Dirty bottoms vs fuel consumption

[PEJ]

I recall seeing a post on here about how there is a lot more growth about this year and all our bottoms are more dirty than usual.

I seem to remember a reference in the thread to an article in MBY saying that fuel consumption went up significantly. Can anyone direct me to this article or any definitive research on fouling and fuel consumption?

My fuel consumption was up by 30% this weekend. I assume that is down to all this extra fouling.

Doing the sums, roughly, I reckon the break even between getting her lifted and scrubbed to get back to the usual clean performance and leaving it alone is about 320 miles. Problem is I don't get out that much and how much more growth will I get in the time it takes me to rack up 320 miles? Impossible to answer. Bloody annoying isn't it!

 

[epervier]

Can't see where you're based, but if Solent run over to Haslar sealift2 you'll be done in about an hour or so, second thoughts it's Cowes week it might be busy.

 

[Firefly625]

went to Alum Bay on Friday had a successful time swimming round the boat with a scrubbing brush and didn't cost me a penny. To be honest it was bloody good exercise, but a 31ft boat with round bilges would be rather easier than yours, you might need to draft in some help!

 

[Cheery]

We stayed in the BVI last November and I swam round the resort owners 30' boat noticing how dirty it was. I mentioned it to one of the staff (my son worked there so I wasn't sticking my nose in) who said he spent 8 hours with a snorkel on using a scrubbing brush. He said it didn't look much different so in future they would motor round to Virgin Gorda, about 8 miles, lift it and power wash it.

 

[Bandit]

The MBM article was June 2009 and the boat was Princess 430 2 x Volvo Penta 63p 370hp.

At 2400 nm a clean hull used 4.53 litres per nm and a dirty hull after 12 months in the water with a dirty hull used 5.84 litres per nm so an increase in fuel burn per nm of 29%.

If you are coming to Guernsey a Lift, Pressure Wash and relaunch is 20% off this month at M&G.

 

[Spi D]

Growth can ruin your mpg completely. Like dragging a carpet around 24h.

In our marina a lifout is GBP 40 and if you arrange it at luchtime they'll let you hang there for an hour

 

[PEJ]

Can't see where you're based, but if Solent run over to Haslar sealift2 you'll be done in about an hour or so, second thoughts it's Cowes week it might be busy.

Yes, I had one done their earlier in the year and it was about £500.00 I think. I'd have to do about 320 miles of fuel usage at the current consumption to spend an extra £500 on fuel. That is a lot of miles for someone who does go much further than Yarmouth from Southampton so I might as well leave it furry until next spring. Annoying though.

 

[PEJ]

The MBM article was June 2009 and the boat was Princess 430 2 x Volvo Penta 63p 370hp.

At 2400 nm a clean hull used 4.53 litres per nm and a dirty hull after 12 months in the water with a dirty hull used 5.84 litres per nm so an increase in fuel burn per nm of 29%.

If you are coming to Guernsey a Lift, Pressure Wash and relaunch is 20% off this month at M&G.

That is pretty much in line with my figures. About 4.2 normally, 5.5 yesterday. It's surprising what a difference a bit of weed can make.

 

[Bandit]

I track miles through the water on my log (not GPS over the ground) and litres used each time I refuel and I see a massive difference after a mid season wash off both in litres per mile and speed.

 

[Anders_P42]

I had boat lifted and jet washed at Sealift before trip to Weymouth in April. Within two months, probably down to lack of usage because of windy weekends, fuel consumption up 20%. I decided to lift and jet wash again as cost of lift circa £133 on my 10.2m, my break even only 13 hours as fuel burn was up 10lph.

Must help reduce wear on engine too, not overloading.

Anders

 

[grumpy_o_g]

ON a diesel engine does throttle lever position relate to fuel consumption? In other words if the lever is halfway forwards will I always be burning say 10 gph? Presumably the other side of the coin is that fuel consumption stays the same but the boat goes slower so that really I should be asking have I had to shove the lever forward to get the same boat speed?

 

[Divemaster1]

ON a diesel engine does throttle lever position relate to fuel consumption? In other words if the lever is halfway forwards will I always be burning say 10 gph? Presumably the other side of the coin is that fuel consumption stays the same but the boat goes slower so that really I should be asking have I had to shove the lever forward to get the same boat speed?

Does not quite work like that .... Propeller(s) move boat ... propeller(s) load determine how many HP is taken out of engine...HP taken out of engine determines fuel burn.... Throttle position set governor (or equivalent electronic device) to maintain X RPM .... Governor will try to achieve said RPM, but the effort (HP) required to achieve said RPM is higher with more friction... So with a clean hull, you may require 200 HP to achieve 1500 RPM, but with higher friction (fouling) you may require 300 HP to achieve same RPM...., but the speed you achieve may be less than what you had with a clean hull (something to do with the way propellers are designed)

 

[About Time]

There is a good way to avoid this issue.... need to say that I have no interest whatsoever in the company selling the product - grab deep in your pocket once and you have no issue at least for the next 15 years. I had my 37 Windy treated with Coppercoat (the original stuff) and it works absolutely great. The boat can stay at the berth for 3 weeks easily with hardly no build up and once we go on plane the growth is wiped off. After the full summer (6 months of season in Denmark) I have lost only abt. 1 kt on the top speed - I can still push her 40 knots by September which is so close to top speed that I do not feel any difference at all. It is a brilliant product and I do not understand why this is not used more frequently by boat owners. You may pay a bigger bill now but you save the cost of antifouling every year (plus the time) and it works for many many years. When she gets out of water for the winter she is just washed down and the bottom is slightly green (the copper treatment is seen) and she is ready for next season. Someone says that every 5-7 years you may have to use a light sanding paper to refreshen the coppercoat but it still after three seasons remain to be seen. Can only recommend it.

 

[grumpy_o_g]

Throttle position set governor (or equivalent electronic device) to maintain X RPM

Ah, that was the bit I hadn't got my head round, thank you...

 

[longjohnsilver]

went to Alum Bay on Friday had a successful time swimming round the boat with a scrubbing brush and didn't cost me a penny. To be honest it was bloody good exercise, but a 31ft boat with round bilges would be rather easier than yours, you might need to draft in some help!

I used to be able to clean the hull of my CI32 in less than an hour of snorkelling. My current 48 footer takes around 2 hours and is hard work, and I'm not as fit as I was, so I prefer to do one side at a time. Having cleaned boats underwater for many years I don't use a brush, a coarse pad is much more effective and far easier and quicker to use. And has been said many times in the past, the most important parts to clean properly are the props. For those i use a metal scraper and then wire wool, I aim to do one side of each blade with one breath. If I'm feeling lazy then I'll use my scuba gear, but I do prefer the freedom of just snorkelling.

 

[TQA]

I have a 44 ft monohull [ raggie ] and cruise year round in an area of exceptionally high fouling.

Using an eight inch wide stainless steel scraper mounted on an eight foot pole I can clean my boat working entirely from the surface, but do use snorkel gear so as to be able to see what I am doing. .

Time required is an hour although nowadays I have a breather after one side. before tackling the other. Having a year round water temp of 80+F helps.