External spinnaker halyard help

[Hydro Therapy]

Hello, I have a Precision 28 and would like to set it up to use a spinnaker. I have a spinnaker from a previous boat I owned. The Precision is a fractional rig. I was thinking I would add a block a few feet above the fore stay/furler. I want to keep it simple so running the halyard externally would be sufficient. The mast is an Isomat but I can't find any markings that tell me the model. I was looking for advise in regards to attaching the block to the mast. I found a masthound on the internet that may be a good option. It is stainless and I'm not sure if that would be a good idea to mount onto a aluminum mast.

Thanks

 

[dlochner]

Precision is still in business, have you contacted them for advice?
Precision Boat Works

 

[justsomeguy]

I was thinking I would add a block a few feet above the fore stay/furler.

I think a "few feet" may be a bit much, where unsupported loads could ramp up if the winds get squirrely.

 

[JRacer]

I think a "few feet" may be a bit much, where unsupported loads could ramp up if the winds get squirrely.

Agree. See the pic. Ours exits the mast about 6 inches +/- above the top of the forestay (and hounds). You get much higher you are asking for the top of the stick to get ripped off in a blow.

 

[justsomeguy]

Mine's quite high above the forestay, maybe 18-20 inches, but I'm hyper-vigilant about what the winds are doing. Needed room for the sock to clear the furler.

 

[Ron20324]

On m B235 I placed a boom bail (bolted through the mast) to hold a spin block. I put a spinnaker shackle guard on the bail on each side of the block. This arrangement allows the block to have a wide swing arc side-to-side.

 

[jssailem]

the block to have a wide swing arc side-to-side.

Ron. This is an important point for anyone considering adding a spinnaker to their sail system.

 

[Jackdaw]

Mine's quite high above the forestay, maybe 18-20 inches, but I'm hyper-vigilant about what the winds are doing. Needed room for the sock to clear the furler.

You really don't actually. Most fractional boats have the spin exit within inches (1-4) of the forestay and are fine with socks. The natural projection of the sail when flying keeps it well clear.

 

[JRacer]

You really don't actually. Most fractional boats have the spin exit within inches (1-4) of the forestay and are fine with socks. The natural projection of the sail when flying keeps it well clear.

Yes, see the pic. That chute uses a sock. It's not completely clear of the top of the forestay but close and it is clear of the furler gear. My estimate of 6 inches +/- in the previous post is a guess. It may be more like 8-12. IMO I would not put the spin halyard any higher than I had to for clean operation so you minimize the loads on the less supported section of the stick above the hounds. Mine is a 7/8 fractional. The symmetrical chute does not use a sock.

 

[Jackdaw]

View attachment 141998

Yes, see the pic. That chute uses a sock. It's not completely clear of the top of the forestay but close and it is clear of the furler gear. My estimate of 6 inches +/- in the previous post is a guess. It may be more like 8-12. IMO I would not put the spin halyard any higher than I had to for clean operation so you minimize the loads on the less supported section of the stick above the hounds. Mine is a 7/8 fractional. The symmetrical chute does not use a sock.

Good advice. These days there is a modern trend (last say 8 years) for fractional boats to fly masthead kites. But in these cases the boats are high ratio fractional (9/10s or greater) and the spar was selected to handle the leveraged load above the hounds. for older 7/8th (or 3/4!) you might be OK up to a foot above the hounds but I'd stop there.

 

[justsomeguy]

You really don't actually.

And the luff of my asym is still too long for light reaching.
I'll let the next owner deal with it.

 

[Jackdaw]

And the luff of my asym is still too long for light reaching.
I'll let the next owner deal with it.

Ah. that's a reason for having it higher as well; so you can straighten the luff!

 

[JRacer]

And the luff of my asym is still too long for light reaching.
I'll let the next owner deal with it.

Sail too big for the boat?

 

[justsomeguy]

Sail too big for the boat?

Ayup. PO used to fly it from the masthead.

 

[Jackdaw]

Back to OPs question, to attach an external block as a fractional spin sheave, these are two most common techniques. The strap-based one on the right is MUCH more secure. The pad on the left relies on a flat forward section of the spar

 

[JRacer]

This is how the J24 (3/4 fractional) was rigged. Spin halyard, forestay (where the hole for the clevis pin is located) and jib halyards all in that exit box and below the upper hounds.

 

[dlochner]

Back to OPs question, to attach an external block as a fractional spin sheave, these are two most common techniques. The strap-based one on the right is MUCH more secure. The pad on the left relies on a flat forward section of the spar

View attachment 142002

Absolutely, the pad eye is relying on the screw threads to hold the pad eye to the mast, at best with a ¼ -20 screw there will be 4 or 5 threads holding things together, unless they somehow the bolts were through bolted. Once the sail is up and full, the sail will be trying to pull the bolts out of the mast. Not much surface area on the threads to hold it together.

The strap puts the tension in shear across 6 bolts. Instead of supporting the load, the bolt threads just keep the bolt attached to the mast. The sail will be putting pressure across the diameter of the bolt and not on the threads.

Another thought, is adding running backstays to support the rig if the halyard block is above the hounds.

 

[Hydro Therapy]

Thanks for the replies, I didn't consider the unsupported load. I will place it about 8-12 inches above the fore stay. The masthound pictured on the right is the same one I was thinking of. This will be a winter project. Need to have the yard lower my mast. I'm not courageous enough to scale the mast.

 

[JRacer]

Thanks for the replies, I didn't consider the unsupported load. I will place it about 8-12 inches above the fore stay. The masthound pictured on the right is the same one I was thinking of. This will be a winter project. Need to have the yard lower my mast. I'm not courageous enough to scale the mast.

Good choice on the placement and the fitting type to use. And, definitely a job to be done on the sawhorses.

 

[jssailem]

masthound pictured on the right is the same one I was thinking of

These guys know their stuff. They have given you spot on info. The Masthound is how I designed attachement for my fractional trailer sailer to accommodate an asymmetrical spinnaker. Worked great. As Dave indicated it is the way that the forces will be pulling on your mast. The Masthound solves that problem. The threaded screws can be sized so that when in the mast they do not interfere with any in mast lines or wires.
Send us a finished image and report of your install.