Takacat 3.4m LX - Tiny Tigga

[chris moody]

I think we are going with a name change. It's either:

Tiny Tigga Too

Taka Tigga

What do you guys think?

[9-R]

It's all quite exiting fine tuning a new boat.

I agree, it can be fun.

If you do get ventilation, you might also try a compression plate for the lower unit just above the prop. Not sure if you remember all of the issues we were having with the poor keel design of our boat. We were having bad rolling air under the hull and ventilation at the prop. Was surprised at the difference my DIY plate made. It did have some minor drag but not as much as a hydrofoil.

Tagga Tigga

[chris moody]

A bigger ventilation plate is the next option if propeller cupping doesn't cure it.

[chris moody]

Finally got the new boat out on the water and I’m very impressed with how it handles. Just playing around with engine height and trim to get the best performance. So far raised about 5mm above the transom and second trim hole out seems to be the optimum setting to minimise ventilation.

Not checked the top speed yet on gps, but it’s more than adequate, & feels slightly quicker than the honwave.
.

[chris moody]

A new propeller was delivered today.

This is a 8.5 x 7.5 which will be cupped once I have the tachometer max revs from the existing 8.9 x 8.3 propeller. The aim is to cup the new prop to give close to 5750 rpm at WOT with one person aboard.

I’ve gone with a smaller pitch as I want to add quite a lot of cupping.

[ChrisParish]

So, what’s cupping?

[Roy54]

I believe it's a slight bend on the edge of the blade, which gives a slight cupped look . Obviously a bit more sophisticated than bending with a pair of pliers though!!

[harrison]

Many of today’s propellers incorporate a slight cup at the trailing edge of the propeller blade, cupping increases this feature. The curved lip on the propeller allows it to get a better bite on the water. This results in reduced ventilation, slipping, and allows for a better hole shot in many cases. A cupped propeller also works very well where the motor can be trimmed so that the propeller is near the surface of the water. The cup will typically result in higher top end speed and less ventilation.

With Chris’s cat better performance will be had if the prop can run nearer the surface.

Cupped/uncupped prop.

[chris moody]

The cunning plan is that the curve to the trailing edge of the blades will remove the ventilation that I'm getting just as I climb up onto the plane. It's performing fine the rest of the time, but it's ventilating every time I go from displacement to planning mode.

If the cupping doesn't completely cure the ventilation I'll then investigate hydrofoils (doel fins), however I'm not really a fan of those devices.

Speed wise I will be happy if I can achieve somewhere between 17 and 20 kts once I get the cupping, pitch, trim and engine height all correct.

[chris moody]

The other cunning plan for more speed is weight loss. I'm already 1 stone 1 pound lighter than I was on the maiden voyage. I should be able to shed a couple more pounds in weight before the next sea trial in March