fiberglass hull thickness

[Gianf1041]

How much could an 8 mt fiberglass hull with an average thickness of 20 mm weigh?

 

[fallguy]

A lot!

Solid frp of 3/4" is thicker than needed for an 8 meter hull.

 

[rxcomposite]

A lot!

Solid frp of 3/4" is thicker than needed for an 8 meter hull.

Relax. It could be only 1/16" wide.

 

[Gianf1041]

Gulp! ......... 1/16 "of an inch is about 1.6 mm ..........; to understand ....... 20 mm around the bottom to arrive at about 9-8 mm of the sides ........ it is only a rough evaluation to set a project start ............. 7mm foam core or structural felt, biaxial fabric 8 -5-3 layers, resin, gel coat ...... just to get about 8 mm of the sides.
Maybe I'm exaggerating ??

 

[ondarvr]

The weight of a laminate can be quickly estimated

Every 1/8” thick square foot of laminate will weigh approximately one pound.

So multiply the square footage by the number of 1/8” inches of laminate.

1 square foot at 1” thick would weigh approximately 8 lbs.

 

[Gianf1041]

Thank you for your suggestion !

 

[rxcomposite]

You are not exaggerating. You simply did not provide information that you know. You did not even mentioned that it is a cored laminate that is why it is so thick. You also know the layup schedule but you did not post.
It is simple but tedious. For every layer of roving or biax, the ratio is 1:1, that is for every kilo of glass you use, you use 1 kilo of resin. Chopped mat ratio 1:2.3. For every kilo of glass you use, multiply that by 2.3 to find the amount of resin. Since fibers are sold in unit weight per square meter, you will be able to calculate how much the laminate will weigh when the resin and the fiber is added together.

Say you will use 600 gr/m2 of WR for the first layer, that will be 0.6 kg/m2. You will use the same amount of resin so, 0.6 + 0.6 = 1.2 kg/m2.
For CSM, say 600 gr/m2 (0.6 kg/m2). To find resin weight, multiply 0.6kg by 2.3=1.38. Add the two so it is 0.6 + 1.38= 1.98 kg/m2.
Foam is sold by its density. Say 100 kg/cu meter. To find how much a 7mm foam will weigh, slice the 1 meter (1,000 mm) high foam every 7 mm. 1,000mm/7mm= 143 parts. That means 100 kg of foam/143 slice = 0.699 kg per slice/per m2.

Gel coat thickness vary but 700 kg/m2 is pretty standard. So 0.7 kg/m2.

Since you have different thicknesses for bottom and sides, you must find the total area first for each.
Multiply the unit weight of the WR LAMINATE by the number of layer x area (bottom or sides)
Multiply the unit weight of the CSM LAMINATE by the number of layer x area
Multiply the unit weight of the FOAM x area
Multiply the unit weight of the Gel coat x area

Add everything.

 

[Mr Efficiency]

This is a fairly simple calculation, at the basic level of analysis for the purposes of a 'project", reading the initial post I thought it was a case of someone trying to work out the weight of an existing boat.

 

[fallguy]

Relax. It could be only 1/16" wide.

I was trying to prime the pump and get him to spill the scantlings is all.

 

[Gianf1041]

It is not an existing boat but it is a beginning of a project ......... to have a basic starting point, then I will develop the project with more precise calculations. Thank you all for your technical support.

 

[Gianf1041]

Let's say that the idea is the sandwich with a balsa or foam core .......... let's say 7mm, + two sides respectively 6mm + 6mm x 8-10 layers of impregnated biaxial fabric with a thickness of about 20mm.

 

[Gianf1041]

we say that approximate weight bare boat + deck + deckhouse .......... less than 500 kg tot. ???

 

[BlueBell]

This reminds me of the most refined question from the late PAR:

"How long is a piece of string?"

 

[Mr Efficiency]

we say that approximate weight bare boat + deck + deckhouse .......... less than 500 kg tot. ???

Way too light, that calculation has gone wrong.

 

[ondarvr]

Without knowing any actual dimensions, my quick estimate would be in the 1,850 pound (839 kg) range for a solid 13mm laminate for just the hull. No core, no stringers or other structures.

It could easily go up from there depending on the exact dimensions.