LB26

Power Boats only. Please include the boat type in your question.
les2021
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Re: LB26

Post by les2021 »

Evening Jacques

Have you had time to look at thruster tunnel location yet ?

Cheers

Les

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Re: LB26

Post by jacquesmm »

No, I have to work on the 3D model and can't do that on my tablet.
I'll work on the computer later today.
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Re: LB26

Post by jacquesmm »

Image

That is the proposed location of the center of a 125 mm diameter tube, 200 mm in front of the 1st frame, 200 mm below the BL (= DWL).

Vetus indicates minimum 135 mm below DWL, you could go a little higher than what I show but those things are not as effective close to the surface.. The lower edge of the tube is a little above where Vetus shows if but there is not much room down there.

Image

That is a view of the tube. In the drawing, it is 1 meter long total. Don't make it shorter than 600 mm, that is the length of the section at the top. The thin red line is at 500 mm.
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les2021
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Re: LB26

Post by les2021 »

Hi Jacques

Thanks for the thruster details.
I am away for my partners birthday in Italy so have no drawings etc.
My engine supplier has sent me an email regarding the gearbox.
Can you have a read and advise please.
Many Thanks
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Re: LB26

Post by jacquesmm »

Down angle: certainly, it saves room in the cockpit.
Reduction ratio for the prop I suggest is 2:1 but a 1.5:1 will also work with less pitch like a 19x19.
Make certain that your local prop supplier will allow you to test a prop. I based my calculations on a 3 blade Michigan Wheel.
A 19x19 is common but 19 by 21 is sometimes difficult to find in which case a 1.5:1 gear is a better choice.
That is why I wrote "Check with prop manufacturer". Props and reduction go together.
BTW, almost all engine manufacturers will do a free prop and gear reduction analysis. It will give you a choice of reduction gears and props.
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les2021
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Re: LB26

Post by les2021 »

Jacques

Can you help out on this one !!! My apologise if I should already know these answers.


Hello Les,

Hope you are well.

We need a final approximate displacement.
So is it 2.450 kg all inclusive? (including passengers and how many, fuel etc) OR
Is it 2.450+105kg water+300kg fuel+4 pax@80kg ea (320kg)= 3.175kg

Please let me know. Sorry to insist this is essential. Also I need to rush in placing the order with the proper gearbox due to imminent price changes.

Many thanks

Displacement at DWL 2450kg
PPI ar DWL 130kg/cm
Water and waste water 105 litres
Passengers 2 - 8 ( average 4 I would say )
Fuel max 360 litres

As you can see I need to get this order in quick.... would appreciate a quick response.

Sorry for pushing on this one.

Les

fallguy1000
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Re: LB26

Post by fallguy1000 »

Displacement in a boat is to dwl which generally includes specified items, here, water, fuel, engine are specified.

Displacement does not equal vessel weight. It is only a measure of how much water is moved when the boat rests on her designed lines.

If JM does not respond; I'd design based on 4 passengers added.

Or 2450 plus 320 or 2770 low to 3000, high. Then consider the impacts of gearing too high or too low and decide.

It is very easy for amateur builds to gain weight. Things like countertops, windlasses and chain, bowthruster and batteries to support one, etc.

And so, err on the high. You can even use the dealer's 3175 and be pretty safe.
My boat build is here -------->

viewtopic.php?f=12&t=62495

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Re: LB26

Post by jacquesmm »

I must find my spreadsheet but it is probably based on the same load than other boats of that size: 2 persons, tanks half full and some gear. Ground tackle is probably 50 lbs., 150 lbs. for misc., hardware. That is what I usually base my weights on.

Are you having second thoughts about engine HP or top speed?
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les2021
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Re: LB26

Post by les2021 »

Hi Jacques

No the speed is not important to me. The question is purely to do with gearbox as requested by the supplier, so for his calc's he just needs to know the total weight.

Cheers

Les

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Re: LB26

Post by les2021 »

Jacques

See reply from supplier.


Dear Les,

According to the data and our calculations a fully laden boat at 3000kg is at the maximum weight for 2/1 ratio.
1.5/1 is out of the question, a 2.5/1 which was not discussed by the designer, is to be considered.
I see further below the engine model is stated as 4.390TDI. Indeed that was a 200hp NANNI engine but WOT RPM was at 3.400 instead of 3.600 that the new engine T4.205 has.
3.400 WOT RPM would favor the 1.5 ratio if boat was very light. As I see they mention 2.450kg as the figure where they make the speed calculation. Not sure if this will be the final figure, as said.
I suggest that care is taken to restrict laden weight at 3000kg and as such we proceed with the 2/1 ratio.
At this displacement (3000kg) the boat should make approx. 24 knots maximum speed, ie approx. 27.5 mph. Cruise speed approx. 20 knots (23 mph).

I remain at your disposal.

Kind regards

Let me know your thoughts.

Les

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