Top Speed of the Flicka 20 (w/ Motor)

[SailorElliot]

Hello!

I was wondering what the top speed of the Flicka 20 via motor in the ocean (1-3 foot waves).

Thanks,
Elliot

 

[sail sfbay]

Maximum displacement hull speed = 1.34 x sqrt (LWL). So for LWL of 18.17 ft SailboatData.com - FLICKA 20 Sailboat top speed = 1.34 x sqrt 18.17 = 5.7 knots..............now that's fast!!

 

[jon hansen]

........... but, "hull speed" should never be confused with "top speed".

your question is so vague that it is hard to answer. what is it you want to know?

 

[Sailor Sue]

Maximum displacement hull speed = 1.34 x sqrt (LWL). So for LWL of 18.17 ft SailboatData.com - FLICKA 20 Sailboat top speed = 1.34 x sqrt 18.17 = 5.7 knots..............now that's fast!!

I think 5.7 kts for a 20 foot boat in 1 to 3 foot waves would be very unlikely!

 

[jon hansen]

you heading into the waves? you heading with the waves? ..........

 

[jon hansen]

is there wind?

 

[JohnShannon]

Top speed is just shy of the speed of light. What has been observed is that the power required to get close to hull speed is fairly modest and the power required to get past hull speed is large.

 

[Alan Gomes]

I think 5.7 kts for a 20 foot boat in 1 to 3 foot waves would be very unlikely!

What engine is in your Flicka? They were commonly powered with a Yanmar 1GM--the same engine I have in my Ericson 26-2. If so, your boat is underpowered for its 6,000# weight and would likely not hit hull speed with that engine even in calm conditions, much less against any kind of waves.

My boat has a longer waterline than yours, displaces slightly less, and is a faster hull shape. On my boat I can hit 5.8 kts. if I run it flat out in calm conditions. At cruising speed--again, calm conditions--I motor nominally at 5.4.

As for adding "waves" into the mix: It's hard to estimate based on simply saying "1 to 3 foot waves" because there may well be a headwind driving that, and 1 foot waves will slow the boat less than 3 foot waves, obviously. But just to throw out a wild guess, on my boat when the conditions get somewhat lumpy I might be look at the mid 4's. You will get less than this.

Again, this assumes you have a Yanmar 1GM with an appropriately sized prop.

Of course, the best thing to do is to take the boat out in those conditions and see for yourself. There are so many variables that can affect the speed that you actually see in your particular case.

 

[dlochner]

If the wind is blowing and there are 1-3 ft waves it will be faster to sail than motor.

When passage planning it best to assume a much lower speed than hull speed. In theory our hull speed is somewhat over 7 knots and in calm water we can easily get that speed at lower than max rpm. However, when we are passage planning we plan to average 5 knots and are pleasantly surprised if we average much more than that.

It is also important to consider fuel consumption. In calm water motoring at 6 knots we burn around 2 quarts an hour. At 7 knots in the same condition we burn over 3 gallons per hour. Of course these numbers will be different for a Flicka 20 than a Sabre 362, but the 50% increase in consumption will pretty much hold true as you move from a comfortable cruising speed to close to theoretical hull speed.

 

[Alan Gomes]

If the wind is blowing and there are 1-3 ft waves it will be faster to sail than motor.

Not necessarily if the destination is directly upwind, especially granting that the Flicka's upwind performance is something less than stellar. (I assume we are talking VMG here.)

At any rate, the question posed is how fast the Flicka can motor into 1-3 foot waves and not whether it can motor as fast as it sails.

 

[JohnShannon]

Do you possess said Flicka? What do you see in practice, are you concerned it is too low?

 

[Joe]

A Flicka, though very, very seaworthy and robust, is NOT a fast boat,
but it IS a great one! Especially those built by Pacific Seacraft.

 

[jssailem]

It is possible to give you any number -3 to +7 knots and it could be right for the conditions.

 

[jssailem]

To really understand your boats top speed you have two basic options.

1. go out in the ocean and do a test run
2. Go to class - ASA 103 introduces Coastal Navigation.

my choice would be grab a friend, scrap the barnacles of the boats bottom, a bucket of beers and go out in the water and give you boat a test.

 

[SailorElliot]

Hello!

Sorry I made my initial post so unclear. For future reference, I cruised at over 5 knots with 2500RPM (Yanmar 1GM10) going into 1 foot swells with no wind.

 

[Justin_NSA]

It's all about the journey, not the destination

 

[sail sfbay]

I cruised at over 5 knots with 2500RPM...............that's relatively fast for a 20 ft sailboat.

 

[JohnShannon]

The questions will keep coming, GPS speed, or speed through the water? Did you have a headwind? a tailwind? How did the exhaust smoke look? All in all sounds like you have a healthy motor/prop combo.

 

[dlochner]

Hello!

Sorry I made my initial post so unclear. For future reference, I cruised at over 5 knots with 2500RPM (Yanmar 1GM10) going into 1 foot swells with no wind.

That is about as fast as it will go. How are you determining boat speed, with a knot meter? or GPS? Has the knot meter been calibrated? Is is calibrated in nautical miles per hour or statue miles per hour?

 

[Alan Gomes]

Hello!

Sorry I made my initial post so unclear. For future reference, I cruised at over 5 knots with 2500RPM (Yanmar 1GM10) going into 1 foot swells with no wind.

While that speed is good for that boat, I'm not sure that the fact that you are making it at 2500 rpm is necessarily a good thing. That is, it's possible you are over propped.

Rather than asking how fast your propulsion system can push the boat, I think you need to ask whether it is working as designed. Once you know that, then your speed under various conditions is going to be what it is, and you'll come to know what it is specifically as you actually take out the boat in those situations.

You have a 1GM10 vs. a straight 1GM (such as I have), which does give you a couple of extra HP. But nevertheless, your boat is certainly under powered for its 6000# displacement. If you are actually getting over 5 kts. in no wind AND NO FAVORABLE CURRENT, then that is probably as good as it gets for that boat speed-wise. But you do want the engine operating in its favored RPM range. Top RPM for that engine is 3600. If you can get within a few hundred RPM of that IN GEAR and under way (not tied to the dock) then I would say you are not over propped. But if that 2500 is the most you can get running it flat out, then your prop is either too big and/or has too much pitch and should be replaced or re-pitched. And this is irrespective of what speeds you are seeing.

Cruising RPM for your engine is more like 2850-2900. It is rated to run continuously at 3400 if you needed to, but it should be very happy running it at ~2900, give or take for day to day use. Note that the Yanmar tach is inaccurate, so you should buy (or borrow) a cheap optical tach so you can make a deviation table of how far off your tach is at any given RPM setting. (The error is not linear.)

Having the correct prop is very important to get the most out of any engine, and can affect not only the speeds you see but also the life of the engine itself.