Thursday, August 26, 2010

505 Double Pole Conversion - Part 1

Because two poles are better than one...?

Over the past two weeks, I have been converting 7346 to the new must-have 505 boat candy double spinnaker pole system. First of all thank you to Macy and Brendan and others in the US who provided a lot of good information to help the rest of us rig the system with minimal hassle. I am not done yet, but seeing other people's ideas always makes it easier to execute.

The double mast fitting that I used was sourced by JB from South Africa. I was very impressed by the fit and finish of both the end fittings and the mast fitting. I stole the extra spinnaker pole for this off of JB's broken boom. The issue with using once-single poles is that they will likely be too short for the double setup. The rule states that the pole length must not exceed 2516mm. The interpretation I have heard for this rule is that if you were to remove the pole from the boat and measure it, that is the total length. Therefore, the ring or thimble on the outer end does not count as part of the pole length. However, the fork fitting on a single setup does. The double allows you to have a longer "effective pole length" due to this rule interpretation.

Although it probably wasn't necessary, I turned up some new outboard ends to get the maximum length from these poles as they had already been cut and used in a single pole system. The provided inboard ends also needed to be turned down to match the dimensions of the spinnaker poles. Note that on the inboard end, the shockcord will pass though the pole then will be dead ended outside the pole. This will keep the launcher line from rubbing on a shockcord knot inside the tube.

A new cleat arrangement was added on the deck on either side of the mast gate. Note that swivel cleats are less necessary with the double pole system as you will only be launching each pole from it's respective side. The cleats can be angled outboard towards the crew. I was set up with auto-twings(R.I.P. great idea) previously, but needed to convert to a separate sheet/guy system for the double poles. I utilized the auto-twing lead along the seat tanks for the guy adjustment line to be lead aft to the skipper.

Below are some shots of the lead mock-up and the shock cord take-up in the back of the boat.

My boat came with some large Harken bullet thru-deck blocks on the foredeck for the twing to pass through. These would not be acceptable for the load and angle of the guy adjustment that I was installing. In an effort to cover the holes and provide a proper lead for the guy, I decided to make some angled risers inspired by a system on Augie Diaz's USA8629. The first step was to make the shape I wanted out of extruded polystyrene foam and to make the boat into a male mold for the part. Packing tape works great for this type of thing.

I laid up the part with 6 layers total of carbon and glass(no science here, just shooting from the hip). I am getting a little better at the vacuum bagging thing, but I think I still have a lot to learn. I tried to keep the vacuum cups off of what the final part would be to avoid dimples. This would have been impossible without bagging.

The part un-molded quite nicely as I coated it lightly with Mclube before the lay up. Epoxy will not bond to the tape, but this makes it come off even easier. The hardest thing to do is get the peel ply and bleed fabric off the part. Start by trimming with scissors and use a knife to start it from the corner. The upper surface would need to be sanded and faired due to the peel ply and male mold method. The surface finish on the underside was quite nice, but making a plug and female mold for this would have been impractical as both port and starboard sides are unique.

The parts were trimmed sanded and faired. They were then painted with rattle-can gloss black. Clear coat carbon would have been added hotness, but it would have been more work.

These parts would accept a Harken 29mm cheek block which would turn the guy through the foredeck at the proper angle. I filled the back of the part with epoxy and colloidal silica then drilled and tapped the part with 10-32 fasteners. These cheeks are designed to take #8 hardware but can be drilled out to accommodate larger ones.

Drilling the diagonal hole for the line to lead was one of the more challenging aspects to this idea. Basically start small and to a lot of measuring/sighting to make sure you are drilling the direction you want to be. I filled the holes and bonded in some G10 tubes in one operation. I was very happy with how this idea worked out.

I also bonded in a G10 tube and backing plate for the forward turning block. The parts were bonded to the deck. Note the two fasteners through the part on the rail are for an eyestrap mounted inside the boat. these were helpful to do before bonding to help make sure it was aligned properly. I coated those fasteners with Mclube before the glue-up so that I could get them out after the epoxy set.

Here are some pictures of the finished guy lead. Note the photo from under deck. The eyestrap is for the final turn of the 5:1 purchase before the control line leads aft along the path that was used previously for the auto-twing line.

The inboard end of the 5:1 purchase is mounted to eyestraps on the CB cap. I also used a 1/8" G10 backing plate under these eyestraps for a bin more strength. Another great use here of the Harken ti-lite doubles. This is a custom part, but I would like to see this become a stock part in the catalog. Because this system uses all 29mm sheaves, there is very little friction. The 16mm blocks are great, but a commonly overlooked factor in control system design is the ratio of line diameter to sheave diameter. The smaller the line or the larger the sheave, the less friction there will be.

The fore guy is a reverse 1:6 purchase. Both poles draw line from the same purchase as shown below.

I am going to be on vacation next week, but when I get back I will have another post detailing the rigged system and how it functions. More pictures can be found HERE.

Monday, August 23, 2010