Tad Roberts

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Oak, 18' Inshore Fisherman

Construction:
Length: 18' 0"
Beam: 7' 0"
Draft: 2' 3"
Displacement: 34,000 lbs (half load)
Power: 28 HP Perkins M30
Top Speed: 9 Knots
Builder:

Comments

The engine for Oak is the same as that of Yellow Cedar, the 28 HP Perkins, but with 1.4:1 reduction gears. With this power Oak will run up to a speed/length (S/L) of 2.2 or FNV of 1.37, which is 9 knots. She is faster than Alder even though she's heavier mostly because of a increase in her power/weight ratio. Alder has one HP for every 350 lbs of boat, while Oak has one HP for every 135 lbs of boat, two and a half times the power!

There are also subtle changes in hullform for the faster boat. Look at Oak's curve of areas and compare it to that of Alder. You can see Oak is much fuller aft and her LCB is at station 5.65, whereas that of Alder is at station 5.4 . Again we come to looking at sterns, note Oak's transom immersion. For her S/L of 2.2 the immersed section area at the transom needs to be about 45% of the area of station six. These broad quarters keep the stern up as she gets going and leaves the stern wave behind.

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