sport boat ride questions

[anthony_marquart]

Here's the issue,

In the corners, the prop is unloading and I think the boat may actually be accelerating. I had a few thoughts..

- the boat still seems to be riding with the tail low in the water. If the tail is low, rudder would lift the hull as if the rudder was tucker under a bit. This lift may be unloading the prop,..

-How could a turn fin cause this?

-x442 BC prop,.

I also tested an ABC prop with a bit more diameter,.. the whole boat was hopping with this prop... BUT, It lifted the transom and showed great potential if I can the setup right for that prop.. I think I would have to run the strut higher for that prop compared to a x series..

what are your thoughts on this problem?

 

[Jeff Barnhart]

Ideally, the turnfin should be running with the bends parallel to the plane of the boat ride and the leading edge of the rudder should be perpendicular to the plane of the boat ride (assuming you are running a blade with no taper in it).

I don't know your boat or where your strut is set, etc. but the X-series props do not generate much lift. There are a number of things that can be wrong to make a sport boat ill-handling.

 

[RodneyPierce]

Anthony, if you back cut the X series prop, you removed all the lift that it had. If it wont pull that prop without a back cut, go down to a 1440 series prop (where I advised you to start at in our previous conversations)

The ABC prop most likely caused the boat to hop due to the amount of lift in that prop assuming it wasnt back cut as well. Or, could have been blade profile/pitch differences as well. A number of things, like Jeff said above, can cause an ill handling sport hull.

 

[anthony_marquart]

I am familiar with the basic rules,.. how about some suggestions?

sorry Rod,.. you hit enter before me. I didn't try the 442 without BC. Got it this way. I don't think its too much prop,.. It will pull it.. This boat has about a 1 inch ride height.. I think I need to get the tail up out of the water more. The ABC had more lift for sure.. needed more time to change the strut height.

I actually got my son to go with me.. he drove the sport boat a little.. just the steering.. he liked it..

 

[RodneyPierce]

try a prop without a back cut.......

 

[Jeff Barnhart]

I'd suggest putting the boat on the setup board and making sure everything is reasonably close to where it should be. Remember, when you raise or lower the strut it changes EVERYTHING. So a small strut adjustment also requires a turn fin adjustment and a rudder adjustment to keep them at the correct angles.

If you adjusted the strut without resetting the fin and rudder, you really just changed three things instead of one. This makes it impossible to learn what your intended change actually did for the boat ride and it can get you running in circles.

 

[lohring]

Tucking the rudder in typically pulls the transom down in the turn. Tilting it back picks the transom up. As Jeff said, the turn fin can pull the sponson down or lift it. I normally setup the boat on a board assuming that the bottom of the strut sets the ride angle. If the transom wants to lift, it may take weight in the back to hold it down. I've seen a lot of transom weight added in a sport hydro. The boat eventually set fast time at the NAMBA Nationals.

Lohring Miller

 

[RobertWurster]

What Strut are you runnig ?Flat or round bottom.If flat i would run a round one.

 

[Bert Dygert]

Anthony,

A few schools of thought. First would say lower the strut and see if the slipping in the corner goes away ( i had this problem with my scale and dropped the strut).The boat could be fighting the skid fin if it has a hook. Either remove the skid fin and see if the hull has the same slipping in the corner or put a straight skid fin on it. Third prop diameter way be to small.

Good Luck

Bert Dygert

 

[Mike Luszcz]

Anthony, check out the GP400 thread of Bert's as I just did a detailed process that should really help! You have got to get that strut deeper than the sponson heel...Everyone seems to want to avoid doing that, and I just cannot figure out why! haha. Just do it, Nike Air....

 

[Mike Luszcz]

Also, throw out all you know about all that other guys sport hydros...this one uses such a different setup!

 

[anthony_marquart]

Ok guys,.. I'm going to get back to the setup board and take some notes. I need to do some real back to back with lifting to non lifting props. and document.. I was a bit discouraged,.. we'll get there..

 

[anthony_marquart]

More testing on the GP310 nitro today.

Making progress,.. Tested a GR 40-52 3blade,.. Ran ok, still not as fast as the x442,. Still having to plant the strut way deep,.. The boat down the straight has absolutely no rooster tail,.. no lift at all in that prop. Still looking forward to getting some 1440 blades with a touch of added pitch. .

I worked on the set up,.. but didn't get to go back through the other props,. still getting hop in the corners, I think the boat may be settling down deeper in the turn, causing it to hop back up,.. flattens out in the straight.

I think the GP310 may prefer a prop around the 41.5-42 mm diameter.. Boat still isn't running as well as when the x442 was on it.. still want to try a lifting prop to get the strut up a bit..

 

[anthony_marquart]

I found the problem.. CG was 3in behind sponson trailing edge.. no wonder I couldn't get the transom up,.. ,.. Going to move the motor forward 1/2 inch and add weight.. the boats already heavy at 5lb,.. going to wallmart for fishing weights!!! hopefully I don't have to add too much..

 

[RobertWurster]

I use angle stock on a two pices of a 4x4 one on each side to hold the angle and let the boat ballence on the point of the angle .works goog.and is cheep.

 

[Jeff Barnhart]

I found the problem.. CG was 3in behind sponson trailing edge.. no wonder I couldn't get the transom up,.. ,.. Going to move the motor forward 1/2 inch and add weight.. the boats already heavy at 5lb,.. going to wallmart for fishing weights!!! hopefully I don't have to add too much..

That'll do it! Its always good having the CG correct.