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Go Back   SailNet Community > Skills and Seamanship > Seamanship & Navigation > Air Draft vs. Bridge Height vs. Heel
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Thread: Air Draft vs. Bridge Height vs. Heel Reply to Thread
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Topic Review (Newest First)
02-07-2012 11:42 PM
sailingfool FWIW don't you have a 8-10 foot tide height there? If so, about half the time you may find enough clearance to squeak under ( maybe skip the masthead fly), or a more modest heel may be needed. Maybe near high tide you'll just need to wait.

I race on a boat with 7 foot draft, low water level in the harbor channel is 5-6 feet, so within an hour or so of low we need to heel the boat as needed. I would say swinging the boom out with two people on the end is good for about 30 degrees.
02-07-2012 08:26 PM
fallard Half an hour is not that long. I have to go through 2 drawbridges-one of which is opened at hourly intervals at :40 past the hour. I've been doing this for 40 plus years. Healing my boat is not an option.

We sailboaters have learned to schedule our sailing around the tides, which are normally on a 6 hour schedule. If you are in so much of a hurry that you can't live with a half hour schedule, maybe you should get a power boat.
02-07-2012 08:06 PM
PCP Get the help of a motor boat. Ty the mast to the motorboat in a way you maintain the 40º heel. Now you have a strange cat but your boat should be stable sailing at 40º of heel and most of the steering can be made by the motor boat.

Regards

Paulo
02-07-2012 07:37 PM
HUGOSALT Heeling to that degree is not a viable option on an ongoing basis.
You mention the big blue sea, might you have a tide, that could range up to 8'+ in your neck of woods. Bridge clearance is published
based on mean high water...so if assumptions above are close you
may have about half time that you clear...??
If close remove vane, but I would bribe a buddy with a dinghy/powerboat and check out first with a few 10' lenghts of pvc.
02-07-2012 06:58 PM
Rockter Your trigonemetry is correct.

The heel angle needed for the 19 ft bridge clearance is given by...

a = invcos{19/25} = 40.53 deg

...and for the 21 ft bridge clearance...

b = invcos{21/25} = 32.86 deg.

Those are first estimates, as the mast will not pivot perfectly around a single point as the boat heels.

Those are quite aggressive heel angles.

It's a risky business though. If you get it wrong, you will smash the masthead and fittings on the bridge. You may even bring the mast down.
.
02-07-2012 06:13 PM
hellosailor Forty degrees is awfully close to halfway broached. If you're going to do that on a regular basis, put the video on utube, sell advertising space and tickets for the live performance, because folks don't get to see that very often.

You probably CAN do it, but wouldn't it be more fun to dynamite the bridge?
(Now kids, don't do that at home, dynamite is strictly for professional use under adult supervision!)
02-07-2012 06:06 PM
AdamLein
Quote:
Originally Posted by CarbonSink62 View Post
the bridge only opens on the half hour it seems like I could save some time.
Lucky you. My bridge is plenty high but I can only buck the tide twice a day.
02-07-2012 04:27 PM
CarbonSink62 I guess 40 deg is pretty far.

I'd feel pretty stoopid if I got stuck under there!

A more moderate heel of 20 deg only shaves 1.5' off the air draft.

So, it's good to know what it would take but not worth the risk for such a small gain.

Thanks for talking me down off the roof.
02-07-2012 04:08 PM
sailortjk1 Every half hour is very fortunate if you ask me. How much time are you going to save?
Not worth the risk in my opinion.

Does the mast step have a tabernacle? See where I am going with this? If you’re in such a rush to get out, it might ne easier to drop the stick on an 18’ boat and re-step it on the other side of the bridge.
02-07-2012 04:08 PM
JordanH Will you still have proper steerage and propulsion at 40 degrees of heel?

The mentioned video is this one: Boat Balls - YouTube

How will you attach the water bags to your masthead? If the sheaves are fixed, will the halyard jump out of the track and jam? How long will it take to rig, and will the time (and risk) savings be worth it?

Have you had the boat over that far before? I know our Contessa likes 15-25 degrees of heel, but our narrow hull likes it over that far before it locks in. I wouldn't feel comfortable at 40 degrees... and inanimate objects in the cabin and the animate objects in the cockpit wouldn't like 40 degrees either.
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