PVC foam core thickness?

[Danielsan]

Thx for the extra info, as I said more than welcome.

I am not sure about what you mean whith panel length?

thx for the compliment, If I can establish to make what I am drawing that would be great !!!

Greetz,

Daniel

[Danielsan]

I think I have to get some rest?

a laminate whith a 25 mm core has a lower density 542Kg/m3 with a 40/60resin ratio
than a laminate whith a 20 mm core? 579Kg/m also same ratio

Just as I want to determine the weight per m3

?

Greetz,

I am gooing to sleep, designing from 10 till 24 is more than enough!

Daniel

[rxcomposite]

When you draw the profile of the boat, you will subdivide it it into equal transverse divisions. This is called stations. These stations may either be bulkheads or room divisions. On areas where there is no divisions you have to put in frames to support the laminate. The frames i usually use is the "tophat" design.

When you draw the midship of the boat, you will have to subdivide it longitudinally. These are called longitudinal stiffeners. These are usually smaller in dimensions than the frames.

Normally you would divide the boat so that each panel size is bounded by a longitudinals on each sides and frames on the ends. The center to center distance between frames (or longitudinals) are called frame spacings. For optimum design, the length should be twice as long or grater than the breadth.

This is true whether you are designing with a cored panel or single skin.

The panel bounded by the frames and longi is the panel size. Panel size means the inside length and breadth. Do not confuse the panel size by the spacings.

Density of the core is as defined by the manufacturer. When you add a laminate of both sides, this is called laminate density. The more laminate (skin) you add, the greater the laminate density but the core density stays the same.

I forgot to tell you that in my analysis, the fiberglass was holding up to the stresses but the core was a wee bit high on shear stress. A touch on the keys (30 instead of 25) solved the problem. I then backed down to using 180 gr/m3 and there was no problem. I can go to a thicker core and reduce laminate thickness but that is fine tuning. when you get all your dimensions final, lets see what we can do.

Have some sleep.

[Danielsan]

Ok I am at the same wave length as you are. I think
So the panel length is the distance between two stations: so when making tophat stations (40x40mm) with the centers spaced at 500mm it will give a panel length of 460mm?

As yo calculated the panel length at 1000-900mm it is shure it will have to endure more severe loads. But in order to reduce the stresses couldnt we go to 500-600mm
spacing for the stations? I have to say that the bow to midschip will be filled with bouyancy foam to create the floorplate and some extra bouyancy in case it would sink. I hope not. Will add pic when at home.

The thing is I calculated the price using foam core with a much lower density I think 80Kg/m3 and I allready get a high price so what if I would have to use 30mm with 180-200Kg/m3 then I will have to stick to traditional glass construction.

Seen from stern to midship I will have heavy parts.(jet + engine + feul+ watertank)
So I intend to put more logitudinal reinforcements from the stern to past midships So the hull wont crack in two in the midship. Waht about this?

THX in advance for your precious time.

Daniel

[Danielsan]

Hi RX,

I did some more drawing concerning the stiffners I put the stations at 600mm
the longitudinals are put a bit random.

I would think that this is way to much for a liitle thing like this?
what do you think?

Greetz,

Daniel
I don't see my attached files, so here are the links

Frames A http://boatdesign.net/forums/attachm...tid=2484&stc=1
Extra buoyancy foam http://boatdesign.net/forums/attachm...tid=2485&stc=1
Frames B http://boatdesign.net/forums/attachm...tid=2486&stc=1

[rxcomposite]

Yes, you are correct. Spacing minus the base width of stiffeners. That is panel length. Goes the same way for panel breadth.

I usually divide the LWL by equal spacing. Grat for simpsons rule. If i have unusual placement of bulkhead in some areas, i divide still the station to get half station. so 6.1 m DWL/6= 1.0something right?

If you divided your waterline by 12 and have 500mm. spacing, then it will be more rigid and i will have to recalc again because then a thinner laminate and lower density core will do at the expense of more work putting up all the added stringers. This is what design spiral is about. Number chasing does not end until you get the optimum cost and weight.

Well, you will be producing only one boat but in production, we cannot afford to be a hobbyist. Less work is always better. and we cannot afford to let the part stay in the mold too long as the second unit is waiting to be laid up.

Dont worry about the stern. I calculated at Midship where the greatest stresses is located. There is a reduction of stress at the aft and the bow.

Will take alook in your drawing tommorow. hope you have midship drawing.

Rx

[Danielsan]

THx for all the help.
Today I received some books, but it will take some time to read them and understand them completely.
I got the: Elements of boat strength By Gerr, understanding boat design by Brewer, fiberglass boats by du Plesis, elements of yacht design by Skene, the last one is for when I try to make a sailing yacht in the distant future :-)

greetz,
Daniel

[rxcomposite]

Daniel,

Try to obtain a copy of Sorensens guide to Powerboats. First part explains all types of hull form and behavior of boats. Great overview of what a boat is and its variation on design approach.

Rx