How would you build an 8 foot wide SC22??

[DanBerger]

This one is for Bill:

Let's hypothetically suppose that someone were to have a set of 22 hulls and nothing else--how would you build a boat that was easily trailerable (no telescoping beams, no solid 12 foot beams)?

The idea would be to use available parts from other supercats and to not spend 10 grand on real SC22 parts.

Thinking: 8-8.5 feet beams
Supercat 20 standard rig mast 33'
Supercat 20 sails, boom
Any Supercat steering
Custom trampoline
custom rigging

[Mac M]

Sounds pretty close to a 19XL. Happen to know someone with one for sale

[SC15Av8or]

Dan....

Here is what you get when you do exactly what you are talking about to a SC20

viewtopic.php?f=5&t=669#p2449

http://www.youtube.com/watch?v=31Telh7O ... e=youtu.be


Can't imagine it would be any worse off with a SC22. I will say this it is a pig in light wind.

[Bill Roberts]

The boat you are talking about is already a production boat. It has been available for 5 or 6 years, maybe more. The name of the boat is the ARC21. This is the ARC22 with a 33ft mast and 8.5ft wide. Now, what else do you want?
Changing the boat width from 12ft to 8.5ft is roughly a 29% reduction in righting moment is a 29% reduction in max sail thrust. Therefore righting moment limited boat speed will be reduced by about 14%*. Downwind performance will not be hit so hard because the boat is not righting moment limited sailing downwind. So an estimate of the ARC21 PN would be 50% of the time the PN would be 1.14x57 = 65 sailing to windward and at best 57 sailing downwind the other 50% of the time. The average of these two numbers is 61. What is the PN of an ARC21 in the US Sailing PN Tables?? Look it up, 61.2. Well how about that!
Bill

* Speed varies with thrust**2 or Drag**2.
Therefore if thrust is down by 29%,
then speed will be down by 1.29**0.5 = 1.14 -1 = 14%.

[fjviola]

The 'big' difference in fabricating a SC22 with 8.5ft beams as compared to the ARC21 is:

The ARC-21 utilizes Bill Roberts "Shared Lift" concept in conjunction with low drag, high lift daggerboard and rudder designs that not only improve the ARC-21's windward capabilities but also produce a balanced helm off the wind even when flying a spinnaker. Coupling the ARC-21's "Shared Lift" daggerboard design with its high-efficiency and powerful sail plan produces a combination that will sail higher and faster to windward than any other 8.5ft. wide beachcat on the market. No other beach cat is designed like this, the daggerboard is forward of the main beam and is smaller in area than the rudder, thus the basis for "Shared Lift". ref: http://www.aquarius-sail.com/catamarans/arc21/index.htm

As an owner of the ARC21 (and two former SC17's), I can affirm the "Shared Lift" concept is not only brilliant from a performance level, it absolutely 'opens' up the trampoline 'arena' with the daggerboards forward of the crossbar!

However, "IF" money were not an issue, and I had a more 'permanent' beach where she could reside, 10ft beams would be 'my' standard. This would be a 'good' compromise to 12ft beams (increased speed over 8.5ft beams), as well as be very tempting to 'run' down the road (without having to 'telescope') on a trailer to another launch site.

Therefore, going back to the original question ("How would you build an 8 foot wide SC22??"), why limit the 'horse-power' when another 24" is within REACH ('pun' intended)!

franklin VIOLA

[havliii]

Dan,

I cut down my 20 to achieve trailer-'ability'. The result is simply a stunning boat, she's a breeze to rig and launch, fast and fun to sail. I settled on 9 feet (a little over road legal) but not noticeable. Ten feet is tough to trailer, it gets frighteningly close to mailboxes, sign posts, etc,etc.....

I can sail her light (130 on the wire) or heavy (250 on the wire), with 250 out there, I don't bother to trap, she goes like a 'bat outa heck!' I only suffer below wind speeds of say 3 kts where the 475 lbs of boat weight is a major handicap. (most everything will walk away from me in those conditions)

I would have a ARC 21 in a heartbeat except for the price differential. As with all things I purchased as much performance as I could afford at the time. She's a sweetie, I can only dream what the 21 must be like........

Andy

[havliii]

Dan,

If you have the ARC22 hulls, the cross beams are relatively easy. Tom sells an internal box beam stiffener that will make the boat 'strikerless' ala the SC19 and the ARC21. I took the wire striker and post off my 20 and went this route since the loads are reduced on the narrower beam boat. The strikerless boat is plenty stiff and will handle the loads.

The rest of the work is pretty simple mods, or custom fit out. The bridle off the SC19 works fine and I simply moved the mast hound up 2 inches and was able to use all the existing SC20 standing rigging and some of the holes in the mast at the hound were even reusable.

If you have the hulls this would be an AWESOME boat at 8, 8.5 or 9 feet.

Andy

[DanBerger]

Thanks, Bill--that was pretty much what I was loking for. Remember, I'm the guy who met you in Atlanta to buy your 20 quite a few years ago.

I don't have the hulls, yet, but they are in my area somewhere. This boat is like the Great White Buffalo, because we have all heard of it, but no one has seen it in years and no one knows where it is. I think that if it turns up, it is just going to be the hulls, so I was interested in building a boat from easier-to-come-by parts than the 22. I think the mast and other parts were stolen many years ago.

Having sailed a 20TR with solid beams, I was looking for something easier to manage and I wouldn't ever be racing it. Heck, I'd be OK putting a SC17 rig on it. I would trick out my 15 and use the 22 to take out friends.

The problem is that the owner is very ill and can't communicate and is the only one who knows where it is. I know that some idiot is going to get it at some storage auction and turn it into a duck blind or something. The humanity.

Having Bill's blessing is pretty good too.

[havliii]

Changing the boat width from 12ft to 8.5ft is roughly a 29% reduction in righting moment is a 29% reduction in max sail thrust. Therefore righting moment limited boat speed will be reduced by about 14%*. Downwind performance will not be hit

* Speed varies with thrust**2 or Drag**2.
Therefore if thrust is down by 29%,
then speed will be down by 1.29**0.5 = 1.14 -1 = 14%.

Talk to me about the 19XL (PN 66.5) and the Standard 20 (PN 65), the major difference in these boats is a 3.5 foot reduction in beam and a one foot reduction in length, the rig is the same on both, yet the PN is only a 1.5 percentage point difference. One would figure a greater reduction in speed on the 19XL given the the righting moment is reduced by 29%.

Is one of these PN numbers grossly out of wack?