The Museum of HP Calculators

HP Forum Archive 11

 Poll: What is the most useless function on a scientific calculator?Message #1 Posted by Jeremy on 13 Mar 2003, 10:09 p.m. My vote is for factorial. (n!) The only time I have EVER used that function was for a test in high school just to prove I knew what it was. Other than that, does it have any practical use? There are some other statistical functions that are pretty lame and seldom used too...

 Re: Poll: What is the most useless function on a scientific calculator?Message #2 Posted by Mark on 13 Mar 2003, 10:50 p.m.,in response to message #1 by Jeremy =

 Re: Poll: What is the most useless function on a scientific calculator?Message #3 Posted by Scuba Diver on 13 Mar 2003, 11:19 p.m.,in response to message #2 by Mark Actually, I've used factorials for combinations and permutations when the calc doesn't offer those functions... The most useless function? Well, it only applies to my Sharp EL-9000 "Super Scientific"... ...the ON button!! :) B.

 Re: Poll: What is the most useless function on a scientific calculator?Message #4 Posted by Masao Kinoshita on 13 Mar 2003, 11:47 p.m.,in response to message #2 by Mark A shifted square function on a non-programmable calculator, e.g., HP 27A, gets is my vote. For some reason, I always use [ENTER] [×] instead of [f] [x²]. I think RPN encourages the mind to think more when calculating. The Zen of calculating... to be at one with the numbers. :-) Whereas with algebraic entry, the ultimate goal seems to be for the users to be able to input the equation just like in the textbooks, i.e., just copying. imho

 Re: Poll: What is the most useless function on a scientific calculator?Message #5 Posted by Vieira, Luiz C. (Brazil) on 14 Mar 2003, 1:42 a.m.,in response to message #4 by Masao Kinoshita Hi; in many situations, preserving the T-register contents may be desirable. I almost always use [f][x2] instead of [ENTER^][×] simply because of this. Otherwise, if you want to throw away T-register contents, that's fine. Cheers.

 Re: Poll: What is the most useless function on a scientific calculator?Message #6 Posted by Karl Schneider on 13 Mar 2003, 11:59 p.m.,in response to message #1 by Jeremy True, factorials are seldom used in interactive computations, but they do have real-world applications. For example, if your base calc lacks permutation and combination functions (e.g., HP-17Bii, HP-41CX, HP-28S): P(n,k) = n!/(n-k)! and C(n,k) = n!/(k!*(n-k)!) Q: You bought a "pick six" lottery ticket with the numbers 1-50 in play. What are your chances of winning? A: 1 in 50!/(6!*(50-6)!) = 15,890,700 Q: You pulled the spark plug wires off your 4-cylinder car's distributor cap, and can't quite remember which ones went where. How many ways are there? A: 4! = 24 Q: Same as above, with a V-8? A: 8! = 40,320 (oh, s***!) Factorials are also useful for programming Taylor series -- a calculus topic. Note: If your HP has an "x!" function instead of "n!", it's also a gamma function -- like a continuous factorial that will work with non-integers.

 Re: Poll: What is the most useless function on a scientific calculator?Message #7 Posted by Chris Randle (UK) on 14 Mar 2003, 3:21 p.m.,in response to message #6 by Karl Schneider <> 28S does have Perm & Comb under the Stat menu.

 Re: Poll: What is the most useless function on a scientific calculator?Message #8 Posted by Christof on 14 Mar 2003, 12:02 a.m.,in response to message #1 by Jeremy Well, I do use the n! pretty often. Then again, I consider probability and statistics to be pretty normal everyday tools (and I occasionally go off that more people should use them more often, at least so they can stop being lied to so often wiht manipulated stats) If I was going to pick one based on the machines I use, I'd pick x^2 - but admittedly, this is HP specific. looking around further... on a scientific? % gets a strong vote from me. that's about useless, IMO :)

 Re: Poll: What is the most useless function on a scientific calculator?Message #9 Posted by Karl Schneider on 14 Mar 2003, 12:54 a.m.,in response to message #1 by Jeremy GRAD Who has ever been given an angle measured in gradients? Where is the advantage in the 0-100 scale between vertical and horizontal? "x" grad is not an "x" % slope...

 Re: Poll: What is the most useless function on a scientific calculator?Message #10 Posted by Patrick on 14 Mar 2003, 12:55 a.m.,in response to message #9 by Karl Schneider Ha! We posted the exact same comment at the exact same minute. It MUST be true.

 Re: Poll: What is the most useless function on a scientific calculator?Message #11 Posted by Christof on 14 Mar 2003, 12:57 a.m.,in response to message #9 by Karl Schneider outside of school... I don't think *I* have ever used grads.

 GRADS in Surveying (land measurement)Message #12 Posted by Vieira, Luiz C. (Brazil) on 14 Mar 2003, 1:55 a.m.,in response to message #9 by Karl Schneider Hi; there are still some "active" surveying instruments (land measurement) scalled in GRADS. I know GPS technology is definitely taking place, but not all surveyors can afford a precise GPS station. And some portable GPS do not offer required precision. These old (ancient?) instruments are still being used. Anyway, converting from decimal degrees to grads and back are two operations easy to perform. BTW, is there any scientific HP (not the HP16C) that does not have GRAD angular mode? I cannot remember if any. Cheers. Luiz C. Vieira - Brazil

 Re: GRADS in Surveying (land measurement)Message #13 Posted by GE (France) on 14 Mar 2003, 3:34 a.m.,in response to message #12 by Vieira, Luiz C. (Brazil) You're right, and many recent calculators don't have a GRAD mode. Actually, to push this a little further, I never used DEG in 'real life' either : in maths there is no such thing but Rads, and in physics it's the same as it tends to be more and more maths, even to the point where it defies common sense (quantum theory anyone ?). This is true for students, probably not so for professionals. Actually, in my field (Finance), we never use trigonometric functions (apart from some special cases like deriving normal random numbers from uniform distributions...). My vote would be for hyperbolic functions, these are good for testing the internal precision (like in tanh-1(tanh(15))), but not much else.

 Re: GRADS in Surveying (land measurement)Message #14 Posted by R Lion on 14 Mar 2003, 11:36 a.m.,in response to message #13 by GE (France) Neither n! nor %, definitely: my vote is for hyperbolic functions too. Raul

 Re: GRADS in Surveying (land measurement)Message #15 Posted by Masao Kinoshita on 14 Mar 2003, 8:40 a.m.,in response to message #12 by Vieira, Luiz C. (Brazil) The HP 21A doesn't have GRADS mode. It has a DEG/RAD rocker switch. Thanks for the T-register comment to my post on this thread. It is an important consideration. (I did think of it *after* I did the post.)

 Re: GRADS in Surveying (land measurement)Message #16 Posted by Vieira, Luiz C. (Brazil) on 14 Mar 2003, 9:12 a.m.,in response to message #15 by Masao Kinoshita Hello, Masao; you know what? There are listings for programs to be used in the HP55 that have this particular procedure to comput X². In this particular case, the contents of the Z- and T-registers are irrelevant, and as program steps, [ENTER^] [×] use two steps, but in the HP55, [f] [X²] do not merge in one code, they still use two steps. In other calculators (most of them) this is also something to be considered, if memory space is critical. I once was typing in a program written by an unknown person in my HP41 and I replaced two occurrences of [ENTER^][×] for two [X^2]. The program simply generated wrong results. It considered that the Z-register contents were duplicated, and by using [X²] I removed this occurrence. That's why I posted that note. I'm happy you understood the reason. Thank you, too. I forgot that the HP21 has a switch for DEG and RAD, no GRAD available. Best regards. Luiz C. Vieira - Brazil

 Re: GRADS in Surveying (land measurement)Message #17 Posted by Masao Kinoshita on 14 Mar 2003, 6:02 p.m.,in response to message #16 by Vieira, Luiz C. (Brazil) Hi Luiz, Yes, I agree completely with you. One has to be very careful modifying programs written by other people. I remember that how the numbers were manipulated in the stack was one of the crucial points when programming these calculators, especially the earlier machines with limited program steps. Stack usage must have been a major consideration when programming the HP 55 (and even the HP 65, since not all merged). Thank you for the story behind the post. Masao

 Re: GRADS in Surveying (land measurement)Message #18 Posted by Michael F. Coyle on 14 Mar 2003, 1:05 p.m.,in response to message #15 by Masao Kinoshita Don't forget the HP-35 -- no radians! You were expected to use PI to convert everything to/from degrees.

 Re: Poll: What is the most useless function on a scientific calculator?Message #19 Posted by Patrick on 14 Mar 2003, 12:54 a.m.,in response to message #1 by Jeremy How about grad mode for angles? Academically, I'm a mathematician and I never heard of grads until I picked up I saw them on one of the early HP's. I'm sure someone will pipe up, though, and say they use it. The question is, how prevalent is it?

 Re: Poll: What is the most useless function on a scientific calculator?Message #20 Posted by mapet on 14 Mar 2003, 3:56 a.m.,in response to message #1 by Jeremy cubic root in HP6S...:-)

 Re: Poll: What is the most useless function on a scientific calculator?Message #21 Posted by Axel on 14 Mar 2003, 4:34 a.m.,in response to message #20 by mapet I always found the % key the most useless. It doesn't belong on a scientific calculator. Only non-scientist need the extra multiplication by a factor 100. For statistics and some number theory n! is needed. Especially, I like the implementation of the gamma function on the HP calcs. I only found it on an old Commodore (SR-4190R). On the 40G, it even works for complex arguments! May be, the ti89/92 can do it either, anyone knows? Axel

 Re: Poll: What is the most useless function on a scientific calculator?Message #22 Posted by Frank Wales on 14 Mar 2003, 1:46 p.m.,in response to message #21 by Axel Ah, but '%' has the advantage that it doesn't pop y. So, if you need to know both x per cent of y, and the total of y+x%, for example, then y enter x % (note percentage) + seems slicker to me than the simple arithmetic alternatives where you have to make your own arrangements to duplicate y. In nearly a quarter of a century of use, I can safely say I've never used the LN1+X and E^X-1 functions on the HP-41, and I don't recall them ever appearing on another HP product that wasn't explicitly HP-41 compatible.

 Re: Poll: What is the most useless function on a scientific calculator?Message #23 Posted by Masao Kinoshita on 14 Mar 2003, 5:38 p.m.,in response to message #22 by Frank Wales I do sometimes use HP's version of the % function, which makes more sense to me than the % function that 4-bangers have. But when I need to add a percentage, I usually use multiplication by 1 + 0.nn . For example, to add 5% (Massachusetts (USA) sales tax rate) to \$100, simply multiply 100 by 1.05 and you have \$105. This technique is necessary with Casio's Data Bank Calculator (DBC) watches, which have never (AFAIK) had the % key. I have always worn a Casio Data Bank watch on my wrist since they first appeared, starting with the CD-40. I wore a Seiko C439-5000 calculator watch for 5 years before that (no % key here either). To reiterate, I _like_ HP's % key (a lot better than on the other brands that I have encountered).

 Re: Poll: What is the most useless function on a scientific calculator?Message #24 Posted by Vieira, Luiz C. (Brazil) on 14 Mar 2003, 5:43 a.m.,in response to message #20 by mapet The HP6S itself... (although my own daughter and many of my students have one)

 Re: Poll: What is the most useless function on a scientific calculator?Message #25 Posted by Paul Brogger on 14 Mar 2003, 9:45 a.m.,in response to message #20 by mapet I actually threw my 6s impactuflly, vionlently (and, I confess, with intent to harm) into the trash, angered by mushy, inexact input and key feel. I didn't even think of retrieving it, an have never regretted the action for one second. (I remember an old National Lampoon article, "Games You Can Play With Calcualtors" -- golf, baseball, tennis . . . I think the 6s would be a good candidate for all of those.) But I digress . . . I vote for %. Absolutely brain-dead. That it is implemented is bad enough -- to think that it takes up an extremely rare and valuable (albeit, shifted) position on the HP-32s and -42s keyboards rather than being buried in some dips**t menu somewhere . . . Amazing!

 Re: Poll: What is the most useless function on a scientific calculator?Message #26 Posted by J.Manrique Lopez de la Fuente on 14 Mar 2003, 4:39 a.m.,in response to message #1 by Jeremy Well, using a RPN calc, () are the most useless key I've found ever. Best regards, J.Manrique #1077 HPCC Member

 Re: Poll: What is the most useless function on a scientific calculator?Message #27 Posted by Christof on 14 Mar 2003, 12:40 p.m.,in response to message #26 by J.Manrique Lopez de la Fuente well, () is useful if you have the solver, for example. I suppose it depends on how we limit our definitions. I've got keys here that are utterly useless on a non progammable scientific- or one without Solve. I find it interesting how many variations you get depending on RPN vs AL, 4 level stack vs. 48 style stack. It looks like the only one that I can find to be really useless to me that is present on almost all calculators I own- TI, Commodore, sharp, casio, computex, and of course HP- is % So I will stick with that one :)

 Re: Poll: What is the most useless function on a scientific calculator?Message #28 Posted by Jan (Switzerland) on 14 Mar 2003, 12:58 p.m.,in response to message #26 by J.Manrique Lopez de la Fuente All algebraic signs on my 17BII and 19BII such as ( ) = remark: had they rather implemented SIN, COSm TAN and ARC instead, the 17IIB would be unbeatable pocket calc Jan (Switzerland)

 Re: Poll: What is the most useless function on a scientific calculator?Message #29 Posted by Bill Smith on 14 Mar 2003, 1:01 p.m.,in response to message #1 by Jeremy i agree with the convergence towards the % key. while i never use the n! or probably even the x^2 functions in work, i remember them being important for programming, and in statistics and numerical methods courses. the post with the =, what is that for? it doesn't appear on _any_ of my calculators. ;)

 Re: Poll: What is the most useless function on a scientific calculator?Message #30 Posted by Gordon Dyer on 14 Mar 2003, 1:57 p.m.,in response to message #1 by Jeremy Have a look at my program for HP-11C and HP-41C in the Software Library for this site... this extends your uselessness by many orders of magnitude! But in stats and probability factorials are very useful.

 Re: Poll: What is the most useless function on a scientific calculator?Message #31 Posted by R Lion on 14 Mar 2003, 2:12 p.m.,in response to message #30 by Gordon Dyer I agree!! Raul

 Why all the % bashing here?Message #32 Posted by Michael F. Coyle on 14 Mar 2003, 2:33 p.m.,in response to message #1 by Jeremy I don't want to start a war here, but I like the % function. It's very conveinent for figuring taxes and the like. I also especially like the delta-% -- it provides a simple way to see how some quantity changes. I guess the main point of x^2 is to permit squaring without using up a stack level. Not unlike 12x and 12/ on the financials. My vote for most useless function is a tie -- GRAD and hyperbolics -- never used 'em, probably never will. I'm surprised that none of the non-computer people have mentioned the bit and logical functions. Or the scientific folks the financial functions. This has been an interesting thread. Since everyone would like to get rid of their least-favorite functions, I think I'll write a proposal for a minimum-function scientific and post it here.

 Re: Why all the % bashing here?Message #33 Posted by R Lion on 14 Mar 2003, 2:54 p.m.,in response to message #32 by Michael F. Coyle "I don't want to start a war here, but I like the % function. It's very conveinent for figuring taxes and the like. I also especially like the delta-% -- it provides a simple way to see how some quantity changes." I agree. And I love the %T function too, and I've programmed it in my 15C and in my 42S. Regards Raul

 Re: Why all the % bashing here?Message #34 Posted by Mike Rivera on 14 Mar 2003, 5:06 p.m.,in response to message #32 by Michael F. Coyle I agree - I use the % function regularly on programs I write on my 41CX when I need to keep the stack from changing. It's easier than storing and recalling numbers. I also use the change in % when compairing items (costs, profits, etc.) in my business. Not eveyone uses scientific calculators for "science". I use them because they have great programing capabilities (large memories, lots of conditionals, and Alpha characters on the 41 series) and I like playing with them. I consider high-end scientific programables a "do-all" machines. I have a 25C, 15C, and 41 (CV and CX) and I've never used them for "science" or higher math. Mostly for sales and business use, but I wouldn't trade any of them for a 12C. For me, I never use SIN, COS, etc., or any of the LOG functions (but I still like having them available because .... you never know)! - Mike

 Re: Why all the % bashing here?Message #35 Posted by Christof on 14 Mar 2003, 5:22 p.m.,in response to message #34 by Mike Rivera I think I'm losing the thread. % isn't necessarily a useless one byte instruction- a useless function. having it be a useless key isn't the same. I'd claim that having x!=0? on the keyboard is useless, too. That's hardly meaning that the function is useless for a scientific programmable. now, is it the most useless key on a scientific, an RPN scinetific, a financial, a 'do everything', RPNB versions of all of the above, or a handheld programmable computer (like the 41?) Looking at the HP41 keyboard, with it's tight space, I think I'd prefer vastly to have delta-% than % on the keyboard. Even Better, RUP. so for that case- % still wins with me. though x^2 is a close second. (again, programming is one thing, keys for regular use another) looking at- for example- the old old ti30-slr I have, I'd say % again. and as this calc has no stack, having x^2 and y^x (it does) is pretty useless, too. Replace with a delta% and a xROOT y and I'd be a lot happier. (make it RPN, give it 10 storage registers, and I'd be happier still. but it's TI)

 Re: Why all the % bashing here?Message #36 Posted by Mike Rivera on 14 Mar 2003, 5:29 p.m.,in response to message #35 by Christof You said "Looking at the HP41 keyboard, with it's tight space, I think I'd prefer vastly to have delta-% than % on the keyboard". I see your point and I agree. The regular % function is very useful for programming, but it didn't need it's own key where real estate is very limited. - Mike

 Re: Why all the % bashing here?Message #37 Posted by Christof on 14 Mar 2003, 5:14 p.m.,in response to message #32 by Michael F. Coyle well, I'm not talking abotu financial function and bit operators because most oftne financials aren't on scientific calcs :) and bitwise operations are useful! % is useless for me because it doesn't do anyhting I cna't do just as easily (and with less thought as the gesture is implanted by years of math) with .8 x instead of 8 0 % and part of it is that it is a *scientific* calculator. I am leery of the idea of people needing scientific calculators and not being able to figure out that 80% is .8 x :) delta% is a different key and a differen toperation altogether, though! that one I sometimes like.

 Re: Why all the % bashing here?Message #38 Posted by Frank Wales on 14 Mar 2003, 6:27 p.m.,in response to message #37 by Christof % is useless for me because it doesn't do anyhting I cna't do just as easily (and with less thought as the gesture is implanted by years of math) with .8 x instead of 8 0 % Except '%' doesn't just do that. When I need to work out VAT (sales tax) on an invoice, which must be quoted separately on the invoice and included in the total, I can do: 17.5 % (write down VAT) + (write down total) Much better than: enter enter .175 * (write down VAT) + (write down total) I can't use just one enter, because of stack-lift disable after the first one, and I have a long-ingrained dislike of operations that push the stack unnecessarily.

 Re: Is there such a useless function?Message #40 Posted by Christof on 14 Mar 2003, 5:28 p.m.,in response to message #39 by Vieira, Luiz C. (Brazil) Luiz, I've had to intperpret this as the "most useless keyboard function" from the start. Since most of the scientifics in use around here are programmable, and have many (even hundreds!) of functions not on the keyboard, I have assumed that we weren't trying to weed out functions buried in menus. I can think of ways to streamline a keyboard- to better use the 'real estate'. And I cna see programming uses for some functions I never use in practice- like x^@ and % (many HPs have x^2 as a shifted key, with y^x as an unshifted key, so it is easier to touch type that or hit x ) So I guess we are back at the beginning question- what *is* a useless function? on the keys, off the keys, rpn or alg? programmable or non?

 Re: Is there such a useless function?Message #41 Posted by Vieira, Luiz C. (Brazil) on 14 Mar 2003, 5:41 p.m.,in response to message #40 by Christof Hello, Christof; Your aguments are value and I cannot figure a solution out that's better than the "love-them-or-hate-them" menus. I read another post sometime ago suggesting that key inscriptions should change. You know what? For my biggest surprise, it's possible to be done because there is already an applicable solution: a new "LCD"-type design that can be incorporated in the keyplate. Also, the same technology expands to the keyface itself. Custom keys instead of custom menus... Daring dream, isn't it? This way, we have the "final solution"... not yet implemented. At lest, so far. Best regards. Luiz C. Vieira - Brazil

 Poll: the least used function on a scientific calculator?Message #42 Posted by Nenad Vulic (Croatia) on 15 Mar 2003, 2:49 a.m.,in response to message #1 by Jeremy Interesting that nobody mentioned SIGMA MINUS (at least for the time being). One of my almost everyday jobs is approval of propeller drawings. Designers often omit to specify thickness at r/R=1 and I have to extrapolate it from the thicknesses at r/R=0.9 0.95 and 0.98. If I enter an incorrect value, I simply start from the beginning, avoiding to correct an incorrect entry by SIGMA MINUS. When I have to use a linear regression or something with more than two-three points I use Excel instead of any of my HP's.

 Re: Poll: the least used function on a scientific calculator?Message #43 Posted by Vieira, Luiz C. (Brazil) on 15 Mar 2003, 4:01 a.m.,in response to message #42 by Nenad Vulic (Croatia) Hello, Nenad; I always found this as a big handicap, but in the HP28C/S, HP42S and the HP48/49, this problem was "minimized" with the use of lists. of coures you need memory space for each entry, but the list is an elegant solution for this particular problem. If there are some entries wrongly entered, you simply edit the list, correct them (if it is only one, it's even better) then you store the edit list adn you do not need to enter everything again. You can create a small program in the HP41 to achieve this, and even use X-Memory to store sample data. Have you already tried this? O.K., far from being as fast and easy to edit than Excell. And you'll never need this sort of correction anywhere but at your desk, right? Best regards, pall. Luiz C. Vieira - Brazil

 Statistic functions by listsMessage #44 Posted by Nenad Vulic (Croatia) on 16 Mar 2003, 6:01 a.m.,in response to message #43 by Vieira, Luiz C. (Brazil) Hi Luiz, Thanks for your (as always) valuable information. I have never used this possibility of making lists, but I am going to try.

 Re: Statistic functions by lists - BriefsMessage #45 Posted by Vieira, Luiz C. (Brazil) on 16 Mar 2003, 8:31 a.m.,in response to message #44 by Nenad Vulic (Croatia) Hi, Nenad (and others interested on this subject); In the HP42S you need to explicitly create a N×2 matrix, N equals the number of pairs of data available in the sample, column #1 for X-data, column #2 for Y-data. You should store it in a variable so it can be edited later, if needed. The name of the variable does not need to be an specific, reserved name, but I suggest not using REGS for data safety. This matrix must be recalled to the X-register prior to execution of [Ê+], being Ê the Sigma greek symbol; all matrix contents will be read, line by line, and statistical data - Êx, Êx², Êy, Êy², etc - is generated automatically. If you need to edit Ê-data matrix and use new data set, you need to clear previous data - [CLÊ] - prior to enter new data. In the HP28C/S and HP48/49, ÊDAT is already an N×M matrix. In these calculators, your Ê-data base is allowed to have more than two columns (Ê-variables) and you choose which variables you want to wrok with as for related statistics with two variables (curve fitting, forecasting, tests, etc.). Also, editing ÊDAT in these calculators means edit data base directly, what means you should not clear statistical data because this means cleareing ÊDAT matrix. A lot more exists about this, many other resources. I hope this helps as brief notes. Do you use any of these calculators? If you have an HP41C/CV with X-Functions or an HP41CX, I have (somewhere in here...) a program to deal with statistics data stored in a matrix in the X-memory. If full space is available, standard X-registers may hold about 60 pairs of statistic sample data. It is a bit slow to read data and generate statistical data - Êx, Êx², etc.- but allows handling of lots of pairs without "fear"... If you need the program, tell me. I just have to find it... Best regards, my friend. Luiz C. Vieira - Brazil

 Re: Statistic functions by lists - BriefsMessage #46 Posted by Nenad Vulic (Croatia) on 16 Mar 2003, 2:41 p.m.,in response to message #45 by Vieira, Luiz C. (Brazil) Thank you very much, once again. So, I will have to bring my HP32SII home and take the HP42S or HP28S to work. Honestly, I did not remember the procedure you have described (though I have read both 42S manuals about two years ago).

 Re: Statistic functions by lists - BriefsMessage #47 Posted by Vieira, Luiz C. (Brazil) on 16 Mar 2003, 7:29 p.m.,in response to message #46 by Nenad Vulic (Croatia) Hello, my friend. I'm glad this information is usefull for you somehow. I also hope others read and use, and that's why I'm posting more data instead of e-mailing you, O.K.? If you have the English version of the HP42S Owner's Manual, go to page 237, under Using Statistical Data Stored in a Matrix. The Programming Examples and Techniques has some complementary data in Chapter 6, p. 174, with some applications and examples. I think it may help, too. Hey, I am interested on your activity. Do you deal with sea vessels? What sort of propellers? Can you say a few words about it? Sounds interesting... Best regards, my friend. As always, my pleasure. Luiz C. Vieira - Brazil

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