Amateur Yacht Research Society

AlexQ23

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? If we want to figure what kind of propeller y...

AlexQ23

There was something that retain my attention in Catalyst 61. It concern the tri of Mr. Constantine and her trimming problem. I don't know why the owner have change the motor but I'm pretty sure that it wasn't probably not necessary.... I'm convince that we will be able of increasing the efficiency o...

AlexQ23

Recently I was called to drawn the last Saint Lawrence's yawl still available here in Quebec. Is there anybody that could have any paper or information on this kind of boat? the hull was probably build early 1900 or so. The rig is similar to the one Slocum use on his spray except that it's not a cut...

AlexQ23

Thanks' Robert! I was more looking to something more pragmatic like the one we could found on a real boat. In those data, the speed factor could be adapted with a ratio according to boat length. A sail in a real life with influence of hull and a proper mast and so on, is quite different than the cur...

AlexQ23

Do anybody know where polar diagram from a variety of sails could be found? For example square rig sails, bermudian and so on? I'm really looking to have a real diagram where the wind is coming from all direction. Thanks' in advance.

AlexQ23

A wind vehicule that goes faster than the wind down the wind?? I find this video quite interresting!! Enjoy it!!https://youtu.be/jyQwgBAaBag

AlexQ23

Other few remarks... -I thing that knowing the real thrust out an electric motor is most important than anything else. This value has to be comparing to the residuary resistance of yours hull(s). Keep in mind, that the last link of the kinematic chain is the propeller. And let’s say that the maximum...

AlexQ23

Few things about electric boating... There are at least three different chapters in your tips: The motor that assume the propulsion, the batteries or how the electric power is stored and then the solar panels themselves or how to reload batteries. 1. The motor. I think that first of all it would be ...

AlexQ23

Unfortunately I’m not able to do that due to the location of main sheet holding point. But it’s not so important afterward. But, what is surprising with this boat, is that he is faster before wind! And that’s incredible! So I try to figure how and I find that the drag coefficient of the sails config...

AlexQ23

Hi Robert! Yes, it’s a great idea, but... In fact, I’m not able to put one sail directly behind the other one, with my rig. If one sail sits in the boat axis, the other one lays on windward or leeward side. So, on close reach, close hauled and let’s say, beam reach the comparison with a sloop should...

AlexQ23

2020-12-03_160344.pdf: (236.15 KiB) Downloaded 2603 times

2020-12-03_160344.pdf: (236.15 KiB) Downloaded 2603 times

I still not have enough time to complete my report. But in the mean time I can unveil the polar diagram of the duplex rig. It shows everything and how efficient this rig ! I wish happy holydays to all of you!

AlexQ23

No, it's time to go sleeping for winter! it's already snowing here! And it's also time to put data and words together to complete a report !

AlexQ23

Kasala latest news Let’s say first of all that the boat is a wonder!! She is sailing really well with her roto-duplex rig! A new rig is born! With only two sails, we can reach the same speed (around 5 kn with a 10/12 kn wind), no matter the sector the wind is blowing. 30/40° beating the wind dependi...

AlexQ23

Hi Georges, There are few things to be aware of: Construction: I thing foldable plywood would be great for an outrigger. The principle is fully describe in the Gougeon brothers book and could be design by folding some hard paper as template. Profile design: A good start will be to get inspiration by...

AlexQ23

Hi Simon!
This is my own design, Feel free to copy it if you want! But if you do so, it will be easier to keep the pins perpendicular to mast longitudinal axis. I will be soon ready to send you a small video.

AlexQ23

Hi John, I know that is not easy to understand how this hook is operating. But be patient, in a few weeks or so I will make a small video for you. But the principle is often the same. You raise the halyard till the hooks clamp in a pin that go true both sides of the mast in front of the mast groove ...

AlexQ23

Hi John! Thanks for the explanation. here are the pictures!

AlexQ23

Hi john! I took some pictures but how can I post it to this topic? But axially my system is a bit different. There are some attachment going thru the mast at top and at each reefing line length. And then you have a hook that hols on those attachment both side of the mast groove. On each hook you fin...

AlexQ23

Hi John, I'm probably not aware as you are but it's exactly what's I imagine. Atmospheric pressure are measured in mm of Hg and 1 mm of Hg is equal to 13,6 mm of water. So I tough that this gauge will do the job. But actually you still have to connect it with the sail, and that's an other matter. I ...

AlexQ23

I don't know if it can help, but Dwyer makes some Magnehilic differential sensors very accurate rated as low as 10 mm of water. One tube can be set in the extrados for example and the other one inside the mast. Hope you the best!

AlexQ23

Sad news, indeed. So let me present all my sympathy to Mister Ball's family. Wish an happy new year for all the AYRS members. It will be a testing season for Kasala collecting data on hull resistance, rig efficiency and collect the polar curves. So hopefully you will be able to have something to inc...

AlexQ23

The purpose of the winch is triple: As you mentioned, it helps to hoist the keel, but also to raise the mast and finally it could help to raise the sails. But it never serve to handle the sails. As I mentioned earlier I have design and install a hook that locked the halyard when sails up. An interre...

AlexQ23

Kasala latest news! The boat is now fully completed and we make our first trial with the sails on, a few days ago. It was a light air test, around 6 to 8 km/h. However the boat react admiralty well. He is well balanced, lively and performed better than expected especially up wind. I was really surpr...

AlexQ23

Hi Robert! Could you thing at a blimp/kite that could be shaped like an thick hollow square box inflated with hydrogen or helium. Horizontal surfaces could be your wings and the vertical surfaces could serve to maintain the direction. You can also curve them (10% of C) to outside at an angle of abou...

AlexQ23

Is there anybody that has already used a cfd like javafoil or xfoil to do some prediction with the sails of their boat? I found something curious with one of this program and I really want to share it with someone.

AlexQ23

Hi John! Thank's for your comments. What you call a yuloh, in my case I call it a sculling oar. They are smaller and also not attached to the bottom floor. In fact, it works differently but with the same principle. As soon as I will be able to finalize the design of the paddle I will surely post it ...

AlexQ23

Hi Robert,
Marchaj mention this type of rig on page 126 in"Aero-hydrodynamics of sailing" and it seems that it's in Cowes that this boat was tested. May be there...?

AlexQ23

The launching of the boat was a success! Great stability, perfect trim, eases for load up and down the trailer. The only black spot is that the scull I design and fully tested in static (swimming pool) stall when we reach a certain speed on the boat. So, I made another sculling oar, more traditional...

AlexQ23

So, this concept boat is not so far from my rig! Thank's for the info.
For the hull drag test, do you thing that pushing the boat could be better than to tow it? We will not have the problem with wake disturbance and my dynamometer can be use in both direction.

AlexQ23

Hi John! Yes this is a good summary of what the Kasala project is! Nice done! The “well known fact” comes from the famous experiments carried out by Croseck and that you can found in different books like “the Sailing Yacht” of Juan Baader or “Architecture du Voilier- tome 1” of Pierre Gutelle. They ...

AlexQ23

Thank you for your comments. I agree with you that electronics are not essentials in this stage. Later, I planned to install a bi-data so I can get the speed/log and a dept sounder. From the GPS you can only record the ground speed and sometimes it’s not enough. The comparison between the different ...

AlexQ23

Hull impact resistance: This matter will probably interest all the available brain in this forum! Classification rules don’t really take puncture resistance of a hull in to account. This is especially true, when you design a new light unit and when you are working with rigid hull material like plywo...

AlexQ23

Sorry guys, it seems that the pictures don't go through. So lets try it...

AlexQ23

Effective design appears when you can dedicate different purpose on a single element. For example, the support tube of crutches has a multifunction task: - It hold a step - It support the telescopic mast holder - It receive the strap holder - The rudder control system is bolted on - And for sure, it...

AlexQ23

Hi John! Thanks’ for your compliments. It’s an interesting topic you bring here. For sure, that when we select a keel profile we assume that it works in a laminar flow. But it’s true that it is rarely the case. However, I don’t think that the choice of a keel profile has something to do with the sit...

AlexQ23

Select the right keel profile. A few weeks ago I complete installation of Kasala keel inside his trunk. Everything was going fine and the simple lifting system I adopt, allows a 10 years old boy to raise or lower the keel. It’s a 6:1 pulley system install on top of the cab, completed with an externa...

AlexQ23

Good decision! If I could help I will be more than happy to joint the team. Suggestion: when you get all size and dimension of the frame, why not propose to members a kind of design contest as a first draft or so? And after that you can decide where to go?

AlexQ23

I’m sorry, but I never use a junk rig and I don’t know anything about it. But, what I know is that I never see any winning racing sailboat equipped with such a rig. Bernard Moitessier sails with such rig when young but he never keeps it on her later craft. A square top sail is quite specific. The to...

AlexQ23

Hello Robert, http://i66.tinypic.com/2uhu8vr.jpg For sure a wishbone could surely do the work too! But... - Some are not so effective for fine tuning the sails. - The reefing is not as simple as it looks - With a rigid mast and a square top sails they are not particularly recommended - When the sail...

AlexQ23

I think that if you think to build a metal hull it's mainly to increase the impact resistance, isn't it? For you information there is a coating available called Line-X that can bring any object almost unbreakable. And this is not propaganda! It works for real. And there is some representative in UK....

AlexQ23

I'm glad that you find the boat interesting! Unfortunately, the rig is integrally part of the project and another type of rig can not be fixed on those hull without affecting balance, stability and efficiency . But sails performances can be demonstrated with polar curves. Also, competing with other ...

AlexQ23

Few words again on roto-duplex rig: It doesn’t seem that this rig arouse much enthusiasm. But we all know that sailors are conservative and are allergic to drastic change. Wind is a free energy and trying to improve efficiency of a sailing arrangement is for poor interest for a great majority of us....

AlexQ23

On most catamaran the rudders are vertical. By contrast on beam transom monohull, the rudders are angling about 15 or 20°. This create some friction in mechanical linkage and increase the stiffness of the tiller. Diabolo rubber are often use to realize those attachment. With a duplex rig, like with ...

AlexQ23

Well notice! Yes there is some pressure (or traction) on side mast base. This pressure could be estimated at 5000 N (1100 lbs) per side including an appropriate safety factor. In fact the rail is a hight quality grade aluminium "U" shape channel, perfectly bend and lay on his side on deck. Originaly...

AlexQ23

http://i65.tinypic.com/t5shsp.jpg http://i68.tinypic.com/1178kk7.jpg Roto-duplex rig. Duplex rig also called twin cat rig or bi-plan rig consist of 2 masts lying side by side symmetrically at sheer line or mainly on each hull of a catamaran. This rig is rarely used on monohull due to the fact that,...

AlexQ23

A boat is a choice of parameters and you have to keep in mind that Kasala is a laboratory. I'm the kind of helsman who like to sail with a long stick up to my shoulder and between two fingers! You can not do that with twin rudders. The tiller is often tough and not really pleasant to handle. Minimiz...

AlexQ23

Hello! Here are the pictures of the oscillating rudder.

AlexQ23

Rather than words, a picture will show you what I call an oscillating rudder. But if you want to rename it, feel free! And here is the explanation I give in the presentation: “I decided to use a single rudder, even if the hull shape, from a plan view, looks like a wedge. With this kind of hull, when...

AlexQ23

Designing a small boat is not an easy task. The principal difficulty encountered comes from the weight of the crew members that could totalise almost half the entire mass of the boat it-self. The mobility of this weight compromised greatly boat lines and stability. So, imagine now, that you want to ...

AlexQ23

Hello! I have a great project that I want to propose to Howard Fund. Is-it still active? Can we still submit some lines? If yes, will it be better to send it by mail or e-mai? Let me know. Thank you.

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