mikef
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Reged: 16/05/2001
Posts: 8964
Loc: chesham, bucks and palma,major...
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Good point about each blade having a different pitch, jfm. I suppose it's possible that one or both of the first props were dinged at some stage and not accurately repaired
No, that triangular trim plate thingy is not accessible. There is a separate lazarette under the bathing platform and the rudder linkage mechanism is accessible from the back of that
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jfm
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Reged: 16/05/2001
Posts: 7487
Loc: London/Antibes
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Yes, I deliberately wasn't specific about whether the solid block CNC milling method used a cuboid solid ingot or an oversize casting. That's a fine point of weighing the casting cost against the wastage from milling the solid cuboid. Of course all the milling waste/swarf is recycled so the lost metal cost aint that high.
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jfm
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Reged: 16/05/2001
Posts: 7487
Loc: London/Antibes
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I meant how are the tillers attached to the rubber shafts, and how do the tillers go into the boat? I was referring to the two little triangle block shape things, one at top of each rudder shaft. Are the tillers attached in there, so are those two triangle block things hollow, with a hole cut thru the trnasom (behind the "footprint" of those triangle thingies) to allow the tillers to pass thru the trnasom?
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mikef
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Reged: 16/05/2001
Posts: 8964
Loc: chesham, bucks and palma,major...
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Quote:
Mikef, i'm sure you're right with your different prop theory, but if the boat was out the water I guess you also had it antifouled and all the stern gear cleaned up, could the 2 knots be due to a different type of a/f?
No, houghn, I'm comparing the performance directly after my 2007 lift out with the performance directly after this year's lift out so, on both occasions, condition of hull and sterngear was the same. Type of antifoul paint used was same as well
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mikef
regular
Reged: 16/05/2001
Posts: 8964
Loc: chesham, bucks and palma,major...
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Sorry, I misunderstood. Yes those triangular bits are hollow and there's a hole through the transom. The triangular bits are triangular to allow the left/right movement of the rudder linkage or tillers as you refer
Btw, I forgot to mention, jfm. When I lifted the boat this year, the fouling on the hull was definitely less than what It was when I lifted the boat last year indicating that, at least in Majorca, water temps were probably lower last year than previous year. I took some pics with my phone but I can't work out how to download them! The boatyard did'nt even want to repaint the antifoul because they thought it would last another year but I insisted they slapped one coat of paint on the hull, mainly so that I could carry out a like for like test on the different props. Because it was just one coat, I decided to use the same antifoul paint (Titan) as last time rather than the Micron self eroding type which I wanted to try following your experience but I would have needed 2/3 coats for that which would have been a lot more expensive
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jfm
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Reged: 16/05/2001
Posts: 7487
Loc: London/Antibes
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Thnaks
So it sounds like lots of boats (well, yours+mine+houghn's) had much less fouling than usual. Yup, must be some macro effect like water temp or something. Let's compare again next year - mine, houghn's and Magnum's all have M66 so at least we'll be able to compare that with your Titan. A friend of me+ Magnum has a new hattan 70 in Antibes (it unloaded from ship in Genoa this morning and is running to its new home berth in Antibes as I type) and I'll find out from him what s/seeker painted on it, so we can include that in the comparison - he is parked in TCM's old berth, aka Barnacle Central
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MapisM
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Reged: 11/03/2002
Posts: 2894
Loc: Italy
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Hmmm.... I don't disagree with other comments re.multiple variables affecting props performance, but!
Achieving such a proportional increase in rpm and speed can hardly be due just to different "quality" imho, considering that the two sets appear to be made by the same producer (are they?).
Unless of course the previous props had something wrong, but to an extent that should be visible somehow, or at least perceivable in terms of vibrations.
What you're describing reminds me of a boat where a throttle leverage was badly regulated, thus not allowing one engine to deliver its max power. A few millimiters in cables excursions were responsible for a 4kts difference.
I understand you didn't try both sets under exactly the same conditions, but just set1 last year and set2 now.
Are you sure nothing happened elsewhere in between?
It would be interesting to swap all those props and re-test the boat, trying all the four combinations.
A nice way to kill the time and make some exercise during those boring hours at anchor in hot weather, either...
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mikef
regular
Reged: 16/05/2001
Posts: 8964
Loc: chesham, bucks and palma,major...
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No difference in vibrations, Mario. Both sets of props feel quite smooth. I've had the throttle mechanism checked and I've also checked it myself for both engines. The mechanisms open fully
Swapping props is not cheap. I'm not a diver and it would cost me hundreds of euros to hire a diver for an exercise like this! Anyway I'm satisfied that I made a fair comparison and there is a difference. The only problem is why 
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MapisM
regular
Reged: 11/03/2002
Posts: 2894
Loc: Italy
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Agreed, hiring a diver is not worth the expense, no doubt about it.
You should consider some basic diving experience, though.
Boating and diving are a wonderful combination - aside from swapping props, I mean!... 
And in med warm waters, that's less demanding that you might have heard in the UK, either.
With apologies for the off topic...
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mikef
regular
Reged: 16/05/2001
Posts: 8964
Loc: chesham, bucks and palma,major...
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You're right but I'm too lazy although I do a bit of snorkelling. It's not the diving itself that I mind but taking 30 mins to squeeze yourself into a silly rubber suit and having to manhandle lumps of metal with air in them. Anyway there is nothing to see in the Med. There is no marine wildlife at all except jellyfish
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