Aluminium boat building - 25ft fisherman

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lucastefanel
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Re: Aluminium boat building - 25ft fisherman

Post by lucastefanel »

Hi guys,

thanks for your feedbacks, these are the replies that i was looking for.
Now i'm bit confused about strakes position.
My intention is to use Aluminium 6082 L profile 30x100mm Thk 5mm.
Is it a good idea to put shorter L side over stingers? in this way longer side will be closer to CL... :doh:
whit this layout i souldn't face any problem on trailer...
Probably this week end i will start to fully weld the hull, i expect argon bottles and welding wire burn!! :lol: :lol: :lol: :lol:

Cheers!

fallguy1000
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Re: Aluminium boat building - 25ft fisherman

Post by fallguy1000 »

For an aluminum boat with a thick enough hull, you may not be concerned with bunking, but trailering rollers and bunking needs to be considered for many boats.

That said, you need to consider the waterline. The last thing you want is to hop up on plane and be above the strakes!

https://www.aeromarineresearch.com/tbdp ... rails.html
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viewtopic.php?f=12&t=62495

fallguy1000
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Re: Aluminium boat building - 25ft fisherman

Post by fallguy1000 »

Here is an article he wrote. Only to get the last three pages you have to email him.

https://aeromarineresearch.com/publicat ... b2015.html
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fallguy1000
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Re: Aluminium boat building - 25ft fisherman

Post by fallguy1000 »

I think you need to know where the boat rides up on plane; not the static waterline. Then you go halfway out. Let's say you are on plane and 24" of water each side, first strake would be less than 12" from keel.

Largely guessing here. But then if you are going really fast and top speed, you want at least one strake still helping.

Then the angle to water at the stern should be under 8 degrees per the other article. If you are over that, you might need to cut the short side shorter.

But Mertens might have some better advice if he is asked directly.
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TomW1
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Re: Aluminium boat building - 25ft fisherman

Post by TomW1 »

Sorry duplicate. Tom
Last edited by TomW1 on Tue Jul 20, 2021 3:38 pm, edited 1 time in total.
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses. LT US Navy 1970-1978

TomW1
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Re: Aluminium boat building - 25ft fisherman

Post by TomW1 »

Putting the L side on the stingers is not a good idea. but normally the bunks and rollers are put on the stringers and you do not want the L of the strakes over them. That is the worst place to put them. The welds on them will be subject to more stress over time than any other area.

So plan your trailer for the bunks or rollers to be on the stringers and your strakes to be out side that area.

Tom
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses. LT US Navy 1970-1978

fallguy1000
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Re: Aluminium boat building - 25ft fisherman

Post by fallguy1000 »

TomW1 wrote: Tue Jul 20, 2021 3:32 pm Putting the L side on the stingers is not a good idea. but normally the bunks and rollers are put on the stringers and you do not want the L of the strakes over them. That is the worst place to put them. The welds on them will be subject to more stress over time than any other area.

So plan your trailer for the bunks or rollers to be on the stringers and your strakes to be out side that area.

Tom
Not sure if you don't know the stringer location..
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viewtopic.php?f=12&t=62495

lucastefanel
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Re: Aluminium boat building - 25ft fisherman

Post by lucastefanel »

Thanks for feedbacks guys, also very interesting and technical page!
So, seems that best idea should be to test boat first, then lift she up again with crane and weld L profiles accordingly with how boat is running on water!
Of course, best way to work is now with hull upside down but also i can consider to install profiles later on after some tests.
:doh: :doh:
I'm bit concerned on how to proceed..

TomW1
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Re: Aluminium boat building - 25ft fisherman

Post by TomW1 »

lucastefanel wrote: Thu Jul 22, 2021 7:04 am Thanks for feedbacks guys, also very interesting and technical page!
So, seems that best idea should be to test boat first, then lift she up again with crane and weld L profiles accordingly with how boat is running on water!
Of course, best way to work is now with hull upside down but also i can consider to install profiles later on after some tests.
:doh: :doh:
I'm bit concerned on how to proceed..
I think you need to do them now if you know where your stringers are going to be placed. Less work and hassle later. Let me know the distance from the keel to the chine and I can come up with what size you should have. You should run them all the way to the transom. Also I will need the flat area of the hull, from bow to transom. Also the distance from the keel for each stringer.

Strakes are not the end be all. They help in planing and in turning with there straight edge. But over sized ones can cause problems also. Here is a strake on a Grady White !9
download/file.php?id=21853&mode=view[soundcloud][/soundcloud] Just to the right of the sounder. It only has one, while you will need two.

Hope this helps.

Tom
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses. LT US Navy 1970-1978

TomW1
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Re: Aluminium boat building - 25ft fisherman

Post by TomW1 »

TomW1 wrote: Thu Jul 22, 2021 5:50 pm
lucastefanel wrote: Thu Jul 22, 2021 7:04 am Thanks for feedbacks guys, also very interesting and technical page!
So, seems that best idea should be to test boat first, then lift she up again with crane and weld L profiles accordingly with how boat is running on water!
Of course, best way to work is now with hull upside down but also i can consider to install profiles later on after some tests.
:doh: :doh:
I'm bit concerned on how to proceed..
I think you need to do them now if you know where your stringers are going to be placed. Less work and hassle later. Let me know the distance from the keel to the chine and I can come up with what size you should have. You should run them all the way to the transom. Also I will need the flat area of the hull, from bow to transom. Also the distance from the keel for each stringer.

Strakes are not the end be all. They help in planing and in turning with there straight edge. But over sized ones can cause problems also. Here is a strake on a Grady White !9
download/file.php?id=21853&mode=view[soundcloud][/soundcloud] Just to the right of the sounder. It only has one, while you will need two.

To be honest if your top speed is not going to be much above 45 or so you don't really need strakes as long as you have a good keel and spray rails. They are most effective above 50 mph.

It also looks like you have put spray rails on the chines. Good move.

Hope this helps.

Tom
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses. LT US Navy 1970-1978

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