Search found 17 matches

by Heimfried
Fri Apr 23, 2021 9:36 am
Forum: Power craft & engines
Topic: solar electric propulsion of a power kat, 6.3 m
Replies: 7
Views: 6911

Re: solar electric propulsion of a power kat, 6.3 m

[...] 2. The batteries: there are for sure a lot of different batteries, all suitable to your project. Some are cheaper than other... I just want to mentioned that Caterpillar make a really good hybrid battery available worldwide and at an affordable price. It’s a regular 12V hybrid lead battery of...
by Heimfried
Fri Apr 23, 2021 8:10 am
Forum: Power craft & engines
Topic: solar electric propulsion of a power kat, 6.3 m
Replies: 7
Views: 6911

Re: solar electric propulsion of a power kat, 6.3 m

Thank you Alex, I know about the comparatively large losses of the props. For this reason I try to go in the long term with a large and slow turning prop. I developed a software tool to calculate the shape of props - along the parameters given in the Dictionary of the International Towing Tank Confe...
by Heimfried
Thu Apr 22, 2021 2:19 pm
Forum: Power craft & engines
Topic: solar electric propulsion of a power kat, 6.3 m
Replies: 7
Views: 6911

Re: solar electric propulsion of a power kat, 6.3 m

Thank you John, "... much depends on what kind of boating you want to do" I'll go slow and driving silently, That's the point for us to go electric and (partly) solar. 2014 and 2015 we were sailing a few days with roughly comparable electric boats we hired (but monohulls, 2 kW torqeedo outboard and ...
by Heimfried
Tue Apr 20, 2021 10:28 pm
Forum: Power craft & engines
Topic: solar electric propulsion of a power kat, 6.3 m
Replies: 7
Views: 6911

Re: solar electric propulsion of a power kat, 6.3 m

Thank you Alex for your reply. I like to do calculations and to use mathematical tools, sometimes I write small pieces of software to create my own mathematical tools. But resistance prediction will be not easy in my case. Mainly because the boat has a relatively huge cabin with standing headroom an...
by Heimfried
Sun Apr 11, 2021 9:10 pm
Forum: Power craft & engines
Topic: solar electric propulsion of a power kat, 6.3 m
Replies: 7
Views: 6911

solar electric propulsion of a power kat, 6.3 m

I'm currently building a 6 meter power kat, which will be driven by 2 electric motors, (hopefully) mostly powered by solar panels. State of the build: the semi hulls are fitted on the bridge deck and the cabin is erected and covered. I would like to discuss some questions of electric boat drives wit...
by Heimfried
Sat Oct 24, 2020 4:44 pm
Forum: Theory
Topic: Spline (mathematical)
Replies: 4
Views: 3714

Re: Spline (mathematical)

All good fun, but I cant help thinking that any good drawing software will allow you to draw a curve through a set of points then interpolate between those points. You are obviously right. The question is only which of the possibilities is easier at hand in a case you need it. As I'm not able to wo...
by Heimfried
Sat Oct 24, 2020 12:03 pm
Forum: Theory
Topic: Spline (mathematical)
Replies: 4
Views: 3714

Re: Spline (mathematical)

I sent the folder to you, John, and in a separate email the code. To give you some ideas about the folder I quote the text of its tab 1. How is this folder working? A cubic spline function is calculated from the input table with x and y data, e. g. the offsets of halfbread or height of a boat hull. ...
by Heimfried
Sat Oct 24, 2020 10:25 am
Forum: Forum Technical support
Topic: Attachments
Replies: 2
Views: 3388

Re: Attachments

It's ok then, in my case it is not a "must have".

As a remark: I've nearly the same folder in .xls - it carries the same macros but they are kind of hidden, because the file extension doesn't reveal it. But this file is in German only.

Gruß, Günter
by Heimfried
Thu Oct 22, 2020 9:08 pm
Forum: Forum Technical support
Topic: Attachments
Replies: 2
Views: 3388

Attachments

Hello, looking a few times to the attachments John Perry posted, I noticed that the counter of all three of it stayed at "not downloaded yet" in spite of downloading. Is it for a reason that uploading older excel files (2002) ".xls" is possible but uploading newer ones (2010) ".xlsm and .xlsx" is no...
by Heimfried
Thu Oct 22, 2020 8:55 pm
Forum: Welcome to the AYRS Forums
Topic: Hello from Berlin, Germany
Replies: 6
Views: 3785

Re: Hello from Berlin, Germany

For sure I will be piercing the roof at a number of points. Knowing the dangers I will look closely after this points and sealing them. Having studied physics many years ago I'm a little obsessed with measuring and I own some equipment to measure temperature and humidity and use it regularly. So the...
by Heimfried
Mon Oct 19, 2020 9:47 pm
Forum: Theory
Topic: Spline (mathematical)
Replies: 4
Views: 3714

Spline (mathematical)

Sometimes splines are useful in boat building. Physical splines or - more often used today - mathematical splines. A few years ago I wrote a VBA Excel folder with (natural) cubic splines. Input consists of a set of x-y-coordinates (e.g. half breadth of a waterline) output is graphically displayed an...
by Heimfried
Mon Oct 19, 2020 7:38 pm
Forum: Hulls & Keels
Topic: Boat Hydrostatics visualized
Replies: 3
Views: 2072

Re: Boat Hydrostatics visualized

I aggree that it would be a waste of time for a single amateur to try to compete against professional software. There is only room for developing software tools in niches which are not covered. I would by far not be able to develop a (specialized) CAD Software, I'm not even able to work with it (e.g...
by Heimfried
Mon Oct 19, 2020 5:16 pm
Forum: Welcome to the AYRS Forums
Topic: Hello from Berlin, Germany
Replies: 6
Views: 3785

Re: Hello from Berlin, Germany

Until now I don't think a ventilation of the space between the plywood panels is necessary. For sure there will be some condensation in cold nights. But it will evaporate once the sun shines on that deck. As I work on boat building in a tent and watch temperature and humidity and log their values au...
by Heimfried
Fri Oct 02, 2020 9:16 pm
Forum: Hulls & Keels
Topic: Boat Hydrostatics visualized
Replies: 3
Views: 2072

Re: Boat Hydrostatics visualized

The webpage is a bit further developed. SVG graphics instead of pixel, 3 views from different angles shown simultaneously.

http://www.bootsphysik.de/boot21.php

(Button "English" top right.)

Gruß, Günter
by Heimfried
Wed Sep 16, 2020 9:12 pm
Forum: Hulls & Keels
Topic: Boat Hydrostatics visualized
Replies: 3
Views: 2072

Boat Hydrostatics visualized

Hi everyone, a few years ago I coded a website which showed a kind of calculating sheet regarding boat hydrostatics. It displayed also graphic elements as longitudinal and transversal cross sections of a hull, the shape of the waterline and the righting arm curve. Now I elaborated a webpage with 3D ...
by Heimfried
Sat Aug 15, 2020 11:20 pm
Forum: Welcome to the AYRS Forums
Topic: Hello from Berlin, Germany
Replies: 6
Views: 3785

Re: Hello from Berlin, Germany

Hello John, thank you for your welcome. Regarding my boat building project: I was starting in a former garage which was just large enough to allow the build of one semi hull at a time. So I had to erect a tent (4 m by 8 m) in my garden to accomodate the further assembling of the boat. I'm reporting ...
by Heimfried
Mon Jul 27, 2020 9:09 pm
Forum: Welcome to the AYRS Forums
Topic: Hello from Berlin, Germany
Replies: 6
Views: 3785

Hello from Berlin, Germany

Hello everyone, my name is Günter and I live in Berlin, Germany. Since 2017 I’m building a boat: Cabin-Katamaran 6.3 m (LOA), ply on frame, Bernd Kohler design “ECO62”. She will be driven by electric (outboard) motors, as far solar assisted as possible. I’m interested in measurements of some values ...