Boat Dimension - Newbie Question

[shadowtiger111]

Alright, I'm going to show my newbness here with his question. I did find a post a few years ago that asked this question, but it didn't really answer the original question.


I'm looking around for boats, and displacement I can handle. That seems to be consistent. I'm looking for a boat to go around the great loop.



My QUESTION is on clearance: Some of the routes are 15, 17 and 19. In order to complete the entire loop, you'd need a vessel that can go under 15 feet. So far the only trawler I found dimensions for via the owners manual, was for a Grand Banks (I was using the Grand Banks as a control when I look at Trawlers, thats it.) Anyway, in the description it had said it had been around the great loop, but then, I started looking at the dimensions to see which route I could take, and found it was like, 22-24 feet. So does the owner manual say total height from bottom to mast? Or waterline to mast? Even if thats the case, thats still not going to give clearance. So what the heck?


Down-low: How do I figure out how the trawler can handle the entire great loop?

 

[rslifkin]

Unless you can find a clearance diagram that shows height to various parts of the boat or talk to someone that owns the boat in question and can measure, it's hard to know ahead of time. If you're looking at a boat in person, measure the height of the tallest non-removable (or non-foldable) object and then reach item above that so you know what height bridge you can fit under and what has to be lowered for various heights.

 

[slowgoesit]

On one boat, I was told the bridge clearance was 22'. I physically measured it, and it is 28'.

Moral of the story is don't test any measurements given by someone else by going under a bridge . . . .

Measure it yourself!

 

[O C Diver]

As mentioned, there are masts, arches, biminis, enclosures, and antennas that fold down. Some are easy and some take a substantial amount of effort. You will also find boats that did the Great Loop and later had new flybridge enclosures that weren't designed to be folded down. Also understand that these same boats may have added things that increase their clearance such as a new radar antenna. Always best to make your own measurements, not that a boat broker would lie about a thing like that.

My preferred method for measurement is to tie a string to a tennis ball and enlist a friend to stand on a bridge that the boat can clear. Lower the ball till it just touches the water and tie a knot in the string corresponding to the bridge railing. Then drive the boat under the bridge and let the ball just touch the highest point of the boat. Tie another knot in the string corresponding to the bridge railing. The distance between the two knots is the boat's air draft. You can check several spots by tying additional knots in case you're considering relocating items.

Ted

 

[Jeff F]

Masts come down. You only need to be concerned with permanent structure.

The 15 ft section is the western Erie Canal, and it can be bypassed by entering Canada. Other than that with 19 ft you can go pretty much anywhere.

Lots of mid-size trawlers like GB 42, Monk 36 etc travel the western Erie. Sometimes a bit of prep like lowering radar arch is needed.

 

[Bacchus]

Just a caution if you see a boat that is reported to have completed the loop. Be sure to confirm what route was used. & any important water level conditions for "tight" sections. Just because a boat has complete the loop successfully doesn't mean it will be OK if you choose a different route or water levels are significantly different. For the most part canal levels are more consistent than Great
Lakes levels but there can be short term / local conditions that can make a difference... especially early season when many are trying to navigate NY canal sections.

 

[PhilPB]

This is interesting and has answered a couple questions I've had about my boat. The PO's widow told me that her husband was prepping the boat for the loop but never gave any details. Now this thread answers why he hinged the mast and had the bimini made in a way to easily remove the canvas and fold the frame away.

 

[guy with a boat]

Down-low: How do I figure out how the trawler can handle the entire great loop?

Not a bad question at all and, as you are seeing, not as easy to answer as it might seem.

 

[Flatswing]

Alright, I'm going to show my newbness here with his question. I did find a post a few years ago that asked this question, but it didn't really answer the original question. I'm looking around for boats, and displacement I can handle. That seems to be consistent. I'm looking for a boat to go around the great loop.

My QUESTION is on clearance: Some of the routes are 15, 17 and 19. In order to complete the entire loop, you'd need a vessel that can go under 15 feet. So far the only trawler I found dimensions for via the owners manual, was for a Grand Banks (I was using the Grand Banks as a control when I look at Trawlers, thats it.) Anyway, in the description it had said it had been around the great loop, but then, I started looking at the dimensions to see which route I could take, and found it was like, 22-24 feet. So does the owner manual say total height from bottom to mast? Or waterline to mast? Even if thats the case, thats still not going to give clearance. So what the heck. Down-low: How do I figure out how the trawler can handle the entire great loop?

Typically the dimension you need is air draft - with & without mast/radar arch/Bimini folded. Total height from keel only really an issue if you are shipping overland. My GB36 needed 25’ with the mast up but was 17’ with it down. For the Western Erie (15’) & the Champlain Canal (17’) I had to also take down the Bimini. Interestingly my DeFever 49 RPH looks taller but has an (antennas down) airdraft of 22’ mainly because of a fixed anchor light, but I could get down to 16’ maybe15’ 5” if I folded the radar arch & Bimini.

I like the bridge & tennis ball approach for an exact number (make sure water & fuel tanks are near empty & best in salt water) but during purchase you can easily see if you can meet the 15’ or 17’ number with a measuring tape and a level.

 

[O C Diver]

Down-low: How do I figure out how the trawler can handle the entire great loop?

Do what I did. Buy a boat with no fixed structures that protrude above 15'. Then make the structures that protrude above 15', easy to lower. In my case, there was a mast that was 23' above the waterline with the radar and other items attached to it. I removed the mast and attached the other items (other than lights and wind speed indicator) to the roof of the pilothouse. Now my light mast and VHF antenna are easily lowered in under a minute to clear 15'.

Before picture.


A 15' air draft will allow you to go on any East coast ICWs (Intra Coastal Waterway), Erie canal, Champlain canal, Rideau canal, and Trent Severn canal.

Ted

 

[Old Sea Dog]

As has been said, air draft differs depending on which Loop route you take. The lowest fixed bridge is south of Chicago and there is no way around this. Believe air draft of this bridge is 19' 8". So in theory a standard GB 36 with air draft of 19' 2" should be able to fit without folding the mast.
Our plan is to cruise the western Erie canal, so we need to clear 15'. Will need to lower flybridge enclosure and mast. Our mast will need to be modified as previous owner installed solar panel over the aft cabin and above the hinge on the mast. Found a chart book of the NY Erie canal system on board from 1998. Boat may have cruised there before adding semi permanent accessories. Best I can gleen, a GB 36 is just over 11' air draft at flybridge wind screen.

 

[rslifkin]

A 15' air draft will allow you to go on any East coast ICWs (Intra Coastal Waterway), Erie canal, Champlain canal, Rideau canal, and Trent Severn canal.

Yup, right around 15 feet is pretty much the magic number. If you can fit under the 15.5 foot bridge on the Western Erie, there are very few places you can't go (and most of them are places you'd have no reason to go anyway). From what I can remember, if you can fit under a 15 foot bridge, you can save some bridge openings on the ICW, so the extra few inches helps.



Personally, my design target for any changes I make to my boat is to try to keep fixed objects as close to 14' as possible, definitely no more than 14'6".

 

[jgwinks]

As has been said, air draft differs depending on which Loop route you take. The lowest fixed bridge is south of Chicago and there is no way around this. Believe air draft of this bridge is 19' 8". So in theory a standard GB 36 with air draft of 19' 2" should be able to fit without folding the mast.
Our plan is to cruise the western Erie canal, so we need to clear 15'. Will need to lower flybridge enclosure and mast. Our mast will need to be modified as previous owner installed solar panel over the aft cabin and above the hinge on the mast. Found a chart book of the NY Erie canal system on board from 1998. Boat may have cruised there before adding semi permanent accessories. Best I can gleen, a GB 36 is just over 11' air draft at flybridge wind screen.

Funny thing about that bridge south of Chicago. There's a YouTube video (Water We Thinking) where they started under the bridge and they were scraping the bottom. There was a train on the bridge at the time. They backed out and waited till the train passed and went under with an inch to spare. So if it's really tight, go under when there's no train on the bridge. Also plan ahead so your water and fuel tanks are topped up full. That can gain you a couple inches too.

 

[Old Sea Dog]

So the bridge flexed that much with a train on it. Not a warm fuzzy feeling.

 

[jgwinks]

Yea I thought that too, but they probably all do that. Thousands of tons rolling across. They don't appear to be well maintained, always rusty.

 

[shadowtiger111]

Whoa, I did not get any notifications from all these responses. So I apologize for the delayed followup.


This is GREAT information. Right now, I'm finding it extremely difficult to find a straight answer on boat sales pages. I chose the GB as a control in this comparison, because I found the height in the owners manual, and I ASSUMED, that the 22ft height was from Keel to Mast, so anything below the waterline (displacement depth) would be subtracted from that max height. Leaving me an 18ft clearance. I'm ok with the 19ft passage as this moment. Would I like to do 15? Of course, but that may not be possible.



From everyone's suggestions though, it appears it, as everything in the boating world is... Depends. Air depth is new term, and I'll need to learn more about that. Shorter (Y axis) boats I've found, we start to make spacial sacrifices. It's for sure a balancing act, as I knew it would. Depends though, is going to be the word from now on I use when looking at boats. :lol:


A personal observation on boat design (I am NO BOAT DESIGNER): There seems to be a lot of odd design choices from boat to boat manufacturer.


I'm not a huge fan of the taller cruisers, to me that seem less stable (ie top heavy). But again, sacrifices will need to be made. Its a balancing act. I'm just trying to figure out where the goal posts are, and having the answer be: Depends. Makes things a bit more challenging. :lol:

 

[PhilPB]

Whoa, I did not get any notifications from all these responses. So I apologize for the delayed followup.


This is GREAT information. Right now, I'm finding it extremely difficult to find a straight answer on boat sales pages. I chose the GB as a control in this comparison, because I found the height in the owners manual, and I ASSUMED, that the 22ft height was from Keel to Mast, so anything below the waterline (displacement depth) would be subtracted from that max height. Leaving me an 18ft clearance. I'm ok with the 19ft passage as this moment. Would I like to do 15? Of course, but that may not be possible.



From everyone's suggestions though, it appears it, as everything in the boating world is... Depends. Air depth is new term, and I'll need to learn more about that. Shorter (Y axis) boats I've found, we start to make spacial sacrifices. It's for sure a balancing act, as I knew it would. Depends though, is going to be the word from now on I use when looking at boats. :lol:


A personal observation on boat design (I am NO BOAT DESIGNER): There seems to be a lot of odd design choices from boat to boat manufacturer.


I'm not a huge fan of the taller cruisers, to me that seem less stable (ie top heavy). But again, sacrifices will need to be made. Its a balancing act. I'm just trying to figure out where the goal posts are, and having the answer be: Depends. Makes things a bit more challenging. :lol:

One thing for sure it does give you a lot to consider, ponder, dream and postulate about. For all of that and more you are certainly in the right place for all of those. I have yet to find a better place for experience, wisdom amd humor!

 

[shadowtiger111]

Like, if I could combine Saber, GB, and Mainship designs... That'd be awesome. LOL



I kid. Anyway, atleast the wife is lookin at boats too now, and we're coming up with more questions that are nuanced then my initial research had led me to.



The great loop will be our starter location while we learn the ropes and get integrated into the lifestyle and culture. Finding a boat that gives us the closest thing we'll be able to live with is shifting like water against the hull.

 

[O C Diver]

Whoa, I did not get any notifications from all these responses. So I apologize for the delayed followup.


This is GREAT information. Right now, I'm finding it extremely difficult to find a straight answer on boat sales pages. I chose the GB as a control in this comparison, because I found the height in the owners manual, and I ASSUMED, that the 22ft height was from Keel to Mast, so anything below the waterline (displacement depth) would be subtracted from that max height. Leaving me an 18ft clearance. I'm ok with the 19ft passage as this moment. Would I like to do 15? Of course, but that may not be possible.



From everyone's suggestions though, it appears it, as everything in the boating world is... Depends. Air depth is new term, and I'll need to learn more about that. Shorter (Y axis) boats I've found, we start to make spacial sacrifices. It's for sure a balancing act, as I knew it would. Depends though, is going to be the word from now on I use when looking at boats. :lol:


A personal observation on boat design (I am NO BOAT DESIGNER): There seems to be a lot of odd design choices from boat to boat manufacturer.


I'm not a huge fan of the taller cruisers, to me that seem less stable (ie top heavy). But again, sacrifices will need to be made. Its a balancing act. I'm just trying to figure out where the goal posts are, and having the answer be: Depends. Makes things a bit more challenging. :lol:

First of all, it's "air draft", not air depth.

Secondly, it's extremely rare that a manufacturer would list dimensions as a height from keel to the very top. Draft (below the water) and air draft (above the water) are almost always separate. A small part of the reason is that for power boats, the deepest draft is usually at the propellers and the highest air draft is often in the forward half of the boat. Wouldn't be surprised to find the GB you referenced, has a 22' air draft.

If you're in the looking stage, go view boats with a 25' x 1" tape measure. While not as accurate as the ball, string,and bridge technique, measuring the boat in pieces should get you within 2' or so. Determine the highest fixed point such as a pilothouse roof or flybridge enclosure. Then measure at that point from the waterline to the railing. Then measure from the railing to the top of the roof or enclosure. Have someone help you from the stern of the vessel so that the second measurement is at the top of the roof and the tape measure is reasonably vertical. Adding the 2 measurements and adding a guess for a radar or spotlight will get you in the ballpark. While it's important to know your real air draft, in the looking stage, you really only need to get a reasonable number. Most new boaters can't estimate the approximate air draft of a boat within 3 or 4'.

Ted

 

[ranger58sb]

Whoa, I did not get any notifications from all these responses. So I apologize for the delayed followup.

This is GREAT information. Right now, I'm finding it extremely difficult to find a straight answer on boat sales pages. I chose the GB as a control in this comparison, because I found the height in the owners manual, and I ASSUMED, that the 22ft height was from Keel to Mast, so anything below the waterline (displacement depth) would be subtracted from that max height. Leaving me an 18ft clearance. I'm ok with the 19ft passage as this moment. Would I like to do 15? Of course, but that may not be possible.

From everyone's suggestions though, it appears it, as everything in the boating world is... Depends. Air depth is new term, and I'll need to learn more about that. Shorter (Y axis) boats I've found, we start to make spacial sacrifices. It's for sure a balancing act, as I knew it would. Depends though, is going to be the word from now on I use when looking at boats. :lol:

A personal observation on boat design (I am NO BOAT DESIGNER): There seems to be a lot of odd design choices from boat to boat manufacturer.

I'm not a huge fan of the taller cruisers, to me that seem less stable (ie top heavy). But again, sacrifices will need to be made. Its a balancing act. I'm just trying to figure out where the goal posts are, and having the answer be: Depends. Makes things a bit more challenging. :lol:

The Powerboat Guide includes "Clearance" (air draft) for many (but not all) models they describe.

Ours is listed in the PBG as 18' 8" but that only semi-conforms with the dimensional drawings we have from the builder. From those:
- Waterline to top of hardtop, 18' 4"
- Top of hardtop to top of mast light (highest point), 1' 5".
And that would make the combo 19' 9" -- which at least is pretty close to the bridge reads-outs we were able to get while traveling up the ICW.

For comparison, the PBG reports a GB 42 Europa as 22' 9' but cites that as "Clearance, Mast." Another comparison, PBG says the GB Eastbay Flybridge clearance is 16' 6". A mast is pictured, but apparently not included in their "Clearance" figure.

And of course lots of folks don't have flybridge boats. Sabre, Hinckley, Back Cove, Eastbay, Palm Beach, etc... or Tiara, Cruisers, Sea Ray, whatever...

Secondly, it's extremely rare that a manufacturer would list dimensions as a height from keel to the very top. Draft (below the water) and air draft (above the water) are almost always separate.

Ours does, actually, though I only just now noticed it. 20' 8" from keel to top of hardtop... and they list the "top of hardtop to top of mast light" separate. I guess the number would be useful sometime, perhaps for Travel Lift guys? Otherwise, I've not ever needed to know that...

-Chris

 

[CaptTom]

I think most "trawler" style boats in the 32-36' range are designed to be able to clear 15'. Most 40'ers too.

Pick any boat you like. Chances are very good you'll be able to do the loop with it. Of course, measure before you buy, but don't limit yourself until you've verified that some model just won't work.

By the way, this includes flybridge trawlers. Some love 'em, some hate 'em. I'm in the former category. I never run from below. My point is, don't rule those out, either, unless you're sure you'll never use the upper helm either to run the boat, or just as more outdoor living space.

 

[shadowtiger111]

The Powerboat Guide includes "Clearance" (air draft) for many (but not all) models they describe.

Ours is listed in the PBG as 18' 8" but that only semi-conforms with the dimensional drawings we have from the builder. From those:
- Waterline to top of hardtop, 18' 4"
- Top of hardtop to top of mast light (highest point), 1' 5".
And that would make the combo 19' 9" -- which at least is pretty close to the bridge reads-outs we were able to get while traveling up the ICW.

For comparison, the PBG reports a GB 42 Europa as 22' 9' but cites that as "Clearance, Mast." Another comparison, PBG says the GB Eastbay Flybridge clearance is 16' 6". A mast is pictured, but apparently not included in their "Clearance" figure.

And of course lots of folks don't have flybridge boats. Sabre, Hinckley, Back Cove, Eastbay, Palm Beach, etc... or Tiara, Cruisers, Sea Ray, whatever...




Ours does, actually, though I only just now noticed it. 20' 8" from keel to top of hardtop... and they list the "top of hardtop to top of mast light" separate. I guess the number would be useful sometime, perhaps for Travel Lift guys? Otherwise, I've not ever needed to know that...

-Chris

Interesting, I'll check out that guide for sure. It might get us closer approximation. I don't mind having to mod the boat down those last few feet, if able anyway. I'm not a HUGE fan of the Fly bridge, but I can see the benefits. Better visuals. Anyway, thank you all for the responses. I appreciate it. Wife an I watched a presentation from Great Loop association or something. Was pretty interesting.

 

[Jeff F]

You can also join the AGLCA. They're supportive of concerns like these, and hundreds of successful loopers have done it in a variety of boats. I'm sure any mainstream design could be discussed there. This isn't an unusual concern.

 

[shadowtiger111]

You can also join the AGLCA. They're supportive of concerns like these, and hundreds of successful loopers have done it in a variety of boats. I'm sure any mainstream design could be discussed there. This isn't an unusual concern.

That's the presentation we just watched! I'll join them too.


* AGLCA Does require membership fees to join, to use the forum. So I'll bookmark this for the time being.

 

[sledge]

If you do join the AGLCA and start reading... you will see that the majority of loopers find their passage through the Trent-Severn canal and Georgian Bay is their favorite part of the trip. For this as others have stated, you just need to get under the Chicago bridge, listed as 19' 1". There's a guy Captain John that does a nice job summarizing the stats for your question. see this site:
https://captainjohn.org/Boat1.html

...and I have to agree manufacturers (in my experience) do not list air draft because over the years things change; such as their supplier for the radar mast or arch, plus owners add or remove certain things, etc. If you buy a pre-owned boat you have to measure it yourself to be sure.

 

[shadowtiger111]

If you do join the AGLCA and start reading... you will see that the majority of loopers find their passage through the Trent-Severn canal and Georgian Bay is their favorite part of the trip. For this as others have stated, you just need to get under the Chicago bridge, listed as 19' 1". There's a guy Captain John that does a nice job summarizing the stats for your question. see this site:
https://captainjohn.org/Boat1.html

...and I have to agree manufacturers (in my experience) do not list air draft because over the years things change; such as their supplier for the radar mast or arch, plus owners add or remove certain things, etc. If you buy a pre-owned boat you have to measure it yourself to be sure.

I actually found that Capt John's website awhile back, I refer to it often, whenever I get lost in all the confusing information. :lol:


The AGLCA I just learned of last week.

 

[ranger58sb]

I'm not a HUGE fan of the Fly bridge, but I can see the benefits. Better visuals.

Yes, visibility from a flying bridge is generally better than from a raised pilothouse,, which is in turn better than from a standard (non-raised) lower helm.

But there are flybridges, and then there are flybridges.

A bridge with hardtop and open-able or air conditioned/heated enclosure is a whole 'nother living space... even in hotter (greenhouse) and cooler weather. Imagine having a second saloon. And the hardtop makes a nifty place for mounting stuff. But then the boat might not fit under the Chicago bridge. (Ours -- at maybe 19' 9" including the mast light -- possibly wont... because our radar is also up there, and there's a defunct KVH antenna dome too. I could fold down our mast light, but the radar and KVH are fixed.)

Other hardtop benefits: no worries about snow loading in winter months, don't have to fool with shrink wrapping for storage, dismounting the enclosure panels, etc.

A flybridge with folding bimini and enclosure, maybe with temp control, might or might not be great all of the time. Useful in decent weather, but maybe better to be an adjunct helm station versus the only helm station. But then that's what might get you under the Chicago bridge... if you have a flying bridge at all.

-Chris

 

[shadowtiger111]

Yes, visibility from a flying bridge is generally better than from a raised pilothouse,, which is in turn better than from a standard (non-raised) lower helm.

But there are flybridges, and then there are flybridges.

A bridge with hardtop and open-able or air conditioned/heated enclosure is a whole 'nother living space... even in hotter (greenhouse) and cooler weather. Imagine having a second saloon. And the hardtop makes a nifty place for mounting stuff. But then the boat might not fit under the Chicago bridge. (Ours -- at maybe 19' 9" including the mast light -- possibly wont... because our radar is also up there, and there's a defunct KVH antenna dome too. I could fold down our mast light, but the radar and KVH are fixed.)

Other hardtop benefits: no worries about snow loading in winter months, don't have to fool with shrink wrapping for storage, dismounting the enclosure panels, etc.

A flybridge with folding bimini and enclosure, maybe with temp control, might or might not be great all of the time. Useful in decent weather, but maybe better to be an adjunct helm station versus the only helm station. But then that's what might get you under the Chicago bridge... if you have a flying bridge at all.

-Chris

No winter's for us. I'm a desert rat, no way do I wana linger up north more then I need to. :lol:


Bimini I'm ok with, and looking at Nordhaven's lastnight on Youtube of all places, the boat broker actually mentioned the clearance specifically, and even called out the Chicago bridge. Of course, it did have a foldable mast. But, correct me if I'm wrong, that's not a standard feature is it?

 

[ranger58sb]

Bimini I'm ok with, and looking at Nordhaven's lastnight on Youtube of all places, the boat broker actually mentioned the clearance specifically, and even called out the Chicago bridge. Of course, it did have a foldable mast. But, correct me if I'm wrong, that's not a standard feature is it?

Don't know, but maybe somebody here can answer.

-Chris

 

[rgano]

Even though I knew the Air draft of my GB42 with the mast lowered back to a 45-degree angle, I always remeasured it before setting off on a long trip/cruise. I tape the end of my tape measure's tape to the end of an extendable pole of some sort and stick the pole up to the highest point on the boat. I take the tape to a nearby railing, note the reading and then use a level on a small board which extends outboard over the water. Then I run the end of the tape to touch the water and add the two measurements for total air draft.

BTW most trawlers have a pivot at the bottom of their masts. The trick is to install the hard points necessary to support the rigging necessary to safely lower the mast. I used to be able get mine down from 24 feet to 17 feet in 2.5 minutes. 17 feet was enough for all but the lowest bridges in Florida, Mississippi, Alabama and Tennessee.

Photo shows my mast in its normally lowered position under my boat shed. Blow it up to see some of the tackle.