MASH
N/A
The only way to find out would certainly be to remove them but the OP has already said he's replaced them and I'd guess he doesn't think risking the expense of another liftout is worth it if they do indeed prove to have been useful. Whatever else they do they will certainly add considerable drag so it might be worth a try.
No doubt an aerofoil rudder would be more efficient but on a low speed hull the advantage would probably not he worth the extra expense over boilerplate and the difference probably undetectable. Rudders don't cavitate which is a very high speed phenomenon but they can stall - as described that's the breakaway of the laminar flow and consequent loss of "lift". Devices to delay that process on aircraft - I'm not a hydrodynamicist - are best placed at the leading edge of the wing (slats) not the t/e hence my guess that these were associated with astern control. Fitting the plates closer to the pivot would make them less effective in astern I reckon,
The slamming over mentioned is surely only due to poor design which could be caused by flow reversal (unlikely) or too much area ahead of the pivot line (overbalancing) which this rudder does not appear to have, indeed, it looks to have less than ideal. That is why a rudder does exactly this in astern, too much area "ahead" of the pivot line.
I'm pretty confident that the plates as fitted would delay rudder stall in astern at large deflections but unless the OP removes them for sea trials or we get a hydrodynamicist on here we ain't gonna know!
The only other thing I can think of is to help counterract the helical (propwash) flow a bit to make the rudder more effective but that seems a bit fanciful.
Or it may be, as suggested, just something that someone thought was "a good idea".
If it ain't broke don't fix it seems to be a good starting point.
No doubt an aerofoil rudder would be more efficient but on a low speed hull the advantage would probably not he worth the extra expense over boilerplate and the difference probably undetectable. Rudders don't cavitate which is a very high speed phenomenon but they can stall - as described that's the breakaway of the laminar flow and consequent loss of "lift". Devices to delay that process on aircraft - I'm not a hydrodynamicist - are best placed at the leading edge of the wing (slats) not the t/e hence my guess that these were associated with astern control. Fitting the plates closer to the pivot would make them less effective in astern I reckon,
The slamming over mentioned is surely only due to poor design which could be caused by flow reversal (unlikely) or too much area ahead of the pivot line (overbalancing) which this rudder does not appear to have, indeed, it looks to have less than ideal. That is why a rudder does exactly this in astern, too much area "ahead" of the pivot line.
I'm pretty confident that the plates as fitted would delay rudder stall in astern at large deflections but unless the OP removes them for sea trials or we get a hydrodynamicist on here we ain't gonna know!
The only other thing I can think of is to help counterract the helical (propwash) flow a bit to make the rudder more effective but that seems a bit fanciful.
Or it may be, as suggested, just something that someone thought was "a good idea".
If it ain't broke don't fix it seems to be a good starting point.
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