Hull Speed 

The first 90 seconds of this video is the simplest explanation I've ever heard about hull speed. Thanks very much and great job!

Thank you for being so clear and concise! You are a rare phenomenon on RU-vid.

Just listened to a naval architect explain this. Nothing like the explanation you just gave. Common sense. Brilliant.

Soy diseñador y constructor naval. Y a mi juicio tu explicación es brillante no solo por ser cierta, sino también por ser simple y entendible para la gente sin conocimientos técnicos profundos en dinámica de fluidos. Lo bueno, si es breve, dos veces bueno. Saludos.

Superb explanations; you have answered several questions I've had for a while. Clear and concise, excellent, many thanks, Nick.

Very informative without being overly long or boring. Now I want more.

I’m a newb to boating, trying to get my head around planing a marginally powered 8’ inflatable. This is a top notch explanation. Many thanks.

Great job. Well presented. No unnecessary fluff. Adding value and then shutting down.

Wow, three years later I found this. Thank you very much for free school lessons!

Im back. I was here around 2020 and now again in 2022. This is the best, down to earth, useable guide on the internet. Thanks from Denmark! I hope you are still enjoying sailing.

The delivery of the information in this video is just outstanding. As a side note on the principles of shouldering water my grandad had a saying. 'You try to go any faster, and you'll just be draggin' the whole bay behind you."

Hi, thank you, never noticed a smooth way to explain things, thanks again, that was so helpful

i think this is the best explanation i could find on the internet! Great thanks!

Never guessed that spinnaker creates a lift. That's surprisingly cool.

Thank you: clear and to the point. Much appreciated.

Thank you Brad. What a simple and yet comprehensive explanation. You’re an excellent teacher.

A masterclass not only in hydrodynamics but in how to get a message across in simple yet effective terms. I wish this guy was my dad!

Hey mate, self employed marine engineer here. 18 years in the marine industry. Just learnt what hull speed really meant today. Thank you.

A nice explanation. Love the simple wsy of explanation. 😊 And the nice warm feeling of pufin's interior. 😊

Great job, well thought out, to the point and presented without needless side stories, rabbit holes and chit-chat that is prevalent in many RU-vid videos.

This is the most I have learned from a sailing video ever

Perfect example of a clear explanation, well done!

Not being an engineer does not mean that you don't understanding physics and fluid dynamics. You did an excellent job of explaining Hull Speed.Thanls for helping us understand.

very informative & well presented !!! not too little info , not too much info . PERFECT !!!

a wonderfully simple explanation. I spent years sailing as a kid... with some very intelligent guys, but I've never heard hull-speed explained like that.

I recommend that you make more descriptive videos .... You explain things clearer than many others.... Thankyou for posting....

Good video. Clear, simple and right to the heart of the matter.

Brief, concise, comprehensive and very informative clip.

Cheers Brad...once again very well explained mate!

No computer graphics to explain this? Just a whiteboard and a pen? Oh, and you know what you're talking about! Great stuff!

This is the BEST explanation I have EVER listen about displacement hull design, after year of sailing, I had never found SUCH A PERFECT beautiful simple clear explanation. Subscribed immediately, I will watch ALL your video. Thank you! That is what a sea-man should be!

Best explanation I have seen. Brad you don't over complicate things and that makes you an excellent teacher.

Thanks for this video! To the point with just enough technical jargon. You sir are a natural teacher!

Nice and clear explanation of a complex calculation.

The types of sails used really explained a lot. I live in Florida and i like to watch the sail boats and how fast they go. Now I understand they're trying to overcome their hull speed. Thanks for the explanation!

Hi, nice vid and I agreed on most of it. The rule of thumb is right in here, where the estimated hull speed can be derived from the length of the waterline. But as some other(s) noted, the effect of clean bottom or the smoothness of lines mainly affect to the amount of turbulence, thus the amount of power needed to achieve the hull speed. All turbulence created needs energy and that is converted from fuel in the boats propulsion or from wind by sails. So basically, a dirty bottom only increases the needed power, but the boat should still be as slow/fast with that hull length. To go faster than the hull speed, the bow tries to climb over the bow wave, but as some other noted, the effect of wave through at the stern is also in very important role! The stern has its own wake similar to the bow wake (wave) and the hull speed is actually the situation where these two waves interact in the same phase: the bow wave's second wave crest (first one at the bow) has lengthened all the way to the stern and increasing the stern wave which is easily visible from a high stern wave. If going faster than the hull speed, it would mean that the crest of the bow wave would go beyond the stern, thus making a hole under the stern, and sucking the stern down. Together with the bow trying to climb up, this increases the power need exponentially, thus making it impractical situation. What comes to the effect of a bulbous bow and adding a kite sail (spinnaker/gennaker). There your presentation went wrong. The bulbous bow can in small boats increase the waterline length and make it a larger hull speed, in theory, but it also generates its own wave formation as you noted. And this additional wave is easily making more harm since it needs energy from the propulsion such as any turbulence. It is helpful only in large ships that does not operate even close to the theoretical hull speed, based on the waterline length. In those ships the limiting factor is the hull friction due to the large wetted surface, and the wave formation. Every wave you make needs its energy from the propulsion. In ships the bulbous bow is used to counter-effect the bow wave, thus making in result a lower wave. This is especially why it is not seen in sailboats that has to perform in different heeling angles (changing geometry). The bulbous bow is not possible to optimize for different angles and sea states. As for the spinnaker/gennaker help: It does not in general lift the bow, in fact quite the opposite. The force resultant of the sail might point up 10-20 degrees from the horizontal level, but the force is still way above the waterline level, thus making a moment arm that is actually pushing the bow down using the rig as the moment arm. All the dragging force is under waterline and all the pushing force from sails is above the waterline, making a huge moment arm.

The BEST and most comprehensive explanation of HS I have ever seen. Thank you!n😊

When you get on RU-vid to find out why aircraft carriers move so darn fast for their size. Wonderful explanation for veteran and and novice alike.

Wow. I've tired of boating videos because their mostly travelog. Finally someone talking sailing. Thanks.

Novice sailor here. That made more sense to me than anything anybody has attempted to use to explain hull speed to me.

Very straightforward and intelligent video! I learned some surprising things.

So THAT's what it means! Magnificent! Thank you.

Incredible video. clear, concise, and informational. keep it up!

Another well thought out video. Thanks for educating us! An excellent explanation.

You explain this better than anyone on youtube. Wish you were still doing videos.

Thank you captain. You are a great instructor.

This is great. Your explanation of the bow wave was so intuitive. Your right when you say a dirty bottom or bigger keel will create more drag, but I don't think it will reduce your "hull speed". There is a force balance between the power of the engine/sails and the drag from the boat. If you apply more force you can overcome the drag but not the bow wave (aside from vertical lift from sails)

I always wondered what the bulb on the front was for. I thought it was for buoyancy so the nose didn't dive so much. Very well explained from across the pond. 👍

I can't believe this is free. Thanks Cap'n.

Absolutely amazing work, thank you so much for this quality content

Wow!! Splendid explanation, cheers!

This was time well spent. Thank you Man!

That was great. Perfect. Thanks for taking the time.

What a fantastic explanation! And some great tips too. I want more video's.... Sailing Puffin, you are awesome :)

I have to say this was very informative and very clear.. nice work... fair winds to you and Puffin...

Great lesson on hull speed, but a Master Class on teaching by simplicating the subject matter. Thank you.

Great video, Helps me to progress with boat plans. Thanks

Awesome! Love learning this stuff.

Excellent. Congratulations.

well thanks for that. I was able to find it easily, what a beautiful boat... I can't imagine having anything larger than that must have been a handful but just a beautiful boat thanks again

I would love more of these explanations about naval architecture!

Excellent presentation and straight forward info. Many thanks!

Great presentation!

I learned A LOT in your video. Thank you, Sir!

My full respect, you nailed it!

Hi Brad, I really enjoyed this presentation. Thanks for taking the time to put it together and share.

Thanks, much appreciated.

Brad you have done a wonderful thing....you have taught me something I didn't know...actually something I did not know I didn't know. You must have been a teacher in a past life because you are brilliant at it. Thanks you so much for these great videos, please keep 'em coming.

I ve just ENLIGHTENED!!! Thank you sir. Liked and subscribed!

This was great! For one just starting to research for my sailing adventure, this gave some great context for my future boat. Thank you very much for putting the time on it.

Your educational videos are so good, it's a real shame you don't make more. Thank you for the lesson!

An incredibly detailed and inspirational video that helped me pass my sailing edicate class. Thanks so much brad.

Excellent lecture - you have a talent 👍

Thanks Captain, excellent information!

You’re really good in explaining this stuff. Do it more :) Thank you.

Excellent Video, very thoroughly explained. I had a gut instinct about the winged keel and you just explained why it is beneficial...thank you for being a great teacher...

Awesome video, great way of explaining.

Great channel, thanks Cap!

VERY WELL explained! Thank you!

Spent ays reading technical stuff on this, but got no closer to being about to run a simple calculation on a basic hull. Even with the most sophisticated mathematics it turns out to be an estimate anyway, so this simple presentation and formula was a great find. Thanks Brad. Subscribed.

great presentation

Great informative lesson ! Thank you so much!

Concise , clear, and well presented...thank you .

you got a perfect way of teaching!

Would really like to see a video about that for speed boats or ribs. That was a sailing boat Edition but great too

Awesome video

Dude you’re awesome, more videos pls

Excellent and easy to understand, thank you!

I had to do a science project on this and it helped me out a lot. Thanks

Good man at last someone who knows there stuff. Your are a good teacher. 11+Kn well done...Brian London

Ok..very good info thanks puffin

Thank you, sir! Great explanation!

Thank you! This was simple, straight forward and understandable.

Excellent explanation. Thanks.

Terrific! Thank you for this very clear explanation!

Great work

Outstanding explanation.

Great video. Thanks for explaining the huge extension on cargo ships. I always wondered the principal behind them. Although Not enough to Google.

Excellent explanation for a regular guy on a sailboat.

My God, I feel smart now. Thanks for the great video.