Oz hydrofoils.

[chipko]

Optimum motor height on cats seems to be a bit of a black art in my experience.

Can’t get my head round your finding both excessive splashing (leg too deep) and prop ventilating (leg too high) as generally they’re polar opposites.

Taking the excessive splashing out of the equation I’d hazard your motor is better in the first pic mounted without packers, and that’s perhaps still even slightly on the high side. A good starting point I’ve found is to aim for the AV plate level with the underside of tubes and then raise in increments to just below a level where ventilation occurs.

Really can’t see the excessive splashing caused by running leg too deep in your pictures.

On both our cats found AV plate running at, or just above, u/s tubes level a good compromise for decent grip and acceptable splashing.

[maverick58]

Originally Posted by chipko

Optimum motor height on cats seems to be a bit of a black art in my experience.

Can’t get my head round your finding both excessive splashing (leg too deep) and prop ventilating (leg too high) as generally they’re polar opposites.

Taking the excessive splashing out of the equation I’d hazard your motor is better in the first pic mounted without packers, and that’s perhaps still even slightly on the high side. A good starting point I’ve found is to aim for the AV plate level with the underside of tubes and then raise in increments to just below a level where ventilation occurs.

Really can’t see the excessive splashing caused by running leg too deep in your pictures.

On both our cats found AV plate running at, or just above, u/s tubes level a good compromise for decent grip and acceptable splashing.


Attachment 142273


Attachment 142274

Yes from what I’ve read so far the cat style boats are tricky to get right. Could be just that flat transom design, I’ve had futuras in the past where that slight V at the back disperses the water more efficiently, I had to jack up my last merc 15 up by 20mm on the zodiac to lose excessive backsplash which worked a treat.

It’s all in testing mode at the mo, jacking up, trying different trim holes to find that sweet spot. It’s not a bad set up by any means, the tohatsu is a strong little motor, blip the throttle and she’s off like a baby racehorse. I Just need to tweek the backsplash at top end speed and keep a dry deck.

[Old seahorse]

Just out of interest, is this spray/ turbulence present at low speed, or does it occur at higher speeds only, since you fitted the permatrim?
Whilst not being any expert, the design of these cats is such that as speed increases, air( and any ripples/ waves), will be pushed through the tunnel beneath the air floor with greater force, and this needs to dissipate on exit. I notice that the front edge of the air floor on the Aquamarina has a large upturn, which I assume gives lift to the boat when underway. That must give a large volume of air being compressed, and later released at the stern.
The early Takacats were similar, but later versions have the tubes rotated inwards, which narrows the”entrance” to the air tunnel, and I think, slightly lowers the front edge of the floor.
I wonder if this was an attempt to reduce spray.

[maverick58]

Originally Posted by Old seahorse

Just out of interest, is this spray/ turbulence present at low speed, or does it occur at higher speeds only, since you fitted the permatrim?
Whilst not being any expert, the design of these cats is such that as speed increases, air( and any ripples/ waves), will be pushed through the tunnel beneath the air floor with greater force, and this needs to dissipate on exit. I notice that the front edge of the air floor on the Aquamarina has a large upturn, which I assume gives lift to the boat when underway. That must give a large volume of air being compressed, and later released at the stern.
The early Takacats were similar, but later versions have the tubes rotated inwards, which narrows the”entrance” to the air tunnel, and I think, slightly lowers the front edge of the floor.
I wonder if this was an attempt to reduce spray.

Hey man!!! Yes, only at high speeds, generally that last 3rd on full throttle. Everything else apart from that is dandy. It’s still producing splashback even with the permatrim fitted. I’ve had the boat out 2day for further testing and to see what it does raised 40mm off the transom, then to 20mm and then standard ride height.

Interestingly the top end speed over all 3 settings came in at 20.7mph at 40mm, 19mph raised 20mm and 19.5-8 on standard height. All 3 settings still Produced splash on holes 2 & 3 despite the new foil. Standard ride height seemed like it was a little bit more punchy out of the hole, with The other 2 more smooth and refined getting on the plane.

I guess it is what it is with these things. It’s a great design, 1 man launch, it’s super light, it’s cheap and cheerful with a lot of fun days to be had with a stonking little motor on the back to stay 1 step out of trouble. This is my 3rd fully inflatable sib and have to say what fun rig it is out on the water. Can’t wait to get it out on some nice chop and see what she can do.

[Old seahorse]

Enjoy it and savour the difference!