Engine sizing

[jddevel]

Advice please and what is the general consensus of opinion. Assuming a 57 foot semi traditional hull what disadvantage will I have with a 38HP Beta engine over a 43HP

one. I have on the odd occasion with "other boat helpers" assisting at locks

experienced for example in hire craft the problem of gates being opened to quickly with the resulting problem of control requiring the engine being run virtually flat out to compensate. On the other hand whilst it is not likely that I`ll be tidal at

anytime, but one never knows. I have also been advised that it does not do a diesel engine any good to spend to much time on low revs - common practice with us as we

tend to really take things slowly. In this situation perhaps a 38HP will suffice.

[Alan de Enfield]

.. in hire craft the problem of gates being opened to quickly.............

 

In my somewhat limited experience it is not possible to open the gates until they are 'ready' ie water the same level either side. Even an inch difference makes it impossible to open the gates.

[PaulG]

Advice please and what is the general consensus of opinion. Assuming a 57 foot semi traditional hull what disadvantage will I have with a 38HP Beta engine over a 43HP

one. I have on the odd occasion with "other boat helpers" assisting at locks

experienced for example in hire craft the problem of gates being opened to quickly with the resulting problem of control requiring the engine being run virtually flat out to compensate. On the other hand whilst it is not likely that I`ll be tidal at

anytime, but one never knows. I have also been advised that it does not do a diesel engine any good to spend to much time on low revs - common practice with us as we

tend to really take things slowly. In this situation perhaps a 38HP will suffice.

For practical purposes, I don't think you would notice the difference between a 38HP and a 43HP engine.

Depends on the power curve, how well it is matched to the prop and gearbox, etc.

By "gates", perhaps you mean "paddles"?

Just learn to use the paddles. There are locks that have a strong "draw", and others where you can just whack 'em wide open.

My boat is a 55 footer with a 27HP engine. This is perfectly adequate on the canals, and perhaps a little underpowered on the river.

IMHO 38 HP will certainly suffice.

[jddevel]

My apologies incorrect name. I meant paddles. Old and getting worse!!!!!

[Tony Brooks]

I think he mean paddles and that is down to lack of experience/interest and maybe not shouting at idiots.

 

I seem to keep repeating that outright power is not the be all and end all. The helmsperson also needs skill in reading the water, getting the boat in the right place, and knowing when its time to tie up and wait.

 

I have brought 35ft GRP wide beam upstream through Maidenhead bridge in flood conditions with just a BMC 1.5 and while in the bridge hole for several minutes that was scary. I took JennyB down tide (54ft about 30 odd HP) through London and felt perfectly safe except when my son decide to try to cut across a bridge pier far too close for my comfort. (that bit is to illustrate the reading the water and putting the boat in the right place).

 

The turn for entry into Limehouse gave me no concerns although it seemed ages drifting downstream broadside on but the boat was turning and i knew it was reliable. Even the turn across current into lime house although untidy was in no way worrying.

 

The boater needs to develop skills and not rely upon raw engine power

[jddevel]

To expand on my earlier error regarding gates/paddles. During a week on the Trent and Mersey/Llangollen at the beginning of August and going through adjacent locks-can`t remember exactly where in-experienced

helpers from another boat who got to the paddles before my "crew" opened them completely both sides with

the frustrating and potentially dangerous result.

[Tony Brooks]

One could argue that you should have been right against the front gates/cill and holding it there on the engine. That way the inflow may have held you in position as it eddied back to the front of the lock.

[Chewbacka]

The beta marine guidelines suggest -

Beta Boat length weight

38 40~50ft 14t

43 50~70ft 18t

50 60~70ft 18t

 

My boat is 56ft with a Beta 43. Even going up the River Severn against a couple of mph current I do not need more than about 1800rpm, so a fair bit in hand. Which would indicate a 38 would be ok, but I have not tried a Beta 38.

I guess it depends upon the price difference between the 2 engines and if there were a strong current would you be prepared to wait for it to slow down???

[jddevel]

I agree whole heartily with you Tony regarding "reading the water" if as a sailor which I like to think I

use to be but now need a more sedate life, one instinctively "thinks" that you must be aware of current,

wind and general weather conditions. I remember only too well coming back for the first time to Denver

Lock on the Ouse how I nearly came a cropper because I mis-calculated in my haste and youth, the tidal run and the speed the weather deteriorated. And that was in a motor cruiser with twin diesels!!!!

[Tony Brooks]

The beta marine guidelines suggest -

Beta Boat length weight

38 40~50ft 14t

43 50~70ft 18t

50 60~70ft 18t

 

My boat is 56ft with a Beta 43. Even going up the River Severn against a couple of mph current I do not need more than about 1800rpm, so a fair bit in hand. Which would indicate a 38 would be ok, but I have not tried a Beta 38.

I guess it depends upon the price difference between the 2 engines and if there were a strong current would you be prepared to wait for it to slow down???

 

I came up the Severn this early summer when the river was rising and flowing faster than normal with no problem although itwa s a bit slow compared with the plastic jobs but then1800 to 200o rpm was plenty as far as I was concerned.

 

A few summers ago we were held up in Oxford with the Thames on red boards. Now I have a fair knowledge of that river so kept an eye on the Osney cut. I knew that if things were worse than I thought there was slack water and even an eddy to help with a turn into Sheepwash coming down stream. As I was pointing up the canal I left the Dukes cut and went down through Kings lock. Just chatted to the lock keeper and told him my intentions. At Godstow the lock keeper (happened to be female) got exceptionally stroppy so rather than argue I said I would turn below the lock and return. The safest way to turn in those conditions and at that place is to stick the bow in still water and put the stern into the flow which I duly did by turning the bow towards the lock lay by and backing the stern into the weir flow. At this procedure the locky was jumping up and down shouting about running aground at the front. Of course the boat just spun round.

 

At no time either going up or down stream, especially on the bends did I feel out of control and was moving far faster than I did in Maidnehead bridge (see above).

 

This shows that raw power is not as important. It also shows that my DV36 (propped at 25hp, just checked the power curves) is more than adequate for A 54ft narrowboat, even in very demanding conditions.

Edited August 30, 2016 by Tony Brooks

[Tiggs]

 

One could argue that you should have been right against the front gates/cill and holding it there on the engine. That way the inflow may have held you in position as it eddied back to the front of the lock.

 

 

IMO this is the correct way to do it and I would (almost) always do it this way with a full length boat in a narrow lock, going up. As far as I am concerned this is what fenders are for - to be pressed up against the cill plates and the lock plates to prevent the boat moving. Even so, paddles should not be raised too quickly.

 

The smaller Beta should be OK I think. You hardly ever need to use the full power anyway. (But maybe think about re-sale - would a buyer be put off asking the same questions given the table of power vs boat length in the other posts?)

Edited August 30, 2016 by Tiggs

[casper ghost]

I guess either engine will be too powerful for normal canal conditions, but that is the modern way. My Dad's 66' boat has a Lister SL2 with almost no power, and yet it was fairly standard when it was fitted 30 years ago. People want to chug much faster these days..

Casp'

[Flyboy]

If both the 38 & the 43 turn the propeller at the same speed, the performance of the boat will be the same with either engine.

[Tony Brooks]

If both the 38 & the 43 turn the propeller at the same speed, the performance of the boat will be the same with either engine.

 

That rather depends upon both props being the same size, which they should not be.

[OldGoat]

Flyboy, on 30 Aug 2016 - 12:30 PM, said:

If both the 38 & the 43 turn the propeller at the same speed, the performance of the boat will be the same with either engine.

Yes -

 

 

Tony Brooks, on 30 Aug 2016 - 12:40 PM, said:

 

That rather depends upon both props being the same size, which they should not be.

and yes again

As with most things in life it's not quite as simple and absolute as one might think.

Especially where the rated power of an engine is quoted at an unrealistic rpm for canal use.

In addition the base engine may be designed for different duties and not as 'solid' as the next in the range.

The smaller ones tend to have a lighter duty gearbox.

The 'needs' of the boat may want higher output alternators which as well as using more power may be impracticable on a small block.

 

You have to look at all the variables....

[magnetman]

38 will be fine.

 

I have never tried it but I suppose one way to throw off the occasional idiot 'helper' might be to deliberately stop the boat on the way into the lock in such a way that the gates can not be closed. Pretend there is something round the prop or whatever. This way you gain a bit of time and allow your crew to get in position and (hopefully) make clear that they are in charge.

 

This could come across as rude but may be better than damage to the boat ?

Typo edit

Edited August 30, 2016 by magnetman

[Guest]

We have a 57ft semitrad with a Vetus 33hp engine. It is slightly overpropped. Last week we breasted up a stricken boat (long story) probably 50 footer and towed it on the Soar against a reasonable flow. Our skin tank is also marginal, but we had no problem whatsoever moving the two boats with 33hp. My boat has never felt underpowered at any time to me. I think 38 will do a good job.

[jddevel]

You`ve all set my mind at rest. Thank you

[FadeToScarlet]

15hp used to be enough to shift 30 tons of loaded motor and 35 tons of loaded butty, horses these days are a bit anaemic obviously.

 

Big blade turning slowly > little egg whisk churning up bubbles.

Edited August 30, 2016 by FadeToScarlet

[Tony Brooks]

We have a 57ft semitrad with a Vetus 33hp engine. It is slightly overpropped. Last week we breasted up a stricken boat (long story) probably 50 footer and towed it on the Soar against a reasonable flow. Our skin tank is also marginal, but we had no problem whatsoever moving the two boats with 33hp. My boat has never felt underpowered at any time to me. I think 38 will do a good job.

 

And unless you are propped so you can get the maximum revs (which you can not) you had rather less than 33 hp at your disposal.

[Onewheeler]

38 will be fine if your prop is well matched. A properly sized prop transforms a boat. You may not be able to use full revs for an extended period on either engine unless your cooling system (i.e. skin tank) is adequate, although it is sometimes nice to be able to wind it up to "number 11" for a few seconds...

[MoominPapa]

15hp used to be enough to shift 30 tons of loaded motor and 35 tons of loaded butty, horses these days are a bit anaemic obviously.

 

Big blade turning slowly > little egg whisk churning up bubbles.

 

We're currently taking 60' and 20+ tons up the tidal and non-tidal Trent quite happily with 18HP.

 

MP.

[OldGoat]

FadeToScarlet, on 30 Aug 2016 - 9:45 PM, said:

15hp used to be enough to shift 30 tons of loaded motor and 35 tons of loaded butty, horses these days are a bit anaemic obviously.

 

Big blade turning slowly > little egg whisk churning up bubbles.

 

 

Tony Brooks, on 31 Aug 2016 - 07:12 AM, said:

 

And unless you are propped so you can get the maximum revs (which you can not) you had rather less than 33 hp at your disposal.

 

The above a precisely the point.

A deep draughted boat with a large propeller plus a slow revving engine will most probably be using its 15 HP output

Not only is the egg whisk analogy apposite - all froth and no substance - but also the modern industrial engines used have their power quoted at 3,600 rpm for the smaller engines and 2,800 for the larger, neither of which you are likely to achieve in practice.

[casper ghost]

 

 

- but also the modern industrial engines used have their power quoted at 3,600 rpm for the smaller engines and 2,800 for the larger, neither of which you are likely to achieve in practice.

I guess if they started fitting 3-1 gearboxes then this might help.

[WotEver]

I guess if they started fitting 3-1 gearboxes then this might help.

Yeah but then the cut would sound like it was full of Transit vans.