Thanks for all the 18 to F18 conversion info. I am measuring and remeasuring now. When finished I will have a 1982 Hobie 18 magnum with square top Tiger main, SX mast, Elliott chute ( cut for tiger), end pole snuffer system, carbon daggers and rudders. Power down haul and 9-1 main sheet system. I plan to race it with the wings on. I assume I will race open class but not sure. Would I run with other 18s' and give them time? Is there a portsmouth rating I would apply? I won't race much so want to be sure about classification before I show up somewhere and they can't decide what to do with me. Thanks in advance.

I will give it a shot http://www.ussailing.org/portsmouth/tables06/modifications06.htm

Well you cant race F18 rating because of your curved beams and wings. I think you are going to take a massive hit in Portsmouth. Do your best, but don’t look at the scores

So you have H18M 71.4 (without wings)

For taller mast than standard .995

For non-class legal mainsail, of greater sail area* than standard main .980

Class normally without spinnaker, genoa, reacher, hooter or wire/rope luff headsail attached to a pole, carrying one or more 0.960

(Any other deviations from standard class configurations, including the addition of wings, can be assessed a penalty of at least 0.995)

Wings 0.995

Illegal downhaul? 0.995

Illegal Mainsheet blocks? 0.995

Assuming your jib is class legal.

71.4 * .995 * .980 * .960 * .995^3 = 65.8397

If you just add the class legal spinnaker to your 18-sx it would be

Hobie SX-18 spi H18SX 71.3

You may also take hits for shroud length, forestay length and boom. Since the hobie 18 is one design, you pretty much have to take a hit for almost anything that you buy that is not specifically a hobie 18 part. I think once everything is done you will have to contact the yardstick for more info.

I am no expert, just trying to help.

Maybe of little or no consulation, but...

8:1 downhaul is class legal, use a cascadeing system.

We've yet to figure how to make/sail the boat faster with the wings , IMO leave them off.

where does it state you get a .995 hit for having a non-stock downhaul and each other non-class legal rigging tweak? What about a tapered mainsheet?

Under the "Other" penalties

Any other deviations from standard class configurations, including the addition of wings, can be assessed a penalty of at least 0.995. Multiple deviations may incur multiple penalties. Penalties may be greater than 0.995. Please identify any such modifications and penalties assigned and include with results reported to the handicap committee and Portsmouth Numbers Committee.

Tapered sheets...not class legal

Flatlander, I've found the wings slow the boat as well. Was going to leave them on to give the wife a better anchor point to hold the chute. Seems I would get some time on 18s' with them on because of the weight. Wouldn't I be racing a 18 sx basically. Larger spin and main on mine, wings were standard on the SX. I don't know how to calculate for carbon daggers, they are one of a kind made by a friend. Appreciate all info from you guys, Thanks

I would start with the rating for the SX.

Then, check the sail area of the Tiger main versus the SX main. If it's the same area, take the hit for it being a square top. If the Tiger main is smaller, it may be a wash.

Leave the wings at home for racing. There used to be a Hobie-18 formula rating, which I believe was essentially a SX without wings. Could be wrong on that. If there is, you can use that as the base rating for no wings. But - if you use the regular Hobie-18 rating, know that there is NO hit for using or not using the wings. In other words the rating for a Hobie-18 and Hobie-18 magnum is the same.

Take the 0.995 hit for non-standard spin against the SX rating.

Rudders and boards - the stock Hobie racing rudders have carbon fiber in them. I'd use them and avoid the hit, they're nice and stiff. As for the boards - if you're going to take a hit for different (carbon) boards, there's something I always wanted to try - making inserts to fill the stock trunks a bit so that you could use a modern high-aspect foil. I always thought another stock Hobie board would work well, say a Tiger or Hobie-20 board, maybe cut down a bit if you find you don't need the length. IF the inserts are done right, they could be removable to return the boat to stock. If you're going to take a hit for non-stock board, go for a non-stock board...

If you start with the SX rating, there shouldn't be any hit for shroud lengths or whatever. Which brings me to my next point:

In most cases a race committee is not going to sweat down to small details for the non-stock rating hits. If you have a non-stock tramp, non-stock blocks, etc., they shouldn't care unless they're anal. They should worry about the big stuff - spin, main, jib, major alterations and refits. If anybody sweats a higher purchase downhaul on a modified '82 H-18 they'r missing the point IMO.

But - when you do show up to race, show up with a sheet detailing the mods you will claim, and calculate out the numbers for the committee to help them along. And don't just do DPN, do all the wind corrected numbers as well.

My $0.02

Good call Keith, I pretty much agree with you on the corrections and certainly agree on the way to approach the RC or scorer. Make it easy on them. Nobody I know would hit you up for cable lengths and purchases if they had already hit you for an oversized main and a spinnaker. The mast supports the oversized main and the shrouds support the mast. So those are all kind of a single mod. At least that would be my way of thinking. going to modern high aspect boards. yeah, that's probably worth some kind of hit. A spinnaker, for sure.

They don't want to make it unfair for you. But they do want to make sure you don't make it unfair for everybody else. So you being one and the others being many they should err slightly, but only within the range of uncertainty, against a highly customized boat.

Everybody needs to remember that the RCs job is to make it a fun and fair game for all of the players.

If, over time, they get a lot of experience with your boat in a variety of conditions then hopefully they will adjust your boat based on how it really can perform when well handled.

I think the results of this kind of major effort is going to be disappointing. We were given brand new Hobie18SXs for a Hobie Nationals at Lake Erie: the results were not pleasing what with all the pitchpoling that went on that week. Later on, I remember that the SX concept boats never appeared to be any better or faster than the stock Hobie 18 except when the chute is up (I still use one of them). Heavier with wings does not mean faster.