Author Topic: GA Payload Capacity  (Read 2386 times)

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Easygoing

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GA Payload Capacity
« on: August 04, 2015, 04:44:42 PM »
Brian, I'm sorry...I believe I have seen the information but I can't remember where it is.  What is the maximum payload the GA is designed to carry?

Cannon

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Re: GA Payload Capacity
« Reply #1 on: August 04, 2015, 09:16:29 PM »
If you look under study plans, it is pretty well spelled out. It will also vary depending on length of the boat.
Remember, the ark was built by amateurs; the Titanic was built by professionals.
Started building Paula J the 2nd Week of June 2015, finished her the second week of July 2016.

Easygoing

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Re: GA Payload Capacity
« Reply #2 on: August 05, 2015, 10:30:57 AM »
If you look under study plans, it is pretty well spelled out. It will also vary depending on length of the boat.

So I downloaded the study plans again (not sure what happened to my first copy) and the only info I find that may apply is the displacement ratings of 3,300 - 6,000 lbs, with 3,800 lbs typical. 

I presume I can safely say 6,000 lbs - my boat's actual weight is the payload capacity?

Brian.Dixon

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Re: GA Payload Capacity
« Reply #3 on: August 05, 2015, 05:52:37 PM »
For the 26-foot boat, 6000# is the max displacement.  If your 26-footer weighed 3500#, then you'd have an additional 2500# available for payload ...gear, ice, fuel, passengers (beyond the first 2 people in the boat), etc.  The 25-footer is pretty close to that.  The 28-footer carries about 300-400# more.

Brian

Easygoing

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Re: GA Payload Capacity
« Reply #4 on: January 24, 2016, 05:27:47 PM »
Hi Brian, hope all is well with you.  Since it is winter time, I'm back to planning my boat.  I wanted to follow up on the payload question I asked a while back. 

I presume the max displacement is determined more by the waterline/handling than the actual strength of the boat?

Is there any way to know what the approximate theoretical strength of a 28' GA is as designed? (by "theoretical strength", I mean how much weight could the boat carry in choppy seas before the wood/epoxy begins to be compromised, not considering boat handling or seaworthiness)

Easygoing

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Re: GA Payload Capacity
« Reply #5 on: January 24, 2016, 10:27:25 PM »
I probably should have added, the reason I raise this question is because I have some heavy things I'm considering adding.  I'm doing the calculations of the weight additions and figuring what the new waterline will be...

I'm looking into adding SeaKeeper (http://www.seakeeper.com/) and that takes a generator. 800 lbs for the Seakeeper alone, more for the generator. 

I'll probably stretch the boat past 28'.  Beam will still be 8.5'.  Adding large fuel tank(s), maybe fish refrigeration, etc.

It all adds weight, and I fully understand that for every action there is a reaction.  I have been studying boats for several years now and understand that any changes I make off the plans are my own and I take full responsibility.

Not wishing to start a bunch of rabbit trails, but wanted to clarify why I was asking the question.  What it comes down to, is if I add a lot of extra weight, I will need to increase displacement some to maintain the desired waterline.  ...and I want to know that the boat is structurally strong enough to handle all the extra weight...

Cannon

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Re: GA Payload Capacity
« Reply #6 on: January 25, 2016, 11:04:30 AM »
Why not go with a flop per stopper type system. More cost effective and arguably more stability in rough seas. I have built in the fundamentals while building my boat, all of the commercial fishing guys use them here and they are used on many sea going yachts worldwide.
I am going to run 20' aluminum outriggers, sixteen foot of which will be 2 1/2 inch sch 40 aircraft grade aluminum.
I have built in blocking and strength points to mount the cross tree which will support the outriggers when not in use.
Flopper stopper is a brand name, and get a pretty penny for their wares, but you can get a commercial fishing version for much less and have the same functionality at Kolstrand, the smaller of which should be more tha adequate for the GA. http://www.kolstrand.com/trolling/stabilizers/
Remember, the ark was built by amateurs; the Titanic was built by professionals.
Started building Paula J the 2nd Week of June 2015, finished her the second week of July 2016.

Easygoing

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Re: GA Payload Capacity
« Reply #7 on: January 25, 2016, 11:30:45 AM »
Why not go with a flop per stopper type system. More cost effective and arguably more stability in rough seas. I have built in the fundamentals while building my boat, all of the commercial fishing guys use them here and they are used on many sea going yachts worldwide.
I am going to run 20' aluminum outriggers, sixteen foot of which will be 2 1/2 inch sch 40 aircraft grade aluminum.
I have built in blocking and strength points to mount the cross tree which will support the outriggers when not in use.
Flopper stopper is a brand name, and get a pretty penny for their wares, but you can get a commercial fishing version for much less and have the same functionality at Kolstrand, the smaller of which should be more tha adequate for the GA. http://www.kolstrand.com/trolling/stabilizers/
Ah, boy, I don' know...  Not sure I want more junk in the water. 4 downriggers alone is almost too much cable in the water for a guy like me. 

BobC

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Re: GA Payload Capacity
« Reply #8 on: January 25, 2016, 08:23:53 PM »
Wow, I guess this just goes to show that there are lots of different ideas out there.  One guy (me) tries to eliminate weight while another installs 800lbs of gyro. and a genset to run it. :)

Easygoing, what makes you think your GA would need a gyro?  All reports I have heard is that they are very stable with very little roll.  There is no report to my knowledge of either Tolman's or GA's suffering from excessive roll.  The flatter deadrise angles combined with the chines make the boat very stable for its size.  Its not like some of the older deep-v soft chine boats that could churn butter in a mild chop.

I think the GA is fully capable structurally of supporting the added weight of the seakeeper but it would pay a dear price in performance, efficiency and handling for something that you may seldom need.  If you encounter a sea state that needs a gyro in this size vessel, it is my guess you will be tossing out everything you don't need to gain bouyancy and stay afloat, not worrying about your wine spilling on the dinette. 

What your attempting IMHO is akin to putting a soft suspension on a race car.  It might improve the ride marginally but it defeats the purpose of having a race car in the first place.  Plywood and epoxy boats are specifically designed for a good weight/strength ratio.  Adding weight is usually counter productive.  It adds up exponentially.


I don't intend any disrespect here.  Your money, your build.  Just wondering what convinced you that a gyro is needed or practical on a boat of this type and size.

Perhaps a retractable keel would be just as good an option and a lot lighter without the need for added space, gas, genset, maintenance, etc.


Brian.Dixon

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Re: GA Payload Capacity
« Reply #9 on: January 25, 2016, 09:20:37 PM »
Hi Brian, hope all is well with you.  Since it is winter time, I'm back to planning my boat.  I wanted to follow up on the payload question I asked a while back. 

I presume the max displacement is determined more by the waterline/handling than the actual strength of the boat?

Is there any way to know what the approximate theoretical strength of a 28' GA is as designed? (by "theoretical strength", I mean how much weight could the boat carry in choppy seas before the wood/epoxy begins to be compromised, not considering boat handling or seaworthiness)

Strength is not the issue ...the boat's are over-strong.  As long as you treat it no worse than how someone might treat a commercially built boat, you'll never get in trouble when it comes to strength.  The issue, instead, is how the transverse metacentric height (GMt) of the boat reduces as you load the boat up ...this means it becomes less self-righting as the load goes up ...and in combination with the boat being very heavy, that could be an issue ...but even with that, you'd be pretty challenged to ever push that  theoretical limit.  I selected the maximum displacement mostly as a function of the waterline.  Sitting too deeply in the water just gets silly after awhile, and it takes a lot more horsepower to get the boat on plane.  6000# for the 26 footer is about right, and you can add an additional 300# or so for a 28 footer.

Brian

Easygoing

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Re: GA Payload Capacity
« Reply #10 on: January 26, 2016, 11:40:09 AM »
Just wondering what convinced you that a gyro is needed or practical on a boat of this type and size.


It probably doesn't need one, but wouldn't it be cool if it did?  I don't mind a slightly heavier boat that uses more fuel but gives me a softer ride.  Yes, I can buy a big boat pre-made, but wouldn't it be neat to totally customize it and when your done you can have the satisfaction of having built it with your own hands.

Easygoing

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Re: GA Payload Capacity
« Reply #11 on: January 26, 2016, 11:41:50 AM »
Hi Brian, hope all is well with you.  Since it is winter time, I'm back to planning my boat.  I wanted to follow up on the payload question I asked a while back. 

I presume the max displacement is determined more by the waterline/handling than the actual strength of the boat?

Is there any way to know what the approximate theoretical strength of a 28' GA is as designed? (by "theoretical strength", I mean how much weight could the boat carry in choppy seas before the wood/epoxy begins to be compromised, not considering boat handling or seaworthiness)

Strength is not the issue ...the boat's are over-strong.  As long as you treat it no worse than how someone might treat a commercially built boat, you'll never get in trouble when it comes to strength.  The issue, instead, is how the transverse metacentric height (GMt) of the boat reduces as you load the boat up ...this means it becomes less self-righting as the load goes up ...and in combination with the boat being very heavy, that could be an issue ...but even with that, you'd be pretty challenged to ever push that  theoretical limit.  I selected the maximum displacement mostly as a function of the waterline.  Sitting too deeply in the water just gets silly after awhile, and it takes a lot more horsepower to get the boat on plane.  6000# for the 26 footer is about right, and you can add an additional 300# or so for a 28 footer.

Brian
Thank you for your reply, Brian.

BobC

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Re: GA Payload Capacity
« Reply #12 on: January 26, 2016, 03:21:47 PM »
Just wondering what convinced you that a gyro is needed or practical on a boat of this type and size.


It probably doesn't need one, but wouldn't it be cool if it did?  I don't mind a slightly heavier boat that uses more fuel but gives me a softer ride.  Yes, I can buy a big boat pre-made, but wouldn't it be neat to totally customize it and when your done you can have the satisfaction of having built it with your own hands.

I guess some might look at it as cool, guess it depends on what circles of friends you run in.  Most the old salts I am around would likely call me a posie if I put a gyro in the boat but they come more from the commercial side of things and less from the luxury side.  They would call me a posie for putting a yacht finish on it as well. LOL.  Names don't mean anything to me though and I say build what you want and enjoy every minute of it despite what I or anyone else thinks.   There are some things that each one of us want to try just to satisfy our own curiosity and we won't be happy til we try it our way.  I applaud that pioneering spirit and to an extent share it as is evidenced by my own efforts to tweek and twiddle with certain design elements.  I applaud Renn and Brian for giving us platforms that are forgiving enough to tolerate our whims and desires without turning turtle or breaking up.

Godspeed in your endeavour. :)

Brian.Dixon

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Re: GA Payload Capacity
« Reply #13 on: January 27, 2016, 05:59:56 AM »
Doing exactly what YOU want, rather  than accepting some cookie cutter duplicate, is one of the best reasons for building your own boat ...that, plus pride of accomplishment is what does it for me :)

Brian

Cannon

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Re: GA Payload Capacity
« Reply #14 on: January 28, 2016, 11:28:18 PM »
Doing exactly what YOU want, rather  than accepting

Brian
That is why you build. My last experience with a factory boat was very frustrating. You get it to the point it is almost there, but you can go no further. I have really enjoyed this build, even more than I anticipated. But now, in the final throngs of birth, I wonder, "what if I had done this instead of that?"

It is a process, and we all want to build a better boat! Easygoing, you should, if you haven't already read, Voyaging Under Power, fourth edition. Great look at stabilizing systems. I bought a copy using bookbinder.com for under five bucks. I am planning on running outriggers on mine with the stabilizers I mentioned in a prior post. Many of the guys I know use them, and they work great in a rougher ocean. You do have to be sure you run them deep enough!
Most only run the 15-16' off the side, so it isn't such a big deal, and they will negligibley affect your mileage, maybe 1 to 1.5 mpg which in heavy swell can make the day much more pleasant. I plan on longer poles because I am afflicted with that virus called fishing.
They are also very effective while anchoring, which will allow you to sleep like a baby...
Remember, the ark was built by amateurs; the Titanic was built by professionals.
Started building Paula J the 2nd Week of June 2015, finished her the second week of July 2016.