Re: A-frame mast construction for the KD 122 Italy two

#9124

OK Ivan, but in my experience the wind comes form the direction that winglet shows, so not on 0° but from at least roughly 35°-40° to 140°, so the circular section is the more conservative option, where is my error?

Re: A-frame mast construction for the KD 122 Italy two

#9123

The other reason for the oval mast instead of round is that the secondary structure of the A frame provides support from side to side but no support from front to back (bow to stern). So the masts need to be very strong fore and aft and not so strong side to side. So for the same weight, an oval provides more strength where it is needed.?

Patrick

Re: Pictorial Questions about 520o

Michael Mitchell

#9122

May I suggest that instead of football we use the term siege?

Show quoted text

On Wed, Dec 22, 2021, 6:42 PM bryanandmarycox <bm.cox@...> wrote:

I am thinking of it as a longer version of the under bridge deck rudder support that is in the 480. But Bernd you refer to it as a foot well which to me suggests that it is open to the upper side of the bridge deck. In other words a foot rest in the middle of the cockpit floor. That surely would weaken the structure to the point of guaranteed failure plus having a shallow triangular well up the centre of the cockpit floor would be a hazard . So what I am saying is that perhaps the term "footwell" is not really the word. The structure is like the 480 rudder support under the bridge deck( cockpit foor/cabin floor) but extends to the very front of the underside of the cabin?

regards Bryan

Re: Pictorial Questions about 520o

#9121

I am thinking of it as a longer version of the under bridge deck rudder support that is in the 480. But Bernd you refer to it as a foot well which to me suggests that it is open to the upper side of the bridge deck. In other words a foot rest in the middle of the cockpit floor. That surely would weaken the structure to the point of guaranteed failure plus having a shallow triangular well up the centre of the cockpit floor would be a hazard . So what I am saying is that perhaps the term "footwell" is not really the word. The structure is like the 480 rudder support under the bridge deck( cockpit foor/cabin floor) but extends to the very front of the underside of the cabin?

regards Bryan

Re: Pictorial Questions about 520o

#9120

Hi mIk

You have the sketch I suppose. You know w by now that this is only the final part of the footwell.
Now, rudder housing, as Brian mentioned it is the same design as for the DUO 480 C
The upper gudgeon for the rudder housing is mounted 150 mm down from the top.
Depending on the distance of the second gudgeon (normally 600mm) the lower gudgeon is mounted on the end of the center footwell.

Cheers

Bernd?

Re: Pictorial Questions about 520o

#9119

Rudder support for central rudder? Similar to the short triangle part under the rear of the 480 bridge deck , except of the 520 it runs to the front of the bridge deck/ cabin. So it is not some sort of a continuous false floor? If it is the rudder support it would not appear on the Eco 6 or 5 as they have twin rudders mounted on the back of the hulls. Bernd will clarify

Re: Seattle Eco 55 power cat build

#9118

Another update... Still cooking right along, hoping for an April launch and road/water trip.
-Jim

Re: A-frame mast construction for the KD 122 Italy two

#9117

Qiuseppe: One Builds it oval as wind resistance has a bigger impact on course and speed the more forward the wind is. i.e - when you're beating to windward the higher the wind resistance the less you can point and the slower your speed to windward will be, whilst when reaching or running wind resistance hardly matters or can even increase your speed the more aft the wind is..

Re: Pictorial Questions about 520o

#9116

开云体育

Hello Mike,

?

Well I can’t figure that out. It does not look like anything I did on my Eco 6, but with only that little segment of drawing it is a bit hard to figure out just where this sits in the overall structure. Hopefully Bernd will have an answer, otherwise some more contextual information would be good. For sure though there are some parts of the plans which are difficult to figure out until you get to that point in the construction and you can see things in three dimensions.

?

David

?

Show quoted text

From: [email protected] <[email protected]> On Behalf Of Michael Mitchell
Sent: Sunday, December 19, 2021 12:11 PM
To: [email protected]
Subject: [K-Designs-Multihull-Sailboats] Pictorial Questions about 520o

?

This section of the 520 has me talking to myself.
Other boats such as the Eco 6 seem to do this part a little differently

Thanks for your help. (some progress being made.

Mike.

KD122 Italy one partial build available

[email protected]

#9115

Hi,
reminder to old and new prospective builders.
Domenico's (and mine) KD122 one partial build is still available near Venice airport.
Asking price Euro 23k, hulls completed, most plywood cut to measure and dry-positioned, fiberglass and several items included.
Please inquire if interested

pics
/g/K-designs-Multihull-Sailboats/photosearch?p=created%2C%2C%2C20%2C2%2C0%2C0&q=KD122+Italy

msgs
/g/K-designs-Multihull-Sailboats/search?p=recentpostdate%252Fsticky%2C%2C%2C20%2C1%2C0%2C0&q=KD122+Italy

Re: A-frame mast construction for the KD 122 Italy two

#9114

Just a question: why build an oval section instead of circular section, in general the wind will come from 30°-135° degrees?

Pictorial Questions about 520o

Michael Mitchell

#9113

This section of the 520 has me talking to myself.
Other boats such as the Eco 6 seem to do this part a little differently

Thanks for your help. (some progress being made.

Mike.

questions.jpg

Re: A-frame mast construction for the KD 122 Italy two

#9112

Yes Bernd I have always thought it since the problem is the lateral thrust (from bow to stern) while the internal part is supported by the internal crosspieces and 4mm steel cables.

?

The oval shape is more beautiful to look at as well as functional but I thought not to make it the same from the base to the top but pyramid-shaped, 45cm at the base and 25cm at the top.

?

I always made the internal beam of the mast in a pyramid shape 15cm at the base and 8cm at the top.

?

The two Douglas fir strips are 7.5cm at the base and 4cm at the top, the latter are then tapered 6cm at the base and 2.5cm at the top.

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I used the floor to tie the central thread, after the two side rows with the measurements and in the end I drew all the pieces

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Once the pieces have been cut, you need a straight bench 60cm x 13m long, this is very important.

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I made a sketch we hope you understand ....

A-frame.jpg

section A- frame.jpg

Re: A-frame mast construction for the KD 122 Italy two

#9111

Domenico

Can you make a sketch to understand things better?
The oval shape is the way to go.?

Byer

Re: Photo 20211123_164336.jpg updated #photo-notice

#9110

Hi,?
Amazing progress,? very impressive.?
Happy holidays?

A-frame mast construction for the KD 122 Italy two

#9109

Hi Bernd as I told you I started building a section of the A-frame mast.

As for some time and in my head I decided to do it in an oval shape, to abandon the idea of PVC pipes (too much fiberglass and sanding work on the pipes) but all in plywood and Douglas fir strips.

13.20m long it will be built entirely in a single block also with the internal crosspieces which will always be made of an oval shape but a little smaller 10cm x 25cm and afterwards it will be all bundled. The base is 43cm x 16cm and 8cm x 25cm at the top all in the shape of a pyramid.

?

I care a lot about this discussion and I would like the whole forum to participate in the discussion to improve and make it strong on all aspects.

bye

Foto? ?/g/K-designs-Multihull-Sailboats/album?id=270891

Re: Photo 20211123_164336.jpg updated #photo-notice

#9108

Hi Domenico

Good progress, have I to tell you that? ;-))
you know by yourself.

Have a nice holiday.
Ciao

Re: Photo 20211123_164336.jpg updated #photo-notice

#9107

Link foto

/g/K-designs-Multihull-Sailboats/album?p=Taken%2C%2C%2C20%2C1%2C40%2C0&jump=1&id=269251

Re: Photo 20211123_164336.jpg updated #photo-notice

#9106

Hi Bernd I have posted more photos on the construction of the KD122, works which include carbon fiber, fiberglass and antivortex fin installation.

On 10 January 2022 we start with the hull finishing with peel ply and then we turn the hulls for the continuation.

Meanwhile in the last days before the break I started drawing and cutting a section of the mast A-frame, I open a new topic on the construction of the mast.

Bye

Re: Polyester Resin

#9105

Hello for me if you have to use these two resins (polyester and vinylester) leave the wood alone.
Bye