Angle of attack VS trim angle?

[Techno]

Wondering if anyone actually knows whats happening here.
Assume an STV or other flat running boat.
Bow angle of say 3*. Is the prop shaft actually level with the water or is it angled to it? If the trim is +3* then it would actually be parrallal with the water. Prop is +3* to the hull so it's zero to the water.
has anyone checked what their pricey trim gauge reads in degrees? From previous question these don't read in degrees.
If you run on #2 what does this indicate kind of thing.

[sho305]

I have a pic of Helmut's STV on my desktop from the side(such a nice ride;) ). I would say the bottom is maybe 2 degrees and the motor -1 to 2 also. They all say a little neg trim is best at arond 100+mph....maybe gives a hair more lift back there too while the air lifts the bow? As well as keeping the bow down of course. Most everyone I know trims level on the trailer and then they know that spot on the gauge.

[Techno]

If your numbers are right then he would have about minus 4 degrees. 2 from the boat and 2 from the trim.
That was what I started thinking about is the boats skewing the trim indication, from the perspective of the water.
Checking zero trim on the trailer is fine but the numbers on the gauge are, I guess just a repeatable number. Odd that they don't make them an actual value.

BTW can't these things be calibrated? At least to set zero for zero?

Now if you take this to a bow high boat that is running a large positive trim just how much of an angle is the prop shaft with the water???

[stvhelm]

My trim gauge reads zero when its trimmed all the way down so when Im running it reads about 5 or 6 on the gauge, I forget excactly. Its been a while with this freekin winter. If you try to set it so 0 on the gauge is 0* trim, it will break the gauge or indicator if you trim it all the way in. the gauges reads 0-10. I wish it it read -3 to +7. this pic shows the angle of trim at speed. Also, I'll let you in on a little secret. I'm allowed an extra 1/2" of height on the power jackplate when Im up and running at wot. if I slow down without lowering the jackplate the motor will lose water pressure and overheat. theres a few extra mph with that last 1/2 inch. "tip"you better have a good size skeg too.

[stvhelm]

maybe this is a better one. the water was not that flat in the other one and the jackplate maybe a little low.

[sho305]

My pic is poor, but on my old 'no-jack' Checkmate I am reading about 5 degrees on the hull and 5 positive on the motor from the water. Maybe needs a jack:D With that flat on top of the inline, I can see the whole top when driving. In fact I bump the trailer button for more trim....after I adjusted it up a little even. Any more and I loose water. No gauge, and no pad on the vee. I bet you guys have good gauges but lots of them are not so good and have play.