1981 Dolphin 20' Commercial

Questions about boat repairs with our resins and fiberglass: hull patches, transoms and stringers, foam, rot etc.
MSRiver
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Re: 1981 Dolphin 20' Commercial

Post by MSRiver » Thu Aug 22, 2019 1:52 pm

Now is that off of running surface or OAL



MSRiver
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Re: 1981 Dolphin 20' Commercial

Post by MSRiver » Fri Aug 23, 2019 9:02 am

Well let me ask another question instead of doing a bunch of calculations. I figure laying everything out with room and have access to inspections plates and where they are located and ease to get to. So from there i was thinking to put the back inspection plate of the gas tank where the sender is either under the bench, which moves the tank about 10" forward, or under the console which will be about 2' forward.

Going further in layout and since the console will determine where the tank will be, I'm trying to figure out how much room i will want/ should have from the the back bulk head to the back seat. In in picture below i have 2' then 16" from seat to console. Im a big guy and need my leg room from the console. But dont want myself riding too far forward. Any insight is helpful on how much room one would want in the back without being too far forward.

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Fuzz
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Re: 1981 Dolphin 20' Commercial

Post by Fuzz » Fri Aug 23, 2019 1:36 pm

I believe the right answer is from the water line. As for where to mount the console I am not sure. You will have the weight of the outboard and other stuff in the back to account for. Batteries are a big one as is a live well if you have one. I do know it is best to have variable weights such as fuel in the centre as that can have a huge effect on trim.

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Re: 1981 Dolphin 20' Commercial

Post by fallguy1000 » Sun Aug 25, 2019 9:58 am

For such a nice boat as this, I would not let an inspection plate dictate.

Most of the guys on this forum have better experience with placing consoles and tanks. I know what I know and this ain't it.

My suggestion is to start a thread called balancing the weight or something.

You'll get a lot more traffic from guys with more experience than me for sure.

Back to what I know. You can easily make a flush inspection plate for your fuel ?sender? and just seal it with 4200 and four screws into an epoxied ply cleat under.

Then the bench can be made moveable a bit as well.

Then when you sea trial; the ideal would be the ability to move things through that one foot range using cleats.

A production boat has the advantage of tweaking and experimenting from boat one to boat 21, etc.

Planning for some adjustment would be ideal...but not easy.

The most stable dynamic weight will be the operator.

So you want your weight and crew to be located right.

This is where the ability to move console for or aft say 6" would be darn handy. Of course this does force hudraulic steering (sort of).
My boat build is here -------->

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fallguy1000
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Re: 1981 Dolphin 20' Commercial

Post by fallguy1000 » Sun Aug 25, 2019 10:03 am

Aspen powercats sea trialed their new outboard version using water jugs to plan fitments.

In a perfect world; you would do the same. Of course this adds some complexity...getting the boat done to a trial state..

Another way to deal with variability is to build super light fitments. Building all foam console and benches; for example...
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MSRiver
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Re: 1981 Dolphin 20' Commercial

Post by MSRiver » Tue Oct 08, 2019 9:08 am

After a little vacation, and enjoying the last of summer and trying to get this project ready for winter, i have most my bulkheads ready to be put in and start the plumbing with chasetubes. Im going to do a false floor for the tank because i really dont have room to go any higher in the front, that way i can fit it as close as i can. I also have to add some bracing to keep the tank stable. While i have opted to not foam it in. I will add another bulkhead right behind where the tank is so i can put all my battery's and wiring while also not having a gas line come through that area.
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I also need to finish up putting two layers of 1708 over the front. I ended up putting a piece of wood to fit the nose fairly well then just crammed glue all in it. Ended up just having to put about 8 relief cuts in it so it would bend and then just put some basic packing wrap down and bricks on top of it to keep the form.
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Now im just hoping the cold can stay away just a couple more weeks before i get locked out.

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Re: 1981 Dolphin 20' Commercial

Post by fallguy1000 » Tue Oct 08, 2019 9:19 am

Allow some expansion room for the tank.

Some guys coat the tank with ?coat tar epoxy?

Not sure why you put the wood up in front on a glass boat.
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MSRiver
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Re: 1981 Dolphin 20' Commercial

Post by MSRiver » Tue Oct 08, 2019 10:22 am

Yeah all the points contacting the tank will have a neoprene pad to allow expansion. It being aluminum i shouldn't expand too much. I did see people coal tar tanks but for the most part thats only when they foam them in. Since itll have air circulating around it it shouldnt need it, while also the beauty of an aluminum tank not rusting.

As far as the wood up front, it originally had a small 8" long piece for the tow hook. I decided to extend it to help the glass take the corner all the way up the nose, while also helping distributing the load that will be on it. I figured id take a lot of glass instead of just putting some wood backing to it to insure the hook doesn't pull out or damage the glass.

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