Choosing a deck core

Agreed. It's not really up to us to second guess Kurt's design. His designs, IMO, are rock solid. Charly will be using a mix of mostly balsa and a foam edge just to make life easier when shaping.

I don't think there is an argument here to make the whole deck from foam, as that's not what's called for in his plans.

Both materials will be used, maybe 10% foam, tops, just as a convenience. As you point out, balsa and plywood are easier to mount things on deck with since you don't have to worry about changing densities where the mounting is to deal with localized compression.

Charly wanted to know about various kinds of foam. I think he got that.

 

Where Exactly is corecells colored past??? Do you know what you are talking about? Damn I have heard everything now,But Really what have YOU ever BUILT? and just how are you a judge? Balsa is a very poor choice for a hull or a deck.

it's compressive strength is another problem as any impact gets transfered to the inside skin and causes damage there as well,instead of adsorbing it

Where corecell would be the ultimate core,SAN is also used for plastic cigarette lighter bodies among other things, balsa would hardly fit this application.There are some very sophisticated people involved with this material, You want a high quality deck bag corecell sheets into it.


Here just pulled:




On the Boat

 

Did you miss the word "previous"?
I said it was a nice looking shape and a nice paint job (particularly in light of the conditions in which you work) - so what does it have to do with this thread? Are you desperate for free advertising? Jeez, dude. Let it drop. Corecell is great stuff, I'm certain of it now. I'm throwing all my balsa out!

 

Dude LOL you seem to have a problem here not me,Free advertising,How did you manage to ever wonder there? Work! sometimes we work in a production facility and then other times a air conditioned specialty plant.

 

Mark, sorry if i offended you, i wasnt specifically refering to you, rather the generic you who always pops up when a thread drifts into a balsa vs foam debate (or any other material debate),you know,the person who rabbidly supports one material while totally dissing the other. All proffesionals that i know can see the virtues of all the different materials and use the one that makes the most sense for a particular application. I believe i said in my post that i do use balsa where it makes sense and sometimes it does. I am going to answer a few of your questions and then drop the subject as its drifted away from the original topic.
My point regarding it being more difficult to engineer a foam panel stems from there being many more types and densities of foam available than balsa and simply choosing say, a 5lb density pvc core and using it everywhere can lead to failiure of the core in areas of high loading while the bond of the skins to the core remain sound suggesting the use of foam of various densities according to load are called for. You could of course just use a heavier density of foam all over and solve the problem but nobody is going to do that because now you are paying much more for your core with no weight saving.
You suggested that "engineering" and "building procedures" are just a difference in semantics. Not so,engineering relates to the process of analyzing the structure and specing the appropriate materials including core whereas building procedures describes just that, how the materials are utilized,examples of which would be tapering the core away as you come to a corner such as topside to deck shelf or transom rather than just running the core into the corner(easier but poor practice) there are many simple procedures that we learned in the 60s which were all but ignored by a lot of builders in the interest of saving a buck that have led to most of the problems experienced by balsa cored boats.
Mark,you suggest doing a test where you stick the claw of a hammer into the edge of a foam cored panel and prying it appart, apparently believing it proves the superiority of balsa as a core not, NOT SO,while the result you suggest is not innacurate (although a little overdramatised) it is a strictly amature and meaningless test,it just shows that the foam will come appart easier than the balsa,(no supprise there) this only matters if the foam is not adequate for its purpose, when someone suggests that a material is "stronger"than another material i just roll my eyes, it only has any meaning if the "weaker" material is innadequate for the purpose it has been speced for.
Steve.

 

Steve W

My point as always about survivability, The crosslinked Foams and Balsa do not offer that, they load then fail where a proper core when overloaded yields slightly giving a large area of safety.

For this very reason the ASTM testing is useless with a core like Corecell or Airex R as it would show that movement as failure. On the simple graph you can see what I am talking about.

http://www.gurit.com/page.asp?secti...99+A%2DFoam+%2D+For+Hulls+%26+Dynamic+Loading

 

Jamestown has a coupkle of choices in corecell A foam that look like they might fit the bill for my needs. They are two by four foot panels with cuts in them so they will contour.

http://www.jamestowndistributors.co...Name=Double-Cut Core-Cell 5lb / cu. Ft Sheets

I haven't compared the price to balsa yet. My hull decks will each use probably sixteen or so panels, provided I can cut them to fit and just butt them together, like a jigsaw puzzle. Can I do that?

Also, my plans specify 150psi min for foam on decks . The chart at corcell's site has different kinds of strengths listed in psi--shear strength, and tensile strength. I wonder if he meant both types of strength, or one specifically. I am not sure if the A500 will cut the mustard. I think that is all Jamestowne offeres.

http://www.gurit.com/page.asp?secti...99+A%2DFoam+%2D+For+Hulls+%26+Dynamic+Loading

 

Hey catbuilder, I have not ruled out doing each whole deck in foam, if I can afford it, and understand how to use it properly, and if it makes the most sense for my particular situation. I sure am learning a lot here already, but am obviously just scratching the surface...

Hey, if you ever come back up this way and have the time, pm me, and stop by and say hello. We could have a beer and beat up on Kurt Hughes ;-)

 

Thanks mark, that makes sense, This is probably a dumb newbie question, but is there a general formula for the amount of area that should be gnarled out of the core, relative to the size of the base of the object being installed? IOW if the stanchion base or whatever, is two square inches, how big should the solid glass portion be? and then, should there still be a backing plate even bigger than that?

 

http://www.yachtsurvey.com/ATC_Core-Cell.htm

 

War Whoop, i have not yet had the pleasure of working with core cell but ive heard nothing but good things about it so i will sure be looking hard at it when the need arises. My experience in new builds has been with Airex,Klegecell,Divinicell and Balsa as well as WRC and many cold molded boats back in the 70s and early 80s,i like them all for various reasons.
Steve.

 

Charly, you need to clarify all these questions with Kurt and try to understand his reasoning for his choices and then share the info with the guys here, im sure it would be interesting for all.
Steve.

 

roger roger. I am still trying to get my head around the whole subject enough first so that I can ask him the right questions, and then understand the answers. I will be happy to share any info.

edit
somewhere I read a lengthy forum exchange between derek kelsal and kurt hughes on the merits of foam vs balsa.
Anyone else here read that? I can't find it now...

edit

here it is
http://groups.yahoo.com/group/multihull_boatbuilder/message/13256?var=0

 

I have used a lot of different core materials I started using Airex in 1982 and LOL there may still be a Rohacell needle roller in the back to this day, I had 40' containers of Pro balsa coming on a regular basis to my factory in the middleeast and I was making the change to foam for my specialty boats before I came back for a break, then 9/11 and here I am.


The White Cat is a one piece boat out of a multiple part mold in back is a 12 meter patrol boat we built a lot of those this plant is @65,000 Sq' by the Airport in Kuwait.

 

Charly, im pretty sure Kelsal was one of the very earliest users of foam cores in boats, period, 40 or so years ago and has seen no reason to switch. A very innovative designer/builder.
Steve.