Lost of speed

[MontyMariner]

we managed to sail all but an hour the 60 nm .

Good going

 

[sailaboutvic]

Your maximum sailing speed is going to be limited by wave drag rather than skin friction so it’s quite possible to have enough power under sail to overcome the effect of fouling but be limited by “hull speed”. Under engine you have much less power and are more likely to see the effect of skin friction. You have eliminated power development and prop problems so drag is the only other variable.

Thanks for that , I appreciate your comment and everyone else too ,
just let me say when we had a badly foul boat in the pass nearer the end of the season , we couldn’t get any where near the speed we getting now under sail.
This is not to say I have discount fouling as the problem.
after saying that I’m sure we do have some fouling ,

when the problem started some weeks ago ,
part of the stern had micro barnacles, which just feel off with my hand , the bow had some slime around the water line which as been removed .
Funny tho from just behind the bow to the just before the stern the hull was clean as far as I could tell .
this happened when we spent 10 days in a marina in Denmark ,
before that stay the boat had no problem ,
the problem was noticeable the day we left ,as you may or may not know within them 10 days I changed my engine mounts
of cause the first think I tho off was I cocked the job up and not got the engine and shaft lined up right .
some time was spend after then re ling the engine tho I couldn’t find any thing wrong no vibration and 0.002 different in coupling distance from one side to the other .
after comment made by Tranona and a chat to Volvo I was set right , that the adjustment and the lining of the engine wouldn’t give me the problem I was getting .
with that in mind and after suggestions from some about fouling I took a trip under and cleaned as much as we could with what we had ,
speed increases after that but still not to what it use to be ,we still was using more rpm and not getting the speed we was .
so not to go on several other things as been investigated the only thing I not manage to check is the key wave in the shaft prop end tho I be surprise if that broken .

I might find once I get to dry out bags of barnacles hanging of the bottom of the keel or we been dragging a net I doubt that’s the case .
but hey stranger things have happen .

 

[B27]

I've just been through re-propping my boat, changing from fixed to folding.

Look at it this way:
There are several factors:
The thrust needed to drive the boat at a certain speed
The prop
The engine turning the prop.

The engine seems to be turning the prop OK.
The drag of the boat doesn't seem too bad as it sails OK.
So it sounds like there is something wrong with the prop.

I would be checking that the prop opens fully, is put together right, hasn't got something wrapped around it etc.
We had something a bit similar on Sigma once, a tangle of rope on the prop stopped it opening properly.
The prop was taking power from the engine, just not very efficient at giving thrust to drive the boat.

That's assuming it's the same prop which used to drive the boat OK.

The other thing is, to be sure it's not the hull fouling, you ideally need to see the boat sailing close hauled in F2 or F3. Or at least close hauled.
Sailing free in a good breeze you can tow another boat and only lose half a knot.

 

[sailaboutvic]

I've just been through re-propping my boat, changing from fixed to folding.

Look at it this way:
There are several factors:
The thrust needed to drive the boat at a certain speed
The prop
The engine turning the prop.

The engine seems to be turning the prop OK.
The drag of the boat doesn't seem too bad as it sails OK.
So it sounds like there is something wrong with the prop.

I would be checking that the prop opens fully, is put together right, hasn't got something wrapped around it etc.
We had something a bit similar on Sigma once, a tangle of rope on the prop stopped it opening properly.
The prop was taking power from the engine, just not very efficient at giving thrust to drive the boat.

That's assuming it's the same prop which used to drive the boat OK.

The other thing is, to be sure it's not the hull fouling, you ideally need to see the boat sailing close hauled in F2 or F3. Or at least close hauled.
Sailing free in a good breeze you can tow another boat and only lose half a knot.

Once again thanks for your comment .
prop open fine I been in 7 or 8 times now checking and cleaning ,
as far as Ican tell the fouling is now min , I did remove some of the stren and the other half clean some slime of the bow .
visibility isn’t great but I can’t see anything that would cause that mount of drag .
yeaturday we entered the inland water of the Netherlands, this morning we motored so far 15 miles , very little wind 2500 rpm is given us 4.5 that very little in these conditions,
I expect more like 5.5/5.8 kts , personally I think iwould need a lot of fouling to lose that amount of speed .
the problem got me puzzled .
as I posted before only one thing hasn’t been checked , that the key in the shaft the prop end .
or maybe it’s is badly fouled and I can’t see it .

as far as the prop goes , it came off in March , it can only be put togather one way for it to work but putting that to one side the boat been to Denmark since March and there been ono problem .

 

[B27]

I'm struggling to imagine how the key failing won't allow the prop to unscrew the nut and fall off?
And I can't see how the prop would spin on the shaft so steadily? It would need a constant level of friction between prop and shaft so the engine revs and prop revs keep steady at a given RPM?

Only thing I can think of is the nut has been tightened onto the end of the shaft, it's reached the end of the thread before pushing the prop firmly onto the taper?
Has a washer or spacer been lost or left out?

Once the proper is properly tightened onto the taper, the key should be idle, it's really there to hold things still while you get the nut done up.
When you undo the nut, the taper should have enough grip that you need an extractor and maybe to heat up the prop boss, to remove the prop.

The prop I bought for my boat needed a spacer washer to work, because the internal taper in the prop boss was shorter than the taper on the shaft.
Maybe your prop is marginal. maybe a washer is out of place or something?

If the prop is spinning on the shaft at all I would be worried the nut will come undone one day soon!
That would mean you lose the prop.

 

[sailaboutvic]

I'm struggling to imagine how the key failing won't allow the prop to unscrew the nut and fall off?
And I can't see how the prop would spin on the shaft so steadily? It would need a constant level of friction between prop and shaft so the engine revs and prop revs keep steady at a given RPM?

Only thing I can think of is the nut has been tightened onto the end of the shaft, it's reached the end of the thread before pushing the prop firmly onto the taper?
Has a washer or spacer been lost or left out?

Once the proper is properly tightened onto the taper, the key should be idle, it's really there to hold things still while you get the nut done up.
When you undo the nut, the taper should have enough grip that you need an extractor and maybe to heat up the prop boss, to remove the prop.

The prop I bought for my boat needed a spacer washer to work, because the internal taper in the prop boss was shorter than the taper on the shaft.
Maybe your prop is marginal. maybe a washer is out of place or something?

If the prop is spinning on the shaft at all I would be worried the nut will come undone one day soon!
That would mean you lose the prop.

At the moment it’s all a guessing game as said until I can dry out I won’t know if there a problem with the prop,
fouling or some thing else , I stopped worrying about it for now , we moving forward and while we moving forward all well .
it just mean going slower while under engine and using more fuel as we using higher rpm .
my concern was that the gearbox was slipping or the prop had a problem but there no moments on the prop and the blades are fine and moving freely ,
there no slipping with the gearbox .
it could be the blades are not opening fully under power but I can’t see any reason why as they are very free.
it has been suggested by the manufacture that a fishing line caught in between the gearing can cause a problem but the water is too muddy to see in between the teeth if an line is caught but by feeling it feels ok .

its does seen it down to the prop or fouling as the engine isn’t under power and the shaft RPM matches to the RPM the engine given at any set time .

 

[bignick]

Another thought…

If something like a cone clutch is slipping, it will only do so above a certain torque. At light load it wouldn’t slip at all and the torque will ramp up quickly in the upper rpm ranges.

It looks like you only checked shaft rpm using the strobe app up to 2500 engine rpm. Since you’ve got the app working now, it would be worth checking shaft RPM at full throttle when underway.

It’s highly unlikely that it is a coupling or clutch slipping, but I think it is still more likely than a prop key shearing.

 

[sailaboutvic]

it was Busy day to day and it’s not over yet .
I thought after all the replys I had to this thread and suggestion I would report back on my finding .
so we dry out I first removed the shaft seal while waiting for the water to drop all the way .
the shaft was died in the middle of the shaft tube , at less now I know the lining of the engine after I replace the mounts was spot on,
one less thing to worry about .
the prop I found nothing obstructing it althought there was a few barnacles in the jaws but nothing that would stop it opening fuller and the key wave was In tack.

would I did find to my surprise especially as the boat only been back in the water for three months and mostly on the go was the leading edge of the keel had a row of barnacles and so too on the bottom .
I wouldn’t had tho there be that much .
we give the copper coat a good rub so hopeful it will work a bit better if not it mean we have to add a few more coats next seasons .
what’s also surprising is under sail there was no noticeable speed lost , where in the pass on other boats if we had that amount of fouling we would find our speed under sail dropped .
maybe we been use to much heavier and bigger boat then this boat .
so now it just a matter of time till 23.00 till we back afloat hopefully we be able to find our way out of the unlit channel to drop a anchor in the river for over night .
finger cross our speed under engine will return to normal .

 

[bignick]

good luck in your quest. I hope your boat speed improves, but if not im sure we can suggest some more things to check!

 

[sailaboutvic]

good luck in your quest. I hope your boat speed improves, but if not im sure we can suggest some more things to check!

We will see to day Nick still in my bunk after a late night .
before drying out I would had sworn it wasn’t a fouling problem mainly because the boat not been launch that long and been on the move other then 10 days when it sat in a marina in Denmark .
but reading a few people blog we know who are also in Denmark and they too seen to be having fouling problems .
So we see.

 

[Chiara’s slave]

We will see to day Nick still in my bunk after a late night .
before drying out I would had sworn it wasn’t a fouling problem mainly because the boat not been launch that long and been on the move other then 10 days when it sat in a marina in Denmark .
but reading a few people blog we know who are also in Denmark and they too seen to be having fouling problems .
So we see.

It’s been a bad year for fouling here in the solent, maybe weather patterns?

 

[johnalison]

We never got any significant fouling in the Baltic, presumably because of the low salinity, but we were continually on the move. I got the impression that the antifouling used over there was less potent than what we get here, but didn’t look into the subject. The water temperature in the Baltic was often quite high, especially in the shallow areas, so there should have been every chance of fouling if it was going to happen.

 

[sailaboutvic]

what is it they say ?
every photo tell a story .

 

[Buck Turgidson]

I’m lucky if o can motor at 3.5 when my hull is a bit fouled

 

[sailaboutvic]

I’m lucky if o can motor at 3.5 when my hull is a bit fouled

Actually it's quite a relief, I started to think we was imaging the speed we did before I worked on the mounts.
She now just glide through the water under engine .

 

[chriss999]

So, was it the fouling on the leading edges?

 

[sailaboutvic]

So, was it the fouling on the leading edges?

Yes on the keel and on the bottom
and a very small amount right on the stern .
prop was clean other then the odd very small barnacles in the jaws but they no way obstructed the blades, just by spinning the shaft from Inside the blades open fully .
Now under 2000 RPM log shows just under 6 kts where before it wouldn't reach 5kts more like 4.5
comparing log reading what we got before the problem and now I say we back to normal.

 

[ianat182]

I did wonder whether your shaft seal is of the type using a jubilee clamp that may have been over-tightened on the prop- shaft to prevent water ingress
However, it seems that that fouling is the culprit, on the keel. but all previous ideas were based on removal of shaft and engine works.

Ianat182

 

[sailaboutvic]

I did wonder whether your shaft seal is of the type using a jubilee clamp that may have been over-tightened on the prop- shaft to prevent water ingress
However, it seems that that fouling is the culprit, on the keel. but all previous ideas were based on removal of shaft and engine works.

Ianat182

Ian if you read all the posting you see that I myself did think it was something to go with the work I did on the mounts even tho talking to Volvo engineer after I ran out of ideas assured me it would have nothing to do with the work I did .

i jumped to the conclusion that as the boat didn’t have a problem before the changing of the mount it had to be something I did.
what I never took into consideration was how 10 days sitting in a marina would fouled a boat that only was clean three months early and been on the go since,
especially one that been copper coat , tho some years back
also add to that there was no noticeable difference in speed under sail.

the sea in Denmark is pretty grey and diving you can’t see much tho I did dive a few time to check the prop was operating correctly and at the same time manage to clean some the the slime alone the water line
but it was impossible to see what going on further down in the water .
admittedly cleaning the slime did improve the speed under engine as I posted at the time but still no where as it should had been .

in over 45 years of owning and doing my own work on boats I never had to change engine mounts and although there nothing difficult about the job other then getting into impossible places to undo bolts ( what new ) I wasn’t sure is a engine wasn’t lined up 100% would it alter the prop pitch enough the cause the problem , it seen now NO .
some here suggest it was fouling and there where right but at the time all I could do is slowly work through ever thing else it could be until I could dry out .
wasn’t going to haul out at the cost of several hundred pound just to find out it wasn’t the problem .
any way in the end it turn out it was lesson learn ,
which is why I always report back if I ask for help here so other can learn from it .
it a real shame some other who ask for help don’t post back as it could help other .