Sink or Swim its that time......

Ike
I agree with every post so far and I am determined to get a usablecraft at the end of it all. As for complicated builds, well it just won't happen. Your quite right about building a house but I would advise a do it yourself builder to chose his foundation type wisely not necessarily learn about every foundation possible.
I would like to make it very clear that this craft will be a simple lightweight affair and not the Titanic II. It will however look as good as I can manage. One thing I won't be making is a tea chest with a mast.
I want to capsize in style.

So far just sketching shapes I have already come to the questions of hull shape and obviously want the pointy end to travel as easy as poss through the water but want it wide enough to sit behind so let the compromises begin (and a whole lot of research).

Regards
Iain

 

I love that Australian freedom.

I have decided to begin with my uncompromised ultimate shape and am working on that first.
I will then start the process of study. Seeing if itcan be done with the skills and materials available. This will obviously change the craft as things progress. My inspiration will be the classic gentlemans launch but it will be inspiration only. I already lovethe idea of stitch and glue and am looking into this process for it's weight benefits.
Idont think I will come up with anything that hasn't been done a million times over but the final reciepe will be a combination of existing ingredients in my own proportions.

 

Acid,

I didn't take any offense to your comments, and I think its great you come with such a large amount of enthusiasm, because that is exacally what it will take to get through the long slog of hours to turn a pile of lumber into a boat.

Given the number of hours to build something like what you have described you are talking about litterly a thousand or more hours of work. Generally for a professional boatbuilder you can figure between 3.5 and 5 lbs of boat built per man hour of work. Though there are exceptions, Maltese Falcon was built at 1.5 lbs per man hour, and navy vessels and large yachts at up to 15 (Refrencing Apex1). After putting all of the time and money into a project like this I hate to see someone get discouraged because the design was faulty from he begining.

Even simple things (for a designer) like determining the proper thickness of the hull is a complicated design spiral with no good starting point. For instance to determin the plank thickness you need to know what the hull shape will be, which effects effeciant speeds, which changes the hull shape, which changes the expected power requirements, which changes the hull shape and expected speed, all of which is modified by the expected running conditions, which..... (add nauseum).

What you are undertaking is a massive project, I am guessing well beyond what you even realize at this point, and just in learning enough to design the boat is likely to take over a year (I am working on the assumption you want this boat to operate at above planning speeds). Even most designers start with either a pre-existing boat and modify it to fit the new design brief of the boat they are now intending. This is why manufacturers almost always start with a small version of a boat then over time add leingth or beam to it instead of just creating whole new boats off of the board. Or you start with a specific boat and say well this is nice, but I want it to go faster, carry more weight, run dryer, be more comfortable in chop, ect.

Acid if a knowelegable boater suggested what you are doing I would tryand talk him out of it, but with little experience on boats honestly you don't even know enough to describe some of the problems you are likely to encounter. This is exactly where a designer comes in handy.

Just remember what you are proposing is kind of like someone who knows nothing about cars except they look cool deciding to build an engine starting with nothing but a block of steel. Technically yes it can be done, but it is a lot more likely they will wind up with a useless hunk of metal than even something found in a trashlot yugo.

 

have you seen the blog
intheboatshed

 

I think you’re all absolutely correct in what you say for a sea going fast boat cruiser or yacht but let me spell my project out. It’s not a big job.


Maximum length................ 18 feet......... Probably nearer 15
Maximum width................. 5 feet............Probably nearer 4
Maximum weight............... whatever I can lift off the car with a few helpers.
Maximum HP.....................7
Maximum speed................ 5-10 knots
Maximum displacement...... 700lbs
Inland, small freshwater lake only. And only on fine days.
Stored dry

Inspired by a mahogany launch, an Indian canoe and the USS Enterprise off star trek. When finished it will not look like any of them but will draw on each of them.
It will be used as a simple day boat and carry myself, my wife and daughter and a glass or two of pomp.
Basically it will be a large canoe with a boat bow and an angled aft. If the weight wasn’t an issue I would go inboard electric but I can’t abide the idea of half a dozen car batteries on standby for a weekends fishing.

It’s the single story extension of the boat building world. Ok it may have a Georgian column or two or a flying buttress thrown in for aesthetics but wont need an architect or structural engineer to look over it, just a conciensias builder who can follow a few simple rules and build on the over engineered side of caution.

I wouldn’t entertain going to sea in anything that hadn’t been professionally designed and tested never mind take my family on such a craft and that includes some of the worlds larger lakes. As I hope you can all see, this isn’t a cruise ship build. One thing I do know about design is that Enzo Ferrari didn’t start with a slide rule and a book of logarithms. He started with a blank sheet and a pencil, and thank god he did.

Iain

 

http://youtu.be/J3ZLE2xmj4Q

 

Geez, I love Riva!

 

That would go well on my roof rack ??????

 

Well it would if you scaled it down

 

After a run out this morning to pick up some ridiculously over priced coloured water for my printer I set to printing off my first stab at a hull.
I like the lines and general shape of the beast but being more acquainted with roof trusses I lack the experience to guestimate whether the bottom will be flat enough to provide the stability I want.
Time to make a model me thinks so with a sheet of mounting board picked up on the way back from the printing shop I set to chopping out a few chines and fighting with half a roll of sticky tape. I think the next time my Daughter may be handed this task as I am great with a hammer and I can even tie a mean fishing fly but sticky tape and two pounds of badly wrapped sausages (my fingers) just don’t get on.
Once in a half filled bath the model floated (always a bonus I guess) and sat nicely in the water and I even filled it with several bottles of nail varnish (not mine) to the level shown on my software for my chosen displacement.
I gave it a shove. I rocked it. I poked it again and sent it on a little trip from comfy back bay to the drippy tap straights. It seemed to be OK.
I’m not sure what I was expecting but it may have been better if a disaster occurred. At least I would have known I was barking up the wrong mast. So it looks like Ill tweak the bits I’m not happy with and begin collecting the bits and pieces for the build. I’m still unsure of the stability but as I hate flat bottomed boats anyway and I will always lean to looks I think Ill go with it. It doesn’t look unlike other boats I have seen so it’s nothing radical but it should come good with a bit of posh wood and the odd chrome fitting.

 

I will happily have a look at the stability aspects if you want. Drop me an e-mail via the forums.

Tim B.

 

Thank you Tim that’s very kind and Ill keep that in mind but I have very few specifications or technical information. I realised this morning that I haven’t put a keel on the dammed thing so back to the Carlson Hull Design Software.

 

A few years back I saw a news report in which the head of Hewlett Packard said, I don't make any money on printers, but I make a lot of money on ink (or words to that affect) The money is in the replacement cartridges (colored water)

 

Thats a model made. Oh and it has a keel on it now.


http://imageshack.us/photo/my-images/843/model1qg.jpg/

http://imageshack.us/photo/my-images/12/model2u.jpg/

http://imageshack.us/photo/my-images/801/model3.jpg/

http://imageshack.us/photo/my-images/405/model4a.jpg/

 

Acid, I see that you have a goal of 700 lbs (around 320 kg) at full displacement.
Now, 2 adult persons plus a kid can weigh around 180-190 kgs (you tell me if that's your family's case. 6 kW electric motor(s) plus batteries, wiring, controller, steering and comands will be around 60-70 kg. Just these two weight items sum to give around 250 kg. It leaves you only 70 kg for the rest of the boat, seating, winshield, small accessories, food and beverage etc.
You have to evaluate well if this weight margin is enough to create a boat as you have intended it. I personally believe you'd be safer assuming around 750-800 lbs full weight.

Now, about the model you have created. It's another good point for you, because you seem to be a man of action. In 3 days you've started from the paper and have created a real-world scale model. so the premises are good, imho.

However, the pics apparently (it's hard from here to evaluate cross-sectional form, and the design waterline is not visible) show a displacement boat, not a semi-planing or planing one. It will limit your speed to around 6-6.5 kts, far from 10 kts you'd like to achieve. Seen from this angle, the hull sections appear to be close to circular, which is not good for the initial roll stability. You need aft volume and flatter aft sections.

The design spiral in front of you is long, but it's a nice first attempt.

Cheers