Rigging an Asymmetrical Spinnaker

[SV_Funday]

I have purchased an asymmetrical spinnaker for my 2007 Beneteau 49. I need help determining the size and load capacity of the following blocks.
- Single Block for tack. Connects to front of bow roller anchor. 7/16 line
- Single snatch block and single block with becket for tweaker. To be mounted 33' from bow.
- Singe block with becket on aft cleat to bring the sheets (7/16") to the aft winch

Beckets will be used with bungee cord to keep blocks from hitting the hull/deck.
Spinnaker area is 1500 sf
I feel the tack block and aft sheet block will take most of the load.

Any help would be appreciated.

Thank you.

 

[Babette04]

Good luck with your engineering question
I found with the fractional rig my spinnaker sock was getting caught in the running for the roller furling.

I popped the mast cap, added two extra sheaves and ran the spinnaker halyard up and through.

there were square “sharp” edges on the mast cap That I rounded/ smoothed with a Dremel drill to prevent fraying of the halyard.

works great

 

[Paul356]

Don't mean to be flip, but it seems like these are questions your sail provider should best answer.

 

[joelm100]

I'm really interested to hear how this project is going for you. I have a new-to-me Hunter 380 and would love to put up an asym one day. Are you using the existing bow roller or are you reinforcing it some how? Did it have the necessary connection points or did you have to drill?

 

[jssailem]

Joel. Though you have a "similar" boat, It is not a guarantee that your boats are going to be the same.

I suggest the best path is to identify how you will connect the boat to the sail. Do you have a solid place to attach the sail? The Bow roller can be a solid connection. I use the bow roller on my boat.

 

[AaronD]

I have purchased an asymmetrical spinnaker for my 2007 Beneteau 49. I need help determining the size and load capacity of the following blocks.
- Single Block for tack. Connects to front of bow roller anchor. 7/16 line
- Single snatch block and single block with becket for tweaker. To be mounted 33' from bow.
- Singe block with becket on aft cleat to bring the sheets (7/16") to the aft winch

Beckets will be used with bungee cord to keep blocks from hitting the hull/deck.
Spinnaker area is 1500 sf
I feel the tack block and aft sheet block will take most of the load.

Any help would be appreciated.

Thank you.

@SV_Funday : You might find the Harken calculators helpful (specifically the genoa sheet load calculator).

Calculators | Harken Marine

www.harken.com

Caveat - there are lots of unstated assumptions baked into those calculators. I would trust your sailmaker more than an opaque online calculator, but it probably gives a good order-of-magnitude estimate, at least for the sheet loads. The tack is harder to estimate. E.g., see the discussions at Assemetric Bow Pole Calculation

 

[Parsons]

Depending on the wind strength you plan to use this spinnaker, 7/16 line (10 mm) line is both comfortable to hold and strong enough for your applications for higher performance line, but for basic line (NE Ropes StaSet), safe working load (at 20% breaking) is less than a ton so you may want to consider selection. Samson Ropes provides a formula to calculate the amount of force on the clew: (windspeed in mph)^2 x 0.004 x (sail area in square feet) = Sheet Load at Clew in pounds - Recreational Marine - Samson Rope . The blocks to handle this line will all be well over a ton, so that will not be a limiting factor on safety. Be careful of splices and knots as those reduce your line strength.

You are incorrect to say that the forces will be greater on the clew and tack than halyard - that force will be divided equally among the three points.

 

[fupls]

The bigger boat the stronger the anchor point for the tack is required. Bow roller is not strong enough to handle the force unless you have some reinforcement underneath. I used to simply attach the tack to bow roller but eventually I installed a removable bowsprit for more safety concerns.

 

[SV_Funday]

Thank you all for your comments and advise. I contacted Beneteau and they sent me the factory Genneker setup PDF. I have attached it in case it can help someone else.

 

[justsomeguy]

Do you have a solid place to attach the sail?

This.

 

[sailme88]

ATN Spinnaker Sleeve and ATN Tacker - YouTubehttps://www.youtube.com › watch