Semi displacement / planing, fuel prices

[henryf]

So where am I now?

I think probably we are going to stick with a planing boat. When you sit down and look at fuel usage I'm not convinced we would actually make enough use of the displacement benefits of a semi displacement boat. Full displacement is definitely out of the question. The risk is we go everywhere at a compromised planing speed and end up saving a few pennies for a reduction in speed from 23 knots to 16

We know how a planing flybridge works for us, maybe we will try a couple of trips at displacement speed to see how we get on and see if we feel the fuel saving is worth the extra time. At least the planing hull gives us options.

I hope the larger boat feels more substantial than our 42 footer. Not because there is anything wrong with the 42 foot boat, quite the contrary but for the extra money I want a sense of extra solidity and maybe the thought was that by going semi-d I would get that.

Deep down I'm probably a frustrated blue water cruiser who's a few million short on budget and 23 and a half hours short of daytime. I haven't been out in a 50 footer yet and I suspect once we are afloat 24 tonnes will feel different to 14 tonnes so that will scratch the itch and help justify the extra spend. It won't just feel like a 5 foot longer version of the current boat for a shed load more money.

Just need to dot the i's and cross the t's on the P42 then roll up the sleeves and put my poker face on......

Henry

 

[BartW]

So where am I now?

for me planing boats with stabs is the way to go,

the one thing that I like about SD boats is:

I've alway's been a fan of trawler boat models, and these are usually SD.
but thats just taste,
they appear to me like real "ships" and thats what I like,
nothing to do with D-SD-P
nothing to do with efficiency, ...

I'm not (yet) convinced that there is much difference in behaviour (in bad sea state) between the 3 types. After all they are just a floating piece of GRP or wood in a huge sea,
and for the limited "holiday" time I spend on her,..a planing boat offers just that bit more enjoyment.
I prefer to stay ashore when the sea state doesn't allow a pleasant cruise,

I'm not planning any ocean crossing, nor any canals cruising (where D boats make sense)

My planing boat is quite heavy,
when the sea state is bad, I can cruise at a SD speed which could make the ride more comfortable (in some conditions).

 

[jfm]

Surely though,if the zero speed stabs work well at zero speed,presumably they also work more effectively at slower speeds than standard stabs,therefore comfortable displacement speed on an SD becomes more of an option for more of the time,maybe?

Also,as your figures confirm,equivalent planing boats do use less fuel and additionally,because their top speeds are typically in the low 30s rather than low 20s for SD,cruising speeds are also significantly higher whilst returning better economy. I guess much of the decision making comes down to which compromise seems to make sense on the day.
However as generally speaking,SD boats are no thirstier than others at D speeds,if D speed for much of the time was acceptable coupled with the ability to go at say 2.5x the speed when necessary,then maybe this compromise could work for some?

Yes to both paras
Ref your 2nd para, it's very much a compromise, and then we each have our own personal factors in making that compromise hence different people have P, SD and D and each is well able to defend his personal choice! Twas ever thus!

 

[MapisM]

I haven't been out in a 50 footer yet and I suspect once we are afloat 24 tonnes will feel different to 14 tonnes so that will scratch the itch and help justify the extra spend. It won't just feel like a 5 foot longer version of the current boat for a shed load more money.

Mmm... Having been on a few planing 40 and 50 footers (though never a Princess, tbh), I would predict that the "just longer version" is precisely the feeling you will get.

Mind, there would be something wrong if it weren't like that.
A planing boat MUST be as light as possible, for any given length/size, because weight is an enemy to fight, in the design of a modern efficient P boat.
Therefore, the additional 10T are not meant to make the boat more substantial, but are simply necessary to keep afloat the bigger thing.
Eventually, the bigger size will also give a somewhat more solid feeling, but nowhere near the difference that the 24/14 ratio might suggest.
And not even the 50/42 ratio. More likely to be a 5 to 10% difference.
No prize for guessing how different the feeling would be between a 24T planing 50 footer and a 70T steel trawler of the same size (yes, there are some whose weight is in this range).

Otoh, I'm not disagreeing at all with your conclusions.
If you still wish to cruise at 20+ kts, a P boat is the way to go.
But if the thinking/hope behind that shed load of money is to get a "more substantial" feeling, think again.
Unless you also need the extra space or you have other reasons, I'd rather stick to your lovely P42.

 

[stillwaters]

You'd probably be right. I'm guessing a 70ft planing boat would be doing about 0.3mpg at 20kts so about 50% better. It all hinges around whether that 70ft SD boat would be more comfortable at D speeds than the 70ft P boat and the jury seems to be out on that one although my personal opinion is that the additional weight and the design of most SD hulls (keel, sharper forefoot, more rounded bilges) do make SD boats better at D speeds. Then, as I said in one of my previous boats, IMHO most SD boats are better laid out and engineered for extended passagemaking and have greater fuel capacity.
In the end it all comes down to what kind of boating you do. If you do planing speeds 90% of the time and d speeds 10%, then you're better off with a planing boat. Vice versa and IMHO, a SD boat is better. If you do 50/50, don't ask me

Yep,agree 100% about the heavier engineering typical of SD and,in particular D boats where,because of the extra volume of hull in the water,there is actually a need to weigh the hull down (eg.50 tonnes disp.= 50 cu.m. underwater) so it might as well be in the construction rather than ballast. Not sure whether all SD boats handle D speeds better than P boats,I rather think this may fall into something I'm not sure has been mentioned yet,that is that it possibly depends on the particular boat rather than the too-sweeping generalisation of broad categories of hull types? Clearly,within categories some are better at some things than others and could even be inferior at others,maybe. Again,it can all depend on the compromise that you go with,ie. do you let the wife have her way and buy the planing boat with a hull designed almost as an afterthought around its requisite accomodation or go for the Olesinski or whatever thoroughbred with maybe compromised forward cabin etc.that no friend/relative should ever be expected to spend a night in (78 footers aside,of course)?

 

[sea-commander]

Henry,

having followed your thread and tried to read between the lines - I'd say that your way to go is the P boat.
I think that you'd miss the option to cruise faster.

But, as MapisM already said, the 50 vs. 42 might just feel like that "longer version". You will get used to the bigger size very soon.

Greetings from Oldenburg, Germany
Chris

 

[henryf]

I may not have put my thoughts and aspirations across very well.

I'm not hoping for a Nordhaven feel to the boat - my word haven't their marketing people done wonders that their name is used in the same way as Hoover! I just want to feel a slightly more substantial or grown up boat. Ultimately I want to keep hold of that lovely feeling of being able to pop up onto the plane without so much as a draw for breath. The P42 and its engine combo is awesome for that, so I understand the weight side of things.

When I was on a P50 the other day I felt things like the genny and the pumps were all a bit more substantial. The genny on the P42 is quiet, the one on the 50 disconcertingly so. The accumulator tank on the fresh water is obviously bigger as the pump takes longer to cut in and when it does it is located out of earshot.

Individually these are all tiny things to the point where most people wouldn't notice them but I do. Ultimately we are going to enjoy the extra space. Friends visiting will have the same standard of cabin we used to and we get the cabin off a small cruise ship - all right so if I rocked up on Independence of the Seas and was greeted by the P50's master cabin I'd go ape **** on the concierge desk but you know what I mean.

We have been spoiled with the P42 in many respects. The cleats are a decent size especially those down near the bathing platform, the deck wash is better than many marina water supplies (take note Southampton town Quay) and the quality and choice of mechanical equipment is second to none but I still look forward to a feeling of substantialism (if such a word exists).

In truth I will only know once we bought something and owned it for a while. I'll let you all know.

Oh, and of course I'm not even going to consider something unless its got under water lights for my fishing.

H.

 

[stillwaters]

You'd probably be right. I'm guessing a 70ft planing boat would be doing about 0.3mpg at 20kts so about 50% better.



Just a thought about this point. Maybe 50% better (will vary between different makes of boat,of course) but,if this really is a typical average
difference between types,the planing boat is probably also going about 50% faster at its cruising/top speed as well as 50% more fuel efficiently.

 

[stillwaters]

When I was on a P50 the other day I felt things like the genny and the pumps were all a bit more substantial. The genny on the P42 is quiet, the one on the 50 disconcertingly so. The accumulator tank on the fresh water is obviously bigger as the pump takes longer to cut in and when it does it is located out of earshot.



Maybe the 4 years or so advance in engineering has made a difference or maybe it's down to the 42 being in such a price-concious sector having to be pared-down a little in places and,as you say,once you get to the P50 the sociotype of buyers have more to spend so expect that much more in return?
Incidentally,having hared around on 40-50 foot planing boats,the big difference I always noticed was not down to weight or engineering but was about the difference the waterline length makes. Say 45ft against 35ft,that 10ft difference (nearly 30% longer) can sometimes mean the difference between enjoying average chop and slamming into everything coming at you.

I assume you've overcome the urge for an Elling. I've seen quite a few across Europe and personally think they're likeably quirky and well built. However,when I was in a marina on a lake in Holland about 3 years ago an E3 was rolling about to a small amount of beam swell - interestingly,I couldn't see another boat moving. Just after that,we moored overnight next to a fairly new E4 that it's owner had just switched to from sailing.The following morning we both set off for the same destination - one side of the Ijsselmeer to the other in what was going to be typical long waves beam-on. Because of his passengers,though (grandkids etc.),he had to do the crossing in a big dogleg,he said because it rolled like a p*g in beam seas. Our similar size SD planed across at 15kn no probs. Sorry to any Elling boat owners,just relating what I was told.

 

[Deleted User YDKXO]

Just a thought about this point. Maybe 50% better (will vary between different makes of boat,of course) but,if this really is a typical average
difference between types,the planing boat is probably also going about 50% faster at its cruising/top speed as well as 50% more fuel efficiently

Yup true, most SD boats' fast cruise is in the teens although you can shoehorn enough power into some of them to hit the mid '20's kts whereas most planing boats will easily cruise in the mid 20's kts. Speaking for myself, my next boat will probably be a SD boat but I'm going to do a couple of charters on SD boats first before I buy anything because I'm really not sure whether the slow cruising speed and higher fuel consumption of a SD boat will piss me off. Maybe a charter first is the way to go for you before you buy?
Just going off on a tangent a bit, I like what Beneteau have done with their range of Fast Trawlers which seem to offer a little bit of the best of both worlds. Seaworthy hulls which are supposed to be good at both SD and D speeds but capable of 20kt+ cruising and importantly with fuel consumption that seems comparable to a planing boat. Of course, the Beneteau finish is not upto the standard of some other builders

 

[henryf]

Re the Elling E4 we may yet end up making a trip over to Holland just to scratch the itch. I love the look of the boat, actually more so than the P50. Elling themselves are happy to admit that the most comfortable ride is often at 15-16 knots. I hadn't given roll at anchor much thought.

I think the difference in noises and so on between the 42 and 50 was more to do with amount of stuff between me and the pump / genny. Princess will also no doubt fit some larger equipment but as mentioned previously the 42 is definitely not lacking. Everything is good gear where ever you look.

Even the V39, their cheapest boat at London surprised me, corners hadn't been cut in an attempt to built to a budget.

As with the 42 I won't really know until I've crawled around and had a good look in all the nooks and crannies. The good thing staying with Princess if that's the route we go is I know the level of support I will get from them as a company which is superb. It's easy to get complacent and assume all builders / retailers are the same.

Henry

 

[Kawasaki]

[QUOTE

Oh, and of course I'm not even going to consider something unless its got under water lights for my fishing.

H.[/QUOTE]

Right and Proper
You are obviously a discerning Mariner
Interesting thread btw

 

[stillwaters]

Re the Elling E4 we may yet end up making a trip over to Holland just to scratch the itch. I love the look of the boat, actually more so than the P50. Elling themselves are happy to admit that the most comfortable ride is often at 15-16 knots. I hadn't given roll at anchor much thought.

I think the difference in noises and so on between the 42 and 50 was more to do with amount of stuff between me and the pump / genny. Princess will also no doubt fit some larger equipment but as mentioned previously the 42 is definitely not lacking. Everything is good gear where ever you look.

Even the V39, their cheapest boat at London surprised me, corners hadn't been cut in an attempt to built to a budget.

As with the 42 I won't really know until I've crawled around and had a good look in all the nooks and crannies. The good thing staying with Princess if that's the route we go is I know the level of support I will get from them as a company which is superb. It's easy to get complacent and assume all builders / retailers are the same.

Henry

Whichever one you go for,you obviously have an eye for quality as both are clearly quality builders. I too prefer the look of the Elling but then I'm always attracted to anything styled with a little more imagination than the norm and the Eliings certainly have a charm all of their own. Have you read the articles,in MBY I think,of the owners who went to the Canaries,it might be helpful? Just one engine,though (I don't count the optional get-home one,of course). I went from one to two and could never go back again,to me it's like ones' first experience of aircon or heated seats in a car,if you know what I mean?

 

[Deleted User YDKXO]

Eventually, the bigger size will also give a somewhat more solid feeling, but nowhere near the difference that the 24/14 ratio might suggest.
And not even the 50/42 ratio. More likely to be a 5 to 10% difference.
No prize for guessing how different the feeling would be between a 24T planing 50 footer and a 70T steel trawler of the same size (yes, there are some whose weight is in this range).

No, I don't agree with that. Having had many planing flybridge boats in the 30-55ft bracket over the years, you definitely feel the difference between a 40ft boat and a 50ft one. The length, more specifically the waterline length, is critical for determining how comfortable the boat is in the kind of moderate F4-5 head sea conditions many of us find ourselves in. It may mean the difference between making comfortable progress at 15kts in the 50ft boat and struggling along at d speeds in the 40ft boat. Also the beam makes a difference to how much the boat rolls in a beam sea and at anchor. A 50ft boat just has a more controlled movement at sea compared to a 40ft one and if I had to quantify how different it will feel, I would say 25-30% better
Of course, the ride in a 70ft steel trawler will be on a completely different planet in comparison

 

[MapisM]

No, I don't agree with that.

Well, you actually do, to some extent.
I said that the improvement is nowhere near the 24/14 ratio (which would mean 70% better), and your 25-30% is well below that.
Your ratio is closer to the length ratio: in fact, 50/40 is exactly +25%.

As I said, I've also tried some P boats in that bracket, and always found the differences to be less substantial.
Of course, it also depends on the builder, design choices, etc.
Besides, quantifying the "ride quality" improvement in percentage is not something very scientific.

But the whole point was whether LOA matters more or less than the boat weight/hull etc., and in my experience there is not any doubt that the latter can make MUCH more difference.
Within a reasonable bracket of course - I'm not saying that a planing 70 footer is less stable than a 30' Linssen!
But if you re-read my previous post, I wasn't talking of a 70' steel trawler, but of a 70T 50' steel trawler.
And trust me, when moving from one of those to a similar size P boat, the feeling is not much different than when moving from any boat to its tender.
It must be tried to be believed.

 

[Erik C]

Apparently a 60ft Elling E5 is in the making. That should be an interesting boat as well.

 

[Deleted User YDKXO]

Well, you actually do, to some extent

That sounds exactly like what my wife would say

Besides, quantifying the "ride quality" improvement in percentage is not something very scientific.

Yes there's a whole lot more to how a boat feels at sea than just dimensions. IMHO, the ergonomics are equally if not more important. The helmsman needs a good supportive seat, the visibility through the screens needs to be as unimpeded as possible, the throttles need to be to hand, the radar and plotter need to be easily visible and controllable without stretching and the wipers have to be easily controlled and cover a good proportion of the screen. If any of those things are wrong, a boat can feel uncomfortable to steer in a rough sea. Also, it is important that drawers and lockers stay shut; there's nothing more upsetting than watching the contents of the fridge fall onto the floor as you fall off a wave. In this sense, I would rather be in a well designed and constructed 40 footer in a rough sea than a 50 footer that is less well designed, irrespective of how good the hull is supposed to be

But the whole point was whether LOA matters more or less than the boat weight/hull etc., and in my experience there is not any doubt that the latter can make MUCH more difference

.
I tend to agree that weight is a major factor providing of course it's in the right place ie low down not high up. A RNLI lifeboatman once said to me that a good heavy boat is always better at sea than a good light one

 

[stillwaters]

Yup true, most SD boats' fast cruise is in the teens although you can shoehorn enough power into some of them to hit the mid '20's kts whereas most planing boats will easily cruise in the mid 20's kts. Speaking for myself, my next boat will probably be a SD boat but I'm going to do a couple of charters on SD boats first before I buy anything because I'm really not sure whether the slow cruising speed and higher fuel consumption of a SD boat will piss me off. Maybe a charter first is the way to go for you before you buy?
Just going off on a tangent a bit, I like what Beneteau have done with their range of Fast Trawlers which seem to offer a little bit of the best of both worlds. Seaworthy hulls which are supposed to be good at both SD and D speeds but capable of 20kt+ cruising and importantly with fuel consumption that seems comparable to a planing boat. Of course, the Beneteau finish is not upto the standard of some other builders

Yes,maybe chartering first would suit both of us though not certain we would be evaluating the same thing. I already know,after 4 years with a thirsty-at-planing-speeds SD that the sudden fall-off in economy pisses me off.Personally,I would like to know how effective stabilisers are on a SD,particularly at D speeds.I can't think I would ever consider a future SD or D boat without them.However,I still tend to prefer the appeal of D & SD - I agree with BartW and perhaps yourself,there's just something about the solid ship-like feel of some of them which most planing boats don't quite capture. I drool every time I see one of the bigger Selene's,for instance and I love the go-anywhere versality and personality of my current SD.
I assume the Beneteau is the Swift 52. Looks useful and a good size compromise especially for finding mooring slots. The MBM test suggested a high teens cruising speed at around 0.6mpg,suggest that both the speed and economy might drop quite a bit with fouling,though.
Best of luck whichever way you go.

 

[stillwaters]

.
I tend to agree that weight is a major factor providing of course it's in the right place ie low down not high up. A RNLI lifeboatman once said to me that a good heavy boat is always better at sea than a good light one

Surely more weight comes into its own on displacement boats as MapisM pointed out and,as you say here.However,I agree with your earlier point that W/L length is of more use in a planing hull where weight tends to be a liability. Certainly in my experience,the ability to ride the next wave by virtue of say an extra 10ft of length has actually made the difference to whether some boats,or maybe more importantly their crews,have gone out at all.

 

[benjenbav]

The 50ft v 40ft thing: I would think the P50 will feel 50% bigger rather than the 25% suggested by the difference in length because it's higher, wider and heavier as well as just longer. I suspect that the difference between 14tons and 24 is probably going to be a better indication of the difference in how they feel than the difference between 40 and 50 feet.