Lost of speed

[sailaboutvic]

Really pleased the strobe thing worked.

In terms of likelihood, I would put my money on light fouling or perception or a mixture of both. Comparison with other boats or with sailing speeds are inconclusive as there are other variables.

Where are you? Cuxhaven has scrubbing posts (I went through similar thoughts to you after struggling through the Kiel Canal 29 years ago in time, and got in just after dark!) - but I guess you are well past there.

We on Nordeney , to morrow making our way to Netherlands, just hope the southern winds forecaster turn up and blow hard and keep blowing hard .

I wish I knew about the post in Cuxhaven .
once I’m back in the Orwell I book the post In SYH .

yes agree there are many Variables but when a 22 footer with a small outboard pass you under engine and we doing 2800 rpm there isn’t much doubt,

we have much data over the last two months to compair it too , we definitely got a problem.

we run around 2100 in a mixer of condition, wind , current but 2000/2100 gives us 1.6 LPM and a good 5 kts and a bit .
we now running at 2800 using 2.5/3 LPM and just about getting what we was getting before.
going up the canal we avg 5.7 kts coming back 4.6 kts using 700 rpm more .

 

[sailaboutvic]

Just want to thank everyone for all the input in this thread and the other thread .

 

[Pye_End]

we have much data over the last two months to compair it too , we definitely got a problem.

Apologies, I didn't mean to imply you didn't.

I find, what with fouling affecting a log directly and indirectly; other boats having different configurations; sail having so much more power than engine etc etc. on my own boat only to find everything comes right after a quick scrub - the different bits of information don't always add up or come together coherently. Only flat calm motoring comparisons are much use, but even this can have it's difficulties in assessment due to log or surrounding area fouling, so you end up trying to make sure you have a tide/current free bit of water to assess the current accuracy of the log (fortunately for you the canals are pretty useful!), and so forth.

I have a table of flat calm boat speeds logged at different rpms when she is clean and first in the water for exactly the process that you are going through!

 

[johnalison]

Just want to thank everyone for all the input in this thread and the other thread .

I’m sorry that your cruise has been somewhat marred by this problem. Apart from the engine matter, I have been enjoying sailing with you vicariously.

 

[sailaboutvic]

Apologies, I didn't mean to imply you didn't.

I find, what with fouling affecting a log directly and indirectly; other boats having different configurations; sail having so much more power than engine etc etc. on my own boat only to find everything comes right after a quick scrub - the different bits of information don't always add up or come together coherently. Only flat calm motoring comparisons are much use, but even this can have it's difficulties in assessment due to log or surrounding area fouling, so you end up trying to make sure you have a tide/current free bit of water to assess the current accuracy of the log (fortunately for you the canals are pretty useful!), and so forth.

I have a table of flat calm boat speeds logged at different rpms when she is clean and first in the water for exactly the process that you are going through!

I’m just getting very frustrated now with the problem , I been in and out of the water and begin to look like a wet seal .
im not a lover of swimming in dark muddy cold waters .
I taken note what everyone said and slowly worked through everything ,
the strobe suggestion was a big break through , at less now I know it’s not the gearbox and the engine RPM are right although I never tho it wasn’t , you get to know your own engine .
suggestion about exhaust elbow I very doubt as anything to do with this problem but I will be removing it once back .
i also plain once I dry out to pull the shaft seal back and just check how central the shaft is in the tube.

I still hope someone will come up with some other suggestion but it’s looking unlikely Now .
one can live in hope

 

[LittleSister]

engine rpm checked ok ,can’t be lost of power
shaft rpm checked ok , can’t be clutch slipping ,
prop checked ok I can’t see any thing to stop it opening ,
sailing speed ok cant be fouling ,
must be missing some thing ,

Sherlock Holmes, he say 'When you have eliminated all which is impossible then whatever remains, however improbable, must be the truth."

​

Obviously, you have found a warp in the space/time continuum!

 

[Chiara’s slave]

The thing to remember is that your rig is so much more powerful than the engine. Even a layer of slime causes drag, and 2hilst you might still reach hull speed with the sails, you might not with the engine. Someone else has mentioned this, maybe not in those exact terms. This sort of thing is much clearer to us multihullers, cos we don’t have a hull speed as such. We feel the drag under both sail and motor, just at different speeds. Stroke your bottom, if I may say that. Bare hand, is it antifoul, or slime. Little hairs grown on that stuff too, they are the death of boat speed. I scrub every week, takes an hour in a wetsuit and fins, scrubbing brush then scouring pad. It’s the difference between 8 and 14 knots in a F4 to us. If ypur hull speed is 7 though, your sails will drive you up to that if theres enough power in the wind. Your diesel has a finite number of HP, and maybe cannot.

 

[AntarcticPilot]

Sherlock Holmes, he say 'When you have eliminated all which is impossible then whatever remains, however improbable, must be the truth."

​

Obviously, you have found a warp in the space/time continuum!

I don't suppose any of your new engine mounts are like this? That would certainly mess up space and time!

 

[Ardenfour]

I have an engine with the same exhaust elbow I could still get 3600rpm but with reduced power and it was the exhaust elbow restricted with carbon,thats why I said early signs,keep using the engine and eventually you will have reduced revs,as you should be aware these exhaust elbows are known for it.

How can power be reduced if you still got the same revs?

 

[Chiara’s slave]

How can power be reduced if you still got the same revs?

Variable pitch prop? Otherwise you’re spot on, that’s what I based my last post on.

 

[jamie N]

Given that the shaft RPM has remained constant, the loss of speed is either a reduction in thrust by the prop, OR an increase in drag.
Sailing speed, without the engine hasn't been affected, thus the drag theory doesn't work.
The possibility of the RPM-efficiency readings having altered somewhat over this event, seems to be remote, which again indicates a reduction in thrust.
All of the above have been investigated by the OP, which isn't a great help, but the prop being part of this issue still gets my vote.

 

[Chiara’s slave]

Given that the shaft RPM has remained constant, the loss of speed is either a reduction in thrust by the prop, OR an increase in drag.
Sailing speed, without the engine hasn't been affected, thus the drag theory doesn't work.
The possibility of the RPM-efficiency readings having altered somewhat over this event, seems to be remote, which again indicates a reduction in thrust.
All of the above have been investigated by the OP, which isn't a great help, but the prop being part of this issue still gets my vote.

Drag. If the sails have the power to achieve hull speed with fouling, then the speed will appear unchanged

 

[johnalison]

Drag. If the sails have the power to achieve hull speed with fouling, then the speed will appear unchanged

I wouldn’t exclude a moderate amount of fouling either. I had a different but perhaps not unrelated experience a few years ago. Towards the end of the season my otherwise well-behaved boat developed a strong pull to port, both under sail and power, which was enough to make sailing unenjoyable. So far as I knew, no damage had been sustained, and the effect was noticeable even at very slow speeds of around a couple of knots. On lifting, no misalignment was seen and only normal fouling, but after the usual cleaning and a/f the boat on relaunch was back to normal.

 

[bignick]

I’m very pleased the strobe app is working for you. I’d recommend you also put a piece of tape on the shaft itself and measure the rpm of that, to confirm that the coupling isn’t slipping on the shaft at full load. You could additionally mark the junction between the shaft and coupling with a blob of paint to check for relative movement.

A couple more suggestions: - when I said earlier that you need to check the blades are opening fully, I mean that all 3 blades should all be opening to 90 deg relative to the shaft axis (even if they move relatively freely up to that point). If they only open to 80 degrees or so, because something is stuck in the slot, then you won’t be getting the full thrust, because all the pitch and camber figures will be out. It wouldn’t take much to cause the symptoms you describe. Equally, if the blades are tilting too far forward (have you still got the three nylon bump stops in front of the blades?) you will see a loss in performance.

something else that could slow you down a bit, aside from fouling, would be too much weight on the boat. you’ve not put your boat in cruising mode and filled it to the gunwhales with junk have you?

PS. Out of curiosity, has the prop been removed at any point from the shaft?

 

[sailaboutvic]

Good morning guys .
I know people being are just being helpful suggestions fouling ,
we on the go again 13 kts southern, we on a close reach 7.6 kts through the water 6. 6 over the ground ,
surly if foulingwas a. Problem. We wouldn’t be doing this speed under sail.
log was calibrate not long a. ago plus taken into account SOG it’s about right .

at less we sailing again

 

[sailaboutvic]

Hi Nick
the thing you suggested I did when I tested the shaft ,im a bit head of you there but thanks anyway .

the blade are opening fully without any effect , a light touch , being on a gear / teeth they all open the same distance,if one jammed they all would .

we have very ltttle weight these day now we stop living full time on board ,
when we sold our moddy 42 and empty our stuff the water line went up so much it look silly .

on your last point , yes the prop was removed in March when I had to take the shaft out , it was the only way we could get the cutlass bearing out ,
the shaft has key wave , quite a big key ( lump of metal ) I can’t see that breaking , but who knows.

as long as the wind blow we be fine , although we got some motoring to do when we enter the Netherlands,
once back home I start from scratch, check the shaft is central, remove prop and check key and off cause check the hull.
one way or the other I get to the bottom of it .
and ofcause I let you all know .

 

[Buck Turgidson]

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.

 

[peteK]

How can power be reduced if you still got the same revs?

In my case I could still get 3600rpm when not under load.

 

[Bodach na mara]

Nobody has commented on statement that the engine is "using fuel like there is no tomorrow." To me that suggests that the engine is producing more power than usual to reach the required rpm. Or maybe I have misread and the engine is having to be run faster than usual to reach the cruising speed. The first case implies increased resistance to turning the prop possibly caused by distortion in the prop geometry which the second suggests higher than normal resistance to moving the hull through the water.

 

[sailaboutvic]

Nobody has commented on statement that the engine is "using fuel like there is no tomorrow." To me that suggests that the engine is producing more power than usual to reach the required rpm. Or maybe I have misread and the engine is having to be run faster than usual to reach the cruising speed. The first case implies increased resistance to turning the prop possibly caused by distortion in the prop geometry which the second suggests higher than normal resistance to moving the hull through the water.

Yes you have missed read sorry to say ,the reason it’s using more fuel is because we are having to run at a much higher rev then we normally do.
to day it’s been a much better day , that’s not to say the problem is sorted .
we managed to sail all but an hour the 60 nm .