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Hi all I'm new to the forum and fe boats so I'm unsure if this is being posted in the correct place… but here goes anyway. Upon reading threads on the ose site, I'm confused to whether raising or lowering the strut on a catamaran lowers or raises the entire hull or just on one end of the cat and having the opposite effect on the other end. Also by lifting or lowering the strut does it lift the hull or lower it. Any help will be appreciated.
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Can I please have some expert opinions, as I'm having issues with trimming the boat correctly. -
this was taken out of the instruction maual for the NEW Aquacraft Lucas Oil Catamaran RTR....
Strut: Tilting the strut down or lowering it tightens the ride
of the boat. A “tighter ride” will help stabilize the boat but at
the risk of more power consumption as well as a loss of speed.
It’s also important to note that this “tight ride” could cause the
motor controller and/or motor to overheat. Tilting the strut up
or raising it loosens the boat ride. This looser ride allows the
boat to go faster and likely draw less current, but at the risk of
a blow off (the boat lifting off the water). It’s best to make small
strut adjustments and only make one small change at a time.
Later,
MikeComment
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Correct me if I'm wrong… Tilting the strut down is negative angle if I'm not mistaken, hence lowering the bow and making the hull run wet and putting more stress on components. Lowering the strut puts the prop deeper into the water and lowers the hull which also makes the boat run wet. I was under the impression that when the strut is lowered the hull will raise and run looser. I'm very confused. Anyone else care to give their opinion.Comment
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im curious ???Comment
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Think of it like a teeter totter with the CG of the boat as the pivot point. One end goes up the other down.If my boats upside down then who owns the one I thought I was driving the last two laps?
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So for a catamaran, one action on one end has the opposite re-action on the other end? What about height of the strut?… what is the reaction of the hull from up and down adjustment of the strut?Comment
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There are no opinions involved with this topic:
In "most" cases...
More prop in the water = increasing the tightness of the boat meaning it's running wetter
Less prop in the water = increasing the freeness of the boat meaning it's running much lighter
Regardless of the props classification (lifting vs. non-lifting) prop are always trying to lift the boats tail (or transom) out of the water. You also need to remember that your riding on a pocket of air. Too much air and the boat blows over (end over end). Not enough air and the boat runs really stuck to the water causing heat and slow speeds. Your strut adjustment is the tool used to balance the reaction to lifting in the rear and riding on that air pocket.
Later,
MikeComment
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I raised my strut about 1/8" and it gave me some serious torque roll on my genesisComment
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So Mike, are you saying with less prop in the water (higher strut) the hull lifts, running more free? Opposite with deeper prop (lower strut) puts more of the hull in the water? If I'm not understanding I apologise! What I'm trying to get my head around is what effect a deeper or shallower strut or prop has on a catamaran hull.Comment
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Hi Robbo,
I think siberianhusky's teeter totter analogy is a good way to think about it. If the prop is lower in the water, it wants to try to lift the back up the boat up, but in reality the result is the front of the nose is pushed down (runs wet). If you raise the prop, it tries to lift the back less, and there is less down force on the nose of the boat. Where that actual teeter tooter pivot depends on the COG but also the tunnel lift comes into play so it may not be at the actual COG point.
The angle of the strut does the same thing but different vectors are in play. So to tune the boat you need to play with both the height and the angle, and also the COG. I usually set the height, then move COG around, then change angle, then move COG around, and if I can't find a good result, then change the height and do it again.
I have a Miss Geico and an OPC tunnel and both of them like the prop up high (just below the point where the boat "spins out" on the turns), but then add a little bit of negative angle on the prop shaft to put a tad of down force on the nose (but that's less down force on the nose than lowering the prop).
ChiefComment
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I actually found that I left a hex driver in the hull. That was causing my torque roll and extreme wet running. It slid up into the tip of the right side sponson
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Nortavlag Bulc
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