Setting up a temporary bowsprit

[TiggerToo]

Does anyone have any idea what sort of forces are likely to act on a bowsprit? I am wondering whether a temporary removable one could be set up with the spinnypole.

 

[fireball]

You really want the spinny pole in compression as that is how it is designed - if you're intending to set a cruising chute off it then there will be significant up-sideways force on the pole - so you'll need to stay it - ideally triangulated, 1 below and 1 either side.

That said - if the pole has a thick enough wall and the extension is short then you may well get away with it.

 

[rudolph_hart]

Ours has a standard set-up to use the spi pole as a bowsprit, by poking it through a rubber-lined s/steel eye welded to the pushpit.

Pole is about 100mm dia, is about 4 metres long, and only 1 metre of it protrudes as a bowsprit. The inboard end clips to a bracket on the sidedeck.

To give an idea of forces it can stand, the crusing chute we fly (set?) from it is 13.6 x 7.7m.

Hope this is useful.

 

[lw395]

I was thinking of doing something similar with the cruising chute on my Lightwave, just to get the kite away from the forestay etc. When I bought the kite from Kemps, I did ask what the load might be on the tack, the answer being "Lots".
If I ever get aroung to this I will use a length of ali scaffold, secured to the anchor pulley, with the inboard end bearing down on the forward bulkhead at the back of the anchor well.
Cheaper than bending my carbon pole!
Would be interested in other peoples experiences.
Chris

 

[fireball]

Scaffold is also supposed to be used in compression - you might be better off with a bit of galvanised scaff - I believe it has thicker walls ....

 

[michael_w]

To fly my assy, I've rigged an extra downhaul through the anchor roller and taken it aft. The boat is normally rigged with single sheets + guys and gybes end for end.

The regular spinnaker pole is set very low to skim over the top of the pulpit. The forward down haul is clipped on to the tack along with the guy.

Sets well from very close reach through to about 150 degres AWA. Only pain is being single sheets, it has to be dropped to gybe.

 

[grievesie]

I know it's a bit more expensive than a scaffold pole but I've used a Selden gennaker pole system quite a bit on a Sweden Yachts 390 that I crew on. The pole is 75mm diam alloy with 4mm wall and fits through a ss ring welded to the pulpit/anchor roller - it extends forward of this by about 1m of its 2.5m length and is unsupported. The downhaul runs through the pole to a fairlead fitting on the forward end. The fitting on the aft end is like a spinnaker pole piston that secures to a Wichard folding padeye on the deck. The pole is used with a crusing chute (1100 sq ft) on a Bamar Rollgen furler. The Rollgen halyard needs to be bar tight in order to furl the chute properly but the pole seems to cope with the load OK. Photo shows the boat alongside with the pole deployed.

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I should think this setup could be replicated using a spinnaker pole reasonably cheaply on a smaller boat.

 

[smth448]

Using the spinnaker pole will probably be OK as long as you do not stick it out of the front of the boat too far. It is made to work in compression and you can break them by letting them bend too far round the forestay on a tight reach in a blow. On our J-92 the bowsprit is made for the bending forces applied to it. When sailing on a reach the load on the tack line is higher than the sheet or halyard as the sail is trying to lift the boat up. The bowsprit is carbon fibre with a diameter of about 100mm and a wall thickness of 10mm (ish) so is immensely strong. It still bends like mad under load. If you set an assy from a pole as a bowsprit you will break the pole if you play in too much wind. You could always set up like the Americas cup guys do and use th epole the conventional way but then you might as well use your normal spinnaker

 

[simonfraser]

harken do a page on tack loads for sails

i fly 30 m2 off half a carbon fibre windsurfer mast, stayed 3 ways

 

[William_H]

So you have the choice of unstayed pole not pushed out far or of staying the pole.
The old true bowsprits were always stayed down to the bow at the waterline and aft on each side.
That is what you need to do especially staying downward unless your pole is short enough and large enough to go unsupported.
A spinny pole in normal use is well stayed by the sail and the down haul. olewill

 

[pampas]

Have just made one from thick walled alloy tube that just slides in thick walled box section bolted to deck with 4 bits of 3" angle, protrudes 27" and retracts when not in use, got the idea from that new fangled thingy for £1200 + Works well with the cruising chute and is strong enougth for the the job. Mind this is for a 24`vessel I say vessel as it carrys water as well. /forums/images/graemlins/laugh.gif