28 Bertram Restoration Boat 2

Questions about boat repairs with our resins and fiberglass: hull patches, transoms and stringers, foam, rot etc.
DAYTRIP
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Re: 28 Bertram Restoration Boat 2

Post by DAYTRIP » Mon Mar 19, 2018 9:11 am

So I calculated my balance which would be represented by the pic below. Accounting for the tower and console weights as well as live wells and water I have a CG very close to 6.75’ in front of the transom. If I assumed similar conditions for yours with 300 gallons centered 12’ forward your CG is about 9” forward of mine. Need to talk through your plan a bit to verify locations and weights. That is at rest. My concern is that my CG shifts back a little when running because I empty 2/3 the water in my ballast tanks. The shift appears to only be about 3-6” and I will tell you it feels a lot different in term of handling.


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Mbiggerstaff
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Re: 28 Bertram Restoration Boat 2

Post by Mbiggerstaff » Mon Mar 19, 2018 12:13 pm

My live well is going to be at the transom and the fish box centerline in the cockpit. Don’t think I’m going to have fresh water as I have never really used it anyway. Not going to have any superstructure like you do. Also , my bracket is 36” back not 30 .

DAYTRIP
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Re: 28 Bertram Restoration Boat 2

Post by DAYTRIP » Mon Mar 19, 2018 12:42 pm

I will post a pic of my spreadsheet mike and you can comment. I have batteries, and other misc fixed items in there. You going to have a hardtop/tee top?

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Re: 28 Bertram Restoration Boat 2

Post by DAYTRIP » Mon Mar 19, 2018 1:28 pm

So here is how I am figuring things Mike. Upper left is the at rest condition. Everything is reference off transom. The upper right is what my does while running. I empty 2/3 of the ballast is the only change represented here. You can see that moves the CG back (6.978-6.4615) = about .5 ft or 6". Started filling in some of your info but you can tell me the right or wrong parts. At rest I actually have a bit more weight forward. Running I have a bit less. Come up with some values and we can plug it in. Good reference to guess from :doh: This makes a lot of assumptions like your boat and mine are identical weight wise with the exception of the items below. I should add a line for the increased buoyancy for the bracket. also you are building yours a liitle diffently than I did so that will drive some inaccuracies. I make no guarantees that this is right but it is my thought process.
Last edited by DAYTRIP on Tue Mar 20, 2018 9:02 am, edited 1 time in total.

DAYTRIP
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Re: 28 Bertram Restoration Boat 2

Post by DAYTRIP » Mon Mar 19, 2018 5:24 pm

Hold the phone! I accounted for the brackets on our boats. This makes a huge difference. so at rest my CG is 8.167" forward of the transom which is actually what I targeted early on. When I am running it shift way back to 6.46' from the transom because the bracket doesn't add buoyance nor lift! On your set up above the CG is at 8.383' forward with the bracket you have assuming the boat sits where mine is at. Not bad at rest.When you are running it shifts back to 6.662'. That is slightly in front of mine. Get those other weights and locations figure and we will check it out. What do you think?

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Re: 28 Bertram Restoration Boat 2

Post by Mbiggerstaff » Sun Apr 22, 2018 11:07 am

Work goes on. Have the cockpit just about complete and ready to epoxy all the parts in place. Got the tank completely installed and working my way forward. My daughter and I are at the Charleston boat show selling wahoo lures so I have spent some time looking at boats to nail down my plans for helm and console.

Hard to see in detail but for the hatch gutters I used 1 1/2" cusa and routed a channel 1"wide and 1 1/4" deep. the hatch will fit over the remaining 1/2" rim of cusa. Once I get it all secured I will start making hatches.

Plans for the transom box is live well in the center and battery boxes on each side with cushions on top

Unfortunately i stumbled into a 25' carolina boat that is 80% complete that I could not pass up. Now I have 2 boats in the shop to work on. Will post pix of new project when i have a chance.


here are a few pix from a week ago. Have made some progress since then.


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