opions on rig wanted

[Jack B]

Hi,
i have 17ft triple keeler and want to have some comments on the rig suggested which i believe to strong: diamond shrounds, cap shrouds, two shrounds up to the spreaders, back say forestay. I believe this is a slight overkill, however it must be cosidered this is a dinghy mast, from a firefly i think??
thanks jack

 

[VicS]

Two lower shrouds .... one each side or two pairs?

cap shrouds on swept back spreaders ?

Fractional rig ?

Backstay original for the Firefly or been added?

 

[KenMcCulloch]

It does sound a bit excessive for such a wee boat. Is this a fractional rig with the diamond stays supporting the upper mast, or do the caps go to the masthead? The whole point of diamonds or jumper stays is to support the top section of a mast above the forestay and to transmit the forces from the mainsail and backstay through the rig.

Upper and lower shrouds are often found even on quite small boats especially if the mast section is quite narrow and bendy.

Some pictures might help the jury decide.

 

[Searush]

Dinghy masts are often design to be "bendy", that may be why there are so many stays/shrouds. Cruising boats (& a triple keeler is definitely that!) would normally have a shorter, thicker mast that simply needs to stand up straight.

Don't forget that your boat is MUCH heavier than dinghy & will give less in gusts, so the mast needs to be strong (hence the normally shorter, stiffer design parameters).

 

[Golf Charley]

I agree with all the previous posters and would add the following

The stresses on the mast from the main sail are evenly distributed along the height of the mast, until you start to reef it down

The stresses on a mast for the foresail(s) is a point loading, to wherever the halyard or forestay exits the mast

The previous comment about whether the rig is fractional, ie does the forestay go to the top of the mast, is therefore very relevent,

Non fractional rigs, are in engineering terms simpler, because mast stresses simply depend on forestay and backstay tension

Fractional rigs are more complex, but have the advantage, if set up ok, of being more "tuneable" to suit wind strength and direction.

If this does not make sense, you will get further explanation, but photos would help

 

[William_H]

Mast rigging design

As said it is the stiffness of the boat that makes it more important to have strength in the rigging as compared to the mast's original role as a dinghy mast.
Most dinghy rigs tend to be fractional so I assume yours will be. The degree of fraction is critical. However assuming it is about 3/4 or 7/8 then the top of the mast should not need diamonds for support. (unless it is a really small mast section).
As said however the spreaders should be angled backwards by about 15 degrees and the chain plates should be perhaps 9 inches aft of abeam the mast. This arrangement pushes the middle of the mast forward and that is counteracted by intermediate side stays which also pull from 9 inches aft of abeam the mast. Don't underestimate the downward load from the forestay which can cause a mast to crumple if not supported in the middle.
The backstay could perhaps be omitted which allows for a mainsail with much bigger roach.(as ina dinghy) However a backstay can provide much better rig control in a blow helping to tension the forestay and bend the mast for flatter main with less drag at the top. This backstay can be of spectra or similar rope with a tackle to enable it to be tightened. This is usually done with a pulley on the backstay about 1.5 metres above the deck and 2 branches to the transom one with a tackle. This so that tiller goes in between.
Give us more details good luck olewill

 

[Jack B]

thanks everyone
a few answers
yes it is a fractional rig i would say 3/4 (mast came from a fire fly).
the plan is to have cap shroud on swept back spreaders and two pairs of lower shrods. the backstay is anew idea.
All I have a the moment is the mast,boom and boat no more rigging so we're in the prosses of designing it som we have no pictures of the rig unless you want pictures of the sperate bits.
I am going to have the backstay but I was wondering if the second lower shroud on either side was necsesary
thanks jack