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TOPIC: Matilda has new engine but severe lack of thrust

Matilda has new engine but severe lack of thrust 06 Nov 2019 19:53 #111210

  • Balliol Fowden
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This probably merits a fresh topic but I will carry on!

I have no significant experience of Brunton’s products, but I have never come across one on an inland boat, commercial or private. I have come across cases of them being damaged in seagoing craft.

My concern would be simply whether the propeller will be strong enough to withstand the rigours of inland waterway use, with potential heavy fouling, big bangs from submerged logs and the inevitable groundings. Inland vessels often have smaller tip clearances, which increases the risk of damage.

A good heavy traditional fixed pitch prop is likely to be much more durable, and most good shipyards can repair a bent one very cheaply.

The cynical bit of me would wonder whether the ketch’s previous prop was suitably sized, thus a fair comparison.

The usually acknowledged experts in inland propellers are Joorens in Dordrecht. Suggest you have a chat with them and see what they think.

www.joorenscheepsschroeven.nl/

Balliol.
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Matilda has new engine but severe lack of thrust 06 Nov 2019 15:25 #111203

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Having been impressed by Brunton Autoprop at boat shows, I recently experienced one fitted to a large ketch motorsailer, where the Brunton propeller exceeded my expectations. With its original 3-bladed fixed prop, she averaged nearly 7 knots under power and sail, its 120hp 6-cylinder Isuzu engine turning over at 1,650 rpm. Once an Autoprop was fitted, 6 knots was achieved on engine alone at a mere 1,000 rpm, with a concomitant reduction in noise, vibration and fuel consumption.
 
So I am considering fitting an Autoprop to my 12' wide 54' river barge fitted with a Gardner 6LW and PRM 2:1 reduction box. I’ll take her across the Channel. to navigate European canals and fast-flowing rivers, so it seems the Autoprop might give useful advantages over the current fixed prop, namely: greater oomph in tricky conditions; a reduction in prop-walk; and better performance in astern.

I’m in touch with Bruntons, who've been very helpful and who promise not to recommend any Autoprop unless it’s suitable.

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Matilda has new engine but severe lack of thrust 25 Oct 2019 03:16 #110898

Just a quick follow up for those who made many helpful suggestions. My understanding is that most of the problems with thrust resolved following cleaning of the prop which was encrusted with barnacles.

Ian

Lisette & Ian
Catharina Elisabeth

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Matilda has new engine but severe lack of thrust 01 Oct 2019 15:08 #109992

I have experienced the lack of power you describe twice. I have a 150hp engine running a 20 metre barge.

The first time I was “advised” to change from a 2:1 ratio gearbox to a 3:1 ratio. Could hardly leave the pontoon. Changed back.
The second time was trying to leave Antwerps Willemdok. Propellor clogged with Mussels. Could not move against the wind although could see prop wash. Diver cleared mine and 5 other boats with the same problem.

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Matilda has new engine but severe lack of thrust 30 Sep 2019 21:41 #109976

Hi Bruce.

"The new motor seems to function correctly and initially was only tested to 2000rpm in forward whilst tied to dock, at which point I could pull the boat backwards."

Do you mean this literally, i.e. The ship had a 150 h.p. engine running at 2000 rpm in forward gear, it was secured to bollards to prevent forward movement. "I could pull the boat backwards", does that mean that you individually without mechanised help took hold of a rope or other such item attached to the ship and physically pulled it backwards?

I'm sorry if that sound like I'm being pedantic but I'm just trying to get a detailed mental picture.

Secondary questions:
1) Even though the ship is not loaded to its full water level, is the prop under water?
2) Could you repeat the test and take some photos of the prop wash?

Thanks Paul

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Matilda has new engine but severe lack of thrust 30 Sep 2019 20:05 #109975

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Thankyou for all the comments and thoughts, I am waiting for the diver to arrive this week (possibly) to clear 9m2 at bow and 11m2 at stern. Bow is needed as there is a stick wedged inside the bowthruster from while moored on the Rhone at Vallabregues.
My water tanks are very low, currently holding around 600ltrs out of the 3000ltr capacity, the tank is forward of the engine placement.
As I am unable to move and have been here for 2 months topping up with water has not been practical. Hence to compensate I have 1900ltr of seawater in a combination of barrels which has been cheaper to arrange. Once I can get the 6km to fresh water in Frontignan i will add to tanks and rebalance by removing seawater, then head into the etang de thau for a sea trial.

The new motor seems to function correctly and initially was only tested to 2000rpm in forward whilst tied to dock, at which point I could pull the boat backwards.

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Matilda has new engine but severe lack of thrust 30 Sep 2019 14:15 #109965

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Paul Hayes wrote: Hi Balliol

The 110m barges and coasters that come up to Saint Jean de Losne silos for grain often have 30 cm or more of propeller thrashing above water level at close on 20 kpm and bow thruster grills half dry when they arrive empty before being pushed down 2 metres or so with 3000 tonnes of grain.
From what's generally accepted about propellers I would think that they could hardly make headway with so much prop in fresh air, it just shows that there's always an exception to the rule.

Paul

Just for info Paul, these types of barge may have specially designed props, and / or they might normally travel light under water ballast in the hold (or elsewhere), which may have been pumped out just short of destination ready for loading, perhaps to let the hold dry ready for the next cargo. Many Freycinet sized spits and peniche types had tunnels to draw water flow to the prop from beneath. The bigger ships now also tend to have "laden" and "unladen" bow props or combi units, the latter being bottom feeding.

The Luxe motor stern shape is rather prone to ventilation, more so perhaps than many sailing barge conversions (such as David Warren's boat) where the Tjalk or Aak type stern provides a better "counter" effect and the props are often more deep set behind dropped skegs.

Many Luxemotors were fitted with almost half-round tunnels over the prop, extending forward as much as a couple of metres under the flared stern, and I can see from photos of Matilda and the old weld lines that she had a tunnel at one time. On my ship the tunnel was removed long before I bought her because the ship, as a crane ship then, was effectively half loaded at all times and didn't need it, or the drag. I replaced the tunnel with quickly fabricated flat anti-ventilation plates, coincidentally very similar to those on Matilda, as a quick fix when I had some spare time on dock. These are not as extensive as a tunnel and do not draw water from as low down. They are thus less effective than a tunnel and more susceptible to ventilation in lightly bunkered condition. I keep planning to retro- fit a proper tunnel when I can afford it, or have the time, but there is always something else to do!

Balliol.

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Matilda has new engine but severe lack of thrust 29 Sep 2019 20:06 #109933

Hi Balliol
There's been a few threads of late where part of the information has been provided, various feasible theories put forward by helpful folk, which are nowhere near correct. This is obvious when one or two more pieces of the jigsaw are placed face up in the first place.
So I would ask Bruce, (and others in the future) if you are reading this, try to give us as much information as possible.
We, and others have been around machinery long enough to generally make a possible diagnosis given all the details, and if not take an educated guess, or even make a list of possibilities.
I must admit that at times I've looked too deeply, or not deep enough and some of the "simple or silly" things have remained undiagnosed for far too long. Hahaha.
The 110m barges and coasters that come up to Saint Jean de Losne silos for grain often have 30 cm or more of propeller thrashing above water level at close on 20 kpm and bow thruster grills half dry when they arrive empty before being pushed down 2 metres or so with 3000 tonnes of grain.
From what's generally accepted about propellers I would think that they could hardly make headway with so much prop in fresh air, it just shows that there's always an exception to the rule.

Paul

Certainly cleaning the prop and checking the shaft for rope / plastic / weed etc. fouling will help, even if only by eliminating those things from the equation.
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Matilda has new engine but severe lack of thrust 29 Sep 2019 17:31 #109929

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Hi Paul,

At the moment I have gone about as far on this question as one really can.

As for many of these threads where full information is not always available and questions cannot / are not always answered it can become dangerous to pontificate too much from 1000km away.

Example: What revs is the engine making? If the answer is "not enough" then what do you make of the answer? Is the propeller too large, or, in the process of changing the engine might it be the case that the Morse speed control cable has simply not been set up properly, or has been kinked, or damaged............ ? A simple matter if you are standing on top of the engine with your own tools in your hand. Not so easy from a distance without detailed answers, photos etc.

Martin N's case with the Daf is similar. Is it the gearbox slipping or a governor malfunction? If I (or no doubt you) were standing over the engine and able to use our eyes and ears then the correct answer would be pretty obvious, but this one again could be something very simple, or silly, and if that is the case who is it that then looks simple, or silly?

In Bruce's case the test will be what the divers find on the prop, and what happens when the boat is properly trimmed down. If there is still a problem after that then it is thinking caps on again.

Balliol.
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Matilda has new engine but severe lack of thrust 29 Sep 2019 16:09 #109925

Hi Balliol
I follow your thinking and agree with your conclusion. The existing prop may not be perfect but should move the barge.
Do we know whether the new engine is reaching full R.P.M.? Both in neutral and in gear?
How open has the governor been when trying the maneuvers described? After hearing a slow running "Thumper" it's easy to think a high revving engine is running too fast.
I'm making the assumption that the CC capacity of the new engine is a lot smaller than the old one. Do we know exactly which one of the range it is? and the base engine manufacturer?
Best
Paul
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Matilda has new engine but severe lack of thrust 29 Sep 2019 11:25 #109912

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I had a bit of informal private correspondence with Bruce on this matter earlier in the year and I have pasted below the relevant section. Basically we made certain presumptions about the output of the old engine, and presumed also in the absence of full information that the old propeller was reasonably well matched to that engine since the boat had previously performed satisfactorily.

Quote:
"I have used the Vicprop software to calculate the approximate sizings. I have checked this software against a couple of known examples including my own ship, and the results are in line, so the software is probably reasonably accurate, although it must be said that prop sizing is a bit of a black art. I have used WL length 75’, WL beam 15’, moulded draft 3’, displacement 75 tonnes, desired speed 8 knots.

If your Henschel develops ca. 200 HP @ 2100 rpm and is fitted with a 2:1 box then, making certain guesses as to shaft bearings etc. the existing propeller should be about 28” diameter by about 16” pitch. From the photos that looks about right in terms of diameter. It is not possible to do any more than guess the pitch by looking at a photograph but my guess is that this is about right also. If the engine is not developing full revs. (you say 1800) then that might suggest that the existing prop is a little bit too big, or that the old engine is down on power. However, I have taken 28x16 to be the approximate present size.

The Mermaid FPT (presuming 150HP @ 2800 rpm) would, keeping all the other parameters of ship size, proposed speed, bearing numbers etc the same, need a prop of about 22 x 11 size {on 2:1 reduction}, which is much smaller than your present prop."

With a 3:1 box the correct prop size would appear to be about 28 x 17, which is to all intents and purposes what you very probably have at the moment.

So your present prop may well be about right for a 3:1 reduction
{on the new engine}, which is not what you have.

It would seem therefore that you either have to change the prop or change the gearbox."

I believe that Bruce floated this "seat of pants" calc. past Mermaid and that they did not disagree. In very simplistic terms the old engine was theoretically producing ca. 200HP @ 1,100 shaft rpm. The new Mermaid would produce ca. 150HP @ 930 shaft RPM. Direct correlations such as this are not necessarily accurate but the conclusion was that the old prop was probably near enough right, or within "tweakable" limits for subsequent pitch/diameter adjustment at next docking, or at the least to get the ship somewhere else.

I think that the problem is likely to be a fouled propeller coupled with lack of immersion.

Balliol.
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Matilda has new engine but severe lack of thrust 29 Sep 2019 10:28 #109910

Sounds like propeller mismatch to me.
First the shaft revolutions are different.
Second and more importantly is the understanding of a diesel engine power rating.
A rating of say 100 h.p. at 2200 rpm, doesn't mean that this will be achieved all the time, only when "loaded" by a propeller with certain properties.
The same engine running at full revs in neutral (no load) will probably produce no more than 10 h.p. as this is all that is required to overcome friction and other internal loads that make it run.
Your engine supplier will have given a "propeller curve' in their details. For the engine to put it's energy into moving the propeller to maximum efficiency the installed propeller should match or be close to the given curve.
My guess is that you need to talk to a propeller specialist.
Being higher in the water won't help either.

Good luck
Paul Hayes
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Matilda has new engine but severe lack of thrust 28 Sep 2019 13:31 #109882

Don't know if I'm missing something but if the recommended gearbox is 3:1 then at 2000 rpm the prop is turning at a little less than 700 rpm. Previously 1100 rpm gave 550 at the prop so with the same prop the engine needs to be spinning a good bit faster. Propellers are a science that I try to avoid as there is maths and 'power curves' and algebra involved but you may need a prop that can use that extra power, Bigger dia? coarser pitch? 4 blades not 3?
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Matilda has new engine but severe lack of thrust 27 Sep 2019 13:30 #109848

My barge had direct engine mounting. It probably does give a bit more vibration but if they were using the original shaft it was possible you always had solid mounting.
I had a GM engine changed for a Perkins with a prm box in Antwerp by engine specialists who normally work on commercials, they would not use the flexible mounts that came with the new engine. The old engine did about 1700 rpm max and a 3:1 box whilst the new one did 2400 rpm max also with a 3 :1 box. We didn’t change the prop at the time and the max revs the Perkins would do was 1800 so the prop was perfectly matched to the old engine. Later changed the prop and the engine revd more easily with less smoke. The older engines were heavier and probably had more thrust at lower revs than the modern engines which get power at much higher revs.
Your estimated of 400kilos difference is probably on the light side as this would be only 400 liters of water and you have still not got down to your original draught with 1.3 tones .
My barge had good anti cavitation plates but it was not a luxe shaped stern and the 100mm difference in draught didn’t seem to affect the getting under way performance except with the new engine and prop it needed more revs.
I hope you get it sorted out as it’s really frustrating to go to all the trouble and expense of the engine change and still be left with a problem.
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Matilda has new engine but severe lack of thrust 27 Sep 2019 12:20 #109847

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Hi Bruce,

Glad to hear you have some progress!

1. You have anti-ventilation (cavitation) plates fitted above the prop. Are these presently under water or not? If not then your prop will be sucking air down. You need to get the stern down so that the water line was as before, about 100mm above the plates.

2. Barnacles or mussels that have been forming over the summer six months (?) on an immobile prop will make a very major difference to how it performs. You may also have other debris on the prop. You need to check that it is clean, also that there are no extensive clusters of molluscs on the hull forward of the prop.

3. If you are trialing with the boat moored up then it will not be able to "suck down" in the water, so the test is not ideal unless the draft is back down to the previous marks.

4. The gearbox should have an identification plate on the upper face which should include the digits "D3", which would confirm 3:1 reduction.

5. Flexible engine mounts are not essential but they will isolate some of the transmitted noise and vibration. I don't recall if these were fitted with the previous engine but it may be that the new engine had to be bolted directly down onto the beds to achieve correct levels and alignment with the prop shaft (due to differences in the engine leg heights). The alternative would have been to cut away the engine beds and rebuild to allow clearance for flexible mounts.

Balliol.
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Matilda has new engine but severe lack of thrust 27 Sep 2019 09:48 #109844

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The ongoing saga of Matilda continues. She has her new engine. (FPT 150hp) However basic moving attempts show a gross lack of thrust from the prop even at over 2000rpm. She was unable to push her back out from the quay driving against a front rope against a small breeze. Trying to go against a back rope fwd with straight rudder and full revs barely strains the ropes. There is prop wash but its hard to be sure how that compares to previously.

The new engine revs considerably faster than the old. Idle speed was about 700rpm before, cruising 1100 giving about 6-8kmh in a canal.

The old gear box was a PRM 2:1 ratio. The new one was recommended and is PRM 3:1 .

The weight diff of the new/old engine and ancillary equipment is estimated to be 400kg lighter.

Currently she is in salt water near Sete. She was floating an estimated 25cm higher initially. We've added 1.3 ton of water on the back deck so far and is currently 10cm higher. We are trying to get a water haulage to add 3000 litres to her fresh water tank to get her back to something like normal depth. Prior to the 1.3ton of water there was considerably 'spray' from around the prop indicating it was definitely not deep enough.

Current theories as to why so little thrust are :
- significant barnacle growth on the prop (as is evidenced by that on the hull from the 2 months so far shes been here).
- still floating too high vrs her normal 'depth'
- is the new gearbox really 3:1 and is the prop turning at the expected speeds ? How to check ?

Waiting for a diver to inspect/clean the prop.

Also the new engine has been mounted direct to the hull mounting blocks with no rubber vibration pads. Is this normal ? It seems to cause some hull resonances at various revs and is a bit 'louder' than expected.

Comments and suggestions greatly appreciated .. Bruce

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