ScowCat 470

I would really not like to be laying down inside when that boat flipped.
Looks like trying to get out of a coffin.

This is just another attempt to make a world cruiser out of 3 sheets of plywood.
If it's all you can afford, it's better than nothing.

 

Scowcat

Just heard back from Jerome:
Hulls are 470 cm long, 45 cm wide so less than 1/10 ratio. Displacement boat with 2 crew = 550 kg .Max load 600 kg

 

Ok, thanks.
By the way, I have noticed that in my previous post I had used the displacement of the whole boat to calculate the SR of each hull. I have corrected that one.

So my weight estimate was too conservative, it is actually 600 kg. With this data the slenderness ratio raises a bit:

SR = LWL/D^1/3 = 6.1
​

- but not enought to change the previous conclusions. When SR is in the 5-7 range, the wave resistance and the residual resistance have an approximately the same importance, hence the previous conclusions remain valid.

 

Scow Cat 470

I measured the upper waterline* at 4.25m. Divide that by .45= and the L/B=9.44. Moth=11/1
*pix 4, post#1.

 

I don't use the L/B value since it doesn't take into account the displacement of the boat, which is very important for the wave drag.
The Slenderness Ratio SR=LWL/(D^1/3), where D is the volume displacement, is a more comprehensive parameter.

 

From sailing catamarans: http://www.sailingcatamarans.com/hullshapes.htm

The Slenderness Ratio (SLR) or Displacement Length Ratio (DLR) is a measure of the fineness of a hull and is the technically correct coefficient that naval architects use. However, it is easier to visualise the hull waterline length/hull WL Beam ratio (LWL/BWL), so that is more commonly used. That's acceptable, as for a given cross-section shape, the SLR is directly related to LWL/BWL. Higher ratios result in smaller waves. Typically the LWL/BWL ratio will vary from 10:1 for a good cruising boat to 16:1 for a racing boat.

Scowcat=9.44/1

 

Thank you all for your statements, esp. Daiquiri and Doug Lord. Never before I have seen a small catamaran with scow hulls like this and I am still curious how it will sail in a chop or even in undisturbed water.
Since I have learned from tank tests I do not dare to give any opinion before the hulls have been tested. I´ve bought some balsa to make a 1/5 hull for tests and to compare it with "normal" lines. But this needs some time.
I´m not able to test the whole system with bridgedeck to say anything about bridgedeck slamming. But this small catamaran of Jerome Delaunay is very interesting for me - within its given limits.

 

Hi guys, cool to read this thread about one of my design.

This one was a "concept boat study" that was never finish for many reasons.
Part of the challenge was to offer an accomodation in a small cat within a simple constuction method. Self aligning structure with no jig, no lofting, no epoxy join but straight lumber etc...

From my experience in my Scow 450 in various waters, this one should be faster in any conditions, intended that my scows are more for inlands waters.

Cheers,

Jérôme

 

Welcome to the forum, Jerome!

 

Hi Jerome, thanks for joining us.

You have created an unusual kind of vessel, that's for sure.
So, the basic reasons for this hull shape is the simplicity of construction and to provide more interior space for accomodation, did I understand it correctly?

Cheers

 

Hi Daiquiri,

Yes, i like to follow my own way.

Both, ease of construction, confortable bunks.

When i draw a boat, i work in 3D, with the building in mind. So here the work begin with 2 complete separate hulls, that are joined by the central cabin.

http://www.nautline.com/docs/scowcat470_3d1b.jpg

Jérôme

 

Here is your TRIOPS 620 http://www.boatdesign.net/forums/multihulls/small-trimarans-under-20-a-43650-48.html . Please scroll down to 716.

 

Another small Cat

A more conventional small Catamaran from France (4,46m x 2,50m; 2 x 8.85m², displacement unloaded +/- 500kg, draft 0,15/0,75m):







http://www.boat-et-koad.com/plan-de-bateaux-en-bois.php

https://get.google.com/albumarchive...SK_tclymFZZ76LXLsJq65KGraji8Fke2ts?source=pwa

Building SKROWL: https://plus.google.com/photos/116209811814901622777/albums/5851052343753094881

 

there are 2 types of pitching?
forces imposed by sails and those by wave action.
full ends would decrease the sail-induced pitching but worsen the wave pitching/heave.
my 2 cents worth.
full ends would, however, be more forgiving in terms of adding heavy equipment.