Reverse Engineering (conversions And Modifications)

Tad, reasonable feedback but maybe a little criticle naturally the designer will include tanks, machinery, ballast, he will not only do some quick calculations but compare his results to a similar type boat. Remember the builder is a well knowledged backyard builder, by backyard i mean he has previously built boats he just does not do it commercially he would not need engineering info on deck beams, wheelhouse/cabin construction as this info is available in a mulitude of books,As to the condition of the used items thats not the responsibility expected nor requested of the designer. And $5000 in epoxy, $5000 in bolts, i take it you mean $500 each otherwise you are definately off the project. Anyhow this thread has turned into a bit of a blood bath and it's really not worth the effort to continue it from my part. My figures are not that far off, i've been thru it several times but then again i am assuming that the average guy out there that would take on such a project would have a similar knowledge in the process which maybe is a mistake on my part. Also maybe i've just been luckey in finding such a professional to work with, i certailally will appreciate him more after this thread. Best of the season to you, Geo.

 

I just read through this thread and didn't see anything I would consider a personal attack. Perhaps being told your "project' is unfeasible in terms of time and ultimately money compared to other options is being viewed as a personal attack but I don't think that is the case.

Sometimes people get ideas in their heads and are too stubborn to face facts and re-point their direction.

To have a good ending to any project you must start with reality and a through understanding of just what is involved.

I kind of like the idea of the paper airplane going to the moon. You can spend hours and dollars and never come up with a working design. If you want a paper plane in space buy a spot on the next shuttle lunch and send it up that way. LOL Guess my point is why not start with something you know can work rather then something that requires the first question be; is this possible?

Happy New Year everyone.

 

Here are some nice Lifeboat conversions by backyard builders.

 

LandLubber, Noted and thankyou, i'm a Lover not a Fighter and i love to build and sail boats, like the majourity out there have never had the funds to own a good solid boat so rather than buy the economical junk they sell as blue water rated i build my own and on a few ocassions mother nature has seperated the men from the boys in their so called deep sea ivey league vessels. I'm not retiring from the forum that would be deserting the cause being the do it yourselfer out there, In the near future will be posting my conversion/build on the site and see what the naysayers have to say. These forums are bad my words are becoming agressive, The wife has just passed me a stiff 15yr. El Dorado that'll cool me down, Have a good One Geo. of The Rock

 

Do not retire from the forum. Even when we argue we learn things about the topics we argue over. Opinions run strong but light is shed on issues in this way.

 

George: first welcome to the forum. You will be able to find information here of a quality that beats anything else on the web at a price that you can’t refuse! However, the responders reserve the right to be characters! So be patient - some of these guys have been around a long time and have heard it all many times.

The 2nd post was a request for pictures of the semi-finished hull you wish to convert. This really is the first step if folks are going to be able to help you. Alternatively you can identify the design, if you know it, or post an image of the lines if you have a drawing or table. Then you will get the experts involved in what they do best.

 

So so true...sadly, and happens far too often too.

 

Viking, i have done two such projects for customers over the years,the most recent was a beautiful 39ft bright finished double ended motorsailor built in Finland in 1970.The customer bought it very cheap from a storage company,it had been stored indoors for years,the cabin had been removed and then it was abandoned,now this boat had zero decay,zero,not even any discoloration around the plugs over the planking screws in the yellow pine hull.The problem is it had almost all internal ballast in the form of lead pigs.Unfortunatly they had been removed and placed on pallets under the boat and they had been spirited away at some point. So,what to do.Well,it required reverse engineering,the boat had a clearly marked waterline so i leveled it to the waterline,divided the w/l into stations and took the lines off it,came up with a table of offsets and drew a lines drawing and calculated the displacement and LCB.Then i had to weigh it, and balance it on a couple of pieces if pipe to find the center if gravity, i used load cells like the highway patrol uses which i had to rent from out of town and have them shipped each way,then i needed to back out the weight of the cradle which i was able to measure the materials and look up the weights on engineering tables to estimate the cradle weight,of course the LCG of the cradle had to be considered too,all the existing tankage had to be measured,all the weights and locations of everything that would go into the boat had to be estimated, anyway you get the picture, i billed the customer $4500 which was almost as much as he paid for the hull and more than twice what you have allowed for this work. Ive found that when a client buys the project cheap,they have a big problem reconciling the real price for future work, ie, we jobbed out the rebuilding of the 6-354 perkins and again it cost more than the hull. George, i wish you luck and urge you to if at all possible,as has been suggested by others,post pictures of the hull in the hope that someone will recognise it, a little sleuth work in the early days can save you a lot.If someone recognizes it and you can track down the designer,great.
Steve.

 

Once you have the lines drawing the simplest and most accurate way to get weight and CG is to throw the boat in the water and measure flotation. The ease of doing this varies considerably with location, size, etc.......

 

Steve, The thread was not about my build but about reverse engineering as it pertains to conversions or the completion of an interrupted build of which no design info was available. I.E, the steps one would take to determine if the conversion could be built into a reasonable sailboat or motorsailer. OR the steps one would take in continuing that incompleted hull (no keel no ballast)into completion.(the exact work you described in your reply) The idea was to create a thread that would appeal to and inform on the concept of reverse engineering to obtain design info. I was hoping that it would get into a broader description of taking off lines, I.E. recommended # of stations, optimum spacing between stations that would apply to computer input and anyother trick that could be used to do the job. From that i thought surely someone out there would continue on and say ok, A designer could do a quick and dirty estimate of total displacement using a similar size and style boat to get a rought waterline and from that you could get the approx. prismatic coe. and that number will give you an idea if your hull should be oriented toward sail or more of a motorsailer. I.E. easily driven or not. I figured i could then say ok it's going to be a full keeled motorsailer and the process would continue with the idea that the builder would need the designer for certain critical info but certainly not to the point he is supplying general construction info available in a million how to books. Anyhow somehow it all went to hell in a handcart in that there was an actual hull/build about to happen and using reverse engineering was a devils errand so to say, it was all a waste of money, whats wrong with you can't you get the message, all the experts are telling you not to do it. Christ it wasn't my build it was an idea for a thread to show how reverse engineering could be used.My build was started 12 months ago, I am working with one hell of a designer and have already done the lines takeoff, the quick and dirty prismatic and determined it will be on the border line of a heavy crusing/motorsailer build. The interior of the hull has been stripped of all the unwanteds, motor/drive system/ fuel/tank cockpit/wheelhouse/ cabin/ interior layouts all measured out or mocked up,I have completed the floors, drilled for keelbolts, and am in the process of fabricating and installing the full ballast keel incorporating the Brewer Bite style cutout. I have taken detail photos and once the keel is installed i will be far enough ahead to post a fairley steady flow of photos on how i did my conversion using reverse engineering. To be fair i am an experienced builder and have enought smarts when to engage professional help. However it's refreshing to hear a bit of reverse engineering was used in order to re juvinate what sounds like a work of art, any photos? Geo.

 

Part of your problem is you are sending mixed signals.

You say the above and make it sound as if you are just trying to start an interesting informative discussion. Then you say things like.

Which certainly makes it sound as if you are looking for professional advice for a specific project.

 

Here is something which might be of interest to us “less deserving” boat builders. It is well worth the read and has information on the commonly used materials. It’s American and sensible. Who knew??

 

Howardh, your replys are most welcome but counter productive and my understanding of a negative response would be different than yours as it is me who took the step of opening a controversial topic between designers and builders, in otherwords i am the inital target until sufficient numbers of replys grasping and sticking to the thread come in.I think your reading of TAD's replys is wrong, My present understanding is that TAD had grasped it as a what if scenario but i think at that point after all the off track replys i didn't appreciate fully so and after a re read my apologies to him.In hindsight no doubt i could have reworded but try it and regardless the thread takes on a life of its own. To give you opportunity to be exposed to the firing line how about a productive reply in the form of answering the questions i posed in my posting regarding taking off hull lines, in your "careful reading" (my interpertation)of the thread you'll notice that even coaxing by questions(guidance) the thread is hard to control or change once it unfolds. So maybe with your answers,the positive replys(there are several in now) and hindsight on my part we can get it back on the road to the benifit of those out there that can make use of reverse engeneering to start or complete a project. Never too old to learn, Geo.

 

Trial run, posting a photo (dory build) uploaded to Flicker.

http://www.flickr.com/photos/57515368@N05/?saved=1

 

Okay so no one wants to answer the "Why are we doing this" question.....so we'll stick to the how......

But before I do that I have one small short story.....5 or 6 years ago I was hired to "just design the windows" on an 85' motoryacht rebuild. A wooden boat built in 1934 and converted to a dinner cruise vessel, she was a mess which the owner had paid four times too much for. The owner intended to make her a private yacht and the project would take about a year. He built condominiums for a living and knew all about projects.......First thing I did was write a 5 page report on projected budget and why this project was a questionable investment. He went ahead anyway......a few years later, project still far from complete, he admitted he should have listened and should have hired a project manager first thing. After years of work (with no use of the boat) and hundreds of thousands invested, she's worth (market value) about what he paid for her in the first place.......

On this coast we currently have dozens of retired fishing boats for sale cheap, anywhere from $15k to $85k, and these boats make great cruisers when converted. Typically owner's spend roughly twice to three times the purchase price on conversion. Then they get tired of fat moorage bills and try to sell the boat. They find that, because there are already so many of these conversions on the market, the asking price has to be anywhere from $15k to $85k........questionable investments.......

Viking asked about taking lines......

1) How many stations........It depends on the hull shape and what your design goals are. For instance a lifeboat hull has a long straight midships section, no point in a bunch of tightly spaced measurements here. Generally stations are closer at the ends where there is lots of curvature. You might use 5 stations plus stem and transom for a 16' boat. You might use 6 stations on a 30-36' powerboat but 10 on a 36' sailboat with lots of shape, and you might use 10-12 on a 60'......

Only measure one side of the hull.

2) They don't have to be equally spaced if you are using these measurements to create a computer model. The only reason stations need to be equally spaced is if you want to calculate displacement and centers by hand using Simpson's rule. And if that's the case you can add or re-draw section lines wherever you want after you fair the lines drawing. So for lines taking (in the field) sections can be wherever you like. I often use the cross beams of a local shipyard's carriage as section lines......

3) You want to take enough measurements to record the shape reasonably closely, we're talking the nearest 1/4" not millimeters. Recently I've been using buttock measurements rather than sections as longer lines are quicker to fair. I measure and photograph the stem and stern, keel, sheer, and rabbet very carefully, then take offsets at butt 12", 24", and 36"..........

4) Minimizing the assumptions is good so a scale weight is nice to start from......there are lots of options for this. As I said above throw the boat in the water and measure it. A local truck scale if the boat can be trailered, or a crane or jacks and load cells.....or an old scum line if her load condition at that flotation can be ascertained....old photographs are very helpful as well.