Back with Jets and some answers

[Gludy]

"I will return" was promised, so here I am!

I do not yet have the answers to all the points raised in the previous jet threads but here is what I have been able to gather on some of the main points:-

1. What fuel consumption (mpg) would you expect from say a 60 foot 28 ton boat using props crusing at 28 knots? I guess most would answer 0.4 to 0.5 mpg.

2. What engine power would you need for a typical 60 footer, 28 ton, to gove it a top speed of 28 knots? I guess most answers would be between twin 800hp and 1000hp.

So if I pointed out that a properly designed modern twin jet 60 footer weighing 28 tons just required twin 550hp to give it a top speed of 28 knots and if I increased the engines to twin 700hp you would get 34 knots with a cruising fuel consumption at 28 knots of 0.6 mpg - some 10% to 20% more efficient than props - I guess some would raise their eybrows - but this it seems is the case.

Jet engines require a hull shape suited or designed to them.

For a 28 ton, 60 footer normal boat to really plane you probably need to reach 45 knots - yet few can ever really reach this speed - in other words they never really plane - hence a semi-displacement hull of the same length and weight is achieving 34 knots and better fuel economy at crusing speeds.

Lets drop the speed on such a boat and yes, there is a range from between 10 and 18 knots when props, in the right weather may be 10% more efficent. But if I had a boat with a top speed of 34 knots I would be cruising at a speed of 25 to 28 knots anyway.

Add to that that in a force 8 with the wind abaft the boat, you can motor at 30 knots - and it would appear that the claims for such a boat are either a load of b****cks or we may have to re-adjust our thinking on the type of boats we are buying.

Now it is claimed that this 60 footer 28 tonner can also out manouvre any prop job in sight - like moving sideways in a force 5 onto the beam and closing into a tight spot on the pontoon under total control and very gently - not only that but to do this is easy.

As you have guessed I have been doing more homework but this seems to have come up with what I am informed is am myth. That these large boats with planing hulls really do plane properly. It seems that the experts in this back up that they do not - we just think they do.

What does not work is a 60 foot planing hull (little steerage) using jets when the boat is not designed for it.

These days, modern jets have total control throughout every degree of the 360 degrees - no dead bands, easy to control at a snails pace without touching the throttle.

Comments please - constructive if at all possible!

Paul

 

[hlb]

Oh no, not again!!

No one can force me to come here-----------
----- I'm a Volunteer!!!

Haydn

 

[stamfordian]

hi,
all very well but there,s not that many people own 60ft motorboats,have you looked at the economics of a jet boat say with 25/30ft hull,there,s at lot more of these about,and would it be enonomical to fit jet systems ,in new boats /development costs etc ect which would be bourne by the consumer when props are tried and tested and reasonably cheap?.Surely if it were viable the main players Volvo etc would have been marketing the system for years as it,s not a new idea.
I have seen a 27ft jet boat in my local boat yard(oundle marineer/fairline boats factory)the boas name is "Live and let die" and was produced for the film of the same name it has been there for 2 years after beieng used as a dive boat as it never made it onto the big screen.It looks herendous at the stern and opinion thereabouts is that no one will go near it,i think its going to Greece to be a dive boat again.Don,t think the idea will take off ,predudice will see to that.
regards,
T.B.

P.S.forgive spelling <P ID="edit"><FONT SIZE=-1>Edited by stamfordian on Thu Jun 20 21:53:52 2002 (server time).</FONT></P>

 

[Gludy]

"Don,t think the idea will take off ,predudice will see to that."
You may well be right - but the boat you talk about is like chalk to cheese compared to what I am talking about. After all, I can point at a diesel car and explain why it is a load of rubbish but that does not make all deisel cars a load of rubbish.
The fact that performance such as I have quoted is achieved with a particular boat ,eans that it is just prejudice that holds the market back.
Having just geard of yet another disaster with a brand new £1m pound Fairline, it seems that the buying public here is putting up with a lot of rubbish from some, if not most , mainstream manufacturers. They will only change when they have to - but I do not understimate how difficult that can be.


Paul

 

[longjohnsilver]

Planing

Paul, can't see why a 64 footer will only plane at circa 45kts. Always thought that to go above displacement speed boat has to go 1.25 x sq root of waterline length, which for your 60 footer would be approaching 10kts. Can't really believe that it takes another 35kts of speed b4 it starts to plane, would have thought it would get over the hump at about 20kts, if it has any hump at all!

 

[stamfordian]

Yes,
I agree with you that the people are putting up with sub-standard,workmanship in this country,have been for the last 40 years!!.
Sorry back to jet boats...maybe the comparison is chalk and cheese but what are you saying???.Has jetboat tech advanced so it could be intergrated into the volume market ??.mmm maybe, watched a program on sat tonight they were racing jet boats though a very tight course at very high speed...could it be that the future of boat drives is jet??.Maybe ,cars benifit from formular 1,boats ......

 

[Gludy]

Re: Planing

I also thought that. In effect, to go just a little past the 'limit' in a displacment boat just poshed up a big bow wave and the fuel consumption went sky high.

However, the boat I am talking about does 34 knots and weighs 28 ton and it is not a planing hull and yet has fuel consumption about 20% better than the normal 60 footer with a planing hull. The front edge of this semi-displacement hull lifts out of the water almost as muych as the 60 footers I have seen going full blast with their planing hulls.

It was explained to me that for a 60 foot 28 ton to plane properly, it would need a speed of about 45 knots, so in practice, when they are claimed to be planing, it simply lifts its bow up a bit. Its not really planing with only the back end of the boat in the water.

I know someone with a 52 footer new boat and twin 700 hp engines - weight about 21 ton and this has a top speed of 33 knots. Putting the same engines in the typical 60 footer would leave it a bit on the underpowered side - yet the fact is that with a semi-displacement hull and twin 700 hp engines with the modern jet drives, a 28 on boat has a top speed of 34 knots - at a guess the top speed with the same weight and length in a typical 'planing hull' would be, say 25/26 knots. The crusing speed of 29 knots in the jet boat is higher than that, let alone the top speed. Further it copes with heavy seas very well and can keep up speed better than Nelson's and the like.

I am myself having to throw out with the cat much of what I have so far learned.

If what I am saying is right, then it really challenges the way the market has developed ant the typical planing motor cruiser of today.

I I am wrong, then I don't mind - I just learn more - but the evidence is there to check and needs explaining.


Paul

 

[andyball]

Re: Planing

our tiny (6m) v bottomed boat doesn't "really plane" ie....lift well up & run level w/o excessive use of trim until 20-25 knots, so I can see gludy's point about that..

What I can't see is where he's going to get an honest opinion about these superior jet powered 60' ers with the "right" hull from without buying one & trying it out.......if hardly anyone makes 'em, and even less have bought one, who is there to ask,other than the (possibly?) biased builders ?.

 

[Gludy]

"Has jetboat tech advanced so it could be intergrated into the volume market ??." it would appear it has but the volume market has to have hulls etc designed to suit the jets and the jets need to be good modern ones.

You know, since coming into this boating world, I cannot beleive how bad the industry is that serves us. Next year I am blowing a lot on a new boat - yet it seems even I spend a million, I can purchase a terrible quality product back up by even worse service support. If that was a car I was buying for a fraction of the price, I would not tolerate it.



Paul

 

[Gludy]

Re: Planing

I think we should assume that all builders of all boats are biased be they with jets or props.

The boat I am talking about is the new CaraMarine 60 footer with twin hamilton jets of the latest type allowing full 360 degree directional control at low speeds.

I shall be trying the boat out. However, if it achieves 34 knots, cruises at 28 knots - then even that in itself is surprising for a 28 ton boat with twin 700 hp engines and without a planing hull. The boat is being shown at the Southampton boat show, so anyone can see it there.

What has already happened with this hull is that being based on a pilot boat hull, it has been tested bt those who use it all day 365 days a year and the boat has proved very succesful.

So, evem if we stick to just the top speed from such engines with such a hull - an easy thing to check out, the results go against what most have been led to believe.

Paul

 

[tripleace]

Re: Jets

Gludy,

Did you in your travels find a UK based company which sells jets and could advise on conversions?

"Take control & then take the commission"

www.cleverdic.co.uk

 

[Gludy]

Re: Jets

Yes - and they are people you can talk to:-
Hamilton Jet (U.K) Ltd
Unit 4a, The Birches Industrial Estate
East Grinstead, West Sussex
United Kingdom RH19 1XZ
Phone: +44 1342 313 437
Fax: +44 1342 313 438
E-mail: sales@hamjetuk.com





Paul

 

[wakeup]

Re: Jets

Gludy,

Are you getting you advice from a company based in Uniy 4A. I would be especially careful doesn't sound to me like they are of a credible size especially if you're gonna put your money where your mouth is and buy a pair of jets.

Sounds like you've done your homework though and has made some interesting reading on this subject.

Seems to me that the market is more likely to adopt a bottom up approach to converting to jets rather that top down. If jets could be demonstrated to be better than exisitng outbaords and small stern drives then they might stand a chance on the basis that the market can afford to take a chance on them in smaller boats and if sucessful both technically and handling confidence wise, people would demand them when upgrading to bigger boats.

But from what i've read there is big power loss between a prop outboard and jet outbaord so unless this discrepancy can be reveresed then it will never happen. ( I think it was 115bhp became 80bhp at the nozzle which wasn't the case with the prop version)

Your other main plus is handling, Maxum have been marketing their boats with control max system which is basically three small thrusters (1 up front and two at the rear quarters) attached to a computer and a joy stick. It works very well and can spin on a dime and move the boat in any direction. The problem has been the price, its only $10K but punters just don't seem to be buying it, so it would appear TOTAL control isn't a big buying point.

Don't forget the majority of the industry is not just locked into props it is also locked into into V*l* sterndirves and engines so this is a bigger problem to crack than you might think.

If V*L* could be convinced to go jet drives then the industry would follow. It would atleast be an answer to their hydralicing problem as I guess jet drives can hydralic?

It may just be that jetdrives are the best technology to push and steer a boat. Those of us invoilved in the technology industry know that the best technology does not usually win the marketing war.

E.g. IBM PC wasn't the best desktop computer around at the time.
Microsoft wasn't and still isn't the best OS available.
ATM is better than IP but IP is now everywhere.
Cisco routers were never the best but now they are the standard.

The one common thing that made all of the above sucessful were the generous margins that resellers were getting on these these particular products over the competitors.

Build a better, cheaper and higher margin jet drive for the 20ft 40ft market and the market will change overnight. People will start quoting all the other stuff you have quoted as to why there better.

Just my 2cents.




yada yada..

 

[Gludy]

Re: Jets

I am puzzled at what you mean by taking advice from a company based in "Uniy 4A." - please explain.
I am gleaning my information from a number of sources.

As regards efficiency - I have already made my points about the 60 footer and the fact that 20% greater efficiency is claimed and that this is easy to prove.

28 ton 60 footer - top speed 34knots with twin 700HP. Can you get that with any similiar 60 footer of the same weight? No.

My whole discussion has been about boats built with jets replacing the twin ahaft drive prop jobs - I am not talking about small outboard units.

I have just heard that Storboro' from Sweden offer a jet option on their larger 50 fott plus model, not their smaller boats. I am inestigating this now.

As regards handling, there is no doubt that on the 60 footer I am taking about the handling is much easier than twin props and very much more flexible - again, those who have tried this and I will be trying it, are amazed at the slow speed handling and this ais achieved without the complex systems you are talking about.

"E.g. IBM PC wasn't the best desktop computer around at the time.
Microsoft wasn't and still isn't the best OS available.
ATM is better than IP but IP is now everywhere.
Cisco routers were never the best but now they are the standard.
"
I totally agree with those examples and the principle that the best does not always win BUT that does mean that the best sometimes does win!

I am not claiming that jets will win the war - I am simply stating that from my limited research, in the sorts of boats I am talking about, the jet may well often be a better bet.

"Build a better, cheaper and higher margin jet drive for the 20ft 40ft market and the market will change overnight. People will start quoting all the other stuff you have quoted as to why there better.
"
I totall agree with every word of that. It may come, it may not - I hope it does come. I hope that prejudice and ignorance do not win - but that is only a hope. - no more.

Paul

 

[wakeup]

Re: Jets

Whooa, fasten your seatbelt jet boy.

I thought this was an open forum to discuss the merits of jets and how they could benefit over props.

You seem to mention this company that is based in Unit 4a that are the UK experts in jet engines. Well most companies that have addresses at anything Unit A are usually small and insignificant in their market, so I was simply expressing caution about relying on a company of such a size with such a vested interest in jets. Your business alone for the size of engines you are talking about could propably keep them in beer n tabs for a couple of years.


"I am not claiming that jets will win the war - I am simply stating that from my limited research, in the sorts of boats I am talking about, the jet may well often be a better bet" - No but I think you are claiming that jets should win the war based upon their technical superiority.

If you're that convinced put your money where you mouth is and buy one and let MBY do a test drive of it and review it against bog standard prop of same size, engine and hull design.

Seems like you've posted quite a lot of stuff about jets and haven't really been able to prove the case for jets. You're not even comparing apples with apples.

You seem to recommend that in order to get better efficiency for a 60 ft planning hull with a 500hp engines all you need to do is upgrade the engines to 700hp fit jets and oh by the way change your the hull to a semi-displacement ???? Huh DoH.

But I have to agree that there must be some advantage in the spagehtti posted about this because I know from first hand experience that all the inter island ferries that link Stockholm with the Baltic all seem to use jets and having been on serveral they seem to be bloody fast and manouverable.

Anyway you can't light the afterburner when its wet, ive tried ;-)

yada yada..<P ID="edit"><FONT SIZE=-1>Edited by wakeup on Mon Jun 24 17:04:33 2002 (server time).</FONT></P>

 

[jfm]

60 foot Caramarine info

Gludy, do you have a url with info on this boat? I did a quick search but couldn't find anything. Thanks.

 

[chippie]

Re: Jets ,unit 4a

Wakeup, I think you'll find that Hamilton Jets are the company that invented them. Small offices/warehouses are usually used as outposts for the main centre.
I think the head office is still here in NZ.

 

[Gludy]

Re: Jets

"I thought this was an open forum to discuss the merits of jets and how they could benefit over props." - it si and that is what I am trying to do.

I am talking about Hamilton jets which are made in New Zealand and have their main distribution centres in UK and USA - both owned by them, not outside distributors.

" I think you are claiming that jets should win the war based upon their technical superiority.
" - With the information available to me to date, I think they should win but that does not mean to day I think they will win.

"Seems like you've posted quite a lot of stuff about jets and haven't really been able to prove the case for jets. You're not even comparing apples with apples.
" - I do not accept that. I have quoted performance figures which for the particular boat length/weight given, if the figures are true, show the greater efficiency of jets. Further as I do not think any 60 foot Princess/Fairline etc with props even claim these performace figures when fitted with 700hp engines. Yet it is easy to rpove if, for example, the top speed of 34 knots is true by just a short trip in such a boat.

It is others that are not comparing apples with apples, not me. Further claims were made that jets were less efficient but no figures given to prove or demonstrate that - I have given figures which can be verified.

"You seem to recommend that in order to get better efficiency for a 60 ft planning hull with a 500hp engines all you need to do is upgrade the engines to 700hp fit jets and oh by the way change your the hull to a semi-displacement ???? Huh DoH.
" - no I am not! I am saying that a 60 foot, 28 ton semi-displacment boat with twin 700hp and jets outperforms the same boat with the same engines and props. This was to demonstrate in greater efficiency of jets for this boat.

" I know from first hand experience that all the inter island ferries that link Stockholm with the Baltic all seem to use jets and having been on serveral they seem to be bloody fast and manouverable.
" - yes more and more ferries are moving to jets because of a number of reasons - one is the lower maintainance bills on their engines because of the constant load jets give that props can never give - they also make it easy for slow speed manouvering etc.

On my marina pontoon almost everyone has fouled their props on:-
floating fridge - large ropes - nets and rocks. The fact that such a boat has nothing at all sticking out the hull is from the fouling point of view a huge benefit - they will drive over a fishing net. They even stand a better chance of surviving if yoiu hit a floating container

The boat can dry out - hence extending my enjoyment of many more harbours.

The boat is nore efficient.

I have asked that mby do a review of this whole subject - Iam sure the boat manufacturer would jump at the chance. The baot I am looking at - the Cara Marine 60 fotter will be at Southhampton boat show.
"Anyway you can't light the afterburner when its wet, ive tried " - I agree. However, you can sometimes dry it out a little.;-)






Paul

 

[Gludy]

Re: 60 foot Caramarine info

http://www.caramarine.ie/

The versions being built now are much improved over the details on the site - they will send you more up to date info - I have some photos if you want them - email me.

Paul

 

[wakeup]

Re: Jets

OK ok eating some humble over the Unit 4a hamilton comment.

Which marina are you using that has floating fridges in it? Tell us so we can avoid it please.



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