Rigger rear ride steps

[Simon.O.]

I know these can be an issue of debate and I want to hear some views on them.
I am not talking about the big doofy side mounted rear sponsons like some of the fuel riggers have but the under tub narrow ramp that I have seen photos of.
I know the H&M Xzess-3 has one offset and there are a few others that I have seen.

I can see some rationale for them as they take the lifting load off the prop and allow the prop to concentrate on forward power. If that makes sense.

I am interested in them as I think my mini rigger needs one.
It runs a 427, or 432 at the moment and soon to get a 431 for trials.
I load the rear of my riggers to lighten the front and this works well with my two bigger ones.
The small one has a few issues, the prop is not revving out as it does in the small cats (same motor and same prop) I think there is too much downwards load there.

Yes I know the obvious answer is to move the cg forward or to adjust the strut angle. I have done a bit of both but there is not a lot of room for either.

I can see that a rear ride step may be the next logical step to take in tuning this hull.

Here is the question to those of you who run fast and successfull riggers.
Do you have a rear step or not and why ??

Reminder, I do not race or saw but run a mixture of the two and a nuts sport boater.

[andym]

The only small rigger I have had with rear ride pad ( single in middle ) is my raptor, it was faster without it but in oval set up handles better with it. I run the COG @ 35-40% of after plain, strut level with shoe and 5 deg AOA. With out it 25% of after plain but would drop tail in turns some times. Never a problem in the straights even with 7 deg AOA and fin removed when I wanted to see just how fast it went. This is with a 1415 1.5D , hydra 240, 4s 45c pack and modded 645 for SAW runs

[Simon.O.]

The only small rigger I have had with rear ride pad ( single in middle ) is my raptor, it was faster without it but in oval set up handles better with it. I run the COG @ 35-40% of after plain, strut level with shoe and 5 deg AOA. With out it 25% of after plain but would drop tail in turns some times. Never a problem in the straights even with 7 deg AOA and fin removed when I wanted to see just how fast it went. This is with a 1415 1.5D , hydra 240, 4s 45c pack and modded 645 for SAW runs

Andy that all looks like good solid info.
I just need to clarify the way you measure your cg.??
I take my cg as x% of the afterplane measured from the sponson step backwards. Is that the same way you do it ??
I know it the opposite for other hulls (monos and cats) but this seems to be the given convention for riggers and hydros with the afterplane

I like that you run up to 7deg AoA too, that is well aggressive and would send my mid size rigger skywards, in all fairness that is such a mongrel of a hull that there are very few rules that it abides by. It is fawkin quick though.

[andym]

7 deg is aggressive but very fast, not good for going around and around though. After plane as described, from rear of sponson back. When we were checking out just how fast it would go with my limited budget it easily passed a FF gas rigger gps'd at 74mph but was a fire waiting to happen. Motor spun the wheel though and hard!!

[steve-b]

I would use the "ski". Just like you said. Lets the energy from the prop move the boat forward and thats it.
If you do deside to use one i would not use any angle on the strut... again you only want the prop to push the boat forward, not up or down. Is AOA ajustable?
Just my opinion.

Steve.

[Simon.O.]

I have a few blocks sanded and ready to fit and would like a few more opinions.

Do I set a ramp block up for the following
1. Above the shaft centre line
2. With the shaft centre line
3. Below shaft centre line as we would with a cat

As you all know I can sand and shape these pieces as needed but it may help if I can get a start point.

Above or below the shaft for kickoff ??

[NativePaul]

3 below shaft centre line, if you do 1&2 you will have strut and hub in the water negating a lot of the surface drive advantage, unless you still run a lifting angle on your prop so the ski is out of the water normally and is just there to keep hthe back end up if you back off for a turn or in rough weather as I understand they set up the big IC side of tub sponsons to do.

I ripped the ski off my JAE.21FE and with the much smaller than normal prop that I use it handles better without it than it did with it so I think it will be staying off.

It sounds like a lifting prop is the answer to your problem, giving you more lift at the rear and still letting you run the strut flat I'd stick an Octura 1630 on it.

Or how hot is it running? If it is cool adding another cell and the extra RPM will give you more lift from the prop you are using along with more speed, but that could go 2 ways, either or .