36-40ft semi displacement

rustybarge said:
I think this is very sensible advise. There are very few large boat manufactures [none?] producing semi~displ designs because they drink fuel at 14kts, that's why! Even the swift trawler designs like the ST34 and St44 are really planing boats with speeds in the mid 20's.

...but there are planing boats that can plane at slow speed, very popular with commercial operators, like the Botnia targa range which can plane at 10kts, and top out at 35kts. But they have very tight accommodation.....:ambivalence:
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Yup thats correct. Lets face it; most of us who buy motorboats are not blue water cruisers and we like having the ability to cruise at higher speeds because we have busy schedules, limited time and reluctant families so the ability to cruise at 20-25kts is almost a must. We may well often choose to cruise at much lower speeds for fuel efficiency reasons but the ability to put the pedal to the metal is something that most of us want to have when we need it. Boat builders could offer us SD boats that are capable of 25kts+ but as we know SD boats consume way more fuel at these sort of speeds than P boats. So, because boat builders know their markets, they invariably produce P boats or as you point out, faux trawler boats which are sold as rufty tufty SD hulls but in reality are P boats with a keel
Yes of course there is a sizeable chunk of the market who want a SD hulled boat and are happy to forego the speed potential of a P boat but I hazard a guess that most owners of SD boats have more time on their hands to go boating compared to time poor P boat owners
 
kashurst said:
Fuel burn has a lot to do with total weight, wetted area (whats under the water) hull design, and drive system. An SD boat of @ 35ft will have a water line length of @ 30ft. this gives it a maximum hull speed of @ 7kns. (hull speed = 1.3 x Square root (water line length) as a rule of thumb). After that speed any boat will have to shift a lot of water and work hard to go any faster. An SD boat of this size will burn a fair bit of fuel at 12 - 14kns. A similarly sized planing boat will probably burn the same or even less going at 18kns and in calm conditions will probably continue to plane down to @ 15kns. I used to have a Princess 37 of 1980s vintage that would plane at 18kns and keep planing down to @ 15kns doing @ 1.5 - 1.6mpg and that was a very unsophisticated boat by later standards. A planing boat with outdrives will have a better mpg but if its old will cost more in maintenance (search forum for threads on this)
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This is really what I have in mind something like a princess 385 or even a 36ft planning boat probably with TAMD 61s that I can plane @ about 15 knts .If I could get 1.5MPG I think I could live with that but I am only interested in shafts.What I envisage is keeping boat in Plymouth with trips to Fowey,Falmoth,Salcombe and Dartmoth with channel Islands for possible holidays.If a trip to Dartmouth and back is going to cost about £150- £200 quid in fuel as I say I can live with that,but the horror stories of £300-£400 and £1500 to round trip to the Channel Islands would be out of my league.If that were the case a slower semi displacement would be a possible answer but if it means travelling at 8 knts that is a bit limiting.Plus to be honest the insides of planning boats seem much more attractive than the semi displacement boats and this is going to be a big factor in SWIMBOs choice I am ashamed to say !! Am I being realistic with these sorts of costs for a trip to Dartmouth from Plymouth in this sort of boat?
I appeciate conditions can have an effect and people feel much happier talking in terms of fuel burn per HP etc but I am very simple and just want to know how much it is likely to cost in pound notes from people who have done it in similar boats-planning or S/D.Many thanks again from all concerned

Tim
 
TimV
Fairline produced the 36ft hull that was used on the Turbo 36 ( later called the Turbo 38 but same size exactly) The Turbo is an aft cabin boat See: http://www.boatshop24.co.uk/fairline-turbo-36

Fairline produced the Sedan 36 on the same hull an aft cockpit fly bridge boat see :http://www.boatshop24.co.uk/fairline/sedan-36

I prefererred the sedan because it had an aft cockpit which with a canopy made another living space in bad weather and a huge locker underneath. Down side was the ladder to the flybridge.

The hull was excellent and a very good sea boat and one of the most successful hulls they everbuilt probably 60% Turbo and 40% Sedan.

I repowered mine with a pair of 370hp Volvo Penta 63P engines.

Personally I like semi displacement boats mine cruises at 19 1/2 knots My sedan was 22 to 25 cruise. Current SD boat is a good seaboat.

Deleted User

I agree £180k was a figure I plucked out of the air, this was 2000 ish and a Turbo 38 then out of production was about £130k but I still could not re fit out a bare hull for that at the time. I in fact bought a basket case Sedan 36 and spent too much money on it , another lesson learnt.

Best MPG is Outdrive boats , then planning shaft drive then SD. from a sea kindliness point of view best SD, then planning shaft, then outdrive.
 
I have just done a rough calculation
plymouth to falmouth following the coast loosely is @ 40nm
at 1.5mpg that works out at @120L
at £1.10/l thats £130ish quid each way assuming you are going fast.
However the reality is you probably wont go fast all the way - depending on the weather its unlikely you will do that sort of trip more than 10 times a season.
slow down to proper displacement speed say 8kns and you will probably spend £120 there and back.

In my mad boat owning logic I divide the fuel cost in my head by the number of people on board having fun. Fun cost per person is much less so its much more worth it.

If you have a planning hull yes you sacrifice the smoothness of Semi displacements but you have the advantage of speed. And speed = time at sea. Sometimes you might need to get somewhere fast (weather tide, problematic lock made you late etc) and you can blast home. In a SD boat you just cant. At low speeds in the size range you are looking at a shaft drive planning boat doesnt feel that much different to an SD hull.
 
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timv said:
.If a trip to Dartmouth and back is going to cost about £150- £200 quid in fuel as I say I can live with that,but the horror stories of £300-£400 and £1500 to round trip to the Channel Islands would be out of my league.If that were the case a slower semi displacement would be a possible answer but if it means travelling at 8 knts that is a bit limiting.Plus to be honest the insides of planning boats seem much more attractive than the semi displacement boats and this is going to be a big factor in SWIMBOs choice I am ashamed to say !! Am I being realistic with these sorts of costs for a trip to Dartmouth from Plymouth in this sort of boat?
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Tim, I'm sure you are being realistic about fuel costs but perhaps you're not being realistic about the overall cost of boating because the difference between £200 and £400 of fuel will probably be the least of your worries with a boat of this age. Even if you are handy with a spanner and are willing to take on maintenance work yourself, a boat of this size and age is going to cost say, £3-5000 a year to keep on the water and thats if you're lucky and don't experience any major failures. And thats before you start to consider berthing, insurance and improvements to the boat. We all tend to get hung up on the fuel costs of boating but they're only actually one fairly small part of the cost of keeping a boat. Nobody should pretend that owning a boat is anything other than an expensive business but then, as they say, you can't take it with you
 
I think your money would be better spent going smaller and younger.
A 25 year old 12mtr twin engined boat is only suitable for experts with deep pockets.

For your budget maybe a mid 2000 Merry Fisher 925, with a single engine...lots advertised asking £65k to 70k...
Modern recent design only 10 years old
Readily saleable
2 mpg instead of 1mpg
Half the running cost of an old twin engined beast.

...but not much internal space.
 
Rough prices... My 1988 boat, 36ft, open cockpit....

£27k
then re upholster the whole boat..
Then new electronics,

If you go in with eyes open and realistic you can get a lot of boat for your money...
 
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