building my first boat

Dear all,

I need your help gents to build my first sailing boat. I was planning to build a Catalina 31. My vision due to lake of materials and steel in Egypt is to build the hull only by steel and the reaming by fiber and plastics.

My question is, how many steel sheets are needed for hull only? As first step

 

Welcome to the forum.
So roughly, with the same detail that you provide us, I can give you a quick answer:
- calculate the surface area of the entire "Catalina 31" (you will have to do it because I don't think anyone knows it).
- to take into account the waste in the use of sheets, multiply that surface by 1.5. With this you will obtain the number of plates necessary for the hull, deck and superstructure.
- The internal parts (floors, girders, etc.) that are obtained from plates can represent 40% more.
- Take into account a prudent margin (let's say 20%) and don't forget to check port and starboard.
- You will see that I have not talked about thicknesses. There you will have to decide, as a designer, the thickness that you are going to use in each area.
Easy, right?

For any other questions, you know you can count on me.

P.S. : Oh, I forgot, the number of sheets will depend, logically, on the size of the sheets you have available.

 

thanks for your reply, but i still cannot figure out what do u mean by entire surface area .
my check is to build the hull only by 4 mm steel sheet (3m*1.5m)

 

OK, let's try it. Your boat has a hull and that hull has a certain surface area. That surface will be covered with 4 mm panels. Therefore you will need as much surface area of sheets as the surface area of the hull panels. What happens is that, when fitting the individual hull panels into the aforementioned sheets, waste is always produced because the panels that make up the surface of the hull do not coincide, because they are not usually rectangular, with the sheets, which are rectangular. Therefore, a certain margin must be added to the surface of the hull panels to determine the number of sheets necessary.
By the way, and excuse my curiosity, how did you find out your plates have to be 4 mm? The Catalina 310 was designed to be built in GRP and building it in steel means having to do a almost new project because the boat is going to be much heavier, the shapes require the shaping of the steel plates, which is not easy,... . The thickness is not easy to determine.

 

If you want to build a steel boat, buy plans for one. If you can't calculate for yourself how many square meters the hull has, you won't be able to redesign a GRP boat to another material.
As far as I know Egypt doesn't have a shortage of either steel or fiberglass, combining the two materials isn't necessary.

https://dixdesign.com/hb33.htm This boat for example needs 87 square meters of 3mm and 13sqm of 5mm for its hull. That's the net area required, as TANSL said you add cutting waste, so about 150sqm in total. If you buy your steel in 6x2m sheets you need 12.5 sheets, and if you buy it in 3x1.5m you need 33.3 sheets.

 

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