I just came across your channel. It is so refreshing to have a channel that doesn't do soft porn or condocats. I have a 38ft strip cedar cat I built that I work on too, she is currently getting a paint job which is taking a long time. I had the same issue as you when I put my new outboard pods on. As I came home from the slipway where I fitted them, the outboards (Yammie high thrusts) would rev each wave. I didn't do anything with the props, but I extended the depth of the pods. My pods are rotating so they are flush with the bridgedeck when retracted but they now don't ventilate at all when motoring, so maybe you could also extend the mounts to drop the motors when needed. My motors are slightly further forward, this means they don't get kicked out so much as yours may when my cat pitches. Great channel, thanks for showing us a truly interesting boat, with real innovations. Such a breath of fresh air in a world of production cats.
Another solution would be to use 4 blade props that are cupped. To do this and still maintain full RPM of the engine the pitch number is usually reduced by 2 when moving to a 4 blade prop, best to consult with technical services at a reputable marine retailer or contact the manufacture. Four blade props offer more thrust, better maneuverability, better mid range cruising efficiency, and offer a better initial boost to get the boat moving(some call it a hole shot in the US), in a planning hull boat the 4 blade prop will keep the boat on plane at a lower speeds when compared with the standard 3 blade prop. Three bladed props are better for top end speed which is not what you are after. Solas propellers offers aluminum and stainless replacement prop in 4 blade and three, in cupped and non cupped.
As a retired teacher I can only admire your way of explaining difficult things. If you can’t explain things easily it means you don’t understand them (said a fellow named Einstein) Love your videos.
If the underlying problem is that waves are heaving the props up and down in the water, then having the motors further forward (for example on a tilting platform) could help. Depends on (longitudinal location of) the athwartships axis about which the boat pitches. For a cat that's usually near the mast, and of course it varies by center of gravity and hull hydrodynamics. If so, then the props might see more stable water depth nearer the mast, i.e., further forward. For a cat with a wider stern at the waterline, the pitch axis may be further aft.
Thanks for the comments. I've done quite a bit of work on this and it seems thatthe pitch point on most cats is about 1/4 forward of the waterline from the stern. I'm planning a video on pitching, regarding Wild Honey specifically, which you may find interesting :)
@@SailingWildHoney The pitch axis (it really is a point in 3d space, but I called it an axis in 2d space, like a profile view) will be in different places depending on boat design. The forces will act through the center of mass. If the hydrodynamic forces on the hulls were equal fore and aft then the pitch point would be at the center of mass, etc. So depends on design, but may be further forward, especially on a fine stern with less pitch resistance aft.
Thank you. I don't know much about propellers but now I know a bit more. Another way to check balance is to place the propeller horizontally on a cone balancer like a lawn mower blade balancer. Might be a little tricky with a boat prop but maybe it could be done. :)
Perhaps it would be more effective to arrange for the propellers to reach deeper into the water? Add a telescoping piece to the mount that give you an additional 30 cm, and make a replacement hood that can stand hard splashing and being "submerged" occasionally, and add some nice smart replacement for the standard seals for the Choke knob opening in the die cast aluminum body etc. I'm building a set of two electric drives, 70x70 mm brushless motors feed by 100Ah 48V LiPo pack, as replacement for my outboard. I chose to do this because of the cumbersomeness of having a heavy gasoline engine. The new propellers are attached directly to the motor shafts, super tight and lightweight in comparison to commercial solutions. I sail a 1989 formula 28 catamaran, for it I have been using a single 6 hp Tohatsu SailPro that sat just a few dm above the water. Yet it lifted the propeller up and it sucks air when the waves are high. The boat is an old racer, so it’s only 700 kg (8,5 x 5,5 m with 15 m mast), and 6 hp did not take me upwind in hard conditions, but it allowed me to choose the downwind path 😏 Now I hope to be able to go any direction 😄 Thanks for your inspiring videos!
Thank you! Your boat sounds great!! Years ago we did look at electric but it was in it's infancy and we couldn't really afford it. But I did make some fibreglass pods for electric drives, which we then abandonned for the more conventional route. Lowering the engines would be a possibility if the problem with motoring were more severe, but the cupping has been surprisingly effective :)
Your 9.9 has a 5" spacer making it an extra long shaft. I added 5 more spaçers and welded 25" more driveshaft making a 50" shaft. This solved the cavitation problem and was well worth the cost and effort
Interesting study , I did think you were going to look at the height of the water in the tank to determine thrust ( relative difference)? FYI to improve epoxy bond to alum or lead I do a final sand with some wet epoxy on it which keeps the air away from the alum and stop it oxidizing then go straight into laminating . Cheers Warren
Love how you mount the outboards. What type of track is it and how did you mount it? Could you do a video on this? How do you raise and lower them? Steer them? Using outboards seems like way less work than mounting diesels internally. And if the type of cruising changes you can change to bigger or smaller ones. You seemed to suggest that the choice was influenced by being cost-constrained (aren't we all?). But is it not a better solution, or do you have reservations? I'd love to hear as I am mulling over this decision for my own design.
Thanks for your comments, and great questions! The track is a standard large mast track - a discontinued Bainbridge product - and we've built a custom car to go up and down. I've put this on the list for a film in the spring when we're servicing the outboards :)
If you angled the propellers, then the up down motion would not strip the boundary layer on the propellers as much. Normally most boats have their propellers deeper so higher pressure also keeps the boundary layer attached. Only real solution(maybe) would probably be a propeller with its infinite blade tips. Of course currently only designing them for the 150HP market, and they cost $5000 a piece.
I admire your engineering prowess in tackling that modification. I think I would have looked to having a longer engine mount. Not sure your front / aft explanation was quite correct. Moving them a bit forward normally puts them at the highest point of the hull wave. And closer to the point of least pitching. I have a Woods Gypsy, the builder put the mount on the rear beam, very similar to your location. I notice that Richard Woods drawings show the outboard in a cockpit well. If you don’t turn the outboards I can’t see the front / aft make a difference on the manoeuvrability. It is more the distance from the centreline. Of course if you can turn the outboards, as far back does work well. I can turn my motor which is pretty essential as it has a flat bottom. I had a 22’ cat and used a dinghy motor that swivelled 360deg , great for turning and amazing for reversing.
Interesting, thanks for the thoughts! We have a friend who had a 360 mount and yes, it was really great for manouevring. But it was a lot smaller boat. Moving the engines to the pitch point will definitely help, but not an option for us at the moment.
Wow, someone who thinks, I love it! As a previous viewer said, "it's refreshing not to see soft porn and condo cats" your video was so good it made me subscribe! Please keep them coming.
What about a propeller "tube" to eliminate the "water slip" from the rotsting prop? Cupped props only work in one direction, the opposit one lacks thrust. Coming from more powerful outboard engines the stainless steel props gain more bite due to thinner blades which also are more stiff compare to alu at high revv. Really expensive and hard to repare
a kort nozzle? too much drag for a normal sailing prop when not in use - but probably great for this setup since you retract them out of the water when not in use.
Interesting idea! We did consider using them, but felt that the issue we had experienced with the hydrofoil wing would be similar with a tube, in that a ventilation bubble would get trapped in the nozzle
I tried to Google the hull designer - Phil Collins i think you said his name is. I don’ t get any relevant hits :-). Do you have links to other boats he designed??
Yes you're absolutely right @LoanwordEggcorn - sorry we thought we'd replied to this. Phil Morrison also designed Severalles Challenge - a 35ft tri that Laurence liked the look of - Exmouth Challenge, a 60ft tri which became Umopro Jardin, and a F40 cat called Rebel, later called QAB :)
Good morning, my name is Julio, I live in Argentina, would you be kind enough to inform me what design the katamaran is, and if you have an email to contact me. greetings. sorry for my english
Your explanations are excellent. Describing your sequence of prototyping and testing sets you apart from most other sailing videos I've seen.
Thanks for the feedback - happy to hear you are enjoying them :)
I just came across your channel. It is so refreshing to have a channel that doesn't do soft porn or condocats. I have a 38ft strip cedar cat I built that I work on too, she is currently getting a paint job which is taking a long time. I had the same issue as you when I put my new outboard pods on. As I came home from the slipway where I fitted them, the outboards (Yammie high thrusts) would rev each wave. I didn't do anything with the props, but I extended the depth of the pods. My pods are rotating so they are flush with the bridgedeck when retracted but they now don't ventilate at all when motoring, so maybe you could also extend the mounts to drop the motors when needed.
My motors are slightly further forward, this means they don't get kicked out so much as yours may when my cat pitches.
Great channel, thanks for showing us a truly interesting boat, with real innovations. Such a breath of fresh air in a world of production cats.
Really appreciate the feedback, and details of your boat. We'll see how the cupping goes and report back!
Another solution would be to use 4 blade props that are cupped. To do this and still maintain full RPM of the engine the pitch number is usually reduced by 2 when moving to a 4 blade prop, best to consult with technical services at a reputable marine retailer or contact the manufacture. Four blade props offer more thrust, better maneuverability, better mid range cruising efficiency, and offer a better initial boost to get the boat moving(some call it a hole shot in the US), in a planning hull boat the 4 blade prop will keep the boat on plane at a lower speeds when compared with the standard 3 blade prop. Three bladed props are better for top end speed which is not what you are after. Solas propellers offers aluminum and stainless replacement prop in 4 blade and three, in cupped and non cupped.
Fascinating demonstration of intuitive DIY
Thank you! :)
As a retired teacher I can only admire your way of explaining difficult things. If you can’t explain things easily it means you don’t understand them (said a fellow named Einstein) Love your videos.
Thanks for your lovely feedback - really great to hear you have enjoyed them :)
Laurence, I have always loved listening to your engineering explanations. I can wait to see more!
Thanks Giles :)
If the underlying problem is that waves are heaving the props up and down in the water, then having the motors further forward (for example on a tilting platform) could help. Depends on (longitudinal location of) the athwartships axis about which the boat pitches. For a cat that's usually near the mast, and of course it varies by center of gravity and hull hydrodynamics. If so, then the props might see more stable water depth nearer the mast, i.e., further forward.
For a cat with a wider stern at the waterline, the pitch axis may be further aft.
Thanks for the comments. I've done quite a bit of work on this and it seems thatthe pitch point on most cats is about 1/4 forward of the waterline from the stern. I'm planning a video on pitching, regarding Wild Honey specifically, which you may find interesting :)
@@SailingWildHoney The pitch axis (it really is a point in 3d space, but I called it an axis in 2d space, like a profile view) will be in different places depending on boat design. The forces will act through the center of mass. If the hydrodynamic forces on the hulls were equal fore and aft then the pitch point would be at the center of mass, etc.
So depends on design, but may be further forward, especially on a fine stern with less pitch resistance aft.
Thanks for the videos ! You have done an amazing job all around. I love it .
Thanks for the feedback! So glad you're enjoying them :)
Thank you. I don't know much about propellers but now I know a bit more. Another way to check balance is to place the propeller horizontally on a cone balancer like a lawn mower blade balancer. Might be a little tricky with a boat prop but maybe it could be done. :)
Interesting idea! :)
Perhaps it would be more effective to arrange for the propellers to reach deeper into the water? Add a telescoping piece to the mount that give you an additional 30 cm, and make a replacement hood that can stand hard splashing and being "submerged" occasionally, and add some nice smart replacement for the standard seals for the Choke knob opening in the die cast aluminum body etc.
I'm building a set of two electric drives, 70x70 mm brushless motors feed by 100Ah 48V LiPo pack, as replacement for my outboard. I chose to do this because of the cumbersomeness of having a heavy gasoline engine. The new propellers are attached directly to the motor shafts, super tight and lightweight in comparison to commercial solutions.
I sail a 1989 formula 28 catamaran, for it I have been using a single 6 hp Tohatsu SailPro that sat just a few dm above the water. Yet it lifted the propeller up and it sucks air when the waves are high. The boat is an old racer, so it’s only 700 kg (8,5 x 5,5 m with 15 m mast), and 6 hp did not take me upwind in hard conditions, but it allowed me to choose the downwind path 😏 Now I hope to be able to go any direction 😄
Thanks for your inspiring videos!
Thank you! Your boat sounds great!! Years ago we did look at electric but it was in it's infancy and we couldn't really afford it. But I did make some fibreglass pods for electric drives, which we then abandonned for the more conventional route. Lowering the engines would be a possibility if the problem with motoring were more severe, but the cupping has been surprisingly effective :)
Your 9.9 has a 5" spacer making it an extra long shaft.
I added 5 more spaçers and welded 25" more driveshaft making a 50" shaft. This solved the cavitation problem and was well worth the cost and effort
Sounds brilliant - I'd like to see that.
Wow! Interesting solution, and can see how that would work :)
Interesting study , I did think you were going to look at the height of the water in the tank to determine thrust ( relative difference)?
FYI to improve epoxy bond to alum or lead I do a final sand with some wet epoxy on it which keeps the air away from the alum and stop it oxidizing then go straight into laminating .
Cheers Warren
Thanks Warren! Yes, the "experiment" left a lot to be desired :)
Great tip for the epoxy bond
I like your kind of engineering.
Thanks! :)
Love how you mount the outboards. What type of track is it and how did you mount it? Could you do a video on this? How do you raise and lower them? Steer them? Using outboards seems like way less work than mounting diesels internally. And if the type of cruising changes you can change to bigger or smaller ones. You seemed to suggest that the choice was influenced by being cost-constrained (aren't we all?). But is it not a better solution, or do you have reservations? I'd love to hear as I am mulling over this decision for my own design.
Thanks for your comments, and great questions! The track is a standard large mast track - a discontinued Bainbridge product - and we've built a custom car to go up and down. I've put this on the list for a film in the spring when we're servicing the outboards :)
Really enjoied your video. Look foreward to more.
Thanks! More in the pipeline :)
If you angled the propellers, then the up down motion would not strip the boundary layer on the propellers as much. Normally most boats have their propellers deeper so higher pressure also keeps the boundary layer attached. Only real solution(maybe) would probably be a propeller with its infinite blade tips. Of course currently only designing them for the 150HP market, and they cost $5000 a piece.
You're right! And propellors are expensive! But the cupping has been surprisingly effective :)
I admire your engineering prowess in tackling that modification.
I think I would have looked to having a longer engine mount.
Not sure your front / aft explanation was quite correct. Moving them a bit forward normally puts them at the highest point of the hull wave. And closer to the point of least pitching.
I have a Woods Gypsy, the builder put the mount on the rear beam, very similar to your location. I notice that Richard Woods drawings show the outboard in a cockpit well.
If you don’t turn the outboards I can’t see the front / aft make a difference on the manoeuvrability. It is more the distance from the centreline. Of course if you can turn the outboards, as far back does work well. I can turn my motor which is pretty essential as it has a flat bottom.
I had a 22’ cat and used a dinghy motor that swivelled 360deg , great for turning and amazing for reversing.
Interesting, thanks for the thoughts! We have a friend who had a 360 mount and yes, it was really great for manouevring. But it was a lot smaller boat. Moving the engines to the pitch point will definitely help, but not an option for us at the moment.
Wow, someone who thinks, I love it! As a previous viewer said, "it's refreshing not to see soft porn and condo cats" your video was so good it made me subscribe! Please keep them coming.
Really great to hear you enjoyed it - thanks so much for the feedback :)
Magnificent video again - loving them
So glad you like the films - thanks for watching!
Oh, I love your videos thanks so much‼️‼️
So glad you are enjoying them. Thanks for watching!
What about a propeller "tube" to eliminate the "water slip" from the rotsting prop? Cupped props only work in one direction, the opposit one lacks thrust. Coming from more powerful outboard engines the stainless steel props gain more bite due to thinner blades which also are more stiff compare to alu at high revv. Really expensive and hard to repare
a kort nozzle? too much drag for a normal sailing prop when not in use - but probably great for this setup since you retract them out of the water when not in use.
Interesting idea! We did consider using them, but felt that the issue we had experienced with the hydrofoil wing would be similar with a tube, in that a ventilation bubble would get trapped in the nozzle
I tried to Google the hull designer - Phil Collins i think you said his name is. I don’ t get any relevant hits :-). Do you have links to other boats he designed??
Thanks, so pleased you're enjoying the channel :)
Phil Morrison is the hull designer. He is a very famous sailboat designer. For example, he designed the Laser 5000.
Yes you're absolutely right @LoanwordEggcorn - sorry we thought we'd replied to this. Phil Morrison also designed Severalles Challenge - a 35ft tri that Laurence liked the look of - Exmouth Challenge, a 60ft tri which became Umopro Jardin, and a F40 cat called Rebel, later called QAB :)
Liking, subscribing and commenting.
1. Rotating wing mast.
2. Bridge deck clearance?
3. Weight?
4. Length?
5. Construction?
Schionning meets Catana meets Marsaudon meets awesome?
It's no S Class/ Kevlar/ Basalt Fiber Atlantic 57 but I graciously accept your offer of Officer Idiot, 4th Class.
😂 Thanks so much for the comments! Lots more of these areas are in the pipeline for videos :)
Happy I found "" U ""
You need some trained jellyfish to tow the boat instead
I find the music running non stop distracting. Try using room tone to help bridge across your dialogue edits.
Noted. We had a discussion about the music, and one of us is now sitting smug! Thanks for the feedback :)
You don’t need it, not a fan.
If you do think a bit of background helps, waves on a beach perhaps
are you a kiwi
No I'm a Brit who grew up overseas and have picked up a weird accent 😂
Anneal the tips of the "real" props before trying to peen the tips.
Hmmm, interesting. Thank you for the tip :)
Good morning, my name is Julio, I live in Argentina, would you be kind enough to inform me what design the katamaran is, and if you have an email to contact me.
greetings. sorry for my english
Hi there, Julio! Your English is great :) The boat is a Phil Morrison design