Hydro Strut and Rudder Setback

[Mike W]

I have always noticed and wondered why sport type hydros "require" so little setback on rudders and struts because every variation of strut and rudder is available in both mono (longer) and hydro (shorter) setbacks. I understand of course the effective hydrodynamic hull ends at the sponsons, and the remainder is only aerodynamic afterplane and the transom hardware mounting area. Hence the "3-Point Hydro" designation.

So what would be the result if you simply ran the ~3/4" (?) longer mono setbacks on a hydro? Wouldn't it be a little more stability as a result of an effectively longer 3-point hydro? Less tendency to blow off? More rudder authority? Or would the result be negative for some reason? Are 1/8 scales limited in strut setback (under the hull) to disallow taking advantage of this potential benefit? Or is that just for scale appearance?

[phil t]

Strut setback, transom to prop, on most new design the strut can be on the transom. I think that the further the prop form the back will be more load at launch but will make hull run more free at speed. My older Supersport 45 did not like the transom strut at all, hard to launch and would blow off easier, so wee kept it under the boat drive dog just past the transom. Stealth 45 hydro is ok with that setup. Rudder short or long not much different performance.
Scale hydro is a scale appearance rule thing, most are setup with drivedog at or just past the transom.

[Mike W]

Thanks Phil! Looking forward to doing some testing on this to learn more.