TAMD 63P River Use

[John100156]

I am confused.

1800rpm would mean my Sealine F44 is doing about 14 knots (guesstimate) which is right in the hump, pushing lots of water. I would assume that an F43 will be much the same. That's not an economical place to be. I am sure I would use more fuel on a journey of say 20 miles at 1800rpm than I would at either 18 knots or 7 knots covering the same distance. LPH is not really relevant in my book as I don't care how much fuel is burned per hour. I am only interested in the amount of fuel used to cover a specific distance.

I was referring to the following table: reproduced from an actual MB+Y Boat Report in post #16, (similarish size boat, same engines) you will see that the boat on test actually achieved 16.1 Knots (so over the hump pushing less water) at 1800RPM burning 10.8GPH, they recorded 1.5MPG At other speeds the actual MPG recorded was worse.

Now if you upped your revs to say 2400RPM you would certainly get there quicker, but your MPG would be less, because the gallons used for the miles covered would not be per hour. We were of course talking cruising speed range here, not pootling speeds. If you Pootle, as we have already estabablished, greater economies can be had. I see cruising speeds at 'above the hump' RPM, do others?

I would be very interested to receive the speeds your boat achieves at the rev ranges I quoted earlier..... I hope to re-launch my F43 with new AF on 5 March, weather permitting I will take her out and I will record/post the results. Hope the OP doesn't mind us digressing... I think this link should be to the table:-.

http://www.ybw.com/forums/attachment.php?attachmentid=16129&d=1329056641

 

[asteven221]

These figures definately do not match my F44. Are these figures definately from a Sealine F43?

I seem to recall the max RPM in the Volvo manual for the 63's is 2700rpm, so 2800rpm seems to be over doing the revs. Also, can't recall ever seeing an article showing a F43 or F44 with a top speed of nearly 32 knots kitted out with 63's. I am sure 26 to 28 knots is the norm. I think you can get 480hp engines on the F43, so could that be the reason for the quoted speeds?

Given what I have said, I find it difficult to see that 1800rpm wouldn't be anything other than inefficient on my F44. I would guess I would be doing about 14 to 16 knots which I am sure would be in the hump zone. I will admit however that I find it hard to decide whether the boats planning nicely, slightly falling off or not quite on the plane as the boats attitude from both helm positions seem quite bow up to me regardless of speed or trim, other than pootling of course. Certainly it's not obvious to me in the way that it is on a small speed boat or a RIB is when they accelerate.

When comparing my F44, note that my boat has been in the water for over a year now, but as our berth has brackish water my experience suggest the hull will be slimy, but unlikely to have too much other fouling. I would expect your F43 to do a bit better than what I have stated.

So my estimates are:-

750rpm - about 5 knots
1000rpm - 7 knots
1200rpm to 1800rpm - don't do these speeds - ever.
2100 - about 16 knots, but usually go to 2200rpm to stop it dropping off the plane.
2200 - 17.5 knots
2300 - 18 to 19 knots
2400 - 21 knots (ish)
<2400 don't know as I get giddy at these wallet emptying speeds!

Sorry it's not too accurate but it might help.

 

[John100156]

No, not the same boat as an F44/3, as I said, a 'similarish' boat with 370hp TAMD63P Engines. In fact I have just looked up the report that the Forumite posted the table from in #16 and the results were as he reported. The boat Spec., as follows:

Fairline Phantom 38
LOA: 12.3m
Beam: 3.82m
Displacement: 10.5 tonnes (light) & 11.8 tonnes (loaded)
Draught: 1m
Air Draft: 4.3m
Fuel: 900L
Water: 500L
Engines: Twin TAMD63P (370hp @2,800rpm)

So in essence she is a slightly smaller boat with sound and clean hull.

Now when I bought my F43, with 5 up, including Jim Pritchard my surveyor present, we took her out for the sea trial (26NM) around Gib with full tanks, clean hull, etc., we achieved for a short while a constant 2,750 rpm to both engines (just checked the surveyor's report) which I was very happy with, compared with a Vovlo stated full speed at: 2,800rpm.

On my 500NM trip bringing the boat around from Gib-SCM in February, 2011 - we several weather slots to hit and needed to motor a bit, so ran her around 200rpm below maximum for much of the way. Yes, I did use a lot of fuel. We were achieving around the 26 knots mark. She never missed a beat. Anyway, thanks for your information.

If any others have rpm/speed/fuel consumption info or other useful data on F43/4's with these engines, I would find it useful so please publish (assume thats OK with OP otherwise let me know and I'll start a new thread).

I am in SCM on 29 Feb and hope to re-launch 5 Mar., so I will record some speeds against rpm then and will publish the results.

The reason I find this so interesting is because I want to take a trip to and around the Balearics later this year, so the more accurate my data on estimated fuel consumption the better!

 

[Latestarter1]

These figures definately do not match my F44. Are these figures definately from a Sealine F43?

I seem to recall the max RPM in the Volvo manual for the 63's is 2700rpm, so 2800rpm seems to be over doing the revs. Also, can't recall ever seeing an article showing a F43 or F44 with a top speed of nearly 32 knots kitted out with 63's. I am sure 26 to 28 knots is the norm. I think you can get 480hp engines on the F43, so could that be the reason for the quoted speeds?

Given what I have said, I find it difficult to see that 1800rpm wouldn't be anything other than inefficient on my F44. I would guess I would be doing about 14 to 16 knots which I am sure would be in the hump zone. I will admit however that I find it hard to decide whether the boats planning nicely, slightly falling off or not quite on the plane as the boats attitude from both helm positions seem quite bow up to me regardless of speed or trim, other than pootling of course. Certainly it's not obvious to me in the way that it is on a small speed boat or a RIB is when they accelerate.

When comparing my F44, note that my boat has been in the water for over a year now, but as our berth has brackish water my experience suggest the hull will be slimy, but unlikely to have too much other fouling. I would expect your F43 to do a bit better than what I have stated.

So my estimates are:-

750rpm - about 5 knots
1000rpm - 7 knots
1200rpm to 1800rpm - don't do these speeds - ever.
2100 - about 16 knots, but usually go to 2200rpm to stop it dropping off the plane.
2200 - 17.5 knots
2300 - 18 to 19 knots
2400 - 21 knots (ish)
<2400 don't know as I get giddy at these wallet emptying speeds!

Sorry it's not too accurate but it might help.

Volvo 63 certainly has a 2,800 rpm rated speed (Confirmed on data sheet posted) and vessel must be propped accordingly, even if you never go there.

Unless you can be 100% sure of your own displacement never much to be gained comparing one vessel from another, unless they are also 110% sure of their weight.

You will not be far off using the VP spec sheet propeller law curve for any fuel consumption calcs. Yes the VP spec sheet as I pointed out is a little questionable by using a 2.5 propeller law exponent when 2.7 is the accepted #. However as I mentioned, this literature just for selling engines not for serious technical use. When push comes to shove use of the 2.5 fuel curve should still give you a decent margin of safety. The propeller law curve is just a SWAG, at the speeds important to you (over the hump) your true exponent could be in the region of 2.1 which gives you a safety margin for calcs.

If one has an electronic engine you can draw your own hull resistance # and fuel consumption curves for future reference.

 

[Greg2]

If any others have rpm/speed/fuel consumption info or other useful data on F43/4's with these engines, I would find it useful so please publish (assume thats OK with OP otherwise let me know and I'll start a new thread).

Absolutely fine with me......still interesting!