Strongest surfboard made from a pu core?

Whats the stongest board that would be achievable from a PU core without having a beast glassed with 3 x 6oz?

Thicker stringers/multiple stringers?

Different fibers?

Rail channels?

Wider laps?

Epoxy on PU?

PU foam for me is the most available, best price and best to work with thats why this thread is about a PU core.  I’d like to dabble in other techs but when it comes down to price, ease  and accessibilty I can’t get off the PU.

I want a strong bunch of boards where you can go away for a month and not be pulling back cause your worried about destroying your quiver and going home early.  Obviously heavy waves will break anything but…whats achievable from a PU core?

Yeah, huie, there's always a weight penalty for any ''added'' reinforcement. I came up with a slightly simpler twist on Clark's idea; notching the foam along the stringer and laying a piece of wet roving in there. But it added a few ounces and glassers hated it. 

sharkcountry, Greg Loehr started the rail channels (which he passed on to Stretch). GL originally did them on the top and bottom. They increase load-bearing mostly by increasing stiffness, but can help in other ways also (dependent on other factors). 

haaaa’’   marshy you are a cunning cnut you are trying to draw me out so i can be attacked by the

styrene brigade

all i am going to say is  red alert

 

 

                              cheers huie

“A PU core” can be made in a number of different densities, ranging from super-extra-mega-light (super-extra-mega-weak) to “classic” (what was in use 50 years ago), and everything between. Starting with the proper density (according to the type of board you plan to build) will eliminate the need for extra-heavy glassing.

It sounds like your primary criteria is ''break strength''. Going as thick as possible is easiest solution. Big or multiple stringers don't really help that much because that's not where the failures initiate. They do stiffen the structure, which helps a little. Since a stringered PU core is relatively heavy, and a large % of finished board weight, you don't have a lot of options when it comes to skinning. I assume you don't want a heavy, stiff board; and probably not a thick one. This is the ''problem'' PU/PE builders have faced since designs went thin 20 years ago. You are up against the limitations of a structure dominated by core weight.

With a light skin/thin board combo, most of the loads go to the I-beam formed by the stringer and glass directly adjacent to it. The stringer is the web, the glass is the flange. No matter how strong the stringer or skin, the failure will almost always initiate in the skin/core bond where the load is greatest. So trying to enhance that bond yields the most benefit for the least weight/effort/stiffness. Testing done 20 years ago showed one effective way to do this was to cut a slot along both sides of stringer (deckside) about 1/2'' deep, stuff 1/2'' of 1'' wide glass tape down into slot, fold other 1/2'' out away from stringer, and do remainder of lam schedule over. Essentially you are gusseting the I-beam and enhancing bond. Gordon Clark came up with that one.

 

Interesting post Mike.  With all due respec Huie, no cunning plans going on here mate, I’m just on a trip and broke a board yesterday, with more solid waves comming I was just thinking of how to do things better when I get home.  Don’t want this to turn into a Sh!t fight…so lets not go that way.  Mike and Huie you’ve got some high tech builds not asking for them just thinking of tips for the common PU man.  Moulded EPS is too expensive for me.

Nice post.

What about multiple floating stringer inlays of proper lightweight material – in the mid-section?

marsh, I think huie and I are OK.

Not trying to start anything with my post, just trying to suggest a reinforcement that works and give a simple explanation of ''why''.

I reckon if you dont plane or sand the top deck of the blank at all and just shape the bottom up and glass it with blank logos as graphics leaving the solid crust:), that would be the strongest Pu possible!

haaa  andrew  you must be on some heavy stuff over there

i am going down to my workshop in a minute if the old clunker down there lets me i will get back  if not to night

 

    mike interesting take       but the usual howl is ohh the weight .

haaa’’ impossible to deal with them all

 

**                      cheers huie
**

I think the deck channels or love handles in the Stretch boards add strength. There’s a lot of compound curve along the rail, so it must add strength. 

AKA;  "Power rods".

Don't know if Midget is doing it, but SurfBlanks America is into a new "stronger" formula that they are using in all their pours called "Pink".  Added strength to all densities.The strongest stringer lay-up I have ever seen is a "T-Band" Basswood that Clark used to do.  Used to order shortboard blanks with two pieces of Basswood glued up for stringer.  A true "T--Band" (3 piece) Basswood glue up for longboards.  Very strong.  Not the ply "T-Band "that you see these days.   

andrew when you get home make contact.

 

** mcding the pink like the yellow is hp team cores **

i have learnt with my demo boards that the are just a tool for destruction when i go down the real light path

my few dems with this new formula has seen the decks after a lot of cnuts using them and no one realy cares’’

 (are standing up virtualy dent free)

andrew is in oz and not far away from the best foam available to him so he will sort it out

but good thread interesting to here what others take on it is.

 

right now i am using the red formula and the density is consistent through out the blank

my bench mark for good foam is from a glassers perspective  and the best foam i have seen is rohacell h d

the scrap piec in pick is what i final sand blank and this formula is very close to the rohacell

**so al lthough the foam is a bit heavyer it glasses out great **

just my thoughts of coarse

cheers huie

well you could start with putting reinforcement in the blank when they are blowing it but that isn’t going to happen for you. Epoxy is going to be the first step in your light weight durability quest. the structures are also going to help but eventually you are limited by what the core structure can handle. 

hybrid compsand surfblanks superstrong pink core

Correction---------The new formula is being called "Super Strong fomula" and is now being used in all Surfblanks America blanks.   Pink, Yellow, Red, Green etc.  The email I recieved from Marty indicated that Pink and Yellow are available to the general public.  No mention of team only in the Pink.There were weight comparisons etc.  I don't think Surfblanks America would send out an anouncement to the general public if Pink were team only.  Pink is now the lightest foam available from Surfblanks America.

Use better glass fiber : with less crimp (twill, satin or UD). As i am a mechanic teacher, i like theory so I read some research on composit failure. Crimp is one of the principal factor of fatigue failure in glass/resin composits. Test made by an official french organism (for nautic building reglement), show that no crimp stitch glass is 30% better in all mechanical performance than standard plain wave for same weight.

Sorry for my frenglish.

 

mc ding

             dont take this the wrong way but previous  debates about the yellow was a little misleading for the average punter

and i have no idea what surfblanks america are doing?     but  marshy is an   ausie   so i have just posted what i am familiar with

here is a quote from a e mail from midget and i am preety sure it is not just for me.

After the learning curve flattened, it became clear that shortboard production foam should be Green, team rider should be Yellow, and pro surfer should be Pink. Fishes, mini mals and longboards should start at Blue, and yes we have made plenty of Pink longboards.

 

 

    cheers huie