Strut Angle and Placement

[wannabe]

WOW!!! Now you are really asking. Hydros, cruisers, runners and circles could not be any more different. So don't even relate them. They cannot be leaned upon.
Here is a start for your understanding. In a circle flat, you want to balance the boat at your "set" location. Meaning when the boat is "set" you want a balance that carries the nose, but also keeps the rear from dragging. This is completely dependent upon your power. So if you are building an SE style small block boat, you want your prop further under the boat as your difficulty will be not enough power to keep the nose of the boat suspended out of the water. The measurement we care about is front of propeller (rear of the strut) to the back of the cavitation plates. This is the most important number in any of the set up of a flatbottom. More important than engine placement, v-drive placement, driver, battery, etc.(yes, you can add longer cavitation plates to fool the boat into thinking that the strut is further under the boat than it really is.) As your power increases, you get to a sweet spot where the strut likes to be further back in the boat. Then at a point where your torque starts to increase above s typical pro-stock type of horsepower (650 torque, 850hp or so) then the flat actually starts to blow the tail of the boat, causing handling issues and problems to set the boat. (see k-boat power put in a ss type set-up) So you want to move the prop back under the boat again, to counteract that. (or just make longer plates) so the furthest back a strut wants to be is a good pro stock set-up. Then K boats and pump gas small blocks want actually really close to the same measurement. {if you can believe that} The angle of the propshaft to the bottom of the boat at the strut also determines how much the boat will lift out of the water. (Again, a steeper angle can get the boat out of the water, but you are trading upward momentum where if you are racing, you want all of the forward propulsion you can get.) This is why lake boats tend to be more angle than a competition racing boat. A typical super stock will want somewhere between 7.8 and 8.0 degrees of angle at the strut, from the bottom of the boat. Some have gone more shallow, or think that more shallow is O.K. as they have sufficient lift, and want to maximize forward thrust. When you start to creep up in horsepower and torque, you need less angle/lift to get the boat to ride happy. So many high power boats stay under the 8 degree number, when lake boats are regularly in the high 8degree to almost 9. You also have to figure that prop design will also effect this. More ear up front will cause nose lift, and leaning the prop ears back will settle the nose. We have seen boats with under 7.5 degree angles work, and at that point, much depends on the propeller. But boats under 7.5 tend to like only certain props. a good 7.8 or 8.0 will take just about any menkins you throw at it. You also look at how close the strut is the the bottom of the boat. But when it starts to get too close, you are really limited to a smaller diameter prop. But when you find the right prop, and your strut is shallow and close to the boat, that is when things start to really haul the mail. (see Dave Bryants ss91 boat)
So, never assume that a certain plate works for a certain boat. Or type, or class. Everything is the back of that strut to the plate. Take the K034 for instance. The strut is further underneath the boat, so it does not want long K style plates. Take the old SS33. The strut was so far under that boat, it almost did not want plates when it went to a SS format.
The most important thing to ask here, is; If you are going to set your own strut in a flat of any kind, make sure you know what power you are looking for, (lying to yourself and others at this point will be a real problem) and make sure you talk to those that know before you go and assume. Talk to the smart guys twice, then cut once.
When you place your v-drive - there is no magic number. It goes on the end of the prop shaft that is sitting in your strut. Just try and keep it down in the boat - so along the same axis of the prop shaft, but further back {making it down lower in the hull} and your total prop shaft shorter. Then tie off that v-drive with everything you have. As this is the location of all of the forward thrust of the boat.\
Was this too much?