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Re: Dream Builder

Posted: Wed Sep 27, 2017 8:00 pm
by JoeM
Mr Hot Rod wrote:
JoeM wrote:What does this number mean exactly? As in, the stern will sit 4 inches lower?

1) Add the weights of all objects. Add the weight moments.
2) Divide the total moment by the total weight. This is the distance from the datum to the center of gravity.

Here are some links to augment Bill's post :

    → For a sample Hull Balance spreadsheet and Weight Moment Study :

    → Info on how to stretch a hull :

Paul Kane
Kane Custom Boats Ltd.
Chelsea, Quebec

Building the Glen-L Hot Rod :
Glen-L Hot Rod build thread
Kane Custom Boats YouTube channel
Glen-L Boat Video Directory

Thanks! Great information here. I think I am finally understanding.

In my example above the weights are showing that the CG is now 4.08ft behind the cb( at designers 8" behind frame 4).
Selecting the transom as the starting point and redoing the distances the moment weight is 37,780 and after dividing with the actual weight of 2,725 the new cg is 13.86ft from the transom.

Re: Dream Builder

Posted: Mon Oct 02, 2017 8:44 am
by JoeM
I'm going to close this thread out and will have all future questions and stuff in the appropriate sub-forum.

However, I want to give a quick update regarding the CB calculations and weight balancing that this thread became.

I received a few more dimensions(Thanks Curt!) and was able to make a little more accurate diagram of the weights and distances I'm working with in addition to increasing the water tank capacity.

After calculating everything I am now at a point where my weight imbalance changes the designed CB by only about 3" to the stern. Working further I deduced that I only need to find room for an extra 125-275lb forward of frame 5 in order to keep the designed CB. I don't feel that this is too much of an issue.

I do have doubts of the larger water tank fitting the space or being too heavy(I went from a 30 gal to a 60 gal pretty much on frame 7) so I also ran the numbers on my 30 gal plan. At this weight it changes the CB almost 11.75" to the stern. To balance it out I need between 250-600 lbs forward of frame 5 to keep the designed CB.

The 60 gal option appears to be able to be stabilized with little more work. I would probably build it and float it as is before adding any ballast as I didn't take into account the few changes to the berth/head area(which would only increase the weight a bit and I need the final layout to calculate the additional weight).

The 30 gal option does give me a little pause as the CB changing by over 1' seems a bit much. Although I believe it is not too tough to add more weight to bring it closer to stock CB. If I find I have to go this route I would likely try to add a minimum of 200 lb's forward of frame 5 and see how she floats at that point. Mildly tempted to see about putting a small 15-20 gal bait tank on the bow but i'll have to see if I can find the room for the tank and all the plumbing later as I figure out the final layout.

I'm now more confident of the theoretical balance and my ability to do the math. Thanks all. Any future posts on my project will be in the appropriate sub-forums.