my 6 meters harchine cheap boat , any comment ?

[jelfiser]

after evaluating to build a ferrocement boat in previous forum, after reading around web and books, i endly chose for plywood glued on wooden frames, here the hull is made from 6 sheet of 1 cm plywood.
is my first design with freeship , i'm going to refine it in rhinoceros
Any comment?
thanks

[JEM]

The bottom panels near the bow may be difficult to get to bend using 1cm plywood. Looks like a nice craft though.

[jelfiser]

Originally Posted by JEM

The bottom panels near the bow may be difficult to get to bend using 1cm plywood. Looks like a nice craft though.

thank you jem , i adjusted the development and i think now it should work here new images .
also bring prismatic to 53, displacement abot 850
at end of this month i buy materials... hoping should work...

[frosh]

I like the lines of your first version more. Is it slightly beamier? If so, it will provide a little more stability. Also the finer bow at waterline on a relatively short hull for it's weight might pound a bit less into waves.
Either way I doubt you will be able to bend the bottom panels in 10mm plywood. It can easily be done by laminating a half thickness layer onto a second half thickness layer. The joins between pieces in each layer should be staggered or at about 90 degrees to one another.

[lewisboats]

You can also kerf the plywood on the inside to allow bending then fill the kerf lines with epoxy putty and a bit of glass cloth to reinforce. BTW, if you run your mouse pointer over the buttons in the development section of freeship, there is a button to turn off the waterline on the developed panels. The button is in the middle of the row and looks like a bow with a bulb on it.
It makes it easier to see the shape...like below.

Steve

[jelfiser]

to frosh

yeah, you are rhigt, i compared waterlines and following on freeship the nice developement and cp, loose a bit of volume, i' m studing any solution , may be i should make a straight V bow adding a small piece of urethane and fiberglass over it to refine . i'm scared of using 2 layer of half thickness, cause we have to make the hull in less time we can
just a bit of time to broke my head on design and we' ll have a better hull

lewisboats

iknow this metod is used on deks to curve it, i was a little scared to ave as result a poligonal, not fine or less resistent bow... does you have ever used this metod ?

thank you
Francesco

[SeaSpark]

Hoi Jelfiser,

I made some replies in your ferrocement boat thread. Was optimistic about this project, it could have worked and i like people developing ideas that are a bit unconventional.

I'm also glad you switched to plywood construction, bigger chance of a good performing boat. Your design looks great, it is much better than many other first attempts at boat design at this forum!

The bow perhaps will look better without the a bit "negative" curve in the chine at 4.8m section this will also reduce the twist in the plywood. The chine will have to come down a bit for this so the bow will be less sharp, this is not a good thing. I agree with Frosh a fine bow will help your design. To compensate for the chine comming down you can make the foot of the bow deeper this will make the bow more fine.

Do you plan to use epoxy when building? It will make your boat stronger and last longer but good boats have been build without it and it is expencive.

The best of luck with your design!

Jeroen

edit:

Deleted remark about keel area

Perhaps the front sections of this boat can be of some inspiration:

http://www.boatdesign.net/forums/sho...3&postcount=36

Plan of same boat:

http://www.boatdesign.net/forums/sho...4&postcount=14

Lines plan of light displacement boat of same designer:

http://www.boatdesign.net/forums/sho...3&postcount=16

[jelfiser]

hi georen ,
thanks for suggestion on design , i'm making some calcoulation on hydro on stability and making lot of try for chines, cp, cb position ( i think better middle)..
really interesting confrontation, i'm happy to see in some other design the similar chose for some lines
also i'm making some confrontation , i've just made some mesurement on a van de stadt 6 meters meteor, the keel is almost the same area,but deeper. i think to keep same mast eight(7.85) and same sails for finding them easily.
about the use of epoxy , i'll use it less possible, it is too much expensive ,may be in future to preserve boat i'll cover with a thin layer of epoxy or add some renforcement on chines. so just now marine glue and wooden frames
in the mean time ,waiting the end of the month , just dreaming to work to the hull. ...
the images and dimension are not definitive, i was just evaluating weigts and materials, there aren' reinforcement for keel and ...
whn the model is refined i'll plot all parts developed in rhino on a real scale to optimize cuts
for the moment
have a look

[SeaSpark]

While adding the links to sample designs i deleted my remark about keel area. A displacement boat needs more area than a fast planing one, guess your estimate will be close to what is good. I will try to dig up some basic calculation examples for keel area.

[SeaSpark]

Not basic but very educating:

http://www.vacantisw.com/keel%20design.htm

[jelfiser]

thank you Seaspark for good suggestion and links
so , i searched a bit and make some calcoulation ...i make some small modification and here the graph for 2/4/6/8/10 Kn , here the excell file i made for making them.
it seem to me it should work, but i'm a profane, those are my first calcoulation.
the boat has got a sail with 23 mq , i think i should have to evaulate the force on sail for different wind speeds and compare them with tose... but how should
i know tre relation between wind speed, boat speed and leeway angle ?
may i work for approssimation evaluating large range of values?
bad boat ... she is just making me mad !!!
so soon the other modification

5/08

SORRY I MADE A SMALL MISTAKE, HERE THE RIGHT FILE

[jelfiser]

ok , here some changes on boat , i'm going to test better transversal stability ...
does it look fine ?

[jelfiser]

just added the complete 3d rhinoceros model , for structure i'm going to follow that strange boat i found on same dimension

http://www.svensons.com/boat/?p=SailBoats/Missile

critics and suggestion are well accepted

Francesco

[jelfiser]

here the dispalcament curve and waterlines at 0,+2,+4,-2,-4 degree trim
it seem to me that it should work , but i've never done those analysis
also just added a simple distribution of weights
.. there is someone more experienced who know how does those calcoulation look ?
francesco

here hydrostatic proprietes

Project : small 6 meters boat
Designer : Francesco Belvisi; Francesco_belvisi@yahoo.it
Created by : Francesco Belvisi; Francesco_belvisi@yahoo.it
Comment : plywood sailboat
Filename : C:\DOCUME~1\FRANCE~1.CAV\IMPOST~1\TEMP\v1.4b-1.fbm

Design length : 5.924 [m]
Length over all : 5.908 [m]
Design beam : 1.721 [m]
Beam over all : 1.971 [m]
Design draft : 1.335 [m]
Midship location : 2.962 [m]
Water density : 1.025 [t/m3]
Appendage coefficient : 1.0000
Volume properties:
Displaced volume : 0.939 [m3]
Displacement : 0.963 [tonnes]
Total length of submerged body : 5.628 [m]
Total beam of submerged body : 1.495 [m]
Block coefficient : 0.0836
Prismatic coefficient : 0.5011
Vert. prismatic coefficient : 0.1207
Wetted surface area : 8.858 [m2]
Longitudinal center of buoyancy : 2.922 [m]
Longitudinal center of buoyancy : -0.711 [%]
Vertical center of buoyancy : 1.219 [m]
Midship properties:
Midship section area : 0.333 [m2]
Midship coefficient : 0.1669
Waterplane properties:
Length on waterline : 5.628 [m]
Beam on waterline : 1.495 [m]
Waterplane area : 5.830 [m2]
Waterplane coefficient : 0.6928
Waterplane center of floatation : 2.679 [m]
Entrance angle : 21.259 [degr.]
Transverse moment of inertia : 0.800 [m4]
Longitudinal moment of inertia : 9.275 [m4]
Initial stability:
Transverse metacentric height : 2.071 [m]
Longitudinal metacentric height : 11.092 [m]
Lateral plane:
Lateral area : 2.204 [m2]
Longitudinal center of effort : 2.918 [m]
Vertical center of effort : 0.934 [m]

[jelfiser]

just found the keel !!! youhhh
weight only 56 kg .. needs other 180
,but it seem perfect for the boat
here some pictures