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Gyradius calculationGyradius calculations adapted from the Larsson/Eliasson "Principles of Yacht Design"
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Feel free to fill in your own info. When you're done, you (or I) can roll back the spreadsheet to the base setting.NOTES
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Fill in the yellow cells!
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22Plywood (or core) sheet weight used, enter 22 for 6mm okoume, 27.5 for 6mm meranti, 25 for 1/4" nominal 3-ply fir, 19 for 5.2mm 5-ply, 6.5 for 12mm 5# foam.The weight of a 4'x8' sheet, raw.
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0.72Ply or core weight weight per square foot
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12Hull sheathing used, fiber weight per yard, total of inside and outside, in ounces.Just the cloth weight.
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0.23Sheathing weight per square footNote: 50/50 resin to cloth weight ratio assumed, and there is an extra 5 oz. / yard included for an interior sealer coat and exterior fairing.
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55Frame taping, width x weight, e.g. 6" x 6oz tape = 36 (if you used more than 1 one kind/size of tape, just enter an estimated average).
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1.5Stem, thickness of wood used, inches.
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1.72Stem installed weight
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1Frame 18, enter 1.9 for no cutout, 1 for cutouts per plan.
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2.93Frame 18 installed weight
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4.4Frame 18-53.5, Stringers, add 1.5 for each 4" ply stringer, .7 for each 3/4 x 1.5" stringer. (pounds)
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1Frame 53.5, enter 1 if per plan, or estimate other factor for more or less material.A “factor” is a multiplier: 1 will not change the assumptions used, but 1.1 will increase it by 10%; 0.9 will decrease it by 10%, etc.
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4.55Frame 53.5 installed weight
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4.4Frame 53.5-89.5, Stringers and bunks, add 1.5 for each 4" ply stringer, .7 for each 3/4 x 1.5" stringer, 6 for ply bunks per plan. (pounds)These between-frame cells capture the weight of the stuff between frames, other than the hull and deck skins. Things like stringers, bunks, longitudinal frames, whatever. Some of this is on the plan, some not, so I've included some guidance for values to use, based on what you've actually installed.
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1Frame 89.5, enter 1 if per plan, or estimate other factor for more or less material.
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4.64Frame 89.5 installed weight
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5Frame 89.5-110, Stringers and bunks, add 1 for each 4" ply stringer, .5 for each 3/4 x 1.5" stringer, 5 for ply bunks per plan. (pounds)
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1Frame 110, enter 1 if per plan (short cabin), .2 per plan (long cabin) or estimate other factor for more or less material.
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9.44Frame 110 installed weight
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10.5Frame110-124, Stringers and bunks, add .5 for each 4" ply stringer, .25 for each 3/4 x 1.5" stringer, 9 for 1/2" ply bunks per plan. (pounds)
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1Frame 124, enter 1 if per plan (short cabin) or 1.25 if per plan (long cabin), or estimate other factor for more or less material.
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5.34Frame 124 installed weight
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7.5Frame 124 - 169.5, Stringers and bunks, add 1.6 for each 4" ply stringer, 1 for each 3/4 x 1.5" stringer, 12 for ply bunks per plan. (pounds)
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1Frame 169.5, enter 1 if per plan, or estimate other factor for more or less material.
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5.87Frame 169.5 installed weight
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7.5Frame 169.5 - 214, Stringers, add 1.6 for each 4" ply stringer, 1 for each 3/4 x 1.5" stringer. (pounds)
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0.7Transom, enter 1 if per plan (1/2"), or estimate other factor for more or less material.
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9.32Transom installed weight
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1.2Deck, enter 1.2 if same material and sheathing as hull panels, or a factor for the the weight of other materials.The 1.2 factor is intended to capture the additional weight of nonskid.
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1.3Cockpit sole, enter 1.2 if same material and sheathing as hull panels, or a factor for the the weight of other materials.
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0.8Cabin top, enter 1 if same material and sheathing as hull panels, or a factor for the the weight of other materials.
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1Next enter 1 for a per plan cabin, .5 for flush deck, 0 for extended cockpit floor.This factor is used in the gyradius calcs later, and has no bearing on the weight total.
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Rig
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17Raw mast weight: tube, track, masthead enter 17 for C-Tech, 32 for Dwyer DM-368, 27 for Dwyer DM-4, or other measured weight. (pounds)
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4Standing rigging weight. Enter 7 for 1/8"/3mm wire, or 4 for fiber. (pounds)
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2Enter 1 for single spreader, 2 for double spreader
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53Enter gooseneck height above base of f89.5, inchesThis factor is used in the gyradius calcs later, and has no bearing on the weight total.
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12Weight of rudder(s) and associated fittings (pounds)
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182Total Keel weight (pounds)
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172Bulb weight (pounds)
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Description:
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82001 Optional/not on plan items: enter weight (#), then distance from bow in inches.Speakers
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8892 Optional/not on plan items: enter weight (#), then distance from bow in inches.Stereo
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251203 Optional/not on plan items: enter weight (#), then distance from bow in inches.Battery
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201104 Optional/not on plan items: enter weight (#), then distance from bow in inches.Correctors
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33655 Optional/not on plan items: enter weight (#), then distance from bow in inches.Additional Correctors
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33190.46 Optional/not on plan items: other half of correctors.Additional Correctors← This is based upon the i550 Class rule regarding separation of corrector weights, beyond the first 20 pounds.
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0.95Hull material weight per square foot
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138Hull panel weight
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44Installed frame weight
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51Additional structure weight
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61Deck weight
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122Cockpit weight
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25Cabin top weight
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38Rig weight- mast spreaders boom shrouds
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194Appendage weight
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127Optional installed items
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800Calculated hull weight← NOTE! This total must be made to equal 800# for the gyradius comparisons to be meaningful! Add correctors until it does.
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Mass moments of inertia, =(weight) x (distance to c.g.)^2Simple moments about bow (inch-pounds)
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21,172Stem0
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88,561Hull and structure, 0-18109
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32,969Frame 1853
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173,976Hull and structure, 18-53.51,275
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14,987Frame 53.5243
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76,440Hull and structure, 53.5-89.53,465
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2,124Frame 89.5416
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7,002Hull and structure, 89.5-1103,309
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7Frame 1101,039
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1,464Hull and structure, 110-1244,578
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918Frame 124662
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103,420Hull and structure, 124 - 169.511,798
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20,152Frame 169.5994
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518,913Hull and structure, 169.5 - 21415,216
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99,142Transom1,995
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63,533Optional installed item 11,600
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3,831Optional installed item 2712
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2,078Optional installed item 33,000
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16Optional installed item 42,200
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69,476Optional installed item 52,145
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208,652Optional installed item 66,283
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1,128,621Mast and spreaders2,380
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37,568Boom1,490
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137,686Rudder2,616
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509,555Keel and bulb21,112
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110.9Center of gravity
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Iyy = Mass moment of Inertia = sum of inertia moments above
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3,322(x 1000)
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