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Old 08-30-2011, 08:33 PM   #21
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Hull Shapes----Show us your girl's bottom

Quote:
Mike wrote:
The bottom of the little DeFever looks like my avatar.

Mike, I don't know if your little DeFever is a 34, but here's a picture of mine.

*


-- Edited by bobc on Tuesday 30th of August 2011 08:35:04 PM
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Old 08-30-2011, 08:47 PM   #22
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RE: Hull Shapes----Show us your girl's bottom

Keith- you've got/had some blisters my friend!!
Here is Living Light. I do wish they had carried the keel further aft to better protect the shaft. Someone may know why that was not a good reason???
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Old 08-30-2011, 08:51 PM   #23
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RE: Hull Shapes----Show us your girl's bottom

Eric (or any other hull student!),
Let's compare Bobc's defever 34 and my monk 36. He seems to have rounded chines whereas I have hard chines. His keel goes further aft, etc. What do the differences in these two hull forms tell you about performance of each vessel, cruising speed, etc.?
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Old 08-30-2011, 09:10 PM   #24
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RE: Hull Shapes----Show us your girl's bottom

I've really been enjoying this thread. These are the best bottom photos of Possum's bottom I have on my home computer. I think I've got a better one on my office computer which I'll post tomorrow.

Healhustler, did you know there is a big old hole in the pointy end of your boat? Damn I want a thruster.
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Old 08-30-2011, 09:23 PM   #25
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Hull Shapes----Show us your girl's bottom

Quote:
Woodsong wrote:
Keith- you've got/had some blisters my friend!!
Here is Living Light. I do wish they had carried the keel further aft to better protect the shaft. Someone may know why that was not a good reason???
*Check the rare Monk 36 Twin: yes the shafts are long but if you're going slowly the keel will bump before the props do.* I know from experience.**The hull is semi-displacement because I can raise the bow and wake quite a bit at*top speed.* She wants to get on a plane but I don't have the HP.* For the record I go 7.5*most days.*



-- Edited by Egregious on Tuesday 30th of August 2011 09:25:32 PM


-- Edited by Egregious on Tuesday 30th of August 2011 09:30:39 PM
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Old 08-30-2011, 09:45 PM   #26
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RE: Hull Shapes----Show us your girl's bottom

Tee Hee....
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Old 08-30-2011, 09:59 PM   #27
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RE: Hull Shapes----Show us your girl's bottom

Hope this thread never ends as the most interesting part of a boat is her hull form especially aft. Now that I've seen the DeFever 34 hull I would really like to have one but visability from the lower helm is bad enough to turn me away. Same w the Willard 36. Most of the boats I really want now are wood. Keep the tushes coming.
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Old 08-30-2011, 10:20 PM   #28
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RE: Hull Shapes----Show us your girl's bottom

Quote:
HopCar wrote:
Healhustler, did you know there is a big old hole in the pointy end of your boat? Damn I want a thruster.
*Hopcar: *I see you've photos have you over there at Spencer's place. *I'm sure they'd be happy to throw one in for you. *Nice boat though.
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Old 08-31-2011, 01:21 AM   #29
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RE: Hull Shapes----Show us your girl's bottom

My girl's bottom - very soft - very round - lot's of maintenance

[img]../../download.spark?ID=989860&aBID=115492[/img]

oops -- wrong bottom!!
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Old 08-31-2011, 10:57 AM   #30
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RE: Hull Shapes----Show us your girl's bottom

Nothing remarkable about a Grand Banks hull-- until recently they were all the same regardless of size or model.* Designed by Kenneth Smith in the early 60s this configuration has served well through the mid-2000s.* Provides decent efficiency with low-powered engines (FL120) but with higher power in the larger boat sizes can be driven to cruise speeds of 17-18 knots.

Photos were taken a few years ago during an every-two-years haulout for bottom paint.* On this occasion we also had the props removed and completely reworked which is why they're missing in the photo of the blocked boat.
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Old 08-31-2011, 06:01 PM   #31
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RE: Hull Shapes----Show us your girl's bottom

Quote:
Woodsong wrote:
Keith- you've got/had some blisters my friend!!
Here is Living Light. I do wish they had carried the keel further aft to better protect the shaft. Someone may know why that was not a good reason???
*Yea, the PO told me she had blisters, but I gasped when we hauled her during the survey. Negotiated a price reduction, then spent $25,000 to fix them right. Complete hull peel, post cure with the HotVac system, then re-laminate. Nary a bubble since.
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Old 08-31-2011, 08:27 PM   #32
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RE: Hull Shapes----Show us your girl's bottom

The American Tug hull was designed by Lynn Senour originally as a shrimping boat hull.* Needed to be no more than 34ft, beamy for a lot of fish, and fast enough to get out and back quickly to be as productive as possible.* TOMCO picked up the mold and the AT 34 was born.*
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Old 08-31-2011, 09:27 PM   #33
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RE: Hull Shapes----Show us your girl's bottom

Quote:
Mike wrote:
Bobc -

Ahh,* a Jensen Marine DF 34. Great boat.

When I switched from sail to power that is the boat I wanted, but there are only a few here on the east coast. I ended up with a Jensen Marine DF 38 - called a PassageMaker 40 -* and it is just a slightly larger version of your boat with a tri-cabin arrangement. Exact same hull.

I call it the "little DeFever"* because quite a few of my cruising buddies from Defevercruisers have 41's and they kid me about being "little."* Funny thing though, when we raft up the boats are the same size.

Mr.DeFever calls them all "the 38"

Mike
Palm Coast FL
So your's is the little DeFever.* Why am I suddenly having feelings of inadequacy?*

Mike, we seem to be on the same page, I just made the switch from sail back to power.* I wanted a boat that I felt would be just as comfortable in rough stuff as the Cape Dory I had, and just as easy to single-hand. * I also went with the <s>baby</s> <s>nano</s> pico Defever because I wanted to fit in 35-36' covered moorage. **

Great Laker, as you probably know, your AT34 was built in La Conner, very close to where I keep my DF34.* Nice boat!* Lot's of room inside for a 34, especially in the stateroom, and they still have a usable cockpit.* The AT's seem to be pretty popular here.* I like them better than the smaller Nordic Tugs which are also made locally.* The boat they bring to the boat shows has plexiglass engine hatches on the bridge.* They're kind of cool.
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Old 09-01-2011, 05:50 AM   #34
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RE: Hull Shapes----Show us your girl's bottom

Davis/Defever trawler hull shape
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Old 09-01-2011, 06:36 AM   #35
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Hull Shapes----Show us your girl's bottom

Well, if Moonstruck is not even semi-planing, then I assume she is regarded as true planing hull.* If so then what does that make me old CHB, because she's not that much different, give or take an odd chine strake or two.....sort of...

*


-- Edited by Peter B on Thursday 1st of September 2011 06:38:08 AM
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Old 09-01-2011, 07:48 AM   #36
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Hull Shapes----Show us your girl's bottom

Quote:
Peter B wrote:
Well, if Moonstruck is not even semi-planing, then I assume she is regarded as true planing hull.* If so then what does that make me old CHB, because she's not that much different, give or take an odd chine strake or two.....sort of...

*

*
*Peter B,

I will give my opinion, and wait to see if Eric (Trawler Forum R & D Dept.) throws cold water on it.* First the odd "chine strakes" you mentioned are probably the "lifting strakes" that help get the boat on plane by raising the bow.* They do not carry to the transom.

Your hull, to me, looks like a classic semi-displacement bottom.* Hard chines and flat sections aft.* The wide flat stern should help reduce "squatting".* Put enough power in that hull and she should plane.* However, at lower speeds she is fairly efficient, but not as efficient as a full displacement hull shape.* Grand Banks seams to have started the trend of semi-displacement hulls on trawler style yachts.* Most other Oriental constructors followed suit.* Defevers, Willards, and those based on lobster style hulls mostly have rounded or soft chines.* Even with soft chines the lobster style hulll is semi-displacement as they will plane with enough power.* Most of this style are run at above theoretical hull speed.

Now to how your hull differs from Moonstruck's, your hull has a deaper forefoot that tapers up toward the stern.* You keel starts a the forefoot and ends at the nearly flat section aft.* As Capt. Mike said, Moonstrucks keel runs nearly parallel to the waterline all the way to the stern.* Instead of a "keel" like yours the bottom carries a 16 degree dead rise to the stern.* This and a difference of approx. 880 hp gives Moonstruck a 27 knot cruise speed.


-- Edited by Moonstruck on Thursday 1st of September 2011 07:56:23 AM
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Old 09-01-2011, 09:39 AM   #37
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RE: Hull Shapes----Show us your girl's bottom

Ahhh. Sounds like I've been summoned for cold water dowsing. Photographs are tricky to use to analyze hull shapes. Better than nothing to be sure but can lead one astray. Quarter beam buttock lines tell how well a boat will or won't plane. Remember?... this is a imaginary line fore and aft and parallel to the keel from amidships (roughly) to the transom. But buttock lines can be drawn or imagined that are very close to the keel or very close to the chine. Pure planing boats like yours Don have aft buttock lines all parallel and strait running aft to the transom. You will see that Peters hull has a buttock line at the chine that is as a planing hull but his buttock line at or close to the keel is comparatively steep. That is it runs aft from amidships rising a great deal by the time it gets to the transom. So the inboard buttock lines are not like a planing hull at all. They are rather like a displacement hull. A pure FULL displacement hull will have ALL aft buttock lines running aft all the way to the water surface with NO transom below the water line. Keith's Krogen comes very close. Close enough to be called a full disp hull but actually is not 100% *...more like 97%. But there is an advantage to Keith's 97 in that he can run at hull speed or slightly over better than a 100% hull like a Willard Vega. Another important part of the picture here is the straightness of the buttock lines. Keith's BLs are not too far from strait. I call this type of hull a banana hull whereas the bow is the stem end of the banana and the other end is the stern. My Albin 25 was such a boat. My Willard has anything BUT straight BLs. Very convex. Getting back to Peter's CHB it has a pronounced rise to it's inner BL and a strait BL at the chine. That makes the Quarter beam BL half way between and it has considerable rise. The QBBL is usually giv'in for analysis for this reason. Giv'en enough power (lots) it will go considerably above hull speed but never plane in the way Don's boat does. Peter's CHB is closer to a FD hull than a IG or a GB because the inner buttock lines are steeper and as a result the QBBL is also steeper. So the planing/disp question is answered mostly by the QBBL but with as much transom below the WL as the GB, IG and CHB have they will never come close to the performance of a full disp hull below hull speed. Remember most FD hulls don't cruise at hull speed * ....that is their top speed unless they are over powered ...as most are. So you see Don semi disp hulls really don't have flat runs aft but "flattish" and a bit warped so the bottom is tilted upwards towards the stern. They are a bit like a motorsailer. Not good planing boats and not good disp boats. BUT the vast majority of trawler men are a bit like Marin. He loaths 7 knots and is willing to burn much more fuel to go 8. These semi disp boats are perfect for all such skippers.*
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Old 09-01-2011, 10:55 AM   #38
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RE: Hull Shapes----Show us your girl's bottom

More on hulls.

Look at Jason's hull pics. See the first pic shows his BL at the keel as very steep and convex whereas his chine is almost flat and parallel to the WL. I think Peter's hull is much closer to what the pics show clearly on Jason's hull. Perhaps CHB made more than one hull shape. That's not uncommon. And consider that if the bottom buttock lines curved up to (or above) the WL so there was no submerged transom then that hull would be a full disp hull. Note also that Larry's American Tug shows almost a flat and straight aft run such that his buttock line even right next to the keel is almost straight and flat (very very low angle). I even think I see a bit of hook in the bottom aft of the keel. Speaking of keels if one was to remove it I think anyone would call the AT a planing hull. The keel really has nothing to do w the planing/disp hull question except in a planing mode few NAs would go w that keel because of all the drag. Marin's GB has a little straighter run aft at the keel (that's really where most of these boats differ) that would tend to put it in more of a planing configuration but his boat has a bit less submerged transom which should give it better disp dynamics but give it enough power the boat should squat and assume a more planing shape. That's why (I think) the GBs do fairly well w more power and speed but still perform as well as their brothers at disp speeds.

Don. The lifting strakes have three jobs. In order of importance. They reduce wetted surface (very important in a planing hull). They provide a bit of lift at speed and knock the spray down close to the water where it has a long way to go to get over the rail. No the CHB won't really plane. Actually the lobster hulls are quite efficient at lower planing speeds but cause too much drag and wetted surface at higher planing speeds. I'd say most lobster boats are not semi-displacement but planing hulls intended to be run at slower planing speeds. I think a lobster boat otherwise like yours (disp ect) would be more efficient than your Eastbay at 18 or 20 knots and less efficient at 27. Just a guess. Most people think (incorrectly) that a big trawler like keel makes a hull semi-disp. Not so in my opinion. Has all to do w the hull shape without the keel. You're last paragraph is basically spot on. So I don't think I threw any water on your post. I have offered what I think I know to sharpen up the slightly fuzzy and incomplete parts of your basically good comment. I'm open to facts or opinions that could change any of the above.
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Old 09-01-2011, 10:56 AM   #39
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RE: Hull Shapes----Show us your girl's bottom

Quote:
nomadwilly wrote:
BUT the vast majority of trawler men are a bit like Marin. He loaths 7 knots and is willing t more fuel to go 8. These semi disp boats are perfect for all such skippers.*
Actually I loath eight knots every bit as much as seven.* If fuel prices were not the factor they are we'd have a boat that did 25 knots.* And while it's the accepted term, semi-displacement is not correct.* That's like saying semi-dead.* The term used by the naval architects I've read articles by--- like Tom Fexas--- is semi-planing.

* Semi-displacement is a marketing term coined to help create the image of boats like CHBs, IGs, etc as being close to the "rugged working trawlers" that the manufacturers think their buyers want to pretend they have.* American Marine, creator of the Grand Banks line of boats, never used the term "semi-displacement" to my knowledge, nor did they ever refer to their Grand Banks line as "trawlers."* Their Grand Banks line was always refered to as "diesel cruisers."
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Old 09-01-2011, 12:55 PM   #40
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RE: Hull Shapes----Show us your girl's bottom

Marin,

*The GB line I'm sure will be void of such sins as you say. I am inclined to say semi means "partly" and to apply that word to the planing issue that would mean partly disp or partly planing. Your boat is (as it sits and as you use it) beyond a doubt partly planing as you cruise above hull speed and clearly much more than partly disp. The DeFever 34 is more like a displacement hull than the GB but clearly is not and would thus be partly planing also. When you have a boat that runs well at 18 knots but has a hull that has some part of it's shape that is partly displacement and for that reason that hull could'nt run w Don's planing hull at 30 knots *.....that hull would be "partly" disp or semi-disp. But the word semi-disp brings up an image more like Peter's CHB. Anyway most all trawlers are not FD or planing so are of the huge grey area in between. 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. And GB was right on w "Diesel Cruisers"!!
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