rode for example will make a HUGE difference, even the most basic one bellow 50bucks will make a huge difference in quality. And secondly, add some light, like a led video panel or any constant ligtsuourse in a softbox, I for example often use a 20 pucks 30w LED flood light (for your setup you might need something stronger) that's not even made for productions and strap it to a cheap softbox, and it works perfectly on the cheap! You don't need to spend hundreds of dollars on gear! but these 2 things would improve the look and sound of your vids a lot! Cheers and keep them coming! :)

Great videos. I love that we're bring engineering and fluid dynamics into surfing. There is so much to learn here.

Once again, great stuff! My appreciated

Love your explanation on the buoyancy difference between the foams. Maybe just your percentage calculation could reflect the forces that the paddler feels, rather than the standup surfer. Am thinking it could be 1:30 difference which may be more felt by the paddler??

great video!

Can you provide a quick way to calculate board volume? Thx mate!

Aloha from Hawaii Harry First I want to say thank you for making these videos and that I really love the way you guys break things down to explain them. This might be an odd question, but it caught my attention. You briefly mentioned dyslexia while writing on the board. Maybe that was just in jest, which wouldn't bother me one bit, but I was wondering if that is something you work with? I ask because I am a special education teacher with dyslexia, and I have always found it to be an advantage when teaching, if I take the time and care to explain things the way I understand them. At any rate, excellent content and very well explained. Thank you

So theoretically a concave bottom has more surface area? Right? So more lift? But is it that simple? And what about a double concave? Even more lift or do other factors come in to play? Thanks for vid BTW.