Montucky Skis
Moderators: Head Monkey, kelvin, bigKam, skidesmond, chrismp
- MontuckyMadman
- Posts: 2395
- Joined: Fri Jun 20, 2008 9:41 pm
138-106-122
12oz biax and 4.5oz uni carbon.
Flex feels and skis right. The skis are super light. Like 7lbs per pair.
I do however have some trouble.
The base is really concave, more than ever and the top of the ski is actually convex.
This is weird because the base was over run cheap stuff and 1.5mm thick and my edge was a 1.3mm offset.
I should be able to grind flat, and I thought it was a few days after I pressed, then I skied them and now I look and they are very concave.
I swear it wasn't like that. Best to wait 7 days till you cut and grind?
Heating issue? New double press issue?
Carbon issue?
Really weird.
12oz biax and 4.5oz uni carbon.
Flex feels and skis right. The skis are super light. Like 7lbs per pair.
I do however have some trouble.
The base is really concave, more than ever and the top of the ski is actually convex.
This is weird because the base was over run cheap stuff and 1.5mm thick and my edge was a 1.3mm offset.
I should be able to grind flat, and I thought it was a few days after I pressed, then I skied them and now I look and they are very concave.
I swear it wasn't like that. Best to wait 7 days till you cut and grind?
Heating issue? New double press issue?
Carbon issue?
Really weird.
sammer wrote: I'm still a tang on top guy.
Concave base has been a little bit of a battle for me too...it seems to decrease the longer (4 hours+) I leave the boards in the press to cool under pressure. I have a sense that if we left the cutting and grinding for a few days post cure it may resolve to a more acceptable range. The grinding for sure heats the base and may be an additional issue. I'm actually thinking that a certain amount of "edge high" may be unavoidable unless I create a slightly convex base mold system to "engineer' the issue out.
Last edited by Brazen on Tue Jun 14, 2011 12:13 pm, edited 1 time in total.
"86% of the time it works 100% of the time".
Yeah, the lower pressure makes it less of an issue. Temperature is also critical...I lowered the temp in the press to bring the various materials more into a balance with their shrinkage potential and that helped quite a lot. I.E. , topsheet shrinks 4% base shrinks 10% blah blah blah.
"86% of the time it works 100% of the time".
- MontuckyMadman
- Posts: 2395
- Joined: Fri Jun 20, 2008 9:41 pm
55psi
180F to temp in 45 min, soak for 15 min and shut off heat top and bottom. Maybe I over cooked exacerbating the thermal expansion problem?
I left them in the press over night under pressure to cool.
I have never had it this noticeable with thicker AL and heat only bottom. Used to be 1 hour to temp 180F and 45 min cook to get it hot all the way.
Grinding gets the base and edge slightly warm to touch but not over 100F.
They were flat when I ground them and I swear it happened days later.
I thought we had this licked. Damn.
EDIT this must be the carbon and rate of cooling causing this warpage or post cure issue?
Gonna press another without carbon and see if the same problem happens.
B, should I take the temp down to 165?
My resin says 175.
180F to temp in 45 min, soak for 15 min and shut off heat top and bottom. Maybe I over cooked exacerbating the thermal expansion problem?
I left them in the press over night under pressure to cool.
I have never had it this noticeable with thicker AL and heat only bottom. Used to be 1 hour to temp 180F and 45 min cook to get it hot all the way.
Grinding gets the base and edge slightly warm to touch but not over 100F.
They were flat when I ground them and I swear it happened days later.
I thought we had this licked. Damn.
EDIT this must be the carbon and rate of cooling causing this warpage or post cure issue?
Gonna press another without carbon and see if the same problem happens.
B, should I take the temp down to 165?
My resin says 175.
sammer wrote: I'm still a tang on top guy.
Since I haven't experienced this, but an observation(my) after what you told us.
1. too much heat compared to recommendations. Try another resin.
2. too little resin/(thin)CF between core and base. I remember you saying it was difficult wetting the CF? Maybe it soaked in during pressure? And "sucked" the base with it?
3. Don't underestimate after-curing. (I don't always follow that rule myself... = delam)
Just my thoughts....
1. too much heat compared to recommendations. Try another resin.
2. too little resin/(thin)CF between core and base. I remember you saying it was difficult wetting the CF? Maybe it soaked in during pressure? And "sucked" the base with it?
3. Don't underestimate after-curing. (I don't always follow that rule myself... = delam)
Just my thoughts....
- MontuckyMadman
- Posts: 2395
- Joined: Fri Jun 20, 2008 9:41 pm
... hmmm got me thinking, ... if heat is used to induce camber, does it follow too much heat too quickly will produce a concave base? If so, I have been lucky and avoided this issue because: low watt heater when using 1.97mm cassette and then, 3 mm cassette when using high watt heater.
I think, once you have reached your required Tg, then further change require additional energy, so if changes happen post cure, it points to the required Tg not being met or not being met throughout the ski. If so, it might be worth considering whether using 3mm AL is preferable because it will provide a better heat map during the ramp and soak cycle?
Just thoughts ... adding to what Brazen has said
I think, once you have reached your required Tg, then further change require additional energy, so if changes happen post cure, it points to the required Tg not being met or not being met throughout the ski. If so, it might be worth considering whether using 3mm AL is preferable because it will provide a better heat map during the ramp and soak cycle?
Just thoughts ... adding to what Brazen has said
Last edited by Richuk on Wed Jun 15, 2011 9:35 am, edited 3 times in total.
Could this be an issue with too much epoxy? As in it getting trapped in the base and curing before being able to flow out of the laminate?
Fighting gravity on a daily basis
www.Whiteroomcustomskis.com
www.Whiteroomcustomskis.com
- MontuckyMadman
- Posts: 2395
- Joined: Fri Jun 20, 2008 9:41 pm
There was a bit more than usual on these bases but very thin and not all the way across. Maybe this was it. But I used more epoxy than normal. I would assume this would flow out. I had it under pressure for 15 min before I turned on the heat.Vinman wrote:Could this be an issue with too much epoxy? As in it getting trapped in the base and curing before being able to flow out of the laminate?
I think the base being thicker than than the step caused an issue as well maybe?
EDIT: I think i got excited with double heater and I was bleeding and drunk and it was late and I cooked them to fast maybe causing the concavity on bottom and convexity on top.
sammer wrote: I'm still a tang on top guy.
Hahaha, I can't help but relate. The last board I made at a reduced temp was pretty good to the concavity...it was somewhat arbitrary but I set top and bottom at 148f. I have always brought the temp up in <5 minutes, I guess I'll figure out those ramp settings on my PID's now...the slower climb to temp feels right to me.
"86% of the time it works 100% of the time".
-
- Posts: 1354
- Joined: Mon Sep 17, 2007 7:37 pm