Amateur Yacht Research Society

In the picture above is just one transom of the two demi hulls.

The solar electric outfit and motor mount (with steering) is partly done. More than half of it hopefully.

[...] Another remark concerning the pitch of 117 mm of your actual screw: with btrolling motors, due to the fact that the propeller is behind the motor and is working at various speed this could not be a pitch constant propeller. So it will be a good idea to check it by your self all along the blad...

This is an interresting topic that I want to fully understand. So let's say that you want to achieve 6kn. at full speed with your catamaran. You are using two trolling motors that rotate the propeller shaft at around 1450 RPM at full speed. Am I correct? [...] As I understand it, the full speed RPM...

Theo, did you design your prop yourself? You will certainly know about the free to use online tool "CAESES" basred on the work of the well known propeller experts from the Netherlands. But I had always the impression this will not be very appropriate to props for small boats, because the research is...

Last year I was for months kicked out of my boat building activities by a herniated vertebral disc. So I had to let go the idea of launching the boat 2021. Therefore no data regarding drag. The design displacement is 890 kg but I will for sure not be able to achieve this. For to try to get the boat ...

As mentioned above I'll start with one trolling motor (1.44 kW power in, 24 V DC) at each demihull. These motors are branded "Haswing Protruar 3.0" and are Caroute built. I have to modify the motors a bit (remove the tiller arms etc.) to allow remote stearing from the helm. There is only one standar...

Do you know this:
https://ariesvanegear.com/resources/ ?

[...] 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...

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...

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 ...

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...

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...

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...

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. ...

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

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...

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...

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...

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...

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...

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

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 ...

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 ...

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 ...