Boat porpoise problem

[jf522]

I stand corrected.

[CajunChristian]

Originally Posted by jf522

I stand corrected.

We're all here to learn and share I try to use the most cost effective ways to accomplish things, you know what they say "po folks got po ways".
D

[Gerald]

Originally Posted by CajunChristian

We're all here to learn and share I try to use the most cost effective ways to accomplish things, you know what they say "po folks got po ways".
D

In the interest of learning......

How do you "Hook" the bottom of an aluminum boat like shown in the picture holding the tap measure? I am thinking maybe using a big hammer [sledge hammer???] but think that would probably not look good after a few good hits.

Do you have to put the boat in some kind of big "press" to make the bend in the bottom?


I once tried putting a 15 hp outboard on my 12' Alumacraft boat that is rated for 8 hp max. Just me and the engine, no other weight. I don't know how fast I was going, but once that boat planed out, it felt like it was "dancing" on the smooth water. I don't remember if I tried running WOT, but for me that was too much hp for that 12' boat and did not feel safe.

[CajunChristian]

Originally Posted by Gerald

In the interest of learning......

How do you "Hook" the bottom of an aluminum boat like shown in the picture holding the tap measure? I am thinking maybe using a big hammer [sledge hammer???] but think that would probably not look good after a few good hits.

Do you have to put the boat in some kind of big "press" to make the bend in the bottom?


I once tried putting a 15 hp outboard on my 12' Alumacraft boat that is rated for 8 hp max. Just me and the engine, no other weight. I don't know how fast I was going, but once that boat planed out, it felt like it was "dancing" on the smooth water. I don't remember if I tried running WOT, but for me that was too much hp for that 12' boat and did not feel safe.

\
I use a 12" piece of 2X4 and a loaded rubber hammer. It takes much less blow than you think. I measure with a straight edge constantly to insure a smooth curvature. I usually just slide the boat back about 2' on the tail end of the trailer, lay on my back and tap away. About 10 minutes to completely hook both sides.
You want your boat to sit up on the tail and run, but, you don't want to use all available horsepower to lift the bow.
Stop this video at 2 seconds and notice the trim angle of the engine and how much boat is out of the water.

good3.mp4 Video by 1995US1 | Photobucket

good3.mp4 Video by 1995US1 | Photobucket

Less boat in the water=less drag. Less trim angle=less wasted horsepower. You have, let's say 50hp, how much will you use to lift the bow and how much to push forward? That is what makes our tunnel race boats so fast, air flys the boat and the motor only pushes forward.
Notice the trim angle on this race boat, and notice how much boat is out of the water:

Photobucket (Videos)

Photobucket (Videos)

The ways to control the bow on a loaded aluminum boat is:
weigh the bow down, not practical
trim the engine all the way down, a tremendous waste of horsepower
trim tabs, takes speed away, angle too sharp
hook the rear bottom of the hull, no speed loss

[Gerald]

Originally Posted by CajunChristian

\
I use a 12" piece of 2X4 and a loaded rubber hammer. It takes much less blow than you think. I measure with a straight edge constantly to insure a smooth curvature. I usually just slide the boat back about 2' on the tail end of the trailer, lay on my back and tap away. About 10 minutes to completely hook both sides.
You want your boat to sit up on the tail and run, but, you don't want to use all available horsepower to lift the bow.

Less boat in the water=less drag. Less trim angle=less wasted horsepower.

The ways to control the bow on a loaded aluminum boat is:
weigh the bow down, not practical
trim the engine all the way down, a tremendous waste of horsepower
trim tabs, takes speed away, angle too sharp
hook the rear bottom of the hull, no speed loss

Thanks for the information, it may come in handy some day.

I also have a 16' Alumacraft with a 40 hp Tohatsu [restrictor taken out]. It will run 36 mph at 5750 rpm with the engine trimmed up about 1/3 of the way [on the trim gauge] before it starts to bounce. I probably have too much weight in the back [3 batteries, charger, and 9 gal. gas] to make it run any better.

I get about 35 mph and 5700 rpm with a little heavier load, so I am ok with the performance.

[Feesherman]

Originally Posted by Gerald

Thanks for the information, it may come in handy some day.

I also have a 16' Alumacraft with a 40 hp Tohatsu [restrictor taken out]. It will run 36 mph at 5750 rpm with the engine trimmed up about 1/3 of the way [on the trim gauge] before it starts to bounce. I probably have too much weight in the back [3 batteries, charger, and 9 gal. gas] to make it run any better.

I get about 35 mph and 5700 rpm with a little heavier load, so I am ok with the performance.

U would get better performance if u put some hook in the hull.

[Hydro]

These work for me... Heavy 1652, Four Stroke 40 with trim, 8 gallons of gas, two batteries and my big arse in the back.... Jumps on step, the faster you go the less pitch is in the tabs. WOT they are pretty much even with the bottom of the boat...

I have had them going on two years and put them thru a couple of groundings at Toledo when the water was low, stumps on the river, etc...

Good luck