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Dalslandia

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Everything posted by Dalslandia

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  4. If I remember it correct PayPal only send out email with your name on it, and even so if they do, and something have to be changed or read, I go into the account and read it there. never klick on any links in the mail. Read about one Swed. that pranked someone that sent out a "nigerian" letter, and made an appoinment with them, and had them to buy him lunch.
  5. Saw some where, (Off T) that a narrow beam is, if it was British, EU or other standard, something like 14 or 16 feet wide, but cant remember where I saw that. Before now, a Swedish ship was longer then 12 meter and wider then 4 meter, but now if it is more then 24 meter it is a ship, not a boat. but it still say if it is a privat boat longer then 12 AND wider then 4 meter the PIC need naval licence.
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  9. correct if the efficiency would be constant, at zero speed the efficiency is zero if we see to the work of moving the boat and not the mass of water. What I meant is that there is so many variables that in practis it will not workout to give an correct number of the mass of the boat. We can also use the THP, Thrust HP instead of shaft HP*eff. THP is thrust*V, so if thrust is held constant, THP goes up with speed, or if THP is constant, thrust is going down with speed.
  10. Yes, V is speed or velocity, thrust is Power * efficiency / speed and you see that thrust is reduced with speed if Power and efficiency is held constant. efficiency is increased slightly with speed normaly untill cavitation come in. efficiency is the result of boat speed not the water. propellers have there openwater efficiency and hull its hull efficincy, with the propeller doing its job at the back. Imperial Power is a horse lifting 550 lb-ft/sec or 33000 lb-ft/min (76,04 kg-m/sec) metric horse lift 75 kg one meter in one sec. 5 hp will then make 5*75*0,5/1,8= 104 kg of thrust at 3.5 kts (4 MPH) with an efficiency of 50% thats for theory. in that case of have 50 kg of thrust at zero speed, then let go. in practise the prop will let the Engine rev more at higher speed, if perfectly governend (sp) the rpm will be held constant but fuel and Power will be reduced with higher speed due to unloaded prop, and the prop will probably have a better bite at some speed then static. to make that test correctly to get the mass of the boat, the thrust need to be monitored and held constant. Ps, I do calculate propellers for airplanes.
  11. The Thrust is not constant either, can't use static thrust to calculate dynamic thrust, and the dynamic thrust is reduced with speed, T=P*Eff/V
  12. https://en.wikipedia.org/wiki/Long_ton short ton too
  13. and ships in tons, volume that is, register ton, netto, brutto ... that is 100 cubic foot, 2.83 m^2 and feet fot and inch, lb's pint gallon ... as long as it stated what unit the numbers is in, I don't care. but you are right metric system is coming to the imperial countrys also, inch by inch.
  14. Mike, the tach suggested was a hand held optical, a mechanical will work as you suggest
  15. if it is this gear box it have 6 different gear ratios to chose from www.regalpts.com/PowerTransmissionSolutions/Brands/Velvet%20Drive/V7172pg1.pdf
  16. divide up the straight parts and the curved parts. an circle or ellipse have the area of a X b X pi, or A X B X 0,785 A triangle A X B X 0,5 so a curved pointy part not round at the end and not a triangle A X B X 0,64 A long ton is 1016 kg or 2240 lb fresh water density is 1 (0,99995 kg/dm3 ) at +4C and 0,998 at +20C
  17. sounds like it is correct, not that you are an idiot though can use the length from deadwood to bow, then calculate the stern as one part
  18. The heat exchanger in post #28 look like the oilcooler I have on the Scania D11 for the SCG 700 gearbox
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  20. The value 475 was found on a boat forum the OP had a 1.5 L BMC Diesel, his highest Reading was 425 the 3 other was a lot less,
  21. Without CFD and tow tank test, all that remain is to do practical test. I understand the hull is half planing type? with 85% of the nominal Power I get 9.5 kts and a 17.5 x 12.7 average of two ways to calculate. at 9 kts 17.6 x 12.2 at 8.5 kts 17.6 x 11.7 when limit the diameter to 17.0" the pitch would go up 1" - 1.25" making it a 17x14 I Think you are correct with this.
  22. 475 PSI 33,5 kg/cm2 or something from the net, but sounds high.
  23. Henri, most people online here have steel narrow Canal boats of 10-15 tons and hardly ever go faster then 4 MPH (3.5 kts) unless on a river, and the inflow to the prop is limited by hull and shallow waters
  24. I saw Pictures of Tresfjord 26 boat hull on the net, so can just agree that you have room. I used the Propking spread, the pitch is just not completely linear if you change the diameter, with smaller diameter the Power put more speed to the water, like a jet, and the otherway around if the diameter is greater. so a 18" diameter will have a less pitch then a 16" all other things stay the same. speed/ RPM = pitch, problem is Wake and slip Diameter is depending on Power and RPM Pitch is depending on speed, rpm Wake and slip Wake fraktion depends on hull shape and draft I come Close to 18x12 but was thinking that you said you got 3000 rpm and 8,2 kts, do you Think the Engine is rev limited? if so the speed with a better propeller will be a lot higher The prop king predict 9.5 kts with 85% Power at the propeller, and you are Close to 18x13. if you get it wrong, a prop shop could shange the pitch an inch or two
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