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I just grabbed the 255/1600 numbers off of the wiki page for the SBD (-5 model), looking for a quick example to use. (Five point demerit for me for intellectual slot.) In my youth (a loonng time ago) I wondered why the "old" battleships (e.g. Perl Harbor) that had 25-28 knot top speeds could not be "juiced up" a little to match the 30-33 knot "fast" carriers. Then I learned that resistance (drag) is proportional to the square of the velocity. To increase the value of 'v', you have to overcome v*v^2 = v^3. I remember calculating (in physics class) the power increase required to go from 25knots to 30knots (1.73), which made it clear. It wasn't my greatest ephipony in life (such as there being no Santa Claus) but it impressed upon me the 'power' of the 'exponent' with regard to forces. (Unintentional pun.) It makes something like the receipt of radar echoes even more remarkable, since they decrease inversely to the FOURTH power, 1/d^2 going out and 1/d^2 coming back. This showed me the power of electronic resonance in circuits.Uh, Sam, the R-1820 gave 1000-1350 hp in various versions of the SBD. However, to your point, the speed never varied much. When they got the newer engines something was added (or several somethings) that added a bit more drag.
Wikipedia article on the SBD does not have the 1600 number anywhere in their entry, or 1,600. They list 1,200 HP for the SBD-5.I just grabbed the 255/1600 numbers off of the wiki page for the SBD (-5 model), looking for a quick example to use.
You are correct. I have no idea where I got 1600. Probably from another wiki page tab of "General Characteristics" of something else I had open at the time. In that case, a magic R-2800 would get to 307mph, assuming 2100hp. That's pretty decent and is SB2C speed range. Thanks for catching my error.Wikipedia article on the SBD does not have the 1600 number anywhere in their entry, or 1,600. They list 1,200 HP for the SBD-5.
In my youth (a loonng time ago) I wondered why the "old" battleships (e.g. Perl Harbor) that had 25-28 knot top speeds could not be "juiced up" a little to match the 30-33 knot "fast" carriers.
You had the "middle" BBs from the North Carolina on. They were the short stubby ones.Just a niggle, but those old BBs topped out at 21 kts. We'd have had to both lengthen them and install more/better machinery to even get 24 kts out of 'em.
That's what the Japanese did with the Kongos, FWIW. I think an extra 40 feet and more machinery bumped them from 25 to 28 kts? Working of the top of my head on them, and amenable to correction.
You had the "middle" BBs from the North Carolina on. They were the short stubby ones.
The first 2 were 50 ft longer than the next 4. The "short" ones needed an extra 9,000hp to go 0.5 knots slower.
The older ones did to 21kts as you said and would have needed a total reconstruction to hit 24kts.
One of the "shorties"
View attachment 698597
Note the wave making and the wake here at 15kts.
Also note the lack of any space to put anything between B turret and Y turret.
Despite their large increase in power the Iowa's need their roughly 200 ft of extra length to not only provide room for the engines/boilers but to significantly change wave making resistance to reach 33kts.
You are quite right.The post I was replying to specified "at Pearl Harbor", which includes nothing past a Colorado-class -- i.e., Standard battleship, and 21 kts.
You're absolutely right, the SDs were 680' (-50 ft rom the Washingtons) and needed more shp to stay close. Length-to-beam matters. Pearl Harbor BBs, at most 624 feet, weren't getting anywhere near 28 kts no matter the rebuild, you're better off building from the keel up than trying that. And my main point was that those Standards were 21 kts.
No way they're getting to 30.
You are quite right.
Just pointing out that the 28 knotters would have been impossible to get to 30kts+ so the old ones really had no hope (tow by the Starship Enterprise?)
The Japanese rebuilt most of their old BB with new boilers and engines so people need to look at each class or even ship and see what was done.
Also note that the old Japanese battleships were usually 23-24kt ships to begin with (the Kongo class were 27-27.5 as built) so they had a much better head start.
I would also point out that over driving an existing hull shape leads to a point where the bow rises and the stern sinks and extreme cases leads to the ship (boat) taking in water over the stern. Transom hulls were used to "fake out" the water flow at speed.
View attachment 698603
Ship acted longer than it really was. Downside, they used more fuel at cruising speed.
Some of the Japanese (and Italian) rebuilds tried to modify the "lines" even it they didn't change the length that much.
Practical things like lengthened ship won't fit in as many dry docks for repair were also considered.
Transom stern gets a bit confusing, It is done for several reasons in the "modern" world. Not the least of which is more deck space (or cargo space) for a given length of hull. Especially when you are paying dock fees based on hull length. Dock fee can wipe out any fuel saving
Some of the hull/stern shapes have changed since the very early 1900s. Very few ships/boats could plane like a modern speed boat.
for low speed vessels which is sort of the old hull speed is 1.34 times the square root of the water length rule. 600ft is 24.5 kts, different sterns affected things differently depend on where in the speed range they were. The closer you get to max hull speed the worse the old double ender (giant canoe) becomes. But down at hull speed 0.5 it is really quite efficient.
Actual transom stern on a non-planning hull is often a bit camouflaged
View attachment 698604
Unless the ship is running deep the transom doesn't do anything one way or the other (except lower hull cost and docking fees?)
Go back to the Cruiser and you will see a number of feet of immersion if she was running deep.
Once you get into planning hulls you need a transom stern but the water flow is straight out the back.
View attachment 698605
Low speed with a transom stern can produce quite a bit of burble (turbulence/drag) put the picture on the right has gone right through Destroyer/Cruiser speed and into MTB land.
They do make whole books on this stuff so I have probably mangled it pretty well.
A 2-seat F4U and F6F do not need to be any longer than their 1-seat brethren.and it was the main reason for a lot of the problems with the SB2C - it just really needed to be about 3' longer. I think this would have been an issue for a theoretical two seat Corsair or Hellcat.
I'm a little confused how they fit all those Fulmars on early carriers... I guess the folding wings helped like with the TBF. I assume by the time Albacore was around they had the bigger elevators?
A 2-seat F4U and F6F do not need to be any longer than their 1-seat brethren.
See the other 1-seaters that gave birth to the 2-seaters during or just after the ww2: Spitfire, Hurricane, P-40, P-51, Bf 109, Fw 190, Yak-1/-7 - neither of these grew in length. Even the G.59 was just 4 in longer than the predecessor, G.55. Some of them lost fuel tankage (Bf 109, P-40, Spitfire), some have not. Note that all of these are much smaller A/C than the F4U or F6F.Are you sure about that? I mean, I know it's possible to make a two seat bomber roughly the same size (the SBD isn't too much bigger than a Corsair), but this would definitely add a lot of weight, add drag (especially if the rear seater has a gun mount), take away space used for fuel or oil other needed things, and change the CG.