View Poll Results: What percent of the time are you at Hull speed?
80%+ 21 38.89%
70% 6 11.11%
60% 2 3.70%
50% 4 7.41%
40% 3 5.56%
30% and under 18 33.33%
Voters: 54. You may not vote on this poll

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Old 07-16-2017, 01:00 AM   #21
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Originally Posted by BandB View Post
Wifey B: Ignore us for purposes of what you'll do but the only time I ever have traveled at hull speed has been in a no wake zone. We're not typical though and you're not likely to do as we do. You're likely to go at two speeds, fast and slow, whatever they might happen to be for you. You use the example of 15 knots and 6-7 knots. No one, including probably you, can guess how much you'll go at each. We travel fast and slow, just my slow is faster than most fast's.
Just a thought...

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Old 07-16-2017, 07:56 AM   #22
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Originally Posted by Mrwesson View Post
Going to create a poll but what percentage would you guess you travel at hull speed?

I have a mainship 34 and would like to travel at faster speeds "sometimes" and would love to be able to maintain 15-17knots but also enjoy 6-7knots as well(unless I have a destination/rarely do).
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Originally Posted by nodestination View Post
How do you get 15 from Mainship 34??
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Originally Posted by Jeff F View Post
I have a sistership. Can cruise at about 13 knots if I choose to.

When we had our Mainship III, 220-hp DD 8.2T, I think we routinely cruised at either 7 kts or 10 kts. Sometimes 12 kts if we were in a hurry (impending weather, etc.). 14 kts was flogging it.

Can't answer the poll about use in our current "fast trawler" (see avatar)

Because I mostly don't have a clue. We run at about 7 kts often, and we also run at about 18-19 kts often. Dunno percentage. Possibly slow more often than fast, but possibly shorter distances slow vs. fast, too. The choice is almost all about spur of the moment... except for the very few times we actually want to get somewhere "quickly" or times -- usually out in open Bay -- when sea states aren't "slow-kindly" for our hull form.

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Old 07-16-2017, 07:56 AM   #23
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Our 34LRC hull speed is right in at 7kts @ 1200rpm. Three blade 21x22 props.
Very comfy and relaxing knowing we will get there with lots more fuel in the tanks.
Twin Perkins 6.354 turbos will give us 16-17 kts at 2150 rpm. That is my max sustained cruise. Manufacturer says 2250, but these babys are mine.
Love to just get there sometimes, and almost always push her up awhile on any lengthy day/trip because it is fun!
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Old 07-16-2017, 08:50 AM   #24
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The term hull speed should be abolished from any forum that seeks to educate people.
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Old 07-16-2017, 09:28 AM   #25
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Originally Posted by nodestination View Post
How do you get 15 from Mainship 34??
Mo powa!

Its been done and theres a video of an older mainship 34 on youtube hitting 20kts.

Apparently anything over 16 can get scary in a following sea.

I have a 165 perkins and can get 11 knots on a perfect day. Just pushing water mostly though.

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Originally Posted by Bacchus View Post
We have a MS 34HT and do about 75% 8-9 MPH at 1600-1800rpm which is fairly easy run for the tank at 370.
If I need or want to we can do 12-14 MPH at 2500-2800 rpm.
WOT we can do around 20mph but don't very often or for long.
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Originally Posted by micksbuddy View Post
When I was running my Mainship 34, I spent probly 95+% at 6.5-7kts. For the most part I only ran fast (13-15kts) just to put the engine under load for a while. I enjoyed sitting back and watching the world go by.
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Old 07-16-2017, 09:41 AM   #26
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Good thread.....

I could argue that if you go 8 knots or even double that at 16 there's really not a lot of difference unless you're ocean going. For most of in on small bodies of water, rivers and the ICW, we typically have to slow occasionally anyway, with other boats, slow zones, etc. and then the speed is the same.

Sure on a 50 mile trip the faster speed will get you there perhaps 2 hours faster, maybe and if doing a lot of long range, makes a bit of a difference. But when operating at any speed much less than 25, it's slow, so who cares.

If we have the urge and the ability, just push up the power and get the feeling out of your way and come back to hull speed and enjoy the ride.

I'm still new to trawerling, but am getting the mind set that we are not going anywhere fast.
Depends where on the ICW you are talking about.

There are many places between Norfolk and Miami where you could run at any speed.

Lots of places where traffic and proximity to docks can prevent it also.

But making the snowbird run from Jersey to Florida, after many trips in all kinds of boats, and 5 round trips in my boat at 6.3 knots....I would do a lot to gain a couple knots and knock days off that trip.

Sure I can speed up, travel longer days....but some of those go fast places have little to see, and I have seen enough waves in my life.
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Old 07-16-2017, 10:37 AM   #27
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Originally Posted by BandB View Post
We travel fast and slow, just my slow is faster than most fast's.
OK! I think I got it!
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Old 07-16-2017, 11:22 AM   #28
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Originally Posted by bayview View Post
The term hull speed should be abolished from any forum that seeks to educate people.
By discarding [abolishing as you mention] the term "Hull Speed" from boating lexicon; then, its accurately representative replacement would be??

It [hull speed] being a fairly accurate mathematical determination factor for one of a boat's speed-efficiency "breaking points". A speed factor that truly exists and that stands as a fulcrum to determine many items regarding hull design in comparison to a boat's performance.

What would you term that crucial breaking point of speed for every boat to determine as its maximum speed before "pushing water" and/or eventually reaching plane? i.e. 1.34 X lwl-squared

My boat's "hull speed" is 7.58... what's yours?
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Old 07-16-2017, 11:33 AM   #29
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My boat was designed and built around the premise of a sliding speed scale. I speced. 7-16K cruise with no strain on engines hull etc. I also considered fuel burn in the equation and hull speed opting for a relatively long waterline 46.6 ft. Therefore one K+ less than hull speed at 8K is relatively economical and at 9.2K hull speed things still look fairly good for a 52 ft LOA boat at over 32,000 lb. I usually opt for the compromise of 9-9.4 K where my instruments show 5-6 gal/hr burn above that level the fuel burn steepens. So 90% at hull speed is my best estimate. The other 10% is to clean out the engines sea trail or make a rapids slack.
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Old 07-16-2017, 11:36 AM   #30
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Originally Posted by bayview View Post
The term hull speed should be abolished from any forum that seeks to educate people.
I agree, particularly in reference to semi-displacement designs. We used to talk about hull speed in sailboats back in the seventies, and it was sort of applicable to the traditional designs. Then design and construction started evolving. I sailed a performance design in the eighties with LWL 30 feet or so that would go 8-10+ knots no fuss. And jumping into this world it's hard for me to discern any hull speed related hump in my boat. Time to move on.
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Old 07-16-2017, 12:43 PM   #31
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Quote:
Originally Posted by bayview View Post
The term hull speed should be abolished from any forum that seeks to educate people.
Not at all IMO.
The speed to run is a very important issue and more highly related to boat design that most boaters knowledge. And boat design is not as easy as how to tie a boline.

There is the run what ever speed you want crowd or as fast as you can afford fuel.
There's a lot of non black and white in hull speed discussion but the more you dig the more black and white it gets. The subject of hull speed is very clear though compared to anchor performance. The door you open to get into it is a simple formula. And it explains why aircraft carriers can run in the vicinity of 50 knots.
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Old 07-16-2017, 01:00 PM   #32
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I have a center console that will do 40 knots. I probably run it at hull speed more than half the time. I'm still a sailor trapped in a powerboat. I enjoy going slow.
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Old 07-16-2017, 01:07 PM   #33
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Originally Posted by Nomad Willy View Post
Not at all IMO.
The speed to run is a very important issue and more highly related to boat design that most boaters knowledge. And boat design is not as easy as how to tie a boline.

There is the run what ever speed you want crowd or as fast as you can afford fuel.
There's a lot of non black and white in hull speed discussion but the more you dig the more black and white it gets. The subject of hull speed is very clear though compared to anchor performance. The door you open to get into it is a simple formula. And it explains why aircraft carriers can run in the vicinity of 50 knots.
Exactly! And, a very good example for the importance of boaters being able to learn exactly what determining "Hull Speed" represents.

MOF Eric... I believe some posts ago it is you who began this HS importance discussion. Thank you for doing that.

I can not understand why people chose to [wish to] push hull speed to the curb [into the drink - so to say - lol]. Especially when that calculation is what I believe to be one of if not the most important mathematical scale of hull design, power options and boat performance.
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Old 07-16-2017, 01:33 PM   #34
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Quote:
Originally Posted by bayview View Post
The term hull speed should be abolished from any forum that seeks to educate people.


I can't agree.

Even though the term isn't entirely accurate, I think it is still useful. I don't understand hull design at all, so I think of hull speed as simply that point where the distance between bow and stern wave equal the LWL. A better way to look at this may simply be the upper limit of displacement speed.

In my own simple mind, I think of anything beyond displacement speed as requiring more power to overcome the effects of this wave trough. A SD hull can do it, a planing hull certainly can do it. There are other ways to accomplish it as well but for most of the boats we have they will fall generally into one of those three categories.

Many boats don't have a sharp break at the hull speed in the power/speed curve. Even so, I think that understanding the concept of hull speed still is useful for most operators know.

Think of it this way, is it good for an operator of a planing hull to understand the mechanics of how a boat planes? Sure. If they simply think of the throttle as a speed lever why not just drive the boat right on the edge of the step? The same is true, to a lesser degree for those of us that operate FD hulls. Isn't it good for us to understand, at least a little bit, what happens as we move out of the displacement speed range?
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Old 07-16-2017, 02:15 PM   #35
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Originally Posted by Nomad Willy View Post
...

I can't vote in your poll because I'm never at hull speed.
With a FD boat I'm never at hull speed either. But I did vote - "30% and under" includes 0% I assume.

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Old 07-16-2017, 03:38 PM   #36
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About 50/50. Best economy is ~7kt single engine so do that if I have time. Otherwise, 15kt. Top speed ~18kt. Not retired.
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Old 07-16-2017, 04:20 PM   #37
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Can't exceed hull speed. Normally cruise at one know below. Occasionally go hull speed, usually when fighting a strong current, but this results in a 135 percent increase in fuel rate.
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Old 07-16-2017, 04:39 PM   #38
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And it explains why aircraft carriers can run in the vicinity of 50 knots.
And why submarines can outrun them :-)

Not suggesting it's not useful theory. But for someone with a SD boat and a high hp/disp configuration - which is any fast trawler - it's nothing more than a footnote.
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Old 07-17-2017, 06:37 AM   #39
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I am running at hull speed 30percent or less since I am mainly going out for weekends and couldn't go many places at hull speed.
At 7 knots, I burn 2.9 gph and at 14 knots burn 12 gph. So when just cruising around I go slow but when going to a destination, I go fast. It costs me an extra 6 gallons an hour to go the same distance in half the time. I'm wondering if I get a bigger Trawler after I retire, will I be able to adjust to 8 knots? I think so if in the right boat.
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Old 07-17-2017, 06:41 AM   #40
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The other issue for us, is noise. Conversation in our boat is somewhat difficult when traveling at higher RPMs. And, we have Yanmars, which seem to be relatively quiet, from what I have observed. We like easing along at 7 or 8 knots and not having to shout.

But, we are also retired, and rarely on a schedule or in a pinch for time. I realize not everyone has that luxury.
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