If I buy plans for a boat that are copywritten, build and sail the boat and decide that I would like to try to improve the boat in a small way. Maybe narrow the stern or a little more beam or–you get the idea. What are my obligations to the original designer? How much does it have to change before it’s no longer a copywrite infringement? Legally? Morally? Is there any common standards? Opinions?

Don -

A very long time ago a freind and I bought a set of plans for a 15’6" open canoe, which we subsequently built and then spent a damp, shoulder aching summer exploring the upper reaches of the rivers Fal, Fowey & Helford in Cornwall. Needless to say, the attraction of paddling wore very thin, so much so that we went ‘back to the drawing board’ and rebuilt it with subtle ‘tweaks’ here and there to the hull (slightly deeper rocker & incorporation of an offset dagger board case) together with fore, aft & side decks and a balanced lug yawl rig. Having spent the best part of the summer ‘cruising’ we then took it to an amateur boat builders rally where the original designer was in attendence.

He was utterly delighted with our modifications - sailed it more than we did over the weekend & took plenty of photographs and asked if he could use some of them for his new brochures. The exuberance of youth & award for best modification to an established design won us over and to this day the photograph of our combined creation canstill be seen at the following website - (it’s the 2nd one up from the bottom of page with 1 green & 1 white sail)

Anyway, getting back to your original questions, in my experience there were no issues, and I would of thought that the changes you have in mind shouldn;t be problematic if firstly, you don’t intend to produce it commercially (that’s the important bit) secondly, although you’re modifying an existing design I would of thought it’s still, in essence, that design. If you have a moral dilemma, speak to the designer if possible - unless they’re a bit of a prima donna & they do it for a living I’d think they’d welcome any improvements. If it were me I’d probably just get on with it…

I’m guessing that you’re thinking of playing around with an IOM plan & altering LCFs/LCBs etc. If so good luck & keep us informed of your developments



I have always made my own boats. I started with the free US1M “Mistral” plans and built a mould and 3 or 4 boats. Then I discovered a group of IOM sailors down Island. I pulled a hull out of my Mistral mold, put 4 kg of lead in it and put progressively longer sticks across the beam until it floated with the bow and stern just touching the water. This gave me a Mistral with an 8 3/4" beam that displaced about 4 kg, an IOM. It actually sails very well. Everyone that sails it likes it. I made two more boats using the general shape of a Mistral. A little fuller here, al ittle smaller there, with moderate success. I just bought the plans for Brad Gibsons “Ska” and as I was looking over the lines I found myself thinking,“I wonder what would happen if—”. As the Mistral plans were free there was no problems but the Ska is copywritten. I don’t know if I should be sending Mr. Gibson $20 before each mod. That prompted this post.



I guess an email to Brad Gibson would be the way ahead explaining what you’re thinking of doing and see what comes back.

With your ideas for the modifications, I assume that the hulls will evolve until you achieve the desired outcome - do you also intend to build one as per the original lines to act as a ‘control’ for your experimentation?

Once again, good luck,



I’m about halfway into the Ska. I have had problems determining mast/fin location(weather helm) with past boats and as I make my own sails there is a chance that my sails are the problem so I want to build a known good design with my sails to see what happens.
As for the modification we usually have lightish winds around here and I thought that maybe the Ska’s full forward sections might be a bit of overkill for this area. I will finish it and sail it and if it never nosedives I will think about narrowing it a bit. I was talking to a guy that has a Ska and he says it points really high. As this may be a function of the full forward sections narrowing it may be a mistake.

You know sometimes I really hate this obsession, everything depends on everything else.


Hi Don,

I think your last comment applies to all of us!

Regarding the Ska, once your hull is finished, could you borrow a suit of sails of known pointing abilities to compare with your own sails? While previous posts on LCB etc will certainly have some bearing on pointing ability, experience in big boats has shown that good sails are equally if not more important. A badly designed yacht will never make good progress to windward (and there are plenty of them about) however, a well designed yacht with bad sails will also struggle. When my wife & I bought our last boat the sails were a disaster waiting to happen: not very old but very cheap and stretched almost beyond recognition. A new set from an experienced sail maker made the world of difference. For a given wind strength, say 15 knts, she would point 10 degrees higher, 1.5 knts faster and light as a feather on the helm.

Hope you make good progress with Ska and the sails.



I know this is an almost dead topic, but here is my opinion anyway. If you are only building it for yourself/friends there is no problem at all. If you plan to sell the modified hull, you may or may not have a legal right to it, but I still believe that that is wrong. I would think that as long as you do not sell it, most designers would be very interested in what you do and how it turns out.

Hi Greg
No topic is dead until it is answered completely and in this hobby I don’t think that can happen:) . When I bought the plans for the Ska the contract I agreed to was to build one boat for personal use so I can’t build another without sending BG more money.

I think that you can made as many boats you like for personal use only.
This remains valid until you decide to make a commercial bussiness and in this case you will infringe the copyright .