KamaII
 

http://www.youtube.com/watch?v=ln3Y1A_RNCM

Found this clip on youtube of navatek 25 seafari

what the heck : are those fins on the sides?

Good question! Kinda funky.

tim nice soft ride wish mine was ready

what are those on the sides???

Sponsons. He added them to give it more lateral stability and stern lift.

The Kama II belongs to forum member Bigfluke. He has three other 25 Seafaris including one that was converted to a CC. He's the president of Navatek Ltd. in Honolulu. It's worth a visit to their web site for a look around. They're doing some cool stuff with lifting bodies and anti-slamming monohulls

http://www.navatekltd.com/sam.html

The SAM 9 meter is an unmanned vessel they developed for Homeland Security and the hull is based off the 25 Seafari with the sponsons added.

Tim,
Thanks for posting the link. Very cool.

Dave

Makes a lot of sense. With twins and such an extreme deepV, the boat might could use both stern lift and stability. Looks like it worked. Not sure, but the boat seemed a little bit more stable in a beam sea than mine. I wonder how it works at rest? The boat can be pretty tippy at rest and in a big, steep beam sea, the side to side motion gets pretty wild. I thought along the same lines as those sponsons, but could not see a good way to attach something temporarily.

Dave, do you have any info on how well the sponsons worked?

Looked at the Navetek website, answered my question.

Thanks to Bigshrimpin for posting that, fascinating.

Definatly the best running video of a seacraft on the web

This is fun. Navetek has a bunch of other videos up on utube including this one:

http://www.youtube.com/watch?v=32Zvx2swW5U

Main subject is a 51 ft speedboat running fast into a decent size swell. Right behind it and keeping up just fine is one of their 25 ft seafaris.

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:

Terry - I'm pretty sure it's #40 John Steinback rigged as a single outboard . . . last 2 pages of the race results. Came in #1 in single outboard division for a few races.

http://www.moeslyseacraft.com/upload...lts-jmp1-6.jpg

Largest 21 I`ve ever seen. I was out of sight inside. Thank you.

Cheers,
GFS

Conner, I never asked him about the boat with the big chines. On the boat with the sponsoons he said that he was trying to create more lateral stability and correct the heeling to port side which my boat does do a little as well. Here is one of his e mails addressing this.


"The attached SeaCraft 25' picture shows the boat before modifications. We have been tricking it out with outboard sponson additions (ama in Hawaiian) to improve stability and are presently installing engines and fuel layout which gives an extremely forward LCG to improve seakeeping via lower running trim and higher moment of inertia. With this LCG you don't get much bow rise to get on plane. We have some patent pending tricks to the running hull bottom to provide increased forebody lift and ventilation to increase efficiency via better trim and less wetted area to offset the drag that is the negative of a such a forward LCG. Bottom line is that with a LCG of 37% of waterline length, we get the same speed as one set up race boat style at 27% LCG. Design lightship is 5300# and max displacement 7500#. While we have played with other hulls that have as good a head sea ride it is an unbelievable hull that even at these full load displacements we haven't been able to stuff the boat running downsea.

We used the amas instead of large trim tabs to achieve transverse stability at rest as well as running. Also, the amas stopped the chine walking and port heeling we were getting with all the single engine 25's we've tested. The other advantage of our final layout of pushing the engines and fuel so far forward is the clear aft deck area for fishing, coolers and other payload. The engine box serves to give us a raised command bridge."

strick

I remember shipping that red 25 to Hono, 4 maybe 5 years back "Avalon" from NY, I think...the same week I looked at a 24' Airslot out of curiosity. I thought what what would their respective designers talk about over a few adult beverages? :rolleyes:

Clearly Big fluke had already considered their merits...

Big, was Steinbacks blue "40" a 21'? and would he have been running a single 140 hp tower of power?

Strick, is Chet kin folk? Interesting note from Big fluke.

Interesting stuff, Strick. A lot between the lines when I think about mine.

I never noticed either chine walk or port lean, but mine is a duoprop that should eliminate the lean and I almost never run fast enough to chine walk. I wonder if those two are connected? It does want to porpoise a bit when light, as bigfluke noted somewhere else.

Love the ama idea for stability at rest, but how much drag does it add? Should be quite a bit, but with his engine hp, who cares.

I wonder how our single V8s compare with his calculations of CG. CG going from 27 to 37 should change the CG point about 2 feet (i think). Going from a double six to a single v8 should be about 6-700 lbs less in the stern, moving the CG higher by a substantial degree, but I don't know how to do the calculation. Blue Heron, any help? I know mine doesn't have much bow rise to get on plane, especially when loaded heavy.

Big Flukes boat is HEAVY, I figure mine light is at something like 1000 lbs lighter than his and 7500 lb is a huge load. He must have a whole bunch of those pig weights.

That's interesting, I looked at a 24' Airslot just before buying my 20' SF. It had a big tower on it and the guy was asking for about what the tower was worth. If I had a few more feet in my parking space, I would probably wound up with that and put a bracket on it. I'd be in it even more deep than I already am however.

Is anyone in touch with BigFluke anymore? The air cushion amas is an interesting idea.

Is there more than the Amas/ sponsons? The video is now is 720P and I got two or 3 good screen grabs. I think those are alignment/ registration marks for installation or video. Unless they are lateral steps??

Note the spray rail that morphs into a lifting strake as it transitions aft. It sheds whisker spray, reducing drag, and provides more lift to support the forward CG he was running. Look at the beginning of the video when he's in displacement mode. The boat is loaded down with a CG pretty far forward.

http://www.wellcraftv20.com/gallery/...258_Medium.jpg

It's interesting to see BigFlukes 25 mods . . . I wonder if those black marks might be showing LCG?

Good eye! I thought that line on the hull looked funny. Mine is under 4 feet of snow, so I could only go by memory.

I keep thinking about building sponsons for my 25, and think I know how I might build them, but not sure what shape. But that spray rail/ strake thing is another feature. Was that for the one that had a big diesel in it, maybe pushed forward. So that might not be needed on something with a puny SBC in it?

Strick-

If you can make it so we can see the images again, that would be great? I know I can't see them- I get a notice about lacking permissions?

If you are comfortable doing so.

Thanks!

They look to be in about the right spot...

All his pictures have been down for a while, he hosted his pics on his own domain and don't think he keeps it up no more. I wanted to look at his bracket build photos a while back and realized that just about all of his pictures unless quoted are gone now. I did save some of these seafari clips tho, I will try to find them and repost them.

Here's one of them:

http://i1291.photobucket.com/albums/...ps5323dd0c.jpg

Holy crap! What is that and why is it on a 25' SeaFari? Seems WAAAY out of place.

Bigfluke (Steven Loui - President of Navatek LTD) used the 25 seafari hull to research and develop his 9m SAM hull (Seakindly, Anti-Slamming Monohull)


The pic above is a 25 seafari with Weisman outdrive, surface piercing prop and 480 hp Yanmar engine.

This isn't the seafari but it's a video of one of those drives in action

https://www.youtube.com/watch?featur...&v=DINWsjuh-ys

Thanks Frizz and Bigshrimpin! I'll take anything you have!

I don't know if you guys were aware but Navatek makes a line of complex deep vee hull designs, including Sea Blade fishing models 16',17',19' and 22' in fiberglass and aluminum. And up to 30' for commercial users and even larger for the military.
Very interesting hull designs and I can see some comparable ideas on this 25' SeaCraft. Amas, air entrapment tunnels, fine bow, high deadrise, multiple longitudinal and transverse steps, multiple panel running bottom.
30 patents.
Lots of similiarities to the VDH hull.
Read some good reviews of the hull's running ability in rough water; only the layouts aren't that good for fishing.

Home Page: http://www.sea-blade.com/

Small boats: http://www.sea-blade.com/?page_id=8

Link to YouTube video of 17' running in Hawaii: https://www.youtube.com/watch?v=ST3yA9LqnmQ

More videos.

What is a SeaBlade hull: https://www.youtube.com/watch?v=6LmkE-bk5Pc

Some larger models: https://www.youtube.com/watch?v=CT9h4yYopxI

SeaBlade 17 review: https://www.youtube.com/watch?v=gYfwAHKinc0

When I get to Hawaii, I want one of these!