can you decrease plate thickness or use FC for a tug?

Buying a hull in unknown condition means you then haul it out, blast inside and out, then gauge the metal thickness left.....then start replacing plates.....you know nothing until you've spent thousands on finding out if there's anything left......

Have you looked at Jay Benford's 32' tug design? It's available in chined steel, 13' beam, only $1250 usd for plans.........http://www.benford.us/

 

As the vessel is scaled down the proportions don't scale linearly. For example the Length/Beam ratio changes not linearly but approx proportional to B^(.7)

Other scaling factors are chosen to match the characteristics you want. It's a parametric transformation of the hull form, it's never a linear transformation where you just miniaturise a design. The target can include the same displacement it's all about which compromises you want to juggle.

As for the boat for sale; sometimes the rust streaked ones can be quite wholesome, just needing TLC rather than surgery. Only a thorough examination of the plating can tell. Work boats can be better off because the inside plating has been left accessible.

 

yes on top of that- he wants the prop and shaft that comes with it--i have a prop...i was on that boat in october. looked it over. the owner is in his 90's--he states that the hull is in excellent condition..but i cannot do a survey if its in the water...

 

Hey Burt--yeah, I worked on tugboats that were moored directly across form this tug and this boat has been here for years...maybe ten years or more--it has been in freshwater the whole time....I would just save up for a while and buy it(about 21 months) but in that time he might sell it. so...im still looking at options...Ive tired of the research-im at the point where im almost ready to give in...i just want to build now or set money aside for a boat...if i build ill be like you and -pay as i go and have fun doing it...even if its a disaster...

 

Mike--it didnt look to me like the hull leaked at all--it has some rainwater in her... but thats all i know from what I can tell=--it needs a lot of work...wheelhouse has to be blasted and restored...probably the hull needs new pain and blasting...
as for the scaling down--i was told it would be .9 + .9 + .9= 27% reduction in displacement...thats a lot...what i want is for her to sit at the same profile. ie.e when vviewed without something to scale it, a person for example...it would look the same as the original design...this is the conundrum...i am going to look at the benford design too...as suggested...can anyone tell me what bid plans are? his Bids are 250.00 for the design Tad mentioned..but full plans are 1200.00 not bad but i would chnage the wheelhouse to a more commercial look to it. so i dont want to pay for that if it cna be avoided--im hoping bid plans means- pay as you build type of idea???

 

thanks for all the help everyone...im listening...

 

Bid plans are for a yard to give you a quote.

Study plans do not show enough detail for a cost estimation, and the full set of plans is too expensive to buy, just to notice that the boat will be over budget.

 

Great! thanks Richard...I coudnt find that info anywhere.

here is the construction and lines plans--its a big vessel...hence my yard and the size seems to big for me to build full scale...thats my reasons for going smaller-- the beam is then 11.25ft instead of 12.5ft (over the legal limit to move) and then the loa is 40.5 ft.(fits in my backyard) and then the depth is reduced from 7.7 ft to 6.93 ft-- this reduces displ..by 27% so if the displ. is around 45 000 its then 32 850...i havwe the displacment figures coming ...but im guessing right now...

ive been offered some very nice designs to see if I like them--but i just cant seme to let go of my dream boat...i just cant see .9 % being such a big deal ina displacement hull...ill adjust the wieghts accordingly..make sure she- not too heavy and if too light ill ballast her...IF this is what I Do..im making a decision deadline(dread-line?) for end of this month...

 

That´s what the pro´s are good for, they know the business.

And if you would have been less stubborn and defiant, you would have gained a lot more out of us.

I am not wading through the pdf´s, maybe one of the peers does.

Richard

 

Richard--I think you'll like the pdf's..not too difficult to get a picture of the build??

 

I'm not sure if you got the message Tugboat. That's only the case in you miniaturise the hull i.e. scale it down proportionately in all dimensions. But that's not done because it doesn't work very well.
when you scale the proportions should be scaled by different amounts relative to the change in length. Your target displacement could be chosen to be close to that of the original. It's very easy to transform the hull to a new set of parameters and it's very common in the design spiral for new vessel designs too.
For the NA it's a matter of juggling your key expectations for the boat and keeping the classic lines as much as possible whilst juggling the powering and stability requirements.

 

Mike--yes i didnt understand your original completely. my question is then --if its not proportionally scaled--how DO you keep the original lines?? change one dimension and it then alters the whole hull shape and profile and how the boat sits in the water? in order to keep the boat sitting at the "sheer profile" i.e. look the same as at full scale --you must decrease proportionately??? to do otherwise seems counter-intuitive.

so- this is what seems confusing to me:

for example--if i reduced the loa to 40 ft..then the hull fattens if i keep the beam at 12.5 ft making the beam disproportionate???? if the beam is reduced slightly then to compensate- wouldnt it then look nothing like the original??.
since there is no ratio and proportion??..

could I leave the depth at its original?? decrease beam and loa and keep the draft.
I could be wrong but i think thats doable to maintain the same look afloat ?...and if so it shouldnt reduce the displacement as much??
just inquiring...thanks.

 

Tugboat.

I think that design could easily be altered to lose the curves and add some chines , It would be easy to plate up for you and you'd hardly notice the difference afloat. That vessel shape is suitable for a reasonably easy chine conversion. Maybe a little less topside curvature and a single chine . If that was all that stood between you using ferro cement or it's direct strength equivalent Ferr-A-Light then I wouldn't hesitate.

Now there is one use of ferrocement that is worth mentioning (considering your fetish for goo) and that was to take an old steel hull sand blast class 3 minimum, weld studs and mesh and plaster with a good rich pozzolanic mortar (no paint). Some commercial vessels in survey here had this done apparently very successfully but I had no direct involvement. But you still need to descale and treat the inside and that's nearly always where the holes come from.

 

Richard--could i get lines plan from the bids?

 

It never has to have 'exactly' the same relationships, you want it to look similar enough to capture what I'd call the essence of the style, that will suffice. And yes you can look at increasing the displacement relative to length.