hi  seem like a place that i would like to explore...Mull. We have our lochin onshore to refit cutlassbearing and propeller shaft... I hope we can use the boat under our hollyday in a few weeks i will get some pic soon and a movie on our seatrials...the D9 575hk is a very god choise...we have a lochin at our coast with a volvopenta D6 370hk singel and it did 20kn full and march 16-17kn ...  

best regards Tobias

Hi Martin,

What ratio has your gearbox ? 2300 rpm propshaft speed looks a lot to me.

what is making the spitfire noise ? vibrations or open outlet, no silencer ?

with the 300 Iveco ( close to your 280 ) gear ratio 1,5 : 1 and a 22 x 20,5 x 4 prop with 104% blade area and the trim flaps 0 degrees, we get out of Tommie who is carrying 500 ltr. gasoil, 25 ltr. fresh water and some fishing gear ( the only luxury on board is a microwave oven)

at 1266  prop shaft rpm 12 kn.

at 1600 prop shaft rpm 18 kn.

at 1800 prop shaft rpm 22 kn.= 2700 engine rpm, and is using than +85 ltr. gasoil / hour.

You see that the last 200 prop shaft rpm's give 4 kn. !! more speed. This we reach only with a clean bottom. She is 3 months in the water now and has already barnacles and a beard, so the maximum we get out of her now is 19 kn. at 1666 rpm.

br,

kees.

hi Martin,

I think the ratio of your gearbox is to high / shaft speed to low / prop dia to small.

if it's the same design as Tommie, a prop with a bigger diameter is not possible as you need at least 0,15 x the diameter clearance between hull and prop.

your 10 kn. at 1000 rpm are even better as Tommie's 12 kn. at 1266 rpm. ( she needs 66 rpm more) Also the slip ( theoretical and real speed ) of your propellor is better than my prop but at top speed I have 650 prop rpm's more than you and the slip percentage of a prop becomes less with a higher rpm. you see that the last 200 rpm gives me 4 kn. more, so 650 will give...? I really think it's worthwhile to look for another gearbox, there are a lot of good and overhauled ZF gearboxes for sale in UK and they are happy to trade in yours.still there can be a big difference in weight and ballance in the same boats, so changing the prop's pitch or even blade area can be necessary. see pictures, same prop, same engine, same rpm's but greater blade area.

concerning trim tabs, when we bought Tommie the trim tabs where not adjustable as the hydraulic cylinders where replaced with a steel bar and fixed at approx. 10 degrees down. We never sailed with a wetter boat, especially when trottle down, the bow was pushed deep down and the fire brigade cannot produce the amount of water that we had on our windows. A few years ago we replaced the steel bars with electric cylinders and what appears to be the best for Tommie is 0 degrees, so I don't believe in trim tabs, maybe for a full loaded boat they have some use ? Heavy steering, not stabile a higher speed, we had the same, looking behind the trail was if I came from a whisky party. There was 1,5 mm play between rudder shaft and bronze bushing, rudder blade was bended 1 cm. to starboard, little bit of air in steering cylinder.

hi all 

back home after a hole day working on our Lochin and it went well today my targets where done and some more, now its time to sleep and rest... The thing went bad today was that the memory card in my camera was left in the computer at home so no pic to day either... i have mounted a 27x27 propeller now its huge and close to the hull it will be very interesting to test this one... also the skegg has being modified ,,,, new shaft and cutlass bearing ...

Best regards ,Tobias

Hi Martin

I have not tried my propeller yet, have to work on my house and take care of the children ...i hope me and my brother shall go this weekend and do some test...i forgotten the memory card at home last time so no pics were able ....I will not do that again.. 

Best regards Tobias

hi Martin,

here another working girl, 40 ft. sportfishing charter naned Nautilus, working here in Holland

she has a total of 1000 hp on board ( 2 x 500 hp caterpillars)

yes it fly's,  but i am suppriced they can make money at 1,5 pound per liter gas oil.

they ask 80 p/p for fishing less than 25 mn out of shore, and 90 for more then 25 mn.

br,

kees.

hi Dave,

I don't know how fast she is, but it must be pretty fast, as they organize wreck fishing day trips to a wreck that's 52 nm out of Dutch shore. As it is 75 nm in a straight line from Vlissingen Holland to Ramsgate England, they fish on only 23 nm from English shore and return the same day.

If I had to do with Tommy, it would take me 7 hours on cruising speed for 104 nm, so would just have time to catch one fish.

br,

Kees.