Kolibri SeaCat KM-380

[Fenlander]

Like our river trip the other day you have a good bit of sun. That really is a smart looking sib-cat. Despite not liking the nothing in front of you feel at sea with even the Elling she'd appreciate the walk on/off bow at the slip.

[Fenlander]

She'd as in Mrs F.

[Steve509926]

Originally Posted by Fenlander

She'd as in Mrs F.

You cut that one very, very close David! Hopefully "she" hasn't read it yet and you've got away with it.

[Fenlander]

Got to be fleet of foot both in reality and when posting.

[chipko]

Originally Posted by Fenlander

Like our river trip the other day you have a good bit of sun. That really is a smart looking sib-cat. Despite not liking the nothing in front of you feel at sea with even the Elling she'd appreciate the walk on/off bow at the slip.

Thanks, yes a cracking day on the river.
Also liking the looks but a knot or two down on the Elling at the moment, so more work to be done.
Yeah the ‘landing craft’ bows pretty cool….I’ll just have to resist heading full chat up the beach and sprinting off just like the Zapcat boys.

[chipko]

Another couple of outings on the river and a few more observations.
Motor now raised 30mm with no ventilation and much reduced splashing at speed, could probably go a tad higher but happy as is for now. One up plus kit saw 21.5 knots average with the 15hp pulling 5500rpm on an 11” prop.

Now the not such good news.
The last river trip saw some stretches of very flat near glassy water conditions which exposed a potential hull flaw. At fast cruising speeds of over 17/18 knots, occasionally and on very flat water, the air cushion could be lost and the tunnel hull sucked down to water level. This then deforms the floor, creating in effect a hooked hull. Trying to accelerate through this just exacerbates the problem, sucking the stern even lower into the water, raising the bow and lots of splashing from motor. You have to slow down and power back up onto the plane to break the cycle. Have to admit this only seems to occur randomly and on very flat water, but feel my initial concern on the reduced height (100mm) of the tunnel hull is responsible for this phenomenon.

Of course on the sea, where very rarely the water will be glassy smooth, then this issue may never manifest itself. Won’t have the opportunity to find out conclusively until Spring though when back at the coast.

So for now at least, giving the Kolibri a thumbs down from me. Shame as it’s a nice looking piece of kit which performs really well apart from this, but we tend to run mainly maxed out so can do without any untoward little idiosyncrasies lurking in the back of my mind.

For many it would still be a great choice.

[Steve509926]

Originally Posted by chipko

Another couple of outings on the river and a few more observations.
Motor now raised 30mm with no ventilation and much reduced splashing at speed, could probably go a tad higher but happy as is for now. One up plus kit saw 21.5 knots average with the 15hp pulling 5500rpm on an 11” prop.

Now the not such good news.
The last river trip saw some stretches of very flat near glassy water conditions which exposed a potential hull flaw. At fast cruising speeds of over 17/18 knots, occasionally and on very flat water, the air cushion could be lost and the tunnel hull sucked down to water level. This then deforms the floor, creating in effect a hooked hull. Trying to accelerate through this just exacerbates the problem, sucking the stern even lower into the water, raising the bow and lots of splashing from motor. You have to slow down and power back up onto the plane to break the cycle. Have to admit this only seems to occur randomly and on very flat water, but feel my initial concern on the reduced height (100mm) of the tunnel hull is responsible for this phenomenon.

Of course on the sea, where very rarely the water will be glassy smooth, then this issue may never manifest itself. Won’t have the opportunity to find out conclusively until Spring though when back at the coast.

So for now at least, giving the Kolibri a thumbs down from me. Shame as it’s a nice looking piece of kit which performs really well apart from this, but we tend to run mainly maxed out so can do without any untoward little idiosyncrasies lurking in the back of my mind.

For many it would still be a great choice.

I suppose it's fortunate that it is rare that we have flat water, mirror like conditions.
I have experienced a similar problem on Ullswater and Loch Long when Redneck has been "stuck" to the surface of the water and I've not been able to break free and get up on the plane. It feels as though you are pushing a wave of water in front of the sib. On both occasions I was looking forward to achieving maximum speed only to have my hopes dashed.

[Fenlander]

It’s a shame these cats can be problematical to get performing well across all areas. They are so efficient on modest outboards.

Re this issue I’m thinking F1 ground effect and Bernoulli’s principle of gas and liquid dynamics.

[chipko]

Originally Posted by ;Fenlander

Re this issue I’m thinking F1 ground effect and Bernoulli’s principle of gas and liquid dynamics.

Oh bugger!……..and there’s me thinking it’s just the bleedin floors been put in too low…..simples