With the industry model apparently based per below, herewith data and suggested improvements to make it work without favor or bias
Basic Regression code:
=(SQRT(LWP*(1.05+(overhang factor-1)+(BO/LWP*0.15)))*(RSA^(1/3))/(IRC displacement^(1/4)))*(LL/P^(1/3))*((100+HF)/100)*((100 +P/E factor)/100)*Rig factor*((100+age factor)/100)*mbs factor / 1.775
And where:
RSA =( MSA + (JA*0.6*LPG/150)+ (SPA x 0.4)
& RSA for asym’s boats
RSA =( MSA + (JA*0.6*LPG/150)+ (SPA x 0.4*0.8))
& RSA for Dayboat’s
RSA =( MSA + (JA*0.5*LPG/150)+ (SPA x 0.5))
Sportboat’s with asym’s
RSA =( MSA + (JA*0.5*LPG/150)+ (SPA x 0.5*0.8))
Or as apparently used by IRC for Dayboat’s:
RSA =( MSA + (JA*0.35*LPG/150)+ (SPA x 0.65))
With IRC actual HF #. Impact of this is that boats are rated to sail almost twice the downwind distance with spinnaker vs. the upwind distance (to get there) to work with HF#!
Overhang factor:
=(100+(( SO less 5% LWP)*150/IRC displacement))+(Flying bow adjustment))/100
(but limited to total actual SO of 5% of LWP, plus stern o/h factor %) + flying bow +
Flying bow (“x” & “h”), rates at larger of “h” or 50% of “x”
LL/P
As is, but rated at lower of actual, or 1.00 for non-overlapping rigs (<109% LP)
Limited to minimum of 0.90 and maximum of 1.10
Rig factor – per IRC
Age factor
=((((design year +build year)/2)-2007)/3*0.1)
P/E factor
=((P/E)-2.5)
mbs factor
Greater of:
LWP < 8.49m
Less than 0.61 mbs and all LL/P
1 + (0.65 - (mbs/loa)) for all boats less than 10m LWP , or 0.61
8.50m<LWP>9.99m
Less than 0.61 mbs and LL/P <1.0
1 + (0.65 - (mbs/loa)) for all boats less than 10m LWP , or 0.61
Less than 0.65 mbs and LL/P > 1.0
1 + (0.65 - (mbs/loa)) for all boats less than 10m LWP, or 0.65
LWP> 10.00m
0.69 or actual mbs/loa (whichever greater) for yachts over 10.00m LWP
IRC “Super Zero Class”
0.73 or actual mbs/loa (whichever greater) for yachts rated over 1.300(at mbs 0.65)= (super zero)
Hull Factor (SPA use 80% of asym)
= ((MA+SPA)/(Displacement”empty”))*(1/3)*1000
Plus: keel cruise +0.5, bulb keel race +1.0 , very deep fin+ 0.75, very deep high aspect bulb+ 1.5
Less: 1/3 of excess over 8.0
While the above works pretty well, it could be improved with some minor changes:
“Improved” Regression code:
=(SQRT(LWP*(1.05+(overhang factor-1)+(BO/LWP*0.15)))*(RSA^(1/3))/(IRC displacement^(1/4)))*(LL/P^(1/3)) OR ((JA/MA)^(1/4))^(1/3)*((100+HF)/100)*((100 +P/E factor)/100)*Rig factor*((100+age factor)/100)*mbs factor *TW factor *masthead or asym spin factor * Code Zero factor /1.775
- To fix the Performance Cruiser profile, would replace the …..(LL/P)^(1/3)…. with the following equation, where the rig is fractional and LL/P > 1.000………..((JA/MA)^(1/4))^(1/3)…with minimum# at 1.00. This would sort out the rig anomaly where this style of yacht is in “ratings no-where land”
- The MBS/LOA would limit to actual band 0.61 to .65, but would add to MBS (IMS – SMB) measure , in event yacht has a forestay set back from stem, the difference from SF to Forestay (IMS “ SFJ” at 65%) to allow for reduced “J” , but still limited (MBS+(SFJ*0.65) - after adjustment), to the 0.61 to 0.65 range.
- And to solve the issue of bow down measures and huge SO, a “correction” calculation to equate speed advantage with a transom rating as follows:
….((100+transom rating)/100)…..
TW- being transom width at max beam aft, adjusted for raked transoms if measure forward of transom immersion line.
And finally, the flying bow measure, would change to actual calculation as follow:
= “x” *(1-(h/x))*150/DLR*(0.85)
Limited to maximum of actual “x”
- Any boats with rule beating bumps or wings to exploit the mbs factor, shall default to 0.61.
- Big roach mains shall rate in RSA line as follows:
- In common with most regression models, as move away from the core model, the results will become less consistent . Some minimum factors to control this will be:
6.2 RSA/LWP shall not be less than 6.2
6.3 Any yacht with crew mass exceeding 20% bare displacement shall be rated per Dayboat formula…and sail in a separate division..
6.4 Any yacht with raked bows, and with BO/LWP >5%, shall default to MBS (factor) of 0.61 unless can supply an IMS/ORCi or similar approved mbs# measure to prove alternative measurement status. Any yacht with BO/LWP > 7.5% shall default to 0.61 without exception.
6.5 Measurement data (not formula) from IRC, IMS, ORCi or ORR for rig and sail measures shall be acceptable, but LWP shall be IRC “type” measure.
5.5.1 Sistership data for LWP can be used for production models.
- Any Code Zero’s would rate in formula with factor (((155-(LPG/J %))/9000))*(SLU/FL))*100
- To avoid bias of masthead spinnakers on fractional rigs, would “penalty” rate all said spinnakers with following adjustment: …..* (SLU/FL)^(1/4)*…………, where default to greater of actual or 1.000
8.2 Rating penalty shall be greater of asym or spinnaker measure.
- Rig factor would be formalized at follows:
PLUS:
Extra spreaders (each) @ 0.005
Alloy Tapered mast
with taper> 7.5% of “P” @ 0.005
Runners etc (all) @ 0.010
Spreaders with less 5* rake and if
Rate with runners-gross @ (-) 0.05
Carbon Masts per above, with
1.25 x (LOA/10.5) *
1.7/((mass”empty)^(1/3)/(LWP+SO)) = ??
Sail fabric (non- aramid/Kevlar)
Mainsail @ (-) 0.05
Largest Jib/genoa @ (-) 0.05
The above would almost defy optimization (and be” bandit” proof)……and should require no further “fudge” over-rides!!
……….and if too much to follow, send me a direct mail and will send an excel model, just fill in the blocks!
