Remarked errors and vagueness in the manual of the program Maxsurf Resistance

Dear friends,

I write to you concerning program Maxsurf Resistance v. 21.11/2017/ as has noted some errors and I want to straighten out some vague problems.

The remarked errors and vagueness in the manual of the program are following:

1. On page 55/see iges file/-instead of “DL ratio” it is necessary to write “SL ratio”.
2. On page 57/see iges file/-for the series 60 and for Delft instead of "LCB" it is necessary to write “LCB / L”.
3. There are no separately written parameters for method Delft I, II and for method Delft III.
4. There is not in the program the series Delft IV - there are tests of 9 models.
5. The series of models Delft from I up to IV concern for round-bilge yachts.

How to make calculation of resistance and power of model of yachts from one or double chine if remaining parameters correspond to methods Delft?

What other method can be applied to hard-chine yachts approximately in semi-planing mode?

6. The program makes calculation on methods for yachts from series Delft only if the ballast keel is disregarded i.e. if to input the model without it, otherwise the program does not take into account the draft of canoe body and the maximum immersed draft and signals that parameters of the yacht are outside of allowable borders.
7. For method Savitsky pre-planing /see page 5 and iges file/ - to straighten out the text enclosed with a red line.

For what outlines this method concerns - for every ones /including round-bilge/ or only for hard-chine /prismatic with bottom deadrise /?

The problem has arisen as in the specified text is written “planing hull”- for me a hard chine and bottom deadrise is means, i.e. the model have potentials for operation in a gliding mode, but because of different reasons /for example changing of the engine / is necessary to make examination of the possibility to maintain the model in semi-planing or displacement mode.

Except for that in publication Savitsky - Brown, 1976 the example for application of methods Savitsky pre-planing and Savitsky Planing for a gliding vessel with length LWL = 80ft with prismatic outlines /hard chine, spray rail and deadrise of the bottom/ is shown.

At position that these two methods are applied for one model with gliding hard-chine outlines for me this example is acknowledgement of the conclusion that method Savitsky pre-planing cannot be applied to not gliding models that for me is equivalent on round-bilge.

But if to edit the text in the manual on page 5 /enclosed with a red line/ and he looks approximately so:

„ This algorithm is useful for estimating the resistance of a semi - planing hulls with a round bilge or hard chine and speed corresponding to FnV from 1 to 2 /see page 55/, i.e. its pre-planing resistance”.

Then I agree that method Savitsky pre-planing can be applied to any outlines.

But again there is a problem - how to make the resistance calculation of round-bilge vessels with FnV above 2? Likely the answer is only one - on method Lahtiharju /round bilge/ at which FnV = 1,5 - 3,8.

And more one opinion for upper bound of FnV for gliding round-bilge models:

In the book of Russian scientists Egorov I.T., Bun'kov M.M., Sadovnikov Y.M. “Planing ship propulsion and seaworthiness of planning ships” 1978 –on page 106 there is a very important conclusion:

„ The border of intelligent use of the round-bilge outlines for high-speed boats corresponds to Froude numbers FnV < or = 2,5. At major Froude numbers it is necessary to apply a hard-chine geometric shape. ”

8. The borders of parameters for method Wyman are not written.
9. It is not known when it is applied “Holtrop/monohull/” and “Molland/catamaran/” for Form factor.
10. It is not known at what events what values it is necessary to accept for “vertical exaggeration”.
11. What methods can be applied for multihull except for Slender Body?
12. How /on what method / to calculate resistance for multihull in a gliding mode at position that method Slender Body valid only up to FnL ~ 1,0 i.e. if we have FnL> 1,25 or FnV > 3?
13. On method Slender Body at calculation of slenderness ratio L / (V^1/3) for multihull what displacement should be taken - general or separately for each hull?
14. How to receive wave making for a gliding vessel /monohull or multihull/, i.e. for FnV > 3 at position that method Slender Body concerns only to vessels with FnL up to ~1,0 or FnV < 2?

Except for that at gliding we have running trim aft ward, i.e. the bow raised, and on method Slender Body the trim is not taken into account.

Yours faithfully, NA Razmik Baharyan

Rousse - Bulgaria