Thank you very much. Finally - a video showing a boat running in other than flat calm seas. Real conditions, so the ride can be observed. Excellent, appreciated.

When I got my 21 I had some correspondence with big fluke and I might of posted this way back when but it is worth reading...


Cleaning up my home messages and wasn't sure if I answered you. The boat is up and running and we have ventilation problems with the outboards that Jamie positioned somewhat between the keel and mid hull panels. Next week we're modifying the outboard bracket to move the engines further apart like I've seen on some of the old photos. We think if we clear the riser between the keel and mid hull panels we will see cleaner water. To counter the weight of the Armstrong bracket and twin Suzuki 140s, we've had to put 500 pounds of chain in the bow to get her to balance right. She runs great in a head sea, plunges a little too much to my liking in a following sea. Overall, very good forebody but not as good as the SeaCraft 25'. It probably could use more flare in the bow and a big spray rail forward between the chine and keel. What really surprised me is how softly she landed when launching off 3' foot chop on top of 4' long swells. Considering the average deadrise is about 20 degrees compared to the 26 degrees of the SeaCraft 25', she is almost as soft!

The 21' is quite impressive and with the mods we've made to the 25', including a production 30' based on a geosim of it, it is obvious Moesly was a great designer. We are working on a high seakeeping 24-26' RIB with high displacement of ~ 8500 lbs. Based on our tests on the 25', she simply tops out at a displacement of 7500 lbs so it does not make a good parent craft. I was thinking of stretching the 21' to about 24.5' and was curious about the differences between the 21' and the Potter 23'. I have limited experience from riding the 23' over 30 years ago and as best I remember it wasn't that impressed with the ride and remember getting soaked. I need to know more about the 23' to see if stretching the 21' will detract from her seakeeping.

We have used a digital camera and 3d software to create a very accurate solid model of the 21 and 25 and the differences/similarities are amazing. If you keep the keel panel of the 21' as the baseline parallel to the static waterline, the mid and outer panels slope down as they move aft, about 1.5" over 6'.

Anyway, didn't mean to go on so long BTW, the serial # of my 21' is 111.

Interesting stuff, thanks.


This one goes in my long term save file.

Ha . . . all could think about when he said the 21 hull might benefit from some more flare was this boat (21 with spray rails and flare)

http://www.wellcraftv20.com/gallery/...bum07/40_G.jpg

Is. Trader, thanks for re-posting your note from Big fluke. Interesting points on the flair and splash rails.

As I recall, Bushwacker's colleague, Bob - was not as fond of the splash rails idea. I have toyed with the thought of continuing the flair on my 21 and this really validates my thought process.

Nice photo, Big. Any other angles of that hull?
I keep looking at the 21 wondering why the flare didn't continue up and out.

Only thing I could figure was less favorable aerodynamics and less water to shed ...

Very interesting post Terry! Do you know if Big Fluke ever got more info on the 23? It is most definitely NOT a streched 21! The step heights are less on the 23 and there appears to be more deadrise in the outer panels, so Potter apparently did not follow Moesly's design principles when he designed the 23. More deadrise in the outer panels should help the ride, while raising min planing speed and hurting load carrying ability, but the relationship between panels is also different and I'm sure that's very important too. The 21 would plane at about 12 mph with an I/O, and I've never heard of a 23 being able to plane that slow. Big Fluke's impression of the difference in ride between the 21 and 23 are consistent with my experience as well as my friend Bob who owned the Moesly 21 "Unohu". I suspect Bryan/3rd Day has ridden in both the 23 and 21 more recently, so would be interesting to get his comments as well. I understand Potter gave Mr. Moesly a ride in the 23 as soon as they returned from their first circumnavigation trip; Carl, being too much of a gentleman to tell him what he really thought, supposedly just said "Well, there are a few things I would have done differently"!

Gilley, Bob absolutely loved the ride of the 21' Unohu; he's pretty stubborn, and was of the mind set "if it ain't broke, don't fix it"! I wasn't surprised that he wouldn't consider spray rails, as he ran it for over 10 years without trim tabs! He finally changed his mind and added them after following me into Lucaya years ago into a particularly nasty 3' chop. He passed me as I was only running about 15 kts, but I think I was more comfortable than he was at 20 kts! For what it's worth, I think Skip is planning to add spray rails to his 21, and I'm sure he can give you some good design info on them.

Carl once told me, in response to a question about differences between the 21 and later hulls, that he intentionally designed the 21 with very little dynamic lift, "because you're not making much forward progress where there is a lot of vertical motion"! That may explain the lack of flair and the "spray deflector" conventional strakes he added to the 25 and 27' hulls, and the flat at the forward chines on the 20's. I'm sure that staying dry was not a big priority on the race boats! Denny

It's great to get this kind of knowledge, background, and feedback on the hull differences . . . 23 might not be as good as a 21, but it's a damn good riding boat. I can plane in my 23 b/w 11 and 12mph (without tabs too). I suspect the 400lb Pilot house, batterys up front, and a small 370lb motor helps.

Never knew of that video... Thanks Tim for posting it. Bigfluke loves his 25 seafari's I think he keeps one in the stock configuration. The other two he has heavily modified as part of his experimental deep V program. Here are some pictures that he has sent me over the last several years. I dont think he would mind me posting them as he has been extremely helpful to many of us on this board.

Making the sponsoons or Ama's as they are referred to in Hawaii.

http://www.casdvm.com/photos/steven%20Lui/section1.JPG

http://www.casdvm.com/photos/steven%...ttach_side.JPG

http://www.casdvm.com/photos/steven%...inted_dta1.JPG

http://www.casdvm.com/photos/steven%...inted_dta4.JPG


25 seafari with Weisman outdrive, surface piercing prop and 480 hp Yanmar engine!


http://www.casdvm.com/photos/steven%20Lui/DSC01450.JPG

http://www.casdvm.com/photos/steven%...468%281%29.jpg

http://www.casdvm.com/photos/steven%20Lui/DSC01415.JPG

http://www.casdvm.com/photos/steven%20Lui/DSC01428.JPG



He put the fuel tank in the bow on one of his 25's just to see how it would ride!

http://www.casdvm.com/photos/steven%20Lui/DSC01422.JPG



His first 25 he modified the bottom of the boat and then put on some rocker plates. This boat had a 300hp Yamaha on a bracket.


http://www.casdvm.com/photos/steven%...20install1.JPG

http://www.casdvm.com/photos/steven%...20install2.JPG

http://www.casdvm.com/photos/steven%...--15%20kts.JPG


strick

Strick, fabulous pics showing ideas in progress. Great to have access to someone who can do that sort of thing, thanks. Did bigfluke say anything about why he modified the chines? Looks like that mod would substantially increase drag while underway, adding stern lift and making the aft part of the boat dryer. What was his reasoning?

How fast was that 480 hp rocket??

Funny how small this 21 looks...:confused: