Sold my 50, buying the Etec90

[bahama bound]

What ever happened to those spring loaded props that were variable pitch ? I am still running the 17 on my etec .no load .no ballast ! I know I am living a lie and will have to deal with prop at some point I did put my 13 on it and switched back to stainless 17 .I question my tach also ? Motor sounds great .tons of torque but my tach says 4k wot .with the 13 pitch wot was still exactly 4k ??but I was running 28 MPH with the 17 and 26 with the 13 ? I know its harmful at high speeds but what about low speeds ? Would it still hurt the motor at hull speed ? Seems it would be great for fuel economy ?

[Starscream]

**on edit removed a double-post**

[Starscream]

My target is about 5200-5300 RPM with ballast in. Based on previous threads on this forum the peak power delivery is at 5,300 RPM even though the mechanic at the dealership said 5,000 I believe the circumstances on the other threads more than my dealer (who gave me a 17 pitch prop to start). I don't think I will be doing much ballast-out motoring, and if I do I can put back the 14x11 prop. I didn't get a chance to test ballast out yesterday since I was with the family and there was a bit of wind and waves and I don't like to run without ballast with them on board.

If I could tweak an extra mile per hour or so with full ballast that would be great. I need a spare prop anyway so having a 14x9 and a 14x11 seems to be the plan.

What bothers me a bit about running without ballast is some of the previous threads which describe what happens if the keel rope were to break. I plan on replacing mine as a preventative measure but it's one of those things that takes more time and planning than work allows right now. I think we'd have a better chance of not being ejected with the ballast IN if the keel or rudders were to come down suddenly. For that reason, I clipped myself in to the kill switch when running at high speed...something I wasn't in the habit of doing with the BF50.

But holy smokes does that thing suck gas at full throttle. I did a round trip from Pointe Claire in Mtl to Oka beach, about 27 to 30 miles and burned about 6.5 gallons of gas. About 4.5 mpg or something like that...all numbers here are approximate. There is a blue Mac26M at the PCYC...don't know if the owner is member here?

[fouz]

What speed was you running on avg with the 4.8 mpg?

[Starscream]

Most of the time full throttle. Somehow you can't really NOT full throttle it. I tried to vary it a bit for break-in purposes but somehow always ended up at full. There were quite a few stops and starts though.

Hull has anti-fouling, which can't help matters.

[fouz]

WOT and 4.8 mpg is pretty good I think. From my experience and seeing what others post going 6 kts only get you around 10 mpg.

[mastreb]

For the best fuel economy at speed, you want to be 10% back from WOT (at least, that's how my ETEC-60 operates). This will allow the speed to vary about 1 to 2 knots between full speed at WOT and 2 knots back as wave action may dictate, and saves about 20% of fuel for what amounts to a 5% loss of speed. It's been interesting to get real-time fuel usage information as the boat runs. Here's how it works out for my 60:
2 knots--0.1gph
3 knots--0.3gph
4 knots--0.4gph
5 knots--0.5gph
6 knots--1.0gph <--wake & bow wave begin to form
7 knots--1.5gph
8 knots--2gp <-- displacement to planing instability area begins
10 knots--2.5gph
12 knots--3gph <-- displacement to planing instability area ends
14 knots--4 gph
WOT-10%--4.5gph--16 knots ballast out, 14 knots ballast in
WOT--5.5gph--17 knots ballast out, 18 completely empty all stars aligned

Beyond that, I see very little reason to go any speed between 5 knots and WOT-10%. With the fuel use curve on my boat, consumption jumps dramatically in the transition zone between displacement and semi-planing 8..12 knots) and then levels off after that.

Always have been worried about the daggerboard dropping while at WOT. However, I'm pretty convinced that it wouldn't go all the way down at speed. Heck, it won't go all the way down at 5 knots. So it will cause instability, but as long as you're not in an hard bank when that happens, you should have time to drop throttle safely and deal with the problem or limp home at displacement speed.

Not worried about rudders. they'll break off before they roll the boat.

When I run at high speed, I leave the ballast gate and vent valve open. This allows the ballast tank to automatically drain when on a plane as you speed up (takes about two minutes, and you can watch the speed clock up as it goes) and then automatically refill as soon as you go off a plane for increased stability. I consider it to be a safety measure, because if you have to come off a plane suddenly in an emergency, you almost certainly want the added stability without thinking about it.

Obviously before unrolling the sails you'd want to close the ballast gate, and if you wanted to go onto the trailer without ballast in.

Leaving the tank open while motoring at low speed is safe because the gate never comes out of the water on a heel, so it can't drain. It's unsafe to sail with the gate open, however.

[raycarlson]

Anyone worrying about rudders coming down at anywhere near full throttle is worrying about a near impossibility, I have additional lead added to both rudders and dagger board and with any amount of forward motion the dagger board will not move down at all due to frictional forces, and dropping a rudder at any speed will allow it to do nothing but bounce harmlessly on the surface til you drop to idle speed.

[Starscream]

Good to hear that the rudders at least are not a big issue. My concern about the centerboard dropping under power more likely then. There is a good article on this forum about what happened to the poster when the centerboard dropped under power. http://www.macgregorsailors.com/explore ... /index.php. That was with a 50HP probably at 15 mph. I wonder what would happen at 20+? Should I be clipping the kids in? Anyone else have an experience with a sudden centerboard deployment?

[mastreb]

I've not experienced the problem myself excepting the one time I powered up with the board down, and found the boat to be strangely squirrelly, unstable, and unable to get over 12 knots. I dropped speed, realized I'd left the board down, and crossed myself as there was no wood available to knock on.

Based on my knowledge of the dynamics involved and the few reports I've read of it occurring, the dangerous condition occurs only if the board falls while you're in a turn. Here's why:

The X & M boats have four modes of travel:

1) Displacement mode < 7 knots. There is no significant bow wake
2) Semi-displacement mode 8..12 knots. The bow wake is between 0% and 50% back on the waterline.
3) Semi-planing mode 13..20 knots. The bow wake is behind 50% of the waterline
4) Planing mode 20+ knots. The boat is fully up on a plane, i.e. the bow wake is 75%+ behind on the waterline.

In displacement mode, when you turn, the boat behaves like traditional sailboat: It rolls to the outside when turning. For example, when turning to port, the mast will lean slightly to starboard. This is because the inertia of the of boat dominates the forces involved and the wake forces have no significant impact.

In Semi-planing and planing modes, when you turn, the boat behaves like a powerboat: It rolls into the turn. this is because it is acting as an inertial single-track vehicle (like a motorcycle), i.e., the vector of forces is to the outside of the centerline of the vehicle and so it is forced continually towards the middle. (The physics of single track vehicles are complex, so before you tell me I'm wrong please study it so we can at least argue using the same terminology.)

In Semi-Displacement mode, the boat oscillates between modes constantly and is unstable in turns. This is why steering is "squirrelly" on these boats between 8 and 12 knots, whey they have maximum drag and fuel consumption at these speeds, and why you should power over this mode in a straight line until you're semi-planing.

If the boards are down in semi-planing or planing modes, the foil will resist the inside roll necessary for turning on a plane and attempt to force the boat to an outside roll. This causes at a minimum serious steering difficulties, and it can't be over powered: The board can actually force an outside roll over the bow wake and cause a capsize, especially if the ballast is out.

Now, if the board drops on a straight run, the boat will heel to equilibrium between the hull and the board's hydrodynamic lift. This may or may not cause a sudden change in heading, but it will certainly cause a sudden change in heel. In any case, an alert helmsman should be able to drop speed fast enough to prevent it from being any kind of real problem.

With a 26M, a board will not fall significantly into the water even if the rope lets go completely. It'll get a few inches down and act like a skeg, which is enough to cause some steering issues, but it will be forced to the back of the trunk by the water speed and will not fall under its own weight until the boat slows below 5 knots. On a 26M you will also see the daggerboard line go slack suddenly if the board lets go, under all circumstances. This is a substantial inherent safety feature, since the only way to get a 26M to roll over its own board is to already have the board down when you power up. Finally, if the daggerboard line on a 26M lets go and you power down, it will fall all the way through the hull and sink, thus solving all of your problems automatically, excepting those that involve no longer having a daggerboard.

With a 26X, the board is heavy enough to fall significantly even at speed, although I tend to doubt that it would fall all the way. In any case, it will fall if the centerboard line breaks, cause a strange sudden heel at speed.

Bottom line: If the boat suddenly handles strangely, drop speed to displacement immediately and assess. Nothing life threatening ever occurs at displacement speeds. Since these breaks would be caused by wave slamming at speed, it's unlikely that they will occur during a turn which is the only time they're truly dangerous.

I assess the risk to life of an unintentional board drop to be about as likely as lightning. So stay away from Florida and you'll be fine.

[seahouse]

Two more things. If the daggerboard uphaul line should completely fail, the daggerboard (which is on the M, and not the centreboarded X - an important distinction for this discussion) will fall only to its fully extended position, because there is (or should be) a second line that arrests its travel at the maximum full-down position. It is the length of that line that sets the correct (“critical”) full-down position, and it functions as a redundancy to the uphaul line to prevent the loss of the daggerboard.

I think that when motoring at low speed that with the daggerboard part way down (say, a foot or so) that some of the wandering at certain speeds is caused by the large amount of clearance that exists between the daggerboard and the daggerboard trunk.

When you are turning one way, the boat direction and roll take a fixed “set” as the board gets “pinned” to one side of the trunk. When that force changes, from any one of a number of influences, the board can flop over to the other side of the trunk and be pinned in the new position, which changes the attitude of the boat. This is another of many reasons for the boat to wander in certain configurations and conditions.

When sailing (the more the dagger is extended, the more prominent its effect), this same thing also happens when you either tack or jibe, but you don't notice it because the change is not instantaneous and there are a number of other factors that mask it.

If anyone wants to demonstrate this for their own edification, drag an oar or paddle in the water (like a rudder) when moving slowly and turn it at an ever-so-slight angle to the direction of travel. Significant forces develop.

-B.

[seahouse]

The physics of single track vehicles are complex, so before you tell me I'm wrong please study it so we can at least argue using the same terminology.

A good one, Matt! A pre-emptive. I'm going to copy and paste that to my clipboard for later use (not for with you of course) if you don't mind. Using that line could save me a lot of typing too.

-B.

[Catigale]

The X & M boats have four modes of travel:

Noooooooooooooooooooo......

Private joke for old timers......

[mastreb]

Here's another great one I use to save time:

"What evidence would you accept as proof that you are incorrect?"

When they invariably can't think of anything or worse tell you there is none, then I just say "Great, then there's no point in arguing about it.”

[seahouse]

That one's even better, smart guy. Ohh! ...my clipboard is filling up!!!