Reply
 
Thread Tools Display Modes
 
Old 09-01-2011, 01:07 PM   #41
Master and Commander
 
markpierce's Avatar
 
City: Vallejo CA
Country: USA
Vessel Name: Carquinez Coot
Vessel Model: 2011 Seahorse Marine Coot hull #6
Join Date: Sep 2010
Posts: 10,265
Hull Shapes----Show us your girl's bottom

The builder describes the Coot as a "pocket cruiser."* Naval architect George Buehler (he modified plans of another designer to create the Coot) describes it as a "trawler yacht ... designed and built along real workboat ideas."* To me, the Coot's bottom lines are very similar to those of many*working*steel trawler fishing vessels.* Under full power with an 80-HP engine, she doesn't exceed hull speed (less than 8 knots).




-- Edited by markpierce on Thursday 1st of September 2011 01:12:43 PM
__________________
Advertisement

markpierce is offline   Reply With Quote
Old 09-01-2011, 01:29 PM   #42
Guru
 
Nomad Willy's Avatar
 
City: Concrete Washington State
Country: USA
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 13,714
RE: Hull Shapes----Show us your girl's bottom

Still haven't caught up here.

Dude, * Never hit a net but your'e right Willy may go right over. Some of our gillnets here in SE are VERY long. I've never come really close to hitting one though. I see the boat at the end of the net and can usually see the white floats over the stern. When I see that I keep looking till I see the big orange ball at the other end of the net. Frequently takes quite awhile.

I see no cup in the Manatee's hull.

Mike, I've always wanted to see your boat's hull in photographs.

Woodsong, * If your keel was longer you have increased directional stability. Boat would slide sideways less readily in cross winds but when you wanted to swing your stern over w a blast of thrust at full rudder you'd get less swing. The DF 34 is a heavier deeper boat than the Monk. There is less submerged transom in the water and a deeper forefoot. The DF will ride smoother, go straighter generally and in quartering seas and it's general stability will depend more on it's beam than the hard chine. The hard chine soft chine is less of an issue than most folks seem to think. At rest the boat will have a bit easier motion in a beam sea w the soft chine like when fishing. With the same power and enough to exceed hull speed the Monk will be faster because of her lighter displacement and lower wetted surface. When the wind's play'in w ya in the harbor the DF will be noticeably friendlier. The DF would be more efficient at 7 knots Probably the Monk at 9 knots. Does that help?
__________________

Nomad Willy is offline   Reply With Quote
Old 09-01-2011, 01:38 PM   #43
Guru
 
Nomad Willy's Avatar
 
City: Concrete Washington State
Country: USA
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 13,714
RE: Hull Shapes----Show us your girl's bottom

Mark I think you have the near perfect trawler hull. You buttock line at the chine says it all. Perfect speed should be almost a knot under hull speed. "Under full power with an 80-HP engine, she doesn't exceed hull speed (less than 8 knots)." Sounds like she's perfectly powered for a FD hull. If I had your boat I'd prolly cruise at 7.2 knots unless there was an ultra smooth spot right below or above that point. If I had my choice of all the boats on this forum I'd take yours. I may be slightly influenced by the new part.
Nomad Willy is offline   Reply With Quote
Old 09-01-2011, 02:46 PM   #44
Scraping Paint
 
City: -
Country: -
Join Date: Oct 2007
Posts: 13,748
RE: Hull Shapes----Show us your girl's bottom

Quote:
nomadwilly wrote:
So for simplicity's sake I'll accept semi-planing or semi disp as meaning the same and inclusive of 95% of all the boats on this forum.
Eric--- It's a nit pick, no question.* But Fexas' explanation is that there are several kinds of planing.* You can be on the full plane, a partial plane, a mushing plane (what in floatplanes is termed "on the hump," and so forth.* But displacement either is or isn't.* Your hull is either capable of going at or below displacement speeds only, hence a displacement hull, or it's not.* If it's going faster than displacement speed, it is achieving at least a small degree of planing, hence "semi-planing."
Marin is offline   Reply With Quote
Old 09-01-2011, 03:07 PM   #45
Master and Commander
 
markpierce's Avatar
 
City: Vallejo CA
Country: USA
Vessel Name: Carquinez Coot
Vessel Model: 2011 Seahorse Marine Coot hull #6
Join Date: Sep 2010
Posts: 10,265
Hull Shapes----Show us your girl's bottom

Quote:
nomadwilly wrote:
*If I had your boat I'd prolly cruise at 7.2 knots unless there was an ultra smooth spot right below or above that point.
*Need about 92% power (2200 RPM) for that speed.* At 75% (1800 RPM) the speed is about 6.5 knots.* I usually don't like to go over 2000 RPM, giving me*about 6.8 knots: that's one knot less than maximum speed! *I'm still in the breaking-in period for the engine.* Between 1600 and 2000 RPM the engine and drive train sound "sweet" (happy at work without strain)*to me.

*


-- Edited by markpierce on Thursday 1st of September 2011 03:10:10 PM
markpierce is offline   Reply With Quote
Old 09-01-2011, 03:15 PM   #46
Senior Member
 
Dswizzler's Avatar
 
City: LaPaz ,Mexico and the Sea of Cortez
Vessel Name: Delta Swizzler
Vessel Model: 1988 58' Vantare
Join Date: Feb 2010
Posts: 215
RE: Hull Shapes----Show us your girl's bottom

Not sure what you call this bottom, but when we found her, she could now get out of her own way. When a new set of props, clean bottom and alittle TLC to the engines she is runing fine now. Heading out for a 25mile run tomorrow night up into the Delta for the long weekend
Attached Thumbnails
Click image for larger version

Name:	dsc02433.jpg
Views:	129
Size:	221.1 KB
ID:	7323  
Dswizzler is offline   Reply With Quote
Old 09-01-2011, 03:21 PM   #47
Senior Member
 
Dswizzler's Avatar
 
City: LaPaz ,Mexico and the Sea of Cortez
Vessel Name: Delta Swizzler
Vessel Model: 1988 58' Vantare
Join Date: Feb 2010
Posts: 215
RE: Hull Shapes----Show us your girl's bottom

Afew more shots ,
Attached Thumbnails
Click image for larger version

Name:	dsc02443.jpg
Views:	128
Size:	82.3 KB
ID:	7324   Click image for larger version

Name:	dsc02438.jpg
Views:	125
Size:	153.5 KB
ID:	7325   Click image for larger version

Name:	dsc02434.jpg
Views:	121
Size:	210.8 KB
ID:	7326  
Dswizzler is offline   Reply With Quote
Old 09-01-2011, 05:13 PM   #48
Guru
 
Nomad Willy's Avatar
 
City: Concrete Washington State
Country: USA
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 13,714
RE: Hull Shapes----Show us your girl's bottom

Mark,

I think you've got rpm and power/load all mixed up. 92% power is where you burn 92% as much fuel as your engine will burn at WOT and I think that's at 2500rpm when your'e propped right. 2200rpm is probably more like 60 or 65hp. At 1800rpm your'e 700 down from max. My Mitsubishi at 700 down is producing about exactly half power and your JD should be at about 60% power (maybe under 50hp) so 55hp looks more likely. I don't like to go over 500rpm down either (2500 for me) but the engines should be happy 2 to 300 down. My max is 7 knots at 3000rpm and the highest cruise (2500) gets me 6.4 knots. 2300 gets 6.15 and that's my usual cruise. Run your Flo-scan numbers Mark and tell me what you get.

*Dswizzler,

Can't really see your hull shape * ....too dark. Nice big boat though.

Marin,

Your NA is very correct but you are not. Overpowered FD hulls (most are overpowered) can and will go over hull speed. My Willard will go 8 knots w 80hp. That's what one of the guys on Willard Boat Owners group on yahoo says. He has an 80hp 4cyl Cummins and I've seen a picture of his boat underway and he's throwing the wake if a 50 footer in that picture. So FD hulls can (w great effort) go over hull speed but hull speed should be their top speed and cruise close to a knot less. And there are full disp hulls that aren't quite 100% "full" disp like Keith's Krogen and Marks Coot. Both have a little submerged transom but I consider them both for all practical purposes full displacement. And my Willard is not semi-disp. Carl's boat is also 100% FD but given enough power it too would exceed hull speed. This is of course is conversational correctness and not dock talk.
Nomad Willy is offline   Reply With Quote
Old 09-01-2011, 05:30 PM   #49
Scraping Paint
 
City: -
Country: -
Join Date: Oct 2007
Posts: 13,748
RE: Hull Shapes----Show us your girl's bottom

Eric--- Yes, I realize that if you put enough power in something it can be driven to higher speeds that it would normally ever go.* Witness some of the naval ships with massive amounts of power that, when applied, can drive the ship at high speeds but the stern is actually lower than the level of the surrounding ocean.* Staggeringly inefficient but efficiency is not the priime objective with these ships.

When I said "at or below hull speeds only," I meant under normal operation.
Marin is offline   Reply With Quote
Old 09-01-2011, 08:08 PM   #50
Scraping Paint
 
City: -
Country: -
Join Date: Oct 2007
Posts: 13,748
RE: Hull Shapes----Show us your girl's bottom

Mike-- Very helpful "lesson" for people like me with a minimal to nonexistant knowledge of how hulls really work. One question I have is what does S/L ratio mean? I've looked superficially on the internet and find plenty of references to the S/L ratio but nothing that says what the "S" and the "L" stand for. Is it speed to length? Or what?*

And how does the term "S/L ratio" apply to the characteristics of a hull?* In other words, what physical*characteristics of a higher S/L ratio*determine that a hull can be driven faster?* I can see the logic of it in your drawings but I'm curious about the actual reasons.

Thanks much,
Marin is offline   Reply With Quote
Old 09-01-2011, 09:10 PM   #51
Master and Commander
 
markpierce's Avatar
 
City: Vallejo CA
Country: USA
Vessel Name: Carquinez Coot
Vessel Model: 2011 Seahorse Marine Coot hull #6
Join Date: Sep 2010
Posts: 10,265
RE: Hull Shapes----Show us your girl's bottom

Quote:
nomadwilly wrote:
Mark,

I think you've got rpm and power/load all mixed up.
*You're right.* The governor limits RPMs to 2400.* The Flowscan isn't yet calibrated: it reads high.* It shows about 5 GPH at 2400 RPM and 2.5 at 2000.
markpierce is offline   Reply With Quote
Old 09-01-2011, 10:09 PM   #52
Guru
 
Nomad Willy's Avatar
 
City: Concrete Washington State
Country: USA
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 13,714
RE: Hull Shapes----Show us your girl's bottom

Thank you Mike. Wonderful drawings. Wish I could do that and if I could I wouda. Pics can explain some things much better than words. I'm known for drawing much on paper napkins in restaurants. It's good that you used the three examples and perfect examples. I've been trying to get this quarter beam line thing across for several years.*

Marin the SL ratio = Speed/Length Ratio. S/L ratio = speed over the water line length. Hull speed is where the wave of the boat (crest to crest) is the same length as the boat. So w my Willy w a WLL of 27.5' the square root of that WLL is 5.243. Hull speed is 1.34 X the square root of the WLL so we have 1.34 X 5.243 = 7 knots. A S/L ratio of less than 1.34 is under hull speed for any vessel as these bow generated waves travel at a fixed speed. They differ in length. An aircraft Carrier has a hull speed of about 50 knots. That's because the wave will be about 1000' long. Obviously length is golden. Visualize your boat going along making a wave. All things that move in the water make waves that travel away like when you throw something in the water and the little waves travel outward one after another ....the first 2nd and on and on until the waves are so weak they can't be seen. As you proceed at hull speed the bow wave is the instigator and the 1st following wave will be right at your stern and if your WLL is 50' the 2nd following wave will be 50' behind the stern. And if it's calm you can see numerous following waves astern all traveling at the same speed as you. If you speed up a bit the waves will still be going at the same speed because of the chacteristics of waves but they will be longer. Aboard a fast OB the 1st following wave may be several boat lengths behind. On a displacement vessel it's most efficient to run a tad bit slower than the 1st following wave so it pushes you ahead slightly. Some large and slow vessels frequently operate on the 2nd or third wave back to establish a returning wave under the stern. With our short boats the 1st returning following wave (sea) is the strongest so we can take maximum advantage of it. With a QBBL that has an angle approximating the shape of the following wave (perhaps 5 or 7 degrees) the wave will do a better job of pushing us along. I don't know how square sterns and flat runs aft affect the waves ability to help us along. I suspect a shape like the wave would be best however a big wide stern would increase lift aft and possibly help even more. Other types of explanations will be more clear than mine to many just because they are worded differently. I respond to physics more than math and numbers so if someone could expand this on a numerical plane it would be very helpful to some or many.
Attached Thumbnails
Click image for larger version

Name:	sth71295.jpg
Views:	109
Size:	118.7 KB
ID:	7329  
Nomad Willy is offline   Reply With Quote
Old 09-01-2011, 10:30 PM   #53
Scraping Paint
 
City: -
Country: -
Join Date: Oct 2007
Posts: 13,748
RE: Hull Shapes----Show us your girl's bottom

Eric--- Great explanation, thank you, and great photo. It really illustrates what you're talking about. You're hired.
Marin is offline   Reply With Quote
Old 09-02-2011, 01:29 PM   #54
Senior Member
 
bobc's Avatar
 
City: Everett
Country: US
Vessel Name: Note by Note
Vessel Model: 34 DeFever
Join Date: Apr 2011
Posts: 133
RE: Hull Shapes----Show us your girl's bottom

Nice drawings and explanation, Mike.* I used the picture below in another post.** From the angle of the chines, it looks like the GB32 in the yard next to me has the potential for going faster -- given enough power.
<table style="width:100%;" cellspacing="2" cellpadding="0"><tbody><tr><td class="gensmall">Attachments</td></tr><tr><td class="gensmall" style="padding-left:25px;">*</td></tr><tr><td colspan="2"><a></a>
View image
</td></tr></tbody></table>
__________________
bobc is offline   Reply With Quote
Old 09-02-2011, 03:02 PM   #55
Guru
 
healhustler's Avatar
 
City: Longboat Key, FL
Country: USA
Vessel Name: Bucky
Vessel Model: Krogen Manatee 36 North Sea
Join Date: Oct 2009
Posts: 4,181
RE: Hull Shapes----Show us your girl's bottom

Absolutely wonderful explanation, drawings, and follow up. *Thanks guys. *Here's an example of a full displacement Krogen doing what Eric is talking about (riding your own 1st wave).

*

healhustler is offline   Reply With Quote
Old 09-02-2011, 04:37 PM   #56
Grand Vizier
 
Delfin's Avatar
 
Join Date: Jan 2010
Posts: 2,495
RE: Hull Shapes----Show us your girl's bottom

Excellent explanations Eric and Mike.* Thanks!
Delfin is offline   Reply With Quote
Old 09-02-2011, 08:18 PM   #57
Scraping Paint
 
City: -
Country: -
Join Date: Oct 2007
Posts: 13,748
Hull Shapes----Show us your girl's bottom

Mike--- So, is your hull, which is very handsome in its lines I think, considered a displacement hull or semi-planing? It appears to me that the afterbody of your hull is more rounded than that of our GB, for example, which is downright flat*albeit slightly Veed.


-- Edited by Marin on Friday 2nd of September 2011 08:22:07 PM
Marin is offline   Reply With Quote
Old 09-03-2011, 11:47 AM   #58
Guru
 
healhustler's Avatar
 
City: Longboat Key, FL
Country: USA
Vessel Name: Bucky
Vessel Model: Krogen Manatee 36 North Sea
Join Date: Oct 2009
Posts: 4,181
RE: Hull Shapes----Show us your girl's bottom

[quote]Mike wrote:
Quote:
I have received a nasty message from a infrequent poster about my qualifications for posting those sketches.

Mike
Palm Coast FL.

*

Mike, I appreciate it just the same. *I'm sure a more precision, articulate and complex explanation could have been made by some other source, but those sources didn't bother to post one of their own. *Perhaps they thought we were looking for an example which most of us can't really relate to. *I have taken the information here just as you have suggested, without making any of it a rule to live by, and find it a refreshing item of note to keep in my basket of considerations. *That's all I think you meant, and that's all that I took it for.
healhustler is offline   Reply With Quote
Old 09-03-2011, 06:46 PM   #59
Guru
 
Nomad Willy's Avatar
 
City: Concrete Washington State
Country: USA
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 13,714
RE: Hull Shapes----Show us your girl's bottom

The Krogan in healhusler's picture shows a boat sitting proudly between the crests of her own wave. A bit over driven as one can see her following wave is aft of her stern. Probably maxed out at about 9.5 knots. Notice how the inertia of the bow wave pulls the water away from the hull amidships exposing a bit of her normally submerged hull sides. I love these Krogen's. Now that I've seen (thanks Mike) her whole hull I lust after these DF 34s too. But in a race I'd say the GB has the advantage. I'm fuzzy about at what speed the GB would start to have less drag though* ...prolly at about 9 or10 knots. Mike, your avitar shows a boat w almost no submerged transom. Is that the DF 34? And is the buttock line at the keel quite convex?
Nomad Willy is offline   Reply With Quote
Old 09-03-2011, 07:21 PM   #60
Master and Commander
 
markpierce's Avatar
 
City: Vallejo CA
Country: USA
Vessel Name: Carquinez Coot
Vessel Model: 2011 Seahorse Marine Coot hull #6
Join Date: Sep 2010
Posts: 10,265
Hull Shapes----Show us your girl's bottom

Quote:
nomadwilly wrote:
The Krogan in healhusler's picture shows a boat sitting proudly between the crests of her own wave. A bit over driven as one can see her following wave is aft of her stern. Probably maxed out at about 9.5 knots. Notice how the inertia of the bow wave pulls the water away from the hull amidships exposing a bit of her normally submerged hull sides.
*We're about a knot below hull speed here, avoiding trying*the climb out of the "valley."



*


-- Edited by markpierce on Saturday 3rd of September 2011 07:26:43 PM
__________________

markpierce is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Bottom Cleaning CPseudonym General Maintenance 57 03-31-2012 09:21 AM
bottom paint how much motion30 General Maintenance 7 06-15-2011 05:02 AM
Hey Pineapple Girl... Woodsong General Discussion 11 03-09-2011 04:25 PM
Bottom painted dwhatty General Maintenance 7 05-04-2010 03:18 AM
Island Girl Products Dougcole General Maintenance 3 03-30-2009 04:19 AM




All times are GMT -5. The time now is 06:38 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012