Shorten the mast at the bottom?

[SvenH]

My boat barely fits underneath a bridge.
Would it be possible to shorten the mast at the bottom without negatively affecting the performance?
There is plenty of space underneath the boom to remove 10 cm .

 

[Wansworth]

Why not

 

[greeny]

My boat barely fits underneath a bridge.
Would it be possible to shorten the mast at the bottom without negatively affecting the performance?
There is plenty of space underneath the boom to remove 10 cm .

Yes but obviously all your shrouds, kicker and mainsheet will need to be adjusted accordingly maybe. It will also change the height of your foresail relative to the deck and therefore the foresail sheet angle to the deck will change slightly. This may mean a change in track position.

EDIT: Oh and also forgot, the forestay will be shorter so will it accommodate the old foresail luff length which may now be circa 10cms too long.

 

[Wansworth]

Yes but obviously all your shrouds, kicker and mainsheet will need to be adjusted according maybe. It will also change the height of your foresail relative to the deck and therefore the foresail sheet angle to the deck will change slightly. This may mean a change in track position.

Ididnt want to mention that?

 

[Minerva]

It feels a lot of work to gain 10cm extra air clearance - hope you don't get any wavelets under your bridge...

 

[Dipper]

My boat barely fits underneath a bridge.
Would it be possible to shorten the mast at the bottom without negatively affecting the performance?
There is plenty of space underneath the boom to remove 10 cm .

Maybe try this?

 

[Wansworth]

Bezos has the same problem,more or less?

 

[Refueler]

I have 3 bridges ... so created A frame to lower / step mast ...

But I am lucky to have deck stepped mast.

Obviously if its just to clear bridge - then I could just lower partly and make fast side stays to control mast from swinging. The video shows mast down for stowing once lowered.

If I had keel stepped - that's a different ball game.

 

[KevinV]

Pump in/pump out water ballast?

You'd need a helluva lot to lower the boat 10cm, much less to heel it over

 

[LittleSister]

You do't say what boat you have, but I would have thought it wouldn't take much of an angle (*see postscript below) of induced heel to pass under the bridge with the current height of the mast.

if you were set on reducing the mast height, I would have thought it would be more sensible to remove the 10cm from the top of the mast.

That would avoid having the boom lower, which is likely to be a pain in the neck (if not serious injury across the back of the skull!), and messing up the mainsheet and kicker angles. You might or might not have to cut down the mainsail slightly. I doubt a 10cm reduction would take much difference at all to the foresail sheeting angle , unless you are a racer (in which case you wouldn't be thinking of reducing the mast height, I guess).

p.s. *The required minimum angle of heel to pass under the bridge should be an easy trigonometry calculation, but I'm rusty. Assuming a 10 metre mast, I think the angle is cosine 9.9/10 (or is it the angle is the cosine of 9.9/10? - somebody kindly reminded me on another thread recently, and I've forgotten already!). I think that pans out to a minimum angle of heel of about 7.8 degrees. For a 20m mast I think it it would be 19.9/20, = only about 5.7 degrees. Someone who knows what they're doing with trig, please check!

p.p.s By my shaky calculations, to get the 85 foot mast under the 65 foot bridge in the video in post #6 would need a minimum heel of 40 degrees, which looks about what they are doing.

p.p.s. If doing this, don't forget to make an extra allowance for waves, the boat being rolled by other boat's wake at crucial moments, changes in water height due to tides and/or changes in freshwater flow, etc!

 

[V1701]

Your wording indicates that it does fit so I would work out a way of making the boat heel enough to give you a bit more peace of mind when going under rather than taking chunks out of the mast. It might be worth asking somebody not on the boat to watch you through to give you a better idea how much clearance you actually have - often more than you think...

 

[Chiara’s slave]

Just rig up some form of ducking stool on the end of the boom, haul it out with your least popular crew member in it.

 

[bignick]

If i was thinking of going under a bridge I’d want significantly more than 10cm clearance!!!!
is 10cm really going to make a worthwhile difference?

 

[dunedin]

If i was thinking of going under a bridge I’d want significantly more than 10cm clearance!!!!
is 10cm really going to make a worthwhile difference?

Actually, in flat water a 1cm clearance is a success - a 1cm non clearance is a bang!
But does depend on how tidal, and whether rain etc impacts actual water heights

 

[Thistle]

My boat barely fits underneath a bridge.
Would it be possible to shorten the mast at the bottom without negatively affecting the performance?
There is plenty of space underneath the boom to remove 10 cm .

Remember that it's the top of the mast that hits the bridge so it's the top that must be taken off, not the foot! Not as daft a suggestion as it may seem at first sight because there are usually lights, wind indicator, VHF aerial, at the masthead so some arrangement for lowering them, perhaps on a hinge, might get you the extra clearance without having to shorten shrouds, cut down sails etc.

 

[Refueler]

Remember that it's the top of the mast that hits the bridge so it's the top that must be taken off, not the foot! Not as daft a suggestion as it may seem at first sight because there are usually lights, wind indicator, VHF aerial, at the masthead so some arrangement for lowering them, perhaps on a hinge, might get you the extra clearance without having to shorten shrouds, cut down sails etc.

Thats something I was thinking about .... its not only the mast itself - but the extras that are usually up there ....

Location : Netherlands ... tidal .. or is it getting under a river bridge that has little tidal range ?

 

[Biggles Wader]

We need some blue sky thinking here------How about making the bridge higher

 

[Refueler]

My boat barely fits underneath a bridge.
Would it be possible to shorten the mast at the bottom without negatively affecting the performance?
There is plenty of space underneath the boom to remove 10 cm .

Any chance you could give us more detail ? Where is bridge ... what is stated clearance of bridge ... what boat you have ..... what is your total air draft including antenna etc ?

Note that bridge clearance is usually stated for HIGH HIGH Spring tides - that is the normal max spring tide ... so this means that often you have more clearance. Applicable of course only where tidal.

Any possibility as I have - to move boat to mooring other side of bridge temporarily when cruising planned ?

 

[LittleSister]

We need some blue sky thinking here------How about making the bridge higher

Or making the water lower?

 

[DanTribe]

But if it won't go under a bridge, surely it's the top that's too high, not the bottom?