So many problems.

BLOODTYPEZX10R · Post by **BLOODTYPEZX10R** » Tue Feb 18, 2014 3:19 pm

I figured this to be the best place to post this.
My frustration is beginning to reach a zenith. A few day ago I was "disassembling" a failed construct and last night I was walking past this board and something caught my eye. The edges that I ripped out (like the guy from the movie Predator) I noticed there was no disturbance of the base or carbon fiber. The only thing that was holding the edged in place is the resin that fills the voids from the teeth. I have also had some concern for the resin itself in that it is too brittle. I measure and heat to exact manufacturers specs and measure my resin carefully(I currently use Forrest ECA032/EMV0043). This particular board I slammed the tail on the concrete and the resin shattered and delaminated at the tail approximately 6" up.
The base material seems to have a relatively good hold, but still it is unusual to bring off the carbon fiber with the base (Isospeed 7200)as I tear it off.
I have also had issues with the core going concave after the board is removed from the mold and during the cooling the concavity will increase until it is cooled to room temp. Given and even further reduction of heat; i.e. outside in colder temps the concavity will increase( the concavity is too much for even tuning, 2.5mm+). If the board is placed back into a heated press the concavity will go away and return to flat until it cools.
Now I do not expect any of you to help me with the core because I make them completely different than anyone does, but I can assure you that the core is as perfect to flat as it can be.
I have become frustrated with all the problems that I am having to work through and is starting to effect my relationship with my wife. I am sure that I will continue on as I have been building boards since'79. Trying to turn this into a production has produced some hurdles. I certainly do not need a resin system that is giving me problems with results and longevity.

MontuckyMadman · Post by **MontuckyMadman** » Tue Feb 18, 2014 4:13 pm

Do you rabbet the core for the edge teeth?

BLOODTYPEZX10R · Post by **BLOODTYPEZX10R** » Tue Feb 18, 2014 4:25 pm

Yes I relieve the core. Thanks MM
It is a heat issue with the base material, as I said the concavity goes away when it is reheated.

vinman · Post by **vinman** » Tue Feb 18, 2014 4:37 pm

Brittle resin could mean that you are resin rich in your layup, not enough pressure to squeeze enough rein out or potentially too much hardener...

How are you measuring your epoxy, by weight or by volume? How closely do you measure? That combo should be a 4:1 ration by weight. I measure this to the gram.

I've used that combo of resin/hardener for close to 25 pair with no issues like you describe.

MontuckyMadman · Post by **MontuckyMadman** » Tue Feb 18, 2014 5:25 pm

are you cooling under pressure?
When we cooled under pressure we had concavity issues.
Perhaps the rabbet is not enough?

BLOODTYPEZX10R · Post by **BLOODTYPEZX10R** » Tue Feb 18, 2014 5:30 pm

Yes the resin is measured by weight to the milligram. All weight of resin is recorded in mixing cup, hardener amount is figured (prior to mixing anything and totals are recorded on mixing cup so all I have to do is tare the cup and add the hardener. Have you tried forced dis-assembly? I would have only guessed that everything was working fine. Pressure, generally 40-50 psi. I am disassembling this board and there is resin and no dry locations. All is wetted out prior to assy.
I am sorry the ECA is 324-ratio is 5:1. Sorry for that. EMV0043 is the resin.
But yes all is measured by weight to the milligram.
Thanks guys, my guess would have been nobody cared.

BLOODTYPEZX10R · Post by **BLOODTYPEZX10R** » Tue Feb 18, 2014 5:36 pm

rebate is measured and even slightly exaggerated. My question then is if it were a rebate issue; why would the concave go away when the heat is returned to the board? No I do not compress cool, I have tried it anyway with no differential in results. The resin system is designed to be heated and fully cured during the heating process, no post-cure wait.
Do you guys use Isospeed 7200 or NSF base materials?

MontuckyMadman · Post by **MontuckyMadman** » Tue Feb 18, 2014 7:02 pm

Perhaps its the mold itself. Is it hand made or cnc cut?
Temp changes affect the plastics very much, rocker and rise and camber and flatness all change with temp changes esspecially dramaitic ones.
could they be getting ground down concave on the grinder?
had that issue for a bit.
Perhaps the rebate is too much?

MontuckyMadman · Post by **MontuckyMadman** » Tue Feb 18, 2014 7:03 pm

Perhaps its the mold itself. Is it hand made or cnc cut?
Temp changes affect the plastics very much, rocker and rise and camber and flatness all change with temp changes esspecially dramaitic ones.
could they be getting ground down concave on the grinder?
had that issue for a bit.
Perhaps the rebate is too much?

BLOODTYPEZX10R · Post by **BLOODTYPEZX10R** » Tue Feb 18, 2014 8:19 pm

The molds are hand-made. The problem happens over multiple molds and molds are always checked for flatness. They are as perfectly flat as really can be, less than .001 across the width. There is absolutely no chance that the press table is bending (I designed and build my press and it is industrial strength, much more substancial than any I have see pics of posted on this forum, It is purpose built, not pieced together from "H" beams with poor welding or bolt together imperfections that lead to flex or fastener failure.)
Like you say and like I have experimented with, plastic has a different thermal expansion rate than resin, metal, composites and wood. I have placed a base cassette in the mold and heated it and even a slight amount of heat will distort. If this is the case then why would the base not expand during the heating process? If this thermal expansion takes place during the curing cycle of the product (it does when I have experimented) then the base expands, the resin cures at the expanded limit of the base and the result during cooling (in my case) is a concave base. This does not occur after the board has been base ground-it will not make it that far. Measurements are made right then and there and over the process of cooling measurements can be made and you can "watch" the concavity grow.
One reason that I am discussing this is I have brought this up before with no real resolution.
All I can say is all rebates are correct, mold is flat, press is no problem, resin is properly measured at proper ratio, resin amounts are recorded before adding and mixing, core is weighed before, and after, residual resin is recorded and account is made prior to next construct. resin is mixed in small batches so no thermal kick occurs while assembly is made.

BLOODTYPEZX10R · Post by **BLOODTYPEZX10R** » Tue Feb 18, 2014 8:38 pm

I do apprecate you taking the time. I am frustrated and upset that this whole thing is contunuing to blow up in my face. I have come to the point that I am afraid to put a prepped core in the press and result in a fail. I have spent time trying to determine what is going wrong and what will go wrong as a result of making a change.

Thanks again for taking the time and providing concern and support.

gozaimaas · Post by **gozaimaas** » Tue Feb 18, 2014 9:58 pm

Maybe stop pressing proper cores and just press test pieces until you sort it our

MontuckyMadman · Post by **MontuckyMadman** » Tue Feb 18, 2014 10:17 pm

Check the tcs and the controllers maybe you are overheating?
2mm is a ton.
boards vs skis different.
i was under the impression almost all boards come out convex and require more grinding vs skis.
not sure... perhaps moisture in The core?
Is the base material the same as the edge offset?
carbon is tricky as the coe is different than glass. The only full carbon skis i have made were way more convex than anything else. Perhaps one of the reasons prepreg is used for this composite.

MontuckyMadman · Post by **MontuckyMadman** » Tue Feb 18, 2014 10:48 pm

Are you useing a metal cattrack?

Dr. Delam · Post by **Dr. Delam** » Tue Feb 18, 2014 10:54 pm

What is your heating setup? Are you heating top and bottom?

Ski Builders Forum

Ski Builders Forum

So many problems.

So many problems.