TW28 build in steel?

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M Cruit

TW28 build in steel?

Post by M Cruit »

Does anybody know if the TW28 (28ft) trawler construction can be converted from composit to steel? If so, are there any designers who can do this?



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Evan_Gatehouse
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Re: TW28 build in steel?

Post by Evan_Gatehouse »

It wouldn't be a good idea. A steel version of the TW28 would be much much heavier. So it would sink much further into the water. Much more than desirable.

If you are building a steel boat, you need to design the hull shape to accommdate the heavier weight. And generally 28' is too small for effective steel construction because it is so heavy.
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Re: TW28 build in steel?

Post by TomW »

Think of it this way the current design has a designed water line of 34" with 7500lbs. If you change the hull to steel and add that weight it then makes the waterline 920PPI/the weight of the steel. Don't know what the will be as I have never calculated one of these boats built in steel.
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Re: TW28 build in steel?

Post by TW28 hull in steel? »

I just purchased the plans and wish to build hull only in steel. So instead 1/2" plywood would be (say) 1/8" steel plate. Yes, hull weight will increase but if foam sandwich is used for superstructure, total weight would increase by (approx.) 20% ? (or something like that).
Also, there are number of boats designed for steel, this one is similar size boat:

https://www.finelineboatplans.com/bruce ... -boat-plan

Any thoughts?

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Re: TW28 build in steel?

Post by Netpackrat »

If you go to the Glen-L website there is a design by Ken Hankinson for a 25' coastal cruiser which can be built in steel, with a listed 27' length option, buildable in wood, steel,or aluminum. The style of hull and use profile is different (TW28 more of an offshore capable boat) but the layout is similar, so depending on how you intend to use your boat,it could be an option.

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Re: TW28 build in steel?

Post by jacquesmm »

TW28 hull in steel? wrote: Thu Oct 31, 2019 3:09 pm I just purchased the plans and wish to build hull only in steel. So instead 1/2" plywood would be (say) 1/8" steel plate. Yes, hull weight will increase but if foam sandwich is used for superstructure, total weight would increase by (approx.) 20% ? (or something like that).
Any thoughts?
From the designer:
That is a difficult project. I have some experience with steel, owned a 33' steel boat and many years ago, worked with a surveyor/project manager who specialized in steel.
I can't redesign the TW28 for steel. Do you have any experience with steel? The hull will be much heavier and there will be no savings in the superstructure weight, it is light as designed.
The other boats you look at have a much higher displacement, more volume under water, a different hull shape.

BTW, why steel? It is a strong material but our material is strong too. My hull design is not for 1/2" plywood. At the keel, the hull is about 1-1/2" thick. Aluminum would work better if you absolutely want a metal hull.
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Re: TW28 build in steel?

Post by TW28 hull in steel? »

jacquesmm wrote: Fri Nov 01, 2019 11:39 am
TW28 hull in steel? wrote: Thu Oct 31, 2019 3:09 pm I just purchased the plans and wish to build hull only in steel. So instead 1/2" plywood would be (say) 1/8" steel plate. Yes, hull weight will increase but if foam sandwich is used for superstructure, total weight would increase by (approx.) 20% ? (or something like that).
Any thoughts?
From the designer:
That is a difficult project. I have some experience with steel, owned a 33' steel boat and many years ago, worked with a surveyor/project manager who specialized in steel.
I can't redesign the TW28 for steel. Do you have any experience with steel? The hull will be much heavier and there will be no savings in the superstructure weight, it is light as designed.
The other boats you look at have a much higher displacement, more volume under water, a different hull shape.

BTW, why steel? It is a strong material but our material is strong too. My hull design is not for 1/2" plywood. At the keel, the hull is about 1-1/2" thick. Aluminum would work better if you absolutely want a metal hull.
Thanks for reply.
Now I am convinced that TW28 cannot be built in steel. Why I asked this question? I don't have time to built it by myself and I couldn't find any builder / workshop with epoxy / plywood experience (and plenty of welders around here in Oman) so this is the reason. TW28 is exactly what I need so I'll have to do my homework ...

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Re: TW28 build in steel?

Post by jacquesmm »

I missed your location: Oman.
Epoxy-plywood is not as difficult as steel but I understand your choice now.
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Re: TW28 build in steel?

Post by TW28 hull in steel? »

TW28 hull in steel? wrote: Sat Nov 02, 2019 8:48 am
jacquesmm wrote: Fri Nov 01, 2019 11:39 am
TW28 hull in steel? wrote: Thu Oct 31, 2019 3:09 pm I just purchased the plans and wish to build hull only in steel. So instead 1/2" plywood would be (say) 1/8" steel plate. Yes, hull weight will increase but if foam sandwich is used for superstructure, total weight would increase by (approx.) 20% ? (or something like that).
Any thoughts?
From the designer:
That is a difficult project. I have some experience with steel, owned a 33' steel boat and many years ago, worked with a surveyor/project manager who specialized in steel.
I can't redesign the TW28 for steel. Do you have any experience with steel? The hull will be much heavier and there will be no savings in the superstructure weight, it is light as designed.
The other boats you look at have a much higher displacement, more volume under water, a different hull shape.

BTW, why steel? It is a strong material but our material is strong too. My hull design is not for 1/2" plywood. At the keel, the hull is about 1-1/2" thick. Aluminum would work better if you absolutely want a metal hull.
Thanks for reply.
Now I am convinced that TW28 cannot be built in steel. Why I asked this question? I don't have time to built it by myself and I couldn't find any builder / workshop with epoxy / plywood experience (and plenty of welders around here in Oman) so this is the reason. TW28 is exactly what I need so I'll have to do my homework ...
Hi Jacques,

I am again with my project after some time.

You mentioned that aluminium could be the solution if I plan to build TW28 in metal and I found builder who can make it in aluminium. So I presume that re-design is needed, however, as per your opinion, would TW28 weight remain similar to the epoxy plywood version?

Thanks,

Dusan

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Re: TW28 build in steel?

Post by TomW1 »

Dusan here is a weight calculator for 6061 aluminum which is what you should you should use in salt water or 5052. I have it set for 1/16 and I checked 1/8 and it is double the weight. The 1/16 is about equal a 4'x8'x1/4" Meranti plywood sheet. https://www.theworldmaterial.com/alumin ... 02700%20kg.

You and your builder will have to convert the plans to aluminum. There will be many places where you can reduce the thickness of the wood due the strength of the aluminum. There have been many builders on here that have done so on there own and made great boats. Good luck with yours.

Tom
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