The use of a decision matrix to prioritize SOR items in the boat design process

Nope. All clients have a skewed idea of what is possible either technically or financially. It is the role of the naval architect to cajole them into understanding their own limitations, whilst still, hopefully, getting the contract.

 

It is possible that I do not design like you, but who cares? Irrelevant.
In your previous post :

In this I differ from you, the design spiral has nothing to do, and you know it (or should know it), with the decision matrix. As I said before (see my previous post), in my opinion, the spiral is the logical process that is followed during the various phases of design. In that process, some decision may be made by the decision matrix method, but it is not necessary at all to use that method to make a decision.
With all due respect, it seems pointless to discuss with you things in which, I am sure, we agree. I have nothing to do and I can waste my time as I like, even with ......, but you, ...,

 

The design spiral is not a magical system. Each iteration is based on a decision for a change. That decision can be done randomly or it can be done scientifically with a verifiable method.
Also, a designer that does not listen to customers will never get a job. There are many methods to address the customer's preferences and needs. For example, Six Sigma calls it the voice of the customer (VOC).

 

Do not be scared, Gonzo, I have not gone crazy, but I agree with you although making a decision randomly does not seem prudent, better support it in logical reasoning, in the experience, after some calculation, by means of the decision matrix, ... Well, it's not me who goes to tell you how to decide, you decide how you want.

 

Still waiting for the example of a BOAT design matrix, that has actually been used, all I see is mumbo-jumbo about how great the idea is ! Or maybe no-one here has one on hand . But wait.....I'm tipping it would be "a private matter between the designer and the customer" and not for publication. I had to "BYO" my own, quickly concocted matrix.

 

We used the technique in a university project where we had an initial hull form and created 5 others by adjusting the main parameters.

The hulls were then compared using the decision matrix technique with criteria including resistance, seakeeping, stability, build cost and fuel economy. Each were given a weighting and multiplied by there score and summed together to achieve an overall score for each hull. The hull with the highest overall score was chosen to refine further.... Confused yet?

This was in the very initial concept phase of the project and went through the design spiral once for each hull.

 

I'm not confused by that summary at all, but the accurate assigning of scores and weightage appears to be the snag. For example if I rate some parameter at 4 instead of five, and weight it at 4 instead of five, the difference in the multiplication is 16 versus 25, a rather large gap.

 

Mr E, maybe you can apply those weights randomly.

 

So for resistance for example, hull 1 with the lowest resistance scores a 5 and hull 2 score would be based on the hull1 (kN) / hull2 (kN) multiplied by 5. This is then multiplied by the weighting which we decided to be 5.

 

The weights are applied subjectively based on our interpretation of the design brief.

 

My concern is there is an element of "picking the numbers out of your ****", with things that are difficult to accurately quantify. And what limits the number of parameters to be considered ? Sounds like painting by numbers.

 

Sure, based on previous experiences, calculations or ... but never randomly.

 

Definitely not randomly. @Mr Efficiency are you talking about the scores or weighting? Like I said it was a measure of the influence of changing hull parameters to see their effect on hull performance at a very early stage in the design process. I understand your doubts and we had them ourselves and the results were still tailored towards what we thought would be the optimum hull for the overall design

 

Both.

 

I've done the waiting, but not the seeing !