Hi All,
Yep we are cruising at 2200rpm with a 1.5-1 box which gives 15.8 knots. She will do 18 and a bit when running flat out at 2400rpm.
Doesn't sound like the prop is far out to me but you re down on speed because you are 400rpm below max. We get about 11-12 knots at 2000rpm.
Hope this helps
stu

Hi Chas,
Yep they seem similar. We tend to run at 2200rpm as nice and efficient there. The engine doesn't mind - 7.6 litre engine is commercially rated and not very stressed. I find the boat is over the hump about then too.
How has your season been?
Work and weather mean Sundance has done very little this year so far, about 70 hours i expect.
Hoping for a better one all round next year!
Regards
stu

Sundance is using a Clements 4 blade prop with a high blade area, about 80-85% i think.
I know of a 33 ive seen with 300hp Cummins with a 2-1 reduction which was running a 23x23 inch prop i think.
Easiest way to sort is to approach Clements or a similar prop company with engine, gearbox and boat details and they will calculate what the best prop for your boat would be.
They do this f.o.c and the correct prop is vital these days to give efficient speed vs fuel burn in these days of fuel companies being thieving bu**ers!
Hope this helps
stu

Hi,

Still looking for a solution, with the price of the go, I'm not interest in making bubbles in the water I'm looking for something like a 23*23", I may be lucky (ebay, 2nd hand...) .
I have mesuse the diameter of my shaft (50mm) and I'm waiting for my yearly docking to mesure the details needed (No idear how I'll find the LCG and so on a 30 years old boat, modified by the time).

If someone has the specs and manufacturer of a propeller on a 33 with 1 to 2 gear box ratio and about 300 hp, I'll be very interet !!!

Cheers

Jerome

Hi Jerome, I second that, welcome to the forum also!! Comparing your prop to Chas's in the pictures, it looks like theres a lot more fresh air between the blades than on chas's prop. I.E. less blade area. Theres also a fairly big gap between the hull and the tip of the blades on the prop as if perhaps its a slightly smaller diameter. We built our Lochin in 2003 and at the time Teighnbridge Propellers were the most recomended by Lochin back then and they were very helpfull calculating our pitch and style of prop for us.They may be worth a phone call also

Regards

Robbie

Hi Jerome

Looking at the latest photo of your prop: Robbie is right, your blade area does look a lot less than mine. I'll be interested in how you get on with it.

Your Lochin looks good and appears to be another of the long wheelhouse versions.

My keel seems similar to yours, very handy if you accidently ground it!

Cheers

Chas

Oh, mine is just "normaly" aground at low tide and floating at high tide, with the range we have, it's way it is . She also resist daily to some collision in the same way (some people call that also pilot boarding ).

I like this hull in rough weather... For a boat of that size, she is passing very well at 5-6 knots.

Hi Chas,
Yep will post one,
Sundance has a cutaway keel and P.Bracket. There fore no protection under the prop. I'm told it makes the vessel a little easier driven and more efficent, also better in a following sea.
But who knows....
Cant beat that shape though... a real classic!

Stu

Hi Chas/Stu

When we had our Lochin 333 built we had a fair dilema with the keel options available. "the cut away keel" with 'P' bracket, i beleive is what simon was calling the setup Stu has and is what we also have on our 333. Its supposed to increase the flow of water to the prop but we asked simon about the full keel option fitted with a keel strap & skeg because we ocassionally use a drying harbour nearby but simon said it would cost us around 1 - 1.5 knots in speed if i remember right?. We just settled on the cutaway keel option & dont really beach her but i definately agree chas, the prop & rudder on ours all look very vulnerable hanging there in fresh air!

Hi Guy's - been away for a few days so haven't picked up on your discussions recently.

The prop issue is one I get asked more about than anything else- it is a dilema and one that can only be answered by determining how the boat is used rather than satisfy a wish list which is usually headed 'how fast can I go!'. Most often asked question is 'how can I make my boat go faster' and of course the answers can be many and various but as a general guide, consider the following:

SINGLE ENGINE - most of the earlier 33's were built in the days when engine power was restrained to around 180hp/200hp which determined shaft angle, propeller diameter and performance and these craft rarely exceeded 18/20 knots. The older boats were built in an era when speed was not necessarily the most important issue because distances travelled were short (there were fish in those days) and sea keeping was a greater priority.

The orginal builder, Frank Nicholls, was a man on a mission, determined to preempt speed emphasis in favour of seaworthiness and very often he would loose a sale rather than build a boat that would effect his reputation for building for the rough and tough. The hull structual strength and integity were more important to him and very often he influenced his customers to follow this path.
Nowadays we have a different senario; the availability of much more engine power and the need to travel greater distances means 'speed' has a greater emphasis.
Sadly, it is not possible to change some boats to provide the most efficient speed potential from these larger engines because in most cases the stern gear configuration will determine how an installation will work.
Most shaft angles are around 11 degrees and this generally will allow a 22/23 inch dia prop with the appropriate clearance to the hull. Propeller design is such that there is an optimum diameter and pitch and generally we try to balance this with a good flow of water over the propeller hence why we favour the cut away keel and 'P' bracket installtion. I even introduced a through hull 'P' arrangement in later boats as this provided a cleaner flow of water and added to the efficiency to a degree.
With a number of older boats where the hull layup was substantial and the weight distribution ill defined, there is a tendancy for power to be lost in attempting to lift the bow. This I describe as the 'see saw' effect where the engine is being asked the lift the bow section because weight is predominately forward on the LCG and therefore is wasted in part. Some of these boats were heavily laid up because they may be used for serious commercial applications such as potting in the short wheelhouse versions. Large open ****pits demand additional structural strength and Frank Nichol's rule was 'more rather than less' so the layup on these boats was very substantial.

Hope that helps guy's!!

Regards, ST

hi all,
happy to be back in the water,
Tommie:
300 HP/2700 rpm. gearbox 1.54 : 1. = Propshaft rpm 1753.
Propellor 22 x 19. Dar 68%
Trimflaps 2 degrees down.
topspeed flat out : 19 kn.
crusing at 1800 rpm 11 kn.

Hi all,

Delivered Tommie's prop last winter at a proppeller company. they changed the pitch from 18'' to 19,5 '' and balanced the prop again. Reached a stunning 22,1 kn. on the gps, but one hour before high tide there can run 4 kn.of current over here, so I will try at dead tide what her real top speed is.What worries me is that there are still prop vibrations an noise at top speed.The propeller company claims that the last few grams are not important but I found in an old schoolbook a formula to calculate the force of an unbalance. It's FC = M X V² : R. where M = unbalance V = circumference speed N = rpm / min. R = radius.The prop has a diameter of 0,559 mtr. Max rpm of the propshaft is 1733 / min. This gives a circumference speed of 50,69 mtr. / sec. ( 182 km / H.) If the unbalance is at the outer diameter, say 30 gram, we get 0,030 x 2569 : 0,28 = 27,4 kg by 1733 rpm. If an unbalance of 20 gram is at 140 mm from center we get 0,020 x 645 : 0,14 = 9,2 kg / 1733 rpm. It looks a lot to me, is this formula wrong ? or has the prop company underrate the very high rpm's ?

nice spring and summer to you all,

kees.

hi Harold,

hope they deliver you a prop close to perfect, what's the blade area they offered ?

To remember you as 'warm water sailor' to the Dutch weather conditions, see see a very concentrated Chantal surround by ocean going vessels, sailing home in the rain, in a grey sea, after a rainy fishing day.

take care,

kees.

hi Chuck, welcome to the forum.

A prop with 68 % blade area  gived a lot of slip ( differance between theoretical and real speed )  at Tommie.

 We changed to a 104 % and reduced the slip with 50%.

 

cheers,

kees.

hi kees, 

hi every body from corsica island. sunny today.. what news there?

i leave there, theris full grade above zero, but to have a new special prop, it's a really long story (they ask me three or four mounths); where did you make yours did they work fast?

regards

jean

thanks jerome,

what do you fishing now in your country; here we catch squids now and all winter 

regards

Hi Chuck,

Most standard props in stock at marine stores here are imported from Taiwan, but it's not always good quality. See on picture a brand new one they send to me, with a conical hole witch is double hexagon. I assume the quality manager had a free day.

Not standard Taiwan props has a very long delivery time, for that reason we let ours casting here local. On request they use Nibral.

delivery time :  3 weeks and casted in bronze only 10% more expensive.

 

regards,

Kees.

Well done Jeans glad your hard work has paid off for you

Martin