New to me swept spreader rig for my build

Bespoke

New member
I have acquired a 53' two spreader (swept) rig from I believe a hunter 40.5.

While not my ideal it has dropped into my lap and I would love some advice. I wish to turn it into a cutter rig. Mast placement on my boat has a j measurement of 18'6". My boat is 44' long. My question is...

My plan calls for a cutter rig with a 53' mast and a rake of (I believe) 18". Will need to confirm. 

Where do I place the three contact point chain plates? 

Do I go straight down and then rake the mast? Do I go straight down then back 18" for the rake? Please help. Need to place these plates as new to me mast going up in two or three weeks. 

Any input would be appreciated 

 

longy

Overlord of Anarchy
6,768
1,127
San Diego
The chainplates need to be placed so that the upper shrouds (V1, V2/D3) are in a straight line from masthead to deck. 18" is an extreme rake, double check that.

 

Go Left

Super Anarchist
4,932
404
Seattle
Presumably there was a designer for your hull?  Why don't you ask them?

Check the angle of the spreaders and contact the Hunter people and see if they have a set of line drawings.  I suspect that the spreaders are set at a 15° angle aft, but it could be as much as 25°.  But the rake should be established by where the center of lateral resistance for your hull is located and how the sailplan's center of effort balances the boat.  

 

Go Left

Super Anarchist
4,932
404
Seattle
The chainplates need to be placed so that the upper shrouds (V1, V2/D3) are in a straight line from masthead to deck. 18" is an extreme rake, double check that.
On a 2 spreader rig, aren't the shrouds labeled D-1, D-2 and V-1 or cap shroud?

 

El Borracho

Verified User
6,665
2,643
Pacific Rim
The chainplates need to be placed so that the upper shrouds (V1, V2/D3) are in a straight line from masthead to deck. 18" is an extreme rake, double check that.
By “in a straight line” do you mean “in a plane”? The first estimate for chain plate position would be the same distance aft and athwartship from the partners as the lower spreader tips are from the mast. Mast rake could cause that point to move aft very slightly. Structural issues could cause the point to move aft and outwards a little bit along the spreader angle.

Some rigs appear to have some curve to the shroud plan as if mast bending forces are desirable as the boat heels. Certainly the opposite is to be avoided.

Probably far more complicated than it first seems. 

 

sailorman44

Member
281
71
CT/FL
You need to talk to a navel architect before you do anything. Well intended armature advice is still amature advice. 

[SIZE=large]That said, I'll tell you what I know. If your new mast is from a not too old Hunter then it is a B&R rig. B&R rigs have swept spreaders, reverse diagonals to[/SIZE][SIZE=large] [/SIZE][SIZE=large]induce[/SIZE][SIZE=large] [/SIZE][SIZE=large]mast bend and rake. Look at any Hunter. 18 inches of rake is not[/SIZE][SIZE=large] [/SIZE][SIZE=large]extreme. My Boat, which has a fractional three spreader B&R rig has a 35 degree sweep on the spreaders, 11 inches of mast bend at the center spreader, 54 inches of rake and no back stay. [/SIZE]

 
Something which hasn't been mentioned is the relationship between the center effort of the sail plan and the center of lateral resistance.


 
Just because the mast has swept spreaders now doesn't mean that they couldn't be straight.  No reason that you couldn't replace/modify the spreaders to be straight. The main reason for swept spreaders is to get rid of the  back stay.  


 

sailman

Super Anarchist
8,323
436
Portsmouth, RI
Based on your location I think your best bet would be to hire Bob Perry to consult on this change.  It's short money to keep the rig upright.

 

longy

Overlord of Anarchy
6,768
1,127
San Diego
On a 2 spreader rig, aren't the shrouds labeled D-1, D-2 and V-1 or cap shroud?
On normal discontinuous rigging

 D = diagonal, V is vertical

So - D1 is lower shroud.  V1 is lowest segment of upper shroud (deck to low spreader)

      D2 is intermediate  Low spdr tip to mast at base of upper spdr)

    V2/D3 is upper shroud from tip of low sprdr, thru tip of upper sprdr, then to mast. No joint at upper spdr tip, just bending over sprdr. If there IS a joint there, than you have a V2 and a D3 separately

 

longy

Overlord of Anarchy
6,768
1,127
San Diego
By “in a straight line” do you mean “in a plane”? The first estimate for chain plate position would be the same distance aft and athwartship from the partners as the lower spreader tips are from the mast. Mast rake could cause that point to move aft very slightly. Structural issues could cause the point to move aft and outwards a little bit along the spreader angle.

Some rigs appear to have some curve to the shroud plan as if mast bending forces are desirable as the boat heels. Certainly the opposite is to be avoided.

Probably far more complicated than it first seems. 
Yes. Move your viewpoint aft until you remove the sprdr sweep angle - now the outer shroud should pass straight down thru sprdr tips and chainplate

 

Go Left

Super Anarchist
4,932
404
Seattle
You need to talk to a navel architect before you do anything. Well intended armature advice is still amature advice. 

[SIZE=large]That said, I'll tell you what I know. If your new mast is from a not too old Hunter then it is a B&R rig. B&R rigs have swept spreaders, reverse diagonals to[/SIZE][SIZE=large] [/SIZE][SIZE=large]induce[/SIZE][SIZE=large] [/SIZE][SIZE=large]mast bend and rake. Look at any Hunter. 18 inches of rake is not[/SIZE][SIZE=large] [/SIZE][SIZE=large]extreme. My Boat, which has a fractional three spreader B&R rig has a 35 degree sweep on the spreaders, 11 inches of mast bend at the center spreader, 54 inches of rake and no back stay. [/SIZE]

 
Something which hasn't been mentioned is the relationship between the center effort of the sail plan and the center of lateral resistance.


 
Just because the mast has swept spreaders now doesn't mean that they couldn't be straight.  No reason that you couldn't replace/modify the spreaders to be straight. The main reason for swept spreaders is to get rid of the  back stay.  
Except in my post nine hours before yours. But who's counting.

 

Bespoke

New member
Based on your location I think your best bet would be to hire Bob Perry to consult on this change.  It's short money to keep the rig upright.
Yes and it is quite possible my plans were on his table when he was a lad.

Boat has never been sailed, or motored for that part. Believe it was a small production run out of Vancouver bc.

Might give old Bob a rash to jar his memory back that far:)

I will reach out to him

Thanks 

 

Bespoke

New member
The chainplates need to be placed so that the upper shrouds (V1, V2/D3) are in a straight line from masthead to deck. 18" is an extreme rake, double check that.
Thanks I did check and what is called for on original sail plan with straight spreaders is 6".

I acquired this complete rig for a deal I could not afford to pass.

I need to making work and will I am sure. Am hoping to launch before years end

 

hdra

Anarchist
652
145
Thanks I did check and what is called for on original sail plan with straight spreaders is 6".

I acquired this complete rig for a deal I could not afford to pass.

I need to making work and will I am sure. Am hoping to launch before years end
Take the savings on the rig and spend $500 of it on a naval architect to help you figure this out.  

 

Bespoke

New member
What kind of yacht is this? Sounds interesting. 
This sailboat is an old barn find. Pretty much abandoned in a marina land shed.

She stared at me for near twenty years across from where I worked. Couldn't take it anymore and had to have a look. 

She was nothing but a cap and hull.

If she wouldn't have looked so good and cried out so loud she would still be there. We all know I probably should have left her there. Six years later...

She is waiting for a bit of dry weather for her final topsides spray and heading for the water. Fully functional and only in need of finish work inside.

I more year while using in water.

She is a small production run of a 1970s Bruce Roberts offshore 44.

Laid up in Vancouver BC 1980 

Never sailed 

Which is  why I believe through early advertising that she once sat on the drafting table of Robert H Perry. 

Only he could tell that story. 

Maybe one day I will hear it

 




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