barryg
Active Member
How much prebend, it says in the book 1/2 the mast width 7/8 ish single swept spreaders rig, seems a lot of tension on the cap shrouds to get there and I have slackend the lowers and back stay is off.
fractional rig setup
- Thread starter barryg
- Start date
NickiCrutchfield
Well-Known Member
Your pre bend is a product caps, backstay and forward lowers. Set the caps up pretty tight, tighten the backstay, then forestay. Tighten the forward lowers to induce the last bit of pre bend. Stabilize with the aft lowers. Then it is just a question of fiddling until you like the shape.
Nicki
Nicki
VicS
Well-Known Member
[ QUOTE ]
it says in the book
[/ QUOTE ] But you dont say which book!
Setting up fractional rigs is a more complex procedure than mast head rigs and does to some extent depend on the angle by which the spreaders are swept back. The Hints and Advice book (595-450 E) published by Selden is pretty good and if that's not the "book" you are referring to then it may well be worth downloading from http://www.seldenmast.com/frameset.cfm?id=5558
You'll find it listed under "Manuals" and "Rigging instruction".
( I do have trouble navigating the Selden website though!)
it says in the book
[/ QUOTE ] But you dont say which book!
Setting up fractional rigs is a more complex procedure than mast head rigs and does to some extent depend on the angle by which the spreaders are swept back. The Hints and Advice book (595-450 E) published by Selden is pretty good and if that's not the "book" you are referring to then it may well be worth downloading from http://www.seldenmast.com/frameset.cfm?id=5558
You'll find it listed under "Manuals" and "Rigging instruction".
( I do have trouble navigating the Selden website though!)
Phoenix of Hamble
Well-Known Member
Yep, its a rubbish website.... trying far to hard to be clever, and succeeding in being unuseable
William_H
Well-Known Member
High Nicki If it is a common fractional rig style then there are no forward lowers. or inner forestay.
The middle of the mast is forced forward by the cap shrouds pressing on the aft swept spreaders.
So cap shrouds induce bend while aft inners reduce the bend.
It follows that the spreaders need to be very robust in producing the aft sweep. I lost a mast through losing the aft sweep on one spreader. So it is worthy checking the structure. ie particularly pop rivets at the back of the mast of the spreader base.
Anyway.... set it up with back stay off (no tension). Loosen the intermediate aft side stays. Tighten the cap shrouds until you get too much static bend then tighten the intermediate side stays to give less bend. The forestay determines the rake only.
The backstay should be easily able to put a lot of bend into the mast.
Of course as said the amount of sweep of the spreaders and amount of set aft from the mast base of the chain plates and the actual fraction of the rig will determine the static bend. ie a 7/8 will not bend as much as a 3/4. (ratio of height of the forestay on the mast to mast height.)
good luck don't try for too much static tension. olewill
The middle of the mast is forced forward by the cap shrouds pressing on the aft swept spreaders.
So cap shrouds induce bend while aft inners reduce the bend.
It follows that the spreaders need to be very robust in producing the aft sweep. I lost a mast through losing the aft sweep on one spreader. So it is worthy checking the structure. ie particularly pop rivets at the back of the mast of the spreader base.
Anyway.... set it up with back stay off (no tension). Loosen the intermediate aft side stays. Tighten the cap shrouds until you get too much static bend then tighten the intermediate side stays to give less bend. The forestay determines the rake only.
The backstay should be easily able to put a lot of bend into the mast.
Of course as said the amount of sweep of the spreaders and amount of set aft from the mast base of the chain plates and the actual fraction of the rig will determine the static bend. ie a 7/8 will not bend as much as a 3/4. (ratio of height of the forestay on the mast to mast height.)
good luck don't try for too much static tension. olewill
VicS
Well-Known Member
[ QUOTE ]
Yep, its a rubbish website
[/ QUOTE ] Especially if you are starting from a bum link
This is the link I should have given but I think you'll have to save the pdf to disk as it does not seem to want to open! http://www.seldenmast.com/firstpage.cfm
Yep, its a rubbish website
[/ QUOTE ] Especially if you are starting from a bum link
This is the link I should have given but I think you'll have to save the pdf to disk as it does not seem to want to open! http://www.seldenmast.com/firstpage.cfm
NickiCrutchfield
Well-Known Member
Apologies all round.Thanks for the correction William.
Missed the word 'fractional'. Must read these things better. I'll delete my previous.
Nicki (humbled)
Missed the word 'fractional'. Must read these things better. I'll delete my previous.
Nicki (humbled)