help about NAV CAD

[cioko]

Hi.
I am interested if anyone had worked with NAV CAD 4.
I have a problem with resistance prediction of a planing hull.I cant get results for low range of speed, between 0-10 kn, an the values of resistance for speeds in preplaning conditions are much greather then those for projected speed of 50 kn.
please, if someone has already worked in this area, give me some advice.
I changed some parameters, and i reached satysfaing results for shaft inclination for about 40 deg, but this is nit the real case, because, in real case, shaft angle ,the acute angle between base line and shaft line is 19 deg.(Arneson surface drive on stern, with surface piercing propellers).
Please, let mi know if you have some help!

[Çemberci]

Dear
Do you think to sell NavCad 4 Program with Key.
Oktay Cemberci

[marshmat]

I cant get results for low range of speed, between 0-10 kn, an the values of resistance for speeds in preplaning conditions are much greather then those for projected speed of 50 kn.
I don't know NavCad too well, but this doesn't seem completely unusual. A code designed for resistance estimates on plane would normally have a low-speed cutoff below which it will produce only gibberish, and so the programmer may have expressly forbidden that code to produce output in the range where it is not valid. And most full-planing hulls tend to have a substantial increase in resistance during the climb to plane, which drops off once the boat is fully on plane.
As to the interpretation of your test parameters and results, I'm afraid I don't have the expertise with NavCad to be of much help.

[cioko]

thanks for your disponibility.I think that the reason for so high values of resistance in preplaning area is the inclination of the propeller shaft.

[Gilbert]

I doubt that the high shaft angle would produce those results. The resistance at 50kn should be outrageously higher than the preplanning condition as you no doubt know.
I don't know anything about navcad. Perhaps you could trick it into thinking the shaft angle was lower somehow, like placing the engine in the bow for instance and see if the result was different.