SC 20 restore part 2

[Bruiser]

Really impressive. She is going to be beautiful.

No question that is looking great.

[Bill Roberts]

Mac M,
You are doing a great job restoring that old SC20. It will be better than new when you get through with it.
Now, from another angle: The SC22 was designed and built so that when someone with an old 20 had some worn out busted up hulls, they could have the factory build them some 22 hulls, probably fiberglass, and all of the hardware from their 20, boards, rudders,tramp tracks, tramp, beams, mast and rigging, shroud chainplates,eye straps, cleats and mainsheet, sails and anything else you can think of is directly a bolt on item from the old 20 to new 22 hulls. And if you live in an area where the wind normally blows 12 to 15 and more, the new boat will be faster with a standard rig rather than with a tall rig. The tall rig is a light air rig. The standard rig is faster in top speed because to center of effort is lower, therefore the boat/sails can be driven harder, more sail thrust from the standard rig for the same amount of maximum righting moment.

And just so you know, the 22 was built from an old 20 hull. The bow was extended to increase the pitchpole resistance needed with the tall rig sail plan. Higher center of effort in the sail plan requires longer bows, further forward center of bouyancy at verge of pitchpole, with more volume and more length back to the boat's center of gravity. This will generate a resistance torque greater than the pitching torque which comes from the sail plan and the boat is more pitchpole resistant.

[Bill Roberts]

Mac M,
Your 7th, 8th and 9th pictures that show the bow curve on the SC20. This needs to be talked about in light of todays new design boats/bows. Remember that we are talking about "beach cats". Beach cats are catamaran sailboats that sail on to and off of the beach. The shape of the bow has much to do with how successful these beach cats are at sailing on to and off of the beach. The H14 and H16 were the first popular beach cats in the US. These were banana hulls with a gentle radius curving the bows up to the deck. These bow shapes were highly influenced by the requirement to sail on to and off of the beach successfully. Other catamarans of the same era had similiar bow designs. How about the Shark catamaran and the Shearwater? How about the Tornado? How about the SC product line and many others? The bows of these boats and many others were designed for sailing on to and off of the beach.
Now here we come into the 21st century and catamaran bow shapes change! Now we see sharp corners where the keel and stem meet and stems with reverse slope that sharpens that corner even more. How do these boats sail on to and off of the beach. The first one of these boats I watched sail on to the beach was the Inter 20 in the Tybee 500 Race. I watched the boats sail on to the Beach at Jensen beach, Fl, not far rom where I live. The wind was on shore about 15 knots. Some of the boats made in, on to, the beach and spun into the wind with no problems but with some fast road crew work. Other boats came on to the beach with a little bow down attitude and the sharp narrow bow of the Inter 20 dug into the sand and the boat stopped abruptly, the rear end flew up in the air and skipper and crew fell forward and the boat pitchpoled and masts were broken and sails torn etc as the boat pitchpoled on to the beach. A couple of other boats came on to the beach, bows dug in, transoms went up, mains flew out against the shroud and the boat did a 90 degree pirouette and then the transoms came down and broke some rudders etc. This pitchpoling and pirouette manuever coming on to the beach was new to sailing for me. I had not seen it happen before at the World 1000 races and other occasions where cats sailed away from and on to the beach at Singer Island and Juno Beach and other nearby beaches. Did the design of the Inter 20 bow have anything to do with the pitchpole and pirouette maneuvers at Jensen Beach? You bet it did.
The next day the surf was big and the boats had a hard time getting off the beach with an onshore wind. Some of the skippers sheeted their mainsails in too quickly and drove their boats into irons with no speed. Then in a panic mode the skipper jerked the tillers to windward to make the boat bare off and some boats broke the top off the rudder and or split the rudder head casting. Why did these parts beak? They did not adequately support the top of rudder in a part down position and under max load conditions and parts broke. The Inter 20 rudderhead assembly and many others today are deep water start rudder systems, rudder full down and locked and then sheet in. This doesn't work sailing off the beach.
Ever wonder why the SC, ARC,RC has never changed the rudderhead casting? The builder understands that he is building a "beach cat" and a strong rudderhead that supports the rudder in a part down position is required for sailing on to and off of the beach. The SC rudderhead casting alloy is ALMAG35. This is the same alloy as used in aircraft landing gears. It costs much more than junk Al castings and it is much much stronger and it is tough. It can take high loads applied abruptly and not crack or break. All SC casting are made with this alloy. Another example of SC quality sticks its head up. You didn't know that did you?

[Mac M]

I didn't!

Thanks for the compliment on the work and all the information Bill. We are planning on bringing this boat to the Mug Race, hope to see you there!

[Bill Roberts]

Mac M,
Get some new sails through Tom and start practicing/sailing ASAP. Then and only then will you be ready to "race" in the Mug Race 2014. If there is a good breeze, 10 knots or more, you will be hard to beat. Practice, Practice, Practice wins races!

[Mac M]

Got my new tramp in last week, very nice! Got it installed this weekend.

[Mac M]

Finished the spin pole, it was quite a task. The dolphin striker wire ended up being a little long so I'll probably have to shorten or make a new one.

The lines coming out of the end of the pole are jib downhaul (yellow) which is 4:1, spinnaker tack (red), and the first part of the jib sheet (green).

[fjviola]

Mac
Great job on your SC20!
What did you end up deciding for a spinnaker Snuffer System on your "Jousting Pole", as my cat mates comically refer to my 'big' ARC pole
franklin

[Mac M]

I went with a SNU similar to what you have. I had it made to a custom length, it's quite long and has some extra girth to it.

[Mac M]

Got the mast up this past weekend and so far everything is fitting up perfectly! I'm setting up most of the systems and making sure the spin snuffer is going to work like I plan before taking it apart and moving it to the lake.





Here's a picture of the jib downhaul (left), jib sheet block (center), and spin sheet tack (right).


Here a picture of the jib sheet rigging (the white line is just temporary will be replaced with bungee for the snuffer). The jib sheet is 3mm Vectran in the pole and to the sail, it switches to 6mm line after exiting the pole.

[Bruiser]

That is a great job. We would love to see you race that in The Mug Race in May. Very impressive work, looks like it will be a really fun boat to sail.

[Mac M]

Thanks, it's been a ton of work and I'm glad it's pretty much over!

I had intended to go to the Mug Race and have taken the days off of work, but it's not looking like it will happen now. I do hope to get it down there for a race you guys will be at. Have to check what y'all are going to.

[Kevin Keller]

Very nice! Starting to make me a little jealous.

[Kevin Keller]

Very nice! Starting to make me a little jealous.

[Mac M]

Got the spin up and sorted out. Time to take it apart yet again and move it to the lake! Just waiting on sails now.....