Reverse Engineering (conversions And Modifications)

DORY build

Dory Build Test Posting Photos

 

Thanks TAD very good stuff for me. I have removed the foam from the interior which I know will change things. (This will make the boat lighter). I am planning to fabricate a full keel (weight and depth to be determined). I like your idea of chucking the hull in the water. I was thinking of making a scaled model to allow me some idea of her water line and to conduct some stability calculations such as finding the hulls point of vanishing stability using a variety of weights. At 28ft long I am thinking of stations every 12 inches and like you said perhaps 6 inches at the bow and stern. cheers

 

lifeboat conversions "The James Caird" very interesting voyage. "Thumper" went miles

Converted Life Boat - Sailed to Brasil and back on a build budget of U$1270 - which to me proves anyone can be sailing if they really want to.

17th July 1954: The navigator of the converted lifeboat 'Aries' enjoys some good weather during a record breaking British attempt at a double North Atlantic Crossing. Original Publication: Picture Post - 7213 - Atlantic Crossing - pub. 1954 (Photo by Alex Dellow/Picture Post/Getty Images

Two Americans, J.M. Hudson and F.E. Fitch, crossed the Atlantic in a special galvanized metal lifeboat in 37 days from New York to England. This 2 1/2 ton vessel is the smallest boat to cross the Atlantic up to this date. It went on to sail to France to be displayed at the Paris Exhibition.

 

Great input TAD, it answers a realistic question, Simpsons rules and computer inputs are entirely different processes. Re the question why, i've been there all my life,logic plays no role in the process because the other half of the equasion requires immediate money and if logic is applied you don't get to even make a run at the dream, it's the trip not necessary a fully successful result that matters for alot of people. As long as one feels they are engaged it satifies the soul. When i look back at photos of my first conversion, man it was ugly but upon launching, wine,flags and friends,I had built a 100 gun first rater and more important i was the captain. I was in no position to lay out an immediate lump sum of cash for a boat but just the fact i was working on a sub standard hull( and i knew it) and building a vessel to the best of it's capabilities and mine too, hey i was in heaven. And what a schooling it was, no formal boatbuilding course can ever match it.Enabiling others to do the same is why i started this thread,but being wiser now i push the engagement of qualified resorses to maximize all aspects of the result. Afterall what designer wouldn't want to help a 20yr old kid trying to convert a 26ft. ships lifeboat into a 100gun first rater.Thanks, Geo.

 

This is what it's all about.

It's the same boat (pun intended) many of us find ourselves in. Most of us can't afford to write a check for $30,000 or even $10,000 to buy a good boat. We can put that much into the project over time, but not all at once.

So the choice for most of us becomes do we buy a boat (or hull) with lots of issues for what we can afford and spend the next few years rebuilding or converting it, or do we start from scratch and build from the ground up. In the end it will cost more, but it's the difference between the project being possible or not. We can build, we can restore / convert, but we cannot afford to buy a boat that will meet our needs.

This is the situation I, and I believe a significant number of people who join this site find ourselves in. We come here for advice and get told "don't do either" which doesn't help make the decision.

 

Hear hear!

 

Hear Hear indeed

 

Thankyou Scunthorp,Battan if you read my last post,the driving factor for many (not all) involved in having to work with an economically acquired, other use, hull or abandoned projects is the lack of an immediate lump sum of money and as such would not be able to afford a substancial cash layout to buy a used boat.Having done some research on your inputs to this forum you of all people should be more positive, being a fan of Slocams Spray which probably is the worlds most famous conversion and no doubt he used alot of reverse engineering as he literally built the boat in reverse. ONE MORE TIME, the topic is REVERSE ENGINEERING,as a tool how do we apply it and in what order should the steps be taken, The logic of why,the logic of costs, only throw the thread off course, the scenario of conversions or completing an abandond hull are just models to refer to in learning the process of applying the tool. This a great tool to have in you kit, Most have the ability to build a vessel straight forward from a set of design blueprints but not all have the knowhow to convert,restore,complete,replicate,modify,a vessel void of blueprints. By using the reverse engineering process as a tool it can create the very design info needed to achieve this for oneself,and for others into the future. Ok, the idea of the topic seems to have generated enought good input to keep the thread going and the only way to do that is do a repeat of what steps we learned,and go back and pose some former unanswered questions which i will do later today. Also, Here's an idea i have(open to discussion) I would like to post a SUMMARY every so often to compile the info on the process so those that want to follow don't have to read thru all the chaff in order to gather the wheat. Hey, this topic is not for everyone,some know how to do this with their brain asleep, but i think it's worth the effort to wake it up a little and glean the info for all. Again never too old to learn, Thanks, Geo.

 

Having seen this "cheap lifeboat conversion" drama played out many times, I must say again that 9 out of 10 of these projects are abandoned in bankruptcy and divorce. In 1971 I worked for a marine contractor who bought all the 39' steel lifeboats from a troop ship being scrapped. There were about 30 of them. A parade of buyers appeared, dreamers and sketchers, hulls were sold, projects started. ONE was finished, a chinese-lug cat schooner that went on to cruise extensively. The rest rusted out or were made into rolly, uncomfortable houseboats.
Lifeboats are designed to sit in readiness on deck, not in the water. They have very full ends for capacity, which makes them slow no matter how you scientifically make pretty drawings for conversion. Unless of wood or FRP, they have a short life in salt water because they're usually thin steel. The bottom is not designed to take a sailing keel and the hull requires floor timbers of some sort to hang it from.
My son lives in a boat built from a wooden lifeboat still, so I'm not entirely ignorant on the matter.
At one time a partner and I converted a 50' antique oyster sloop to a schooner for about $3000. Not pretty or yachty but at least it started life as a sailboat so sailed well. This involved cutting a tree for planking, salvaging drift logs to hew masts from, and much creative scrounging. The boat went to Hawaii.
Conversion is about practicality, not analysis or theory. There is no reason to take off lines, make extensive drawings etc if you know what you're doing.
If not, no amount of planning or computer analysis will save the project. A simple scale deck plan and interior view will suffice. For rig proportions, copy what has worked in the past for similar types, and make it as big as you can because reefing is easier than setting light sails.
Here's a photo of a converted "Collinsville Gillnetter", originally a 1910 powerboat for gillnetting Salmon in SF bay. She was converted by a shop teacher to this practical chinese-lug sloop and sailed for many years. No computers, lines drawings, or epoxy were involved.

 

Viking North,
Maybe my project could be regarded as reverse engineering. It is not always easy to extract valuable information from some opinions which are thrown at such a project by the forum. Some has to be ignored, as they are way out of line and some others make sense and need to be investigated more in detail.

I bought a 28 feet sailing boat plan and for good reasons I needed to reduce it by 13%. This in view . I like to build an electric off shore boat, which gave me the security that whatever happens , the boat is safe. I stripped the boat plan from the ballast, made the mast lower, kept the emergency sail, constructed the rudder in such a way that it can be lifted out of the water, (I use two motors, thus steering is done differently, but need a rudder in case of an emergency) removed some other items I thought are not necessary.

After presenting this to the forum, I had some very (correct) negative remarks. Of which the stability is the real one bothering me the most. Thus what did I do? I visited overseas and ask questions, lots of them and I picked some very valuable constructive answers, which made me doing the following.
a) I worked out the expected weight of the boat, material, etc. +/- 1400 Kg
b) With this, the crew and some equipment to 1600 kg, I worked out the new DWL , the drawn water line. I had the reduced by 13% plan copied. I have paid for it, thus I don’t feel any infringement of rights. I bought 2 very good books “Designing power and sail” by Arthur Edmunds and “Principles of Yacht design” by Lars Larsson. Step by step I did the tedious calculations of pinpointing the new CB and the new VCG and LCG. I took a couple of pins, some wire, a ruler and worked out the new calculations.
c) Hereafter I was able to start worrying about the Righting arm at 30 degrees , 60 degrees and 90 degrees. For me to have a safe boat, it need to be more than 4,6 meterdegrees.
d) To my surprise, it was very vague explained in how to find the new transverse Metacentre. I am still wondering whether I have it correct. On this subject I have invested most of my time. I have the 10 boat stations, each subdivided in another 10 equal spaced lines on the heeled 30 degrees DWL and with 6 pins and some thin copper wire I work out the new area. Yes, I probably could have written a computer program or use Deltship or one of those programs, but this is much more fun)
e) Then I remove two pins and with the other two pins (2 needed to stay where they were) make this area a square one, whereby I can measure the length and the height. This multiplied by the scale factor gives me the area in m2. This I had to do some 60 – 70 times per degree heeled angle, 30, 60 and 90
f) I also worked out with the help of those two books, the wetted surface area and some other important calculations.
Also, nobody in the world was able to tell me how much MINIMUM power I need to go onto the sea with this design, thus what I have done? I am busy making a prototype and will test the power out with the help of a similar existing boat.
Unfortunately, the website does not allow me anymore to up-load the excel files and pictures to a thread. Also I found out, that I cannot edit my threads anymore. Jeff is investigating why not. Thus I have placed 2 pictures on the gallery of the experimental prototype I am making
If all calculations are a disaster and impossible to make the reduced design safe and offshore going to my satisfaction, I will make some other kind of boat and stay in sheltered waters. However the above exercise was very valuable for whatever boat I will make at the end of the day.
In conclusion. I needed to know whether I am able to correct this instability created by removing some of the ballast and reducing the plans by 13%.
Maybe at the end of the day, I will come to the conclusion that it is impossible to do what my dream would like me to do, nothing lost, other than time.

I agree with some comments, the forum could sometimes be more helpful in stating what you have to do to make it too work or proof to yourself that it is not possible, instead of stating: don’t do it. But on the other hand , I learned a lot and advise you and anybody else who would like to do some kind of reversed engineering, to do the measurements, stability and righting arm calculations and whatever calculations needed to make the dream a reality. (or wake up with a hangover)
Bert

 

I don't think "reverse engineering" is the right descriptive for what's being presented here. To me that term means figuring out how something works from the hardware, not re-purposing it. It's about analysis.
Maybe "adaptive engineering" comes closer to the idea. Taking something designed for one use and adapting it to another.
Good thread and an excellent thought-starter.

 

Scunthorp, have you contacted the Bauer dinghy guy yet as i suggested in an earlier post? his was a very nice conversion into a proper sailboat which he sailed across the atlantic, by far the nicest conversion i have read about,it may have been in Good Old Boat magazine. He would know more about the subject than any of us on the forum having actually done it. Just a thought.
Steve.

 

I like the idea, and if i could find an old life boat I would do it myself . a relative of mine converted one back in the 50's , and he said it worked great. i have seen 2 close up .
From what i gather it is a straight forward proposition. Try to get a set of lines if you can ,
or make a set from the hull. Good luck, and please keep us informed of your progress.

 

Steve No mate do you have a link to it?? Cheers

 

Just google Bauer 10 dinghy,his phone # is on the website,i dont know how approachable he is but worth a try.
Steve.