FS17 sole level problem

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TomW
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Post by TomW »

Jacque as a summary he used a 11'(length of sole) straight edge with a level and was bow down 2.5" in current configuration.

First he moved the gas tanks(110 lbs) back to motorwell frame, now bow down 1".

Second filled cooler with 154 lbs of water placed at same frame, now transom is down 1/2"

It appears from this that 210-215 lbs at the motorwell frame is needed to bring his sole level.

Hope this helps.

Jim correct me if I'm wrong.

Tom
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JimMac
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Post by JimMac »

Tom and Jacques- Thats about it. I hope to get some sea hours on it this weekend and report back more on how she handles.

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Post by jacquesmm »

Tom, your reasoning is correct but it is abnormal to have to move so much weight back to get the boat level.
I am 300 miles away but on Monday, I will run a complete spreadsheet with the modifications and post it with the hydrostatics.
I did it for the basic version and we will compare.
I guess that we will discover that there is too much weight forward.
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topwater
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Post by topwater »

Didnt you move youre center consul forward :?:

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Post by jacquesmm »

It's Monday noon and I still did not have the time to start on the spreadsheet: be patient, it may be for tomorrow.
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JimMac
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Post by JimMac »

No problem, I'm using the boat as she is.

One measurement that would help determine if the hull is riding bow down is the distance of the waterline at the bow in relationship to a plumb line dropped from the bow.
If this shows the hull to be on its marks then the only thing left is the sole not being level, which is what I suspect.

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Post by jacquesmm »

Since you modified the bow, to measure at the transom is much more accurate.
I'll try to post the spreadsheet and related drawings today.
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Steven
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Post by Steven »

JimMac wrote:No problem, I'm using the boat as she is.

One measurement that would help determine if the hull is riding bow down is the distance of the waterline at the bow in relationship to a plumb line dropped from the bow.
If this shows the hull to be on its marks then the only thing left is the sole not being level, which is what I suspect.
Hi Jim,

How do you suspect the sole could have ended up not level?

Steve

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Post by jacquesmm »

Spreadsheet done.
It's mostly in metric but it all adds up nicely.
The designed LCB, boat level at DWL, is at 3,378 m from my design origin which is the tip of the bow.
The boat with a small console, a 263 lbs engine on the transom, battery in the console, gas tank in the bow 12 gallons half full, a small anchor etc. in the bow locker, two men at the console (one behind, one next) puts the LCG at 3,341 meters.
That means a difference of 1-1/2" which equals to a few thousands of an inch at the waterline. Move a six pack of beer a few inches and it will be right.
The boat floats as she should be and BTW, that is clear from the pictures, she looks right.
Now, lets try the boat empty but with 12 gallons of fuel forward and some extra 50 lbs for the modified sheer and stuff.
LCG is now at 2.935 mm.
I calculated the new trim for that LCG and the bow goes down 48 mm (1-3/4") and the transom lifts up 100mm = 4". Bad.
This is close to what you measured.
Conclusion:
Your hull shape is correct, the design is correct but because of all the weight at the bow, she will not drain at the dock unless you move some stuff.
I did it once more with standard bow (no 50 lbs of raised sheer and 1/2 a tank) and she drains. Borderline but it drains.
Even then, to be safe, if I leave the boat unattended at the dock, I would keep the battery or the anchor in the stern.
For all builders who plan to leave the boat at the dock, I would move the battery to the stern.
I will zip the Excel file and upload it if somebody is interested but the good news is that the design is right and the JimMac's hull is correctly built.
It's just a matter of too much weight forward in a boat that is sensitive to it.

PS: the question of what outboard weight I use comes back often.
I use the ABYC/USCG weights, not a 2 stroke or 4 stroke weight from a brochure:
http://www.abycinc.org/standards/purpose.cfm#S30
Jacques Mertens - Designer
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jgroves
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Post by jgroves »

JimMac, I would be happy to be your weight... I will move anywhere in the boat you need me. I can fight fish, hold things (preferably the beer) and I don't complain too much. With the proper amount of beer I will gladly sleep in the boat while docked. Just an offer :D .
Jeremy

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