Your hull type

Eric - Your babby's got good looken booty!! :lol:

Willy's baaatumm. Willy's baaatumm.

Kinda tubby but w the big rudder following seas are a walk on the pond.

manyboats said:

KJ,
If you understood what the QBBL is then you'd know it would be 0 degrees.

The planing hull you presented is the opposite ........straight.

Click to expand...

Thank you for the explanation (again), it's perfectly clear to me now.

BTW, the speedboat was meant to be the obvious antithesis of a FD gal.

KJ

Eric - With that boat's smooth butt and that giant size rudder you could patent "following seas" as the 21st Century boating new-energy-source!

Our hull form



photos-annonce
structures-et-cotes


And , may be one day ,the next evolution :
structures-et-cotes

What is the maximum size for an photo ?
I can't insert one may be too big ?

longcours62,
I think you're from Norway and I've seen your boat lines on boatdesign.net. I love both the lines drawing boats and the one that is in your avatar. The latter is a different boat than the one in drawings (I think). About the boats in the lines drawings I'd say they are 96% full displacement. Too much transom immersed to be 100%. But w such a low PC (prismatic coefficient (low = skinny on the ends)) it should have the same (or nearly so) resistance a bit below hull speed as a 100% FD hull. Perhaps this is better than Dashew's boat. Should be easily driven a bit over hull speed also. Just think'in out loud here. Looks like a sailboat designer designed it. Would make a wonderful trawler for these times of costly fuel. It may pitch more than a boat w fuller ends (higher PC) but the efficiency should be well worth it. Seems to me I knew a sailboat, probably a class boat that had almost exactly the same lines including the narrow flat bottom near the keel.
Go to the info on posting to get the photo info you need. Looks like the boat in the avatar has a warped bottom aft......rather straight QBBL's near the chine and steeper by the keel. However that keeps the chine under the WL aft and produces a quiet boat at rest. Lets see some pics of the avatar boat from aft when hauled out.

longcourse62

Might be of help

Sizing Pictures: Following works for more than one format

Open pict
Right click on pict
Punch EDIT at top of box
Punch IMAGE on top line
Punch STRETCH/SKEW in box
Change BOTH STRETCH #’s from 100% to 20% (lower the percent = lower the pict size – adjust accordingly)
Press OK
DON’T TOUCH SKEW – Unless you want pict to become dimensionally “skewed”!
Close picture and punch YES when box appears
Open pict and right click – punch PROPERTIES – check pict KB size

Adjust again if needed. As long as you change BOTH STRETCH #’S equally (and don’t mess with skew) you can enlarge or reduce pict to whatever size you desire without distortion of items in the pict’s ratios.

longcours62; said:

What is the maximum size for an photo ?
I can't insert one may be too big ?

Click to expand...

On the old forum I believe the maximum photo attachment size was 2.5 mb. On the new forum it's smaller, 195 kb for a jpg file. Which I guess might explain why thumbnail photos attached to posts blow up less sharp on this version of the forum than on the first version.

I run everything through Photoshop so I resize any photos I'm going to include in a post to about 900 pixels wide. This is down from a camera original size of about 6,000 pixels wide and the jpg file size goes from 5 to 7 mb to less than 1 mb.

This is the same size setting I used on the old forum but photos "blew up" much sharper on that forum. I've even posted the same photo I've used on the old forum and they are noticeably less sharp here now. So it's not my photo or my computer. I assume there's some compression on photos on the new forum that wasn't there on the old one.

The actual hull lines

of our boat .
The designer who make the hull lines is Joubert, well know in France but
I don't know if also 'over seas'...
The original drawing was for a motor "motor sailor" with no transom, hull deeper (little) and chine 'higher'
The second photo was taken at around 11,4 knt the 'maximum' reasonable speed , booth engines at 2300 rpm.
More economic at 1850 rpm speed 9,8 knots and 1,78 lt per nm
and 'very' (never enough ) on one engine at 1500 rpm speed 7 kn and
0,82lt per nm .

One photo where we can see transom

and appendices.
The pitching is not a problem at all we 'concentrate the weight but the the roll it is not the same because we have a ( too ?!) great stability (like a sail boat ) and the period of roll is also like a sail boat ...without mast

Looks like a planing or semi-planing hull to me. Can't tell from the pics, but appears to have a completely flat hull for most of it's length. The twin keel (of sorts) probably adds to it's stability.
That style hull and superstructure is almost identical to the small inland crew boats here on the Gulf of Mexico.

Good morning 62,
Pictures can be so deceiving. The stern is a lot narrower that it looks in the pics and the bottom is not nearly as flat as it looks in the pics. Your'e right Tony but the lines drawing tells it all. I love your avatar picture longcourse. It's interesting to see the bow wave coming back boiling up under the stern. And the house is so low and trim. Wish more trawlers were more like that. It's strange.....to get a really good boat most often one has to build it himself. How much power do you have in her and what is the working displacement longcourse?

PS....I can see now how the pitching is fully controlled. Both ends are fuller than I had thought.

Another thing I like about this boat is the twin screws and single CL rudder. Most power boats have a great deal of propwash driving hard against the rudder so the net effect is that the rudder tries to pull the boat back. Of course one needs to create more propwash to overcome this ect so more efficiency is clearly the result of the twin screw single rudder installation. The downside of course is that a larger rudder is required without the aid of the propwash. This arrangement should be smoother while going relatively straight as the propwash isn't shaking the propeller. I wonder what the designer's motive was for this arrangement on this boat.

So Eric, am I blind or what? Where are the props on this boat? Or have they been removed in the Travelift and would be on the ends of what look sort of like shafts emerging from the twin "keels" more or less amidships? If so, then I assume the "keels" are to protect the props. With the fin ahead of the rudder, this makes a tripod, so I wonder if this boat is intended to go aground on the big tides they have in the North Sea and sit on the hard every time the tide goes out? It's a pretty common arrangement on sailboats in that part of the world, which have side-by-side keels that act as a stand when the tide goes out from under them.

I find the propwash very desirable to magnify rudder effectiveness and have little concern with the alleged "pulling back."

Eric, did you mean to say "propwash isn't shaking the rudder" rather than shaking the propeller? Haven't experienced that, but then my rudder (like yours) is supported both top and bottom.

Our rudders don't "shake" either, Mark, and they are suspended spade rudders, not supported rudders like yours. The only time we get rudder buffetting is when we have to tie off a shaft because of a precautionary engine shut-down. The locked prop puts out a tremendous amount of turbulence and this buffets the rudder behind it which of course is connected to the other rudder and the steering system. So the wheel wiggles and jerks a bit.

I will try give some details

First all we got from the designer are the on the two pic , just list of numbers.
After that I do all the rest with my wife (may be I am not clear , don't misunderstand !)
We choose just one ruder for the raison wrotte by you before, and also one
rudder is 'less' less job , money, but deeper.
We choose also a quiet big surface of the rudder for keep a good maneuvrablity a small speed (for exemple when we are under our hudge sail plan)
For the hp we have two too bigs engines 2 x 215 hp in reality at 9,8 knts
we 'use' less than 100 hp
we explain here why finaly we fit this engines :
Motorisation - Le blog de long-cours
But sorry again in French , but when you read me you clearly understand why !!
Twin engines of 110/130 hp are clearly enought for our use
with ratio 3/1 for gearbox.
Our actual propellers (not on the photo taken when the unfinished hull arrive at La Rochelle) are 4 blades and 27'X27' , we fill something is wrong with this propellers : they don't take enought hp if we compare with propeller curve given by Perkins....and after few years we don't get any answer from the makers ...
The hp taken by this propeller is exactly the propeller curve of the 130 h Perkins and we have the 215 C.
I could be better to get this power with less rpm.

Our displacement is

33 T at (very) full load (few hundreds kgs of books , tools , wood, spares ... and mess, we living on board since 2003)
Our D/L is around 150
When I wrotte 100 hp at 9,8 knts it is the total (50 x 2)

Marin said:

Our rudders don't "shake" either, Mark, and they are suspended spade rudders, not supported rudders like yours. The only time we get rudder buffetting is when we have to tie off a shaft because of a precautionary engine shut-down. The locked prop puts out a tremendous amount of turbulence and this buffets the rudder behind it which of course is connected to the other rudder and the steering system. So the wheel wiggles and jerks a bit.

Click to expand...

Marin - I agree with you. Our Tolly rudders are similar design to your GB's and don't "shake" during normal operations.

Did your precautionary engine shut-down last for many hours... to where you felt it necessary to tie off a shaft for trany protection? Won't your trany let you free wheel for a period of time at slower speeds with no internal damage? Our 71C BW trany are (according to the factory) OK with extended time of freewheeling prop as long as boat is kept under 8 knts speed. I’ve not needed to run with engine shut down due to precautionary measure... but we do at times run at around 6 knts with one engine shut down - for fuel economy (right at 2 gph). I take care to alternate engine use each hour just to be sure that even though the BW factory says it’s OK... I don’t push the envelope of trany internal lubrication. With one prop under power and one in freewheel, at 6 knts, I don’t notice any rudder vibration/shaking. Guess, as you say, turbulence from locked prop could cause some rudder vibration. I’ll get ambitious and test that some day! - Art

Longcourse,
100 hp on your boat = about 3 hp per ton. Assuming you have a WLL of about 55' your hull speed should be about exactly 10 knots. And w 230 hp on tap and if using 100hp you're at about 47% engine load. Your hull is long and (I think) rather narrow (like the Dashew boat). The power to drive your boat through heavy seas should be low and your windage is very low so you should'nt need much over disp speed power and that seems to be 100 hp so if I were powering this boat I'd opt for about 165 hp or a tad less. Hopefully your 215s are most efficient at about 50% load but most engines are most efficient at about 80% load. I think. Tom are you here? What say you? So not only is your boat a very excellent design it seems to be efficiently powered. I would like to see a picture of your boat at right angles from the side. Out of the water of course.

Mark, Marin,
Of course your rudders are'nt shaking. Your boats are in excellent condition and the rudders are solidly mounted. BUT.....if any of your rudder bearings were loose there would be plenty of shaking. The water slung off the ends of your propeller blades are trying to shake the bottom of your boat too. If your boat light and flexible right above your propellers you will feel the vibration there too and most likely through the rest of the boat as well. The rudder and the bottom of your boat right above the props will be hammered by the propeller wash proportional to the closeness of the parts. Propwash is a bit like a hydraulic jackhammer. And no Marin....the boat was not designed to be beached on her propeller shaft keels. The "keels" are there almost entirely (or entirely) to support the propeller shafts. And yes the propellers have been removed. I'm assuming the faired prop shaft struts or keels are of minimum size (area) to minimize drag. It looks like they may be skewed a bit to conform to the flow of water under the bottom of the boat. The more I see here the more I like.

Side photo

front one and also section of our rudder.
Our lw is 60' and our beam at wl is (around) 14'4"
Sure to time 110 hp is enought
because actualy as wrotte before we need less than two time 50 hp

Art; said:

Did your precautionary engine shut-down last for many hours... to where you felt it necessary to tie off a shaft for trany

Click to expand...

Our shaft log is cooled/lubed by water picked off the engine's raw water cooling system. No running engine, no cooling water to the log and it will quickly overheat and severe damage will occur to the shaft and the log. So if an engine needs to be shut down the shaft must be locked before continuing on the other engine.

Shaft logs cooled/lubed by a pick off from the engine's raw water system is not an uncommon arrangement.

So while our BW Velvet Drive transmissions can be freewheeled "at trolling or sailing speeds" as stated in our BW manual we can't freewheel a shaft exxept at extremely low speeds and even then the log and shaft heat up considerably.

longcours62 said:

front one and also section of our rudder.
Our lw is 60' and our beam at wl is (around) 14'4"
Sure to time 110 hp is enought
because actualy as wrotte before we need less than two time 50 hp

Click to expand...

I am still back in trying to see/understand where the shaft prop come through/out. So does the prop shaft go through the twin keels? Are the twin keels strong enough to support the weight of the boat? Do they also effect the stability/roll of the boat?

It does not take much HP to propel a boat at hull speed through the water. The DD 671 is 165 hp, and I figure at hull speed, 7 to 9 knots only 75 to 100 hp is required.

PhilFill, wrote ..."Are the twin keels strong enough to support the weight of the boat?"
Very very doubtful I'd guess. I do'nt think this boat was designed to be careened.
longcourse,
Close enough. I can see the QBB lines aft and see that it's quite raked and thus steep at the keel (or on center line) and very close to flat at the chine. So the QUARTER beam buttock line is still a moderately steep so I think I was right in the first place as I recall saying it was not quite a FULL disp hull.....in other words it's not as full a disp. hull as it could be. It's better ....I think, than most full disp hulls and the smaller the boat gets the better the hull becomes until it's so narrow it lacks the stability to be of any general practical use. I would love to change Willy into a boat w this hull about 34' long. I'd probably want to add some ballast but the result would be far better than Willy in my opinion. I wish there were 35 to 40 yr old trawlers w a hull like this as I'd probably buy one. Thank's so much for sharing longcourse62.

(Willard 40') full displacement

The propellers

manyboats said:

PhilFill, wrote ..."Are the twin keels strong enough to support the weight of the boat?"
Very very doubtful I'd guess. I do'nt think this boat was designed to be careened.
longcourse,
Close enough. I can see the QBB lines aft and see that it's quite raked and thus steep at the keel (or on center line) and very close to flat at the chine. So the QUARTER beam buttock line is still a moderately steep so I think I was right in the first place as I recall saying it was not quite a FULL disp hull.....in other words it's not as full a disp. hull as it could be. It's better ....I think, than most full disp hulls and the smaller the boat gets the better the hull becomes until it's so narrow it lacks the stability to be of any general practical use. I would love to change Willy into a boat w this hull about 34' long. I'd probably want to add some ballast but the result would be far better than Willy in my opinion. I wish there were 35 to 40 yr old trawlers w a hull like this as I'd probably buy one. Thank's so much for sharing longcourse62.

Click to expand...

Our sterntubes pass in the "twin keels" but they are not twin keel because they are lot aft.
As you can on the pages of number above you have 41 section from the bow to the stern
the "twin keels" begin at the number 28+ and finish around 33.
When we stay ashore or for the tide, the main weight of boat and the main point of contact (if not A vicious rock ) it is between N+ 16 and 18 this point is very strong : watertight bulkhead and pillar (200X200X10)for the mini mast (but sized for an eventually normal sized mast ,just in case and the bottom of the hull at this place is near flat and 1 m wide , the plating of the bottom is 16 mm thick.
Aft it si the 'fin ' who protect and support the rudder.
The base of the "twin keels" at this moment touch the floor
And for more stability we put our daggers board down and block them in this position.
We need nothing more for stay ashore.

For the ballast we have already 6300 pounds and before we had mainly sailing boats it is why we concentrate (as possible) the weight and design a relatively low profile .
It is why we got a (too?) big stability with short roll period...
When we roll in moderate weather we are thinking may be it is a mistake and when we are in bad weather we are thinking it is a good idea

It looks as your boat has hard chimes which would help dampen the roll. Where as the Eagle hull is round, but the keel/bilge is filled with concrete, the tanks and engines are down low, so like your boat most of the weight is down low.

So where are the daggers and how do they block in place?

I am surprised that you boat’s bow wake is flared out which seem to indicated you are going fast than hull speed? So what is the max speed? The Eagle can reach 10 kts but we are pushing a lot of water as shown in the avatar picture.

Until now

Phil Fill said:

It looks as your boat has hard chimes which would help dampen the roll. Where as the Eagle hull is round, but the keel/bilge is filled with concrete, the tanks and engines are down low, so like your boat most of the weight is down low.

So where are the daggers and how do they block in place?

I am surprised that you boat’s bow wake is flared out which seem to indicated you are going fast than hull speed? So what is the max speed? The Eagle can reach 10 kts but we are pushing a lot of water as shown in the avatar picture.

Click to expand...

We don't know our maximum speed for two reasons :
we never push the throttles more than 2300 rpm (and just for few minutes!) for come closer to our friend and his GB50 for make the photo , you can see on the avatar.
Around 11,4 knts at this moment and if our wake flared out like that it is may be our friend waiting the right moment for the photo, the weather forecast said 25 knts wind, may be it help a little but we have no wind indicator and this day we could just "feeling" and we 'feel' less than 25 kts.(and my stomac also and it is a very good specialist for "appreciate" the real weather
and the second raison , we fill something is "wrong" whit our prpellers , we feel they don't 'eat' enought hp they are 4 blades 27'X27', but
The dagger boards are betwen the section 16 and 18 (on the side of the wheelhouse)you can see them on the photo at
Dérives - Le blog de long-cours

longcours62 said:

We don't know our maximum speed for two reasons :
we never push the throttles more than 2300 rpm (and just for few minutes!) for come closer to our friend and his GB50 for make the photo , you can see on the avatar.
Around 11,4 knts at this moment and if our wake flared out like that it is may be our friend waiting the right moment for the photo, the weather forecast said 25 knts wind, may be it help a little but we have no wind indicator and this day we could just "feeling" and we 'feel' less than 25 kts.(and my stomac also and it is a very good specialist for "appreciate" the real weather
and the second raison , we fill something is "wrong" whit our prpellers , we feel they don't 'eat' enought hp they are 4 blades 27'X27', but
The dagger boards are betwen the section 16 and 18 (on the side of the wheelhouse)you can see them on the photo at
Dérives - Le blog de long-cours

Click to expand...

I see them on the deck right behind the door? So how do you let them down and block in place? How far down do they go? Can you adjust them for different depths? Do you notice much difference with them down?

Thanks for the Picture