I have been reading David's excellent accompanying text with the new 3.5" SD kit.
David recommends a ballast tank of around 5" in length on Joel's 1/72 Permit.
I was wondering if its correct mathematically to simply up-scale the ballast tank volume to the 1/72 Seawolf relative to Permit?
I.e.
Using 1:1 submerged displacement of Seawolf vs Permit, the ratio is around 209%.
That is Seawolf submerged displacement is 209% that of a Permit class.
Using this ratio could I compute the volume of the ballast tank for the Permit using the 5" length (V=TTr^2) and multiple that volume by 209% and then work backwards to get the length of the Seawolf ballast tank?
Clearly an assumption being made by my reasoning here is that Seawolf and Permit have identical reserve buoyancy proportions - which is likely not to be the case, but is it close enough for the purposes here of estimating ballast tank size?
I.e. Permit ballast tank volume using 3.5" SD in cubic cm=
3.5" = 8.89cm
r= 8.89cm / 2 = 4.445cm
TTr^2 = PIE x (4.445 x 4.445) =62.07cm
Length (L) = 5" = 12.7cm
Volume (V) =TTr2 x L
V= 62.07 x 12.7 = 788 ml
Seawolf submerged displacement 9,138t
Permit submerged displacement 4,369t
ratio 209%
Estimated Seawolf ballast tank volume 209% larger than Permit.
209% x 788ml = 1646 ml
1646 ml / TTr2 = Length (L)
L= 1646 / (62.07) = 26.53 cm = 10.44"
another easier calc based on the same principle is simply multiply the Permit tank's length 5" x 2.09 = 10.45"
All that stated - is this valid? What other methods should / need be applied?
Please advise.
Thanks
John
David recommends a ballast tank of around 5" in length on Joel's 1/72 Permit.
I was wondering if its correct mathematically to simply up-scale the ballast tank volume to the 1/72 Seawolf relative to Permit?
I.e.
Using 1:1 submerged displacement of Seawolf vs Permit, the ratio is around 209%.
That is Seawolf submerged displacement is 209% that of a Permit class.
Using this ratio could I compute the volume of the ballast tank for the Permit using the 5" length (V=TTr^2) and multiple that volume by 209% and then work backwards to get the length of the Seawolf ballast tank?
Clearly an assumption being made by my reasoning here is that Seawolf and Permit have identical reserve buoyancy proportions - which is likely not to be the case, but is it close enough for the purposes here of estimating ballast tank size?
I.e. Permit ballast tank volume using 3.5" SD in cubic cm=
3.5" = 8.89cm
r= 8.89cm / 2 = 4.445cm
TTr^2 = PIE x (4.445 x 4.445) =62.07cm
Length (L) = 5" = 12.7cm
Volume (V) =TTr2 x L
V= 62.07 x 12.7 = 788 ml
Seawolf submerged displacement 9,138t
Permit submerged displacement 4,369t
ratio 209%
Estimated Seawolf ballast tank volume 209% larger than Permit.
209% x 788ml = 1646 ml
1646 ml / TTr2 = Length (L)
L= 1646 / (62.07) = 26.53 cm = 10.44"
another easier calc based on the same principle is simply multiply the Permit tank's length 5" x 2.09 = 10.45"
All that stated - is this valid? What other methods should / need be applied?
Please advise.
Thanks
John
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