Question for people with "fast trawlers"

Going to create a poll but what percentage would you guess you travel at hull speed?

The reasoning for the question is pretty simple.

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).

I was worried that if I had the power to go 15 knots would I still enjoy slow speed cruising as much.

About 75% hull speed in terms of miles covered. Higher if you are counting hours of course since fast cruise speed for us is about 1.75 hull speed.

Our logs over 10 years showed about 30% of the time at hull speed and 70% at a higher cruising speed. At hull speed we were around 6-7 knots and cruise was like 15-17 knots.

Mrwesson said:

I was worried that if I had the power to go 15 knots would I still enjoy slow speed cruising as much.

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My boat is capable of an 18 knot cruise all day but yesterday I was off shore for three hours at 10 knots and thoroughly enjoyed myself! We often cruise at 8 knots in the bay as people can see more of the city at that speed. (Not to say how much fuel iIsaved.)

Greetings,
Mr. Mrw. Interesting question. TOP speed on our "trawler" is 10 knots full out, flat out. We do NOT do that on a regular basis, only occasionally to see if she will run to the max RPM of our Lehmans (2500). We normally cruise @ 1750 RPM which gives us about 7.5k to 8.0 k.

On the other hand, we have a smaller vessel (1979 Penn Yan Avenger-23' with a GM 350) which we regularly run/cruise @ 3000 RPM giving us a speed of about 23k. Pretty well the ONLY time we run "slowly" is in no wake zones and the usual maneuvering/docking, slowing down for canoes/fishermen/swimmers.

The bottom lines are: The "style" of boating we do with the small boat is lakes, rivers and "restricted" waterways (like the ICW) as opposed to more cruising with the "trawler" (MUCH longer distances, more open water (ocean)).

The difference is in mindset. Enjoying the journey @ 8k as opposed to 23k. Sometimes ya just "Feel the need for speed".

80% at slow speed. MY boat is capable of 22KT cruise, but does 9 Kts comfortably.

IMO it depends on where you boat. I find slow speed appropriate in ICW like places. I may or may not speed up in open water depending on many factors. I purposely plan to not be in a hurry but weather and schedule do change. I would be reluctant to buy a slow only boat.

IMO fuel use in not a consideration because fuel is not determined by engine size but buy operating speed.

Our operating speeds are 7 or 22 knots. If we can get there in a couple hours at 7, we do. Otherwise it eats up too much of our day. However if "there" is just sightseeing, it's always at 7. Or if conditions are poor of course. So in the end in terms of hours it's probably 60% slow for us.

Speed is good.
We all like speed.
It's a question of how much speed. We enjoy our speed of six knots. OK OK sometimes we go 6.45 knots.


Those w urges to go fast once and awhile (the subject of this thread) are then stuck running their boats at a speed that is inappropriate most all the time. Going double the design speed of one's boat is at least silly and perhaps another "S" word applies.

I can't vote in your poll because I'm never at hull speed.

Codger2 said:

My boat is capable of an 18 knot cruise all day but yesterday I was off shore for three hours at 10 knots and thoroughly enjoyed myself! We often cruise at 8 knots in the bay as people can see more of the city at that speed. (Not to say how much fuel iIsaved.)

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10 knots is still way above the hull speed for a 42' boat. 8 knots is likely closer to your hull speed.

"Slow" for many folks with planing boats is still much faster than hull speed. Maybe that is why I see so many planing boats who are not up on a plane so are going "slow" but are kicking out a huge wake.

I don't have the option of running into the teens. I can run my boat at 10 knots fine, max speed is about 12 knots. At 10 knots it is loud, expensive, and digs a huge hole in the water. 7-8 knots, just below hull speed, is quiet and economical. I rarely ever go above 8 knots.

I disagree that there is anything s...... about running faster boats slowly.

Mrwesson said:

Going to create a poll but what percentage would you guess you travel at hull speed?

The reasoning for the question is pretty simple.

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).

I was worried that if I had the power to go 15 knots would I still enjoy slow speed cruising as much.

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How do you get 15 from Mainship 34??

7.7 kts or 18-22kts. Which I choose depends on the cost/time/distance/impatience matrix. That algorithm is complex and not fully understood. Sometimes I just shove the red knob forward and that is that. Felt the need for speed. Works out to about 50/50 slow/fast, guessing.

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.

We never run at actual hull speed, We are either at about 85% or about 170%, normally the former.

To Paraphrase...Poll asks: What %age of time at hull speed?

Just want to say that we never travel at "hull speed", per say. Because... hull speed calced for our boat being 7.58 nmph is not efficient for time of travel or economy of travel.

We do travel a bit below hull speed at 6.5 to 7 knots for economy and we also travel at full plane doing 16 to 17 knots for reduced travel time.

I voted 70% at hull speed... for lack of a choice for traveling slightly below hull speed

WOT on Beluga delivers about 21 knots, engines at 65% load delivers 14 knots, speed producing almost no wake is about 7 knots.

Interestingly, about 12 knots produces the largest wake from Beluga.

On the basis of what (a) CAT recommends I do, and (b) Mr Athens has suggested in several threads on another forum we should all do, I try to run my boat at 70% load about 70% of the time. That is a goal I aim for, perhaps not what I always achieve.

Yes, there is a consequential fuel bill for that...

I dont think if you go faster sometimes it spoils enjoyment of more relaxed cruising. There are times offshore where 10 knots just feels relaxing.

And, as RTF says, on other days you just feel the need for speed...

H.

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.

I have a sistership. Can cruise at about 13 knots if I choose to. For me it's > 90% at less than 7 knots. Often 6. About the only time I go faster is when crossing open water, and even then not unless I'm in a rush. But I by choice spend most of my time on canals and waterways. Last year my season GPS moving speed was 6.4 knots.

While I don't often go faster it's nice to have the option. Repowered this year and thought about installing less power than I had, but didn't want to give up the fast cruise capability.

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.

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.

BandB said:

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.

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Just a thought...

Mrwesson said:

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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nodestination said:

How do you get 15 from Mainship 34??

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Jeff F said:

I have a sistership. Can cruise at about 13 knots if I choose to.

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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.

-Chris

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!

The term hull speed should be abolished from any forum that seeks to educate people.

nodestination said:

How do you get 15 from Mainship 34??

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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.

Bacchus said:

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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micksbuddy said:

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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Seevee said:

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.

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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.

BandB said:

We travel fast and slow, just my slow is faster than most fast's.

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OK! I think I got it!

bayview said:

The term hull speed should be abolished from any forum that seeks to educate people.

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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?

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.

bayview said:

The term hull speed should be abolished from any forum that seeks to educate people.

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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.