mast-mounted optics and bridge clearance

Gary_H · Feb 28, 2011

I would think that there would be a lot of neat possibilites of having a mast mounted camera especially if it had Pan-Tilt and most of all Zoom features.

Tim R. · Feb 28, 2011

That "weather resistant dome" appears to be meant to be mounted under an eave or other structure. If you flip it, I bet it will not be so "weather resistant". Between the moisture leaking in and the UV rays I bet you will be lucky for one whole season. Besides, I do not think this will help you very much. The view from a camera has no depth perception and you will be hard pressed to determine the height of the span before it is too late.

Optical zoom is a great feature if you are completely still. Mount it on a mast and it will be jumping all over the place.

The final problem being that it requires two 110v ac wall brick power supplies. If the output is 12v or less you may be able to get away with not having to use a generator or inverter for power.

Use your well earned boat bucks on something better.

kloudie1 · Feb 28, 2011

Neat idea, Snotter, but I'd think that without some sophisticated camera/video stabilization, the motion up there would keep ya from being able to see very well, except in calm water like the TennTom.. Probably an excellent idea for your exact use !

Dan Johnson · Feb 28, 2011

Snotter...

I remember seeing a pic on the forum some time ago that was about someone who would rent water drums at a bridge site. They would be attached to the end of a boat's boom, swung over the side and filled to the point that they would heel a boat enough to get under the bridge. The main halyard was lead to the boom end for compensation.

The size and weight of your Morgan may bend the boom first before enough heel was obtained, but you get the idea...

PS: why not just mount one of those small, cheap outdoor security cameras the size of your thumb at the masthead as you would only need it on very specific occasions. Less weight and limited functionality but...

capejt · Feb 28, 2011

Something else to consider, though it's not a biggie. These cameras run on 9 volt DC (I used to use them at home). That just means you'd have to run another line up the mast for power, or send someone aloft when a new battery was needed. I also agree with the comments abot the "stability" factor.
I think Raymarine makes something like what you're looking for, but at about twice tghe price of the x10.

kloudie1 · Feb 28, 2011

You can definitely play with the trig and get a solution.. Say you were standing on the bow and your sextant reading is 9 feet above the water.. you get a 77 foot long rope and pull the tip under the largest bridge clearance with the dink (so you are 77 feet back from the clearance section) ..Take a reading on the lowest steel at the point you want to go under.. if you read 30 degrees or more, you would have 53.5 feet of clearance.. That is a lot easier said than done accurately.. I dunno

Stu Jackson · Feb 28, 2011

Since you're probably not the first person who has a mast going under these bridges, shouldn't there be somewhere (online) that posts this information? Don't charts have this stuff (knowing it's an inland waterway and all that)?

An easy way to use kloudie's suggestion is do distance off with your GPS and play the trig. Still easier said than done.

Bill Roosa · Feb 28, 2011

Determining bridge clearance

First things first: If it is on navigable waters the bridge clearance will be on your charts. Measured at MHW so you can be sure that it will be more than that except when there is exceptionally high water or flooding.
The height of the mast is:
H(heeled)=H*cos(angle of heal)
where H is your mast height above the water and the angle of heal is measured from the vertical.

All you need is an inclinometer and a way to heel the boat that much. I have used the halyard attached to a dingy 3/4 full of water in a pinch to get me off the sand bar but it was not pretty and I needed to use a kledg anchor to hold the dingy in place. Since you will have to heel the boat AND move it some distance I don't see how you are going to accomplish it. Course necessity is the mother of invention.

Don12364 · Feb 28, 2011

How would you know it was looking horizontally? If there was a sea horizon behind maybe, but in congested waters you would have difficulty in finding a level.
Even a person moving from cockpit to foredeck could make a clearance look possible when in fact it was not. Tanks empty or full?
BTW I am the worlds most nervous bridge ducker. I do the calculations over and over again - yet am still weak at the knees when the masthead passes under.

I do have a CCTV camera mounted at the base of my mast looking ahead under the jib and showing on a TV below decks. It is a 12V unit originally working from a mains power supply and intended to watch your approach drive and front door. Works just fine and I use it for keeping a lookout when single handed and need to go below to do some navigation (or for a leak). It even spots lobster pot marker buoys.

Jim Kolstoe · Feb 28, 2011

Snotter, for the use you propose, I think you would do as well, and a lot cheaper, to put a laser pointer on a self-leveling mount at the top of your mast, then look to see if the beam hits the bridge as you approach. I don't know of anyone who's tried such a set-up, and I don't need it for lake sailing, but it occurred to me when I read your post.
Good luck. Jim Kolstoe, h23 Kara's Boo

kenn · Feb 28, 2011

Bill R has the definitive answer.

Still.... such a camera could possibly be useful, but you'd really need to lock it's vertical tilt, cos I don't think cheapie pan-tilt mechanisms will reposition the camera reliably.

I would also calibrate the vertical angle in this way:
- Assuming your in-water mast height is X above the water level, I would find some vertical landmark (eg bridge pier

good luck with that) and put a visible mark at X above the water
- I would position the boat maybe 150 yards off of the marked thing and adjust the camera angle so that the mark is centered vertically, then I'd back away then sail towards the mark, confirming that the mark is still reliably in the vertical center. This is about the oly way you're going to set the camera to be looking exactly parallel to the water.

Try not to hit the bridge pier or landmark while doing this.

Many small cameras can be powered by the coax (and there's also easy hacks to add this), so you may only have to run a single coax to the masthead.

[edit] Jim's laser pointer idea is genius. You'd still need to ensure it's aligned to shoot out parallel to the water.

And for God's sake put a switch on it! You don't want lawsuits from tourboats whose higher decks get zapped by your laser.

Gudenuph · Feb 28, 2011

Snotter said:
Come April I will be dropping my mast for a couple of months to do maintenance. I have been considering mounting a pan-tilt video camera such as the one at http://www.x10.com/promotions/vk79a_ed_399_special.html . My reasoning is that having a video camera at the top of the mast that looks straight out would help me to to determine bridge clearance. Since the bridge clearance of my Morgan is 53.5", this would make it possible for me to transit the Ten-Tom waterway with the mast up, provided I figure out how to heal the boat 10 degrees. I would like to hear of what other sailors think and if any others have tried this; or, if there is another way to determine bridge clearance such as using a cheap ladar.

The battery powered, self-leveling lasar beam mentioned earlier in this thread sounds great. It could be hoisted as needed on a spare halyard. I'd tilt it slightly up from horizontal so you could watch the spot decending on the bridge structure. In the dark we used to use a spot light, held as high as possible, aimed at the masthead. We would then watch the masthead's shadow to the same effect. On a bridge we passed under frequently on tidal waters we discovered that if the barnacle-darkened exposure on the bridge pier or bent was taller than it was wide, we could pass safely. Another option would be to find a "witness" rock or object on shore which if uncovered would indicate safe passage.

FWIW, Geohan

All U Get · Mar 1, 2011

Snotter said:
Since the bridge clearance of my Morgan is 53.5", this would make it possible for me to transit the Ten-Tom waterway with the mast up, provided I figure out how to heal the boat 10 degrees. I would like to hear of what other sailors think and if any others have tried this; or, if there is another way to determine bridge clearance such as using a cheap ladar.

Hi Snotter,
A while ago there was a link showing a boat with a bladder full of water pulled abeam to get the heal needed to get under a bridge. The set-up was simple and effective. My question would be some math to determine how much heal would be needed. If my mast height is 50' perpendicular to the water, at 20 degrees what would the height be? If it's a right triangle, I get about 47 feet. Hope this helps. :zzz:
All U Get

sailormanbigd · Mar 1, 2011

i think there is a limit to how much heal angle the motor will operate or should be operated at, so you would need to be towed through the bridge.

sailormanbigd · Mar 1, 2011

also, i could see a capn stareing at the laser pointer light on the bridge overhead and run into the uprights or anything else.

Bill Roosa · Mar 1, 2011

Move all your gear high up in the boat and partially flood her. If you seal up the engine air intake or run a hose up to the cockpit you can run engines underwater. It is a mess to clean up though. Perhaps you should consider renting a different boat for this part of the trip.