Is Papanikolaou's work for estimation ship weight applicable for composite hulls?

[egeabi]

Hi everyone,

I'm currently working on my graduation project and I received a feedback from my professor that I couldn't understand. I took the weight calculation as a reference from Papanikolaou's book below, which I think explains the weight estimation very well (a).

Although the weight estimation method in the book is written for steel-structured ships, it is based on the general theory of "D=∑Wi" (Displacement = Sum All Weight) and I think this can be applied to all kinds of boats. Since the boat in the project is a composite structure boat, I did not use the steel hull weight method in the "Weight of the Hull" section and simply estimate it by using the formula ''Hull Weight = Average Hull Thickness * Surface Area * Material Density''. I applied all the remaining subheadings as in the book. Also, since this is a sailboat, I also took into consideration additional factors such as the rig system and keel. In summary, I modified the method a little.

As stated in the forum post below (b), I made a hypothetical list of the weights and locations of the items/equipments inside and finalized the weight calculation.

My question is,
1- Is this method really still can't be applied to composite structure boats?
2- Is there a special method for composite boats?


I'm open for any advice. Thanks in advance.

- Ege


Maybe to help you, here are the dimensions of the project boat:
L: 23.85m
B: 6.45m
T: 3.40m
D: 60.90 t
Main Mast L: 29.50 m
Boom: 11.00 m

(a) The book: https://www.researchgate.net/publication/265710516_Ship_Design_-_Methodologies_of_Preliminary_Design
(b) The forum post: boat weight estimates https://www.boatdesign.net/threads/boat-weight-estimates.54402/#post754240

 

[TANSL]

The procedure, although it is too simple an approximation, is valid for any material. The only thing you should keep in mind is that, when the weights of fiber mats or fabrics are given, that weight is that of the dry fiber. That is, the weight of the resin, necessary to bind the compound, is not included. That weight, being conservative, can be estimated as equal to the weight of the "dry" material. That is, total weight = 2 * dry fiber weight.
Another problem that will arise is that, in fibers, unlike with homogeneous materials, twice the thickness does not necessarily mean twice the weight.
In short, if your magic formula could be acceptable for homogeneous materials, for composites some corrective factor would have to be applied that takes into account an average weight of the various types of composite that are going to be used in the boat.
(I have not read those books, so they could say something that helps you clarify your doubts more than my comments).

That is intended to answer your question #1. Answering your second question: the method for composite materials should involve previously calculating the composite layout applicable to each area of the boat and thus obtaining its weight/m2 in each panel or the weight/linear meter of each stiffener. Once those weights are calculated, multiply them by two.
It all depends on the approach you want to achieve.

 

[Alik]

We use Mstr=m*L*B*H of structure for weight estimates. For composite small craft to ISO12215-5, it is about m=25...40kg/m3 for glass-based sandwich, 40...55kg/m3 for single skin.
Note that for high speed boat the laminate weight of bottom heavily depends on speed.

 

[egeabi]

@TANSL , @Alik

Thank you for your answers, masters. I started to work on according to your instructions.