Great Loop in 30 Days?

[rslifkin]

Hull speed of our loop boat was around 7.7 knots with a waterline length of about 60'. At 900 RPM we did 10 knots. At 750 RPM we did 8 knots. We were able to reduce our idle to around 600 RPM which gave 6 knots but barely kept the engines running and was not great at maintaining control.

Tows and barges can't maintain 4.3 knots either. Any boat with a waterline length over 30' will struggle with it and I can't imagine any over 40-45' LWL staying under 4.3 knots. Most boats can maintain at something like 1 knot under hull speed. For 40' LWL that's going to be around 5.3 knots. That's likely what you'll get for a 45-50' LOA boat.

I'd imagine your LWL is about 30' giving you 5.5 knots hull speed so your idle of 4.3 makes sense. However, idle will increase proportionately with hull speed and will do so without increasing wake.

33.5' waterline for me, hull speed about 7.7 kts. 6.5 is a good slow cruise, wake and fuel burn go up faster than speed once you get much beyond that.

Idle speed isn't related to hull speed, but it's relative to your engines and top speed. The faster the boat and the smaller the rpm range from idle to WOT, the faster the boat will move at idle (in most cases).

 

[BandB]

33.5' waterline for me, hull speed about 7.7 kts. 6.5 is a good slow cruise, wake and fuel burn go up faster than speed once you get much beyond that.

Idle speed isn't related to hull speed, but it's relative to your engines and top speed. The faster the boat and the smaller the rpm range from idle to WOT, the faster the boat will move at idle (in most cases).

Yes, and no. At the same RPM, you're right that the larger engines will have more hp. However, at idle, the hull speed very much comes into play and the boat with greater hull speed will move faster. just above hull speed, the smaller boat will tend to move quicker with similar top speeds and rpm ranges, as it takes more power to get it from hull to plane. However, below hull speed, the advantage goes definitely to LWL. We have numbers on three Riva's with very similar hulls that we manage, a 44', 52' and 63'. At 1000 RPM they all run 11 knots (note fuel consumption varies greatly by larger engines). However, at 1250 RPM, the 44' is faster, 52' next, 63' slowest. And at 750 RPM, the 63' is fastest (9 knots), 52' next (8 knots) and 44' slowest (7 knots). As they reach hull speed and become displacement boats, the greater the LWL, the faster the boat. All three boats have MAN engines, all three have max RPM of 2300 and all three WOT is 42 knots for the 44', 41 knots for the 52', 41 knots for the 63'. Just think of the formula for displacement speed, all based on LWL (and design of boat).

Now, obviously I've oversimplified things and many factors contribute. The point remains that a boat over 30' and even more over 40' will find it nearly impossible to stay below 5 mph.

 

[rslifkin]

With the really fast boats with low revving diesels, you're absolutely right that you may be close enough to hull speed at idle for it to be a factor (and I think all of your boats fall into that group). But on slower boats, or boats with high revving engines (like mine, WOT is 4200 RPM, idle in gear is ~750, WOT speed is ~25 kts), you'll be far enough below hull speed at idle that speed is mostly a function of prop thrust and the hull won't really be limiting it. So a boat with bigger props and deeper reductions will idle faster due to better low speed thrust (my boat does idle noticeably faster than a neighboring boat of almost identical size and same engines, but with less gear reduction and smaller props). And the larger percentage of max RPM the engines idle at, the harder it'll be to go slow (unless the boat has a low top speed).



If there's no crosswind to worry about, I can drop my speed at idle down to about 3 kts by having just 1 engine in gear (less thrust). But that's not necessarily a practical thing to do in many conditions. As far as RPM to reach hull speed, with my current props (which I think are a little short on blade area, but pitched appropriately) I idle at about 4.2 - 4.3 kts. 900 RPM gets me up to 4.8 - 5 kts, we do 6.5 - 6.7 at 1300 (our typical slow cruise, speed varies a bit with fuel load). If I'm remembering correctly, it takes somewhere around 1600 to get the boat pretty much to hull speed (7.7 kts). Minimum planing cruise for us is ~3000 RPM and 14 kts, more typical would be 3300 and 17 kts (with max continuous at 3400 and 18.5 kts). Definitely a very different speed dynamic than your boats considering the much lower top speed and much wider RPM range on the engines.


On the other hand, there's a 46 foot Sunseeker in the marina that does somewhere around 6 - 7 kts at idle. It tops out in the low 30s, but has pretty low revving diesels and lots of prop. The low speed prop bite is good enough that I've seen the owner put 1 engine in gear to depart the slip and have someone on deck almost fall over from how violently the boat moves.

 

[High Wire]

Average 200 miles per day with no provision for weather. What could go wrong?
Oh wait, the Erie Canal has 10 mph speed limits so time will have to be made up somewhere else. Hopefully he can cruise at 35 knots or so in open water.

 

[rslifkin]

Average 200 miles per day with no provision for weather. What could go wrong?
Oh wait, the Erie Canal has 10 mph speed limits so time will have to be made up somewhere else. Hopefully he can cruise at 35 knots or so in open water.

I expect he'll be relying on running fast for long (10 - 12+ hour) days in places where he can to make up time. It'll be interesting to see if he actually manages to finish in 30 days or not. I wouldn't want to try it, but it's cool to see.

 

[HeadMistress]

Reminds me of the movie years ago, "If it's Tuesday, This Must Be Belgium"


--Peggie

 

[backinblue]

Cannonball Run is fun to watch, but I wouldn't want to do try that either.

 

[Seevee]

Not for most of us, but I can see the attraction of going fast. We have that same attraction in cars and planes, and some folks are wired to just go fast and could give a rats arse on what they're missing.


I could make an argument for a "fast" loop boat. There's times that speed is a huge advantage. Can't out run weather, but you can position yourself better with the speed, if needed.


However, the Loop (for most folks, myself included) is about seeing the sights and the social aspect, interacting with others doing the same.

 

[bowball]

This discussion reminds me of John Mirassou's Great Loop trip with two other buddies in an open, 17' Boston Whaler back in the 80's (87?), followed by his book "Only in America." We have a signed copy of that book on the coffee table on our boat now. One 90-horse Johnson.

Here’s a video of it!

https://youtu.be/6njqtahjBFA

 

[kthoennes]

Oh cool, thanks so much for that video link. I had a brief email exchange with John Mirassou at some point, can't remember why, but he was a very nice guy. We're roughly the same age and I really enjoyed his book. I actually tried to buy a second copy for a boating friend but it's never gone into a subsequent printing so they're rare. Amazon has one for around $70, he sure didn't get that when it was first published. He talked about doing it again at some point but I don't think that ever happened. That book has some memorable moments that have flashed into my memory for some reason. English major, I can't help it. He wrote one striking paragraph for example, describing a moment when he was swimming on a hot summer day, dove underwater, and when he came up, he was accidentally very close to an incredibly beautiful woman standing in the water, backlit by a setting sun. Like a sailor's mermaid apparition. I don't know why it made such an impression, but the whole book and that particular passage made me think, ah yes, that's what 20-something felt like.

 

[bowball]

Oh cool, thanks so much for that video link. I had a brief email exchange with John Mirassou at some point, can't remember why, but he was a very nice guy. We're roughly the same age and I really enjoyed his book.

He wrote one striking paragraph for example, describing a moment when he was swimming on a hot summer day, dove underwater, and when he came up, he was accidentally very close to an incredibly beautiful woman standing in the water, backlit by a setting sun. Like a sailor's mermaid apparition. I don't know why it made such an impression, but the whole book and that particular passage made me think, ah yes, that's what 20-something felt like.

Seems like a fun guy and an epic trip then.

I had a similar moment in my 20’s…sitting on a beach at Club Med in Moorea, Tahiti (now sadly closed) and a beautiful French woman my age gracefully emerged from the surf walking by me like the scene from the movie 10… except being French she was topless. Nothing like being 24.

 

[ScottC]

Just another person making money on the net.

Can't say anything positive/negative about the guy till I had a 5 minute conversation with him.

But the concept of doing the loop in 30 days to me doesn't impress me on so many levels.

+1 !

 

[ScottC]

Hull speed of our loop boat was around 7.7 knots with a waterline length of about 60'. At 900 RPM we did 10 knots. At 750 RPM we did 8 knots. We were able to reduce our idle to around 600 RPM which gave 6 knots but barely kept the engines running and was not great at maintaining control.

Tows and barges can't maintain 4.3 knots either. Any boat with a waterline length over 30' will struggle with it and I can't imagine any over 40-45' LWL staying under 4.3 knots. Most boats can maintain at something like 1 knot under hull speed. For 40' LWL that's going to be around 5.3 knots. That's likely what you'll get for a 45-50' LOA boat.

I'd imagine your LWL is about 30' giving you 5.5 knots hull speed so your idle of 4.3 makes sense. However, idle will increase proportionately with hull speed and will do so without increasing wake.

Enter electric... ;-)

 

[jimfrens]

Some people are just wired differently. When I was young I rode my motorcycle all over the country. I did seven 1000-mile days not by direct intention, just didn't stop (my right shoulder trapazoid muscle still tinges when I think of this).

Peter

We’re cut from the same cloth. Many 1000-mile days, a few 1500 mile days, one 1800 mile day, six of the 11-day Iron Butt Rallies. Delivery jobs are running 12-16 hour days, more if I have crew. But on my own boat, it’s “smell the roses” mode.

 

[BandB]

Reminds me of the movie years ago, "If it's Tuesday, This Must Be Belgium"


--Peggie

That movie title is a sad memory. When I was in college, we went to Europe on Choir tour. As part of that we hit 7 countries in 22 days and gave 10 concerts, but the most insane day was one in which we went hours out of the way to pull up outside a hotel in Brussels, go inside for lunch, come out and continue on our way. That was our entire time in Belgium. And it was on a Tuesday. So our theme was "If it's Tuesday, This Must be Belgium".

Insane tour organizer. After that we arrived where we were scheduled to sing that night at 11:00 PM. We didn't know a concert was planned. However, a huge local crowd was waiting, so we gave a full concert in our travel clothing and mingled and talked to all those there, concluding after 1:00 AM and then going to stay in their homes. They were so kind and appreciative.

 

[HeadMistress]

IMO that's a wonderful memory and a lot more entertaining story to share than most people's vacation photos of all the same "must see" tourist spots. And, unlike most tourists, you actually got to meet local people and spend time with them in their homes wherever your concert was that night. So... you didn't see much of Belgium...a good excuse to go back. It's such a small country you could see all of it in a long weekend.



--Peggie

 

[Benthic2]

He started on the central east coast of Florida and is in New Orleans on Day 25 if anyone is curious.

 

[mncruiser]

He started on the central east coast of Florida and is in New Orleans on Day 25 if anyone is curious.

It seems to me like he’s had time to relax and see a lot of things, I think we were expecting less.

Cool trip, fun to watch!