Round Top skis 19/20

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mammuth
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Re: Round Top skis 19/20

Post by mammuth »

What also helps is to glue a piece of waste wood outside of the abs/pu. Like this the topsheet and fibres dont kink down over the edge and resin gets sucked out more easily
Tom

Wheatlpa
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Re: Round Top skis 19/20

Post by Wheatlpa »

mammuth wrote:
Fri Feb 19, 2021 8:14 am
What also helps is to glue a piece of waste wood outside of the abs/pu. Like this the topsheet and fibres dont kink down over the edge and resin gets sucked out more easily
Another great tip. I use wood side walls anyway so either gluing extra on there or just making the side walls wider is a pretty easy step.

Wheatlpa
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Joined: Fri Feb 12, 2016 11:14 am
Location: Sutton, QC

Re: Round Top skis 19/20

Post by Wheatlpa »

So after skiing the new skis mounted with my 22Design Axls I was having troubles. I was stepping on my tips, the rear ski was chattering because it felt like I couldn't get any weight on it. In short it was frustrating and I felt like maybe I made a mistake with the ski shape. Well, after reading a lot more about mounting location and finding the boot centre I realized that I had used the (very) old school method for tele mounts in using the cord centre and mounting the pins there.

So, I remeasured the effective edge length and it corresponds to the narrowest point on the ski. Set back 4 CM and drilled new holes. Here is a photo with the difference in binding location:

Image

The ski on the right is the new location, this is a big difference for me. I took them out this morning before work and wow, what a difference! I was able to get them over on edge, they were quick and snappy side to side and the rear ski was no longer squirrely, it held a solid edge and made my turns super solid.

Wheatlpa
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Joined: Fri Feb 12, 2016 11:14 am
Location: Sutton, QC

Re: Round Top skis 19/20

Post by Wheatlpa »

I have started the next pair of skis, they will be exactly the same as the first pair but using two layers of 6oz biaxial carbon along with the 22oz FG. I would like to see what the carbon will add to the ski characteristics. My original pair of powder skis has 2 layers of 5.8oz CF and 2 layers of 19oz FG but a fairly thin core. They are perfect in soft snow, not so much on the hard pack. I hope I get these finished before the spring rains come!

I can tell you though, I am getting frustrated with the edge bending. Maybe I am just impatient and rushing through the process but oh man I find that edges are the hardest part of this whole process.

I am using the modified nippers as my bending tool, gentle curves are no problem, but just trying to wrap the edge around the nose and getting it to fit with minimal gaps is testing my ability to remain calm and not throw it all out into the snow....

ah, that was good to get off my chest. I am sure it will get better with practice.

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chrismp
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Re: Round Top skis 19/20

Post by chrismp »

For tighter bends you could try making a second tile nipper with a smaller (maybe even rounded) "nose".

Wheatlpa
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Joined: Fri Feb 12, 2016 11:14 am
Location: Sutton, QC

Re: Round Top skis 19/20

Post by Wheatlpa »

Well I guess I can try and modify my original nippers and see if that will do the trick.

In other news I was in the process of getting the cores ready for pressing tomorrow when I ran into issues while running them through the planer. It seems that my choice of kiln dried maple for the side walls was a mistake. The tips and tail sections started splintering when I was getting down to the 2mm thickness. I am a little stumped as to how I can recover from this. My thought is to smooth off the jaggedy sections and cut back the side walls to an even line and then use tip and tail filler to replace the lost maple. I figure the sidewalls at this point is so thin that they do not provide a whole lot of structure to the ski. Anybody reading this have any thoughts or experience with this?

Image

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pmg
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Re: Round Top skis 19/20

Post by pmg »

I always have the 0.6mm rabbet already in the bottom side when going in the planer. I use this rabbet and add some double sided tape (I add some paper in between to get to 0.6mm thickness) at the tip and tail sections. This keeps the sidewalls in place and keeps them from shattering.

The other thing when getting to the end thinkness is that I never take away more than 0.1mm per run when some part of the core is less than 3mm thick.
I usually start at 1mm at full core thinkness, reduce to about 0.5mm when tip/tail is about 7mm thick, and further reduce down to 0.1mm on the last runs. Takes time but saves the core :)

mammuth
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Re: Round Top skis 19/20

Post by mammuth »

Hot Glue is your friend ;)
Tom

Wheatlpa
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Joined: Fri Feb 12, 2016 11:14 am
Location: Sutton, QC

Re: Round Top skis 19/20

Post by Wheatlpa »

pmg wrote:
Sun Mar 07, 2021 2:04 am
I always have the 0.6mm rabbet already in the bottom side when going in the planer. I use this rabbet and add some double sided tape (I add some paper in between to get to 0.6mm thickness) at the tip and tail sections. This keeps the sidewalls in place and keeps them from shattering.

The other thing when getting to the end thinkness is that I never take away more than 0.1mm per run when some part of the core is less than 3mm thick.
I usually start at 1mm at full core thinkness, reduce to about 0.5mm when tip/tail is about 7mm thick, and further reduce down to 0.1mm on the last runs. Takes time but saves the core :)
I might have been a little aggressive with the depth of cut...live and learn. My issue with the planer I have is that there are no fine measurements on the depth adjuster, they are in 1/8 inch sections so I will have to play around with the machine to figure out how much is taken off with each turn of the adjustment knob.

I also have the rabbet done before planning. I will have to try your method as I also use double sided tape on the tip but will spread it out to the edges as well.

For this build repair I was thinking of trying to glue wood back but I think that will cause more trouble when trying to get it back to the desired thickness so I will just use the tip/tail filler material and bring it down the sides. Not sure how will the ski will work but I don't think it would impact the performance all that much.

Wheatlpa
Posts: 62
Joined: Fri Feb 12, 2016 11:14 am
Location: Sutton, QC

Re: Round Top skis 19/20

Post by Wheatlpa »

Another great day. Dawn patrol this morning and pressed my second pair of skis. They turned out pretty well although I am having issues with the edge to base connection. When I glued them on they seemed to be very tight but when I took them out of the press there are little gaps all along each edge. Not huge gaps but enough to bother me. Photos to come after they have been tuned and epoxy removed.

Here are a couple of shots of the before and after, I think the Honduran Mahogany used for the topsheets really turned out well, and my attempt at engraving the serial number didn't go too badly either!

Details:
Length: 175
dimensions: 132/94/117
Core: 2.5/10.5/2.5 Ash/Poplar with Maple sidewalls
Core length: 143cm

Layers (starting from top)
Wood Veneer
CF - 5.8 oz
FG - 22oz
wood core
FG - 22oz
CF - 5.8oz

started the bottom heat blanket straight to 82 degrees and kept the top blanket about 15 degrees lower until the bottom reached temperature. I held the bottom at 82 and the top at 65 for 20 minutes to get my camber. After 20 minutes I turned up the top blanket to 82 and let them run for 60 minutes at which time I turned them both down to 35 degrees and kept the vacuum running for another hour or so.

Resulting camber is 9mm with pretty flat bases.

Let them cool for another 2-3 hours and then cut the flashing, attacked them with the belt sander and then routed the sidewalls to 14 degrees. Sanded the top sheet with 220 and then 320 grit to smooth out the epoxy before putting on the first coat of Spar urethane. They are looking pretty darn sexy if I do say so myself. I hope they ski as well as the look.

Here are the cores, bases and the carbon fibre in the press. I was just making sure the cores that I bent would sit flat before starting the lay up.
Image

fresh out of the press.
Image

Serial Number for my second pair, cause who knows how many I might make :D
Image

And finally starting to put the Spar Urethane on, before and after, the figure in the veneer is almost too much!
Image

mammuth
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Re: Round Top skis 19/20

Post by mammuth »

Better to start cutting and grinding after 1-2 days if there is no emergency. The epoxy needs 4-6 days to fully cure. Before that you can still influence e.g. the camber when flexing them too strong. Was written here several times....
Tom

Wheatlpa
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Re: Round Top skis 19/20

Post by Wheatlpa »

mammuth wrote:
Mon Mar 15, 2021 6:05 am
Better to start cutting and grinding after 1-2 days if there is no emergency. The epoxy needs 4-6 days to fully cure. Before that you can still influence e.g. the camber when flexing them too strong. Was written here several times....
Interesting. I definitely did not read that. I will make a note of that for the next pair which I am getting ready now. As is usually the case, I seem to be doing and then find out reasons why things are going wrong...at least those lessons will sink in :D mainly because I don't know the questions I need to ask until I run into a problem.

Along those lines I did run into an issue with my base to edge connection. I am not sure if this was because the edges I was using came in a roll and I didn't realize I needed to straighten them out before use or if the bases are not cut out cleanly. I did read (after the fact) that it is a best practice to get the edges back to straight before bending them to the bases shape (thanks Vin for that write up) which I am doing for my next build. I am also taking a lot more time to get the bends to fit better and with out forcing them into shape.

My last pair just got back from the ski shop, they were able to flatten the bases on the belt grinder but there are some gaps between base and edge that I can get my thumb nail into that I probably should fill in (see photo below) but not sure if I should epoxy or simple p-tex, anyone have any thoughts on this?

Image

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chrismp
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Re: Round Top skis 19/20

Post by chrismp »

I would use a thin epoxy and a small syringe to fill in those gaps.

Wheatlpa
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Joined: Fri Feb 12, 2016 11:14 am
Location: Sutton, QC

Re: Round Top skis 19/20

Post by Wheatlpa »

chrismp wrote:
Wed Mar 17, 2021 2:26 am
I would use a thin epoxy and a small syringe to fill in those gaps.
Thanks for the confirmation. I have ordered some syringes and I am looking up how to thin my Entropy epoxy (several drops of acetone seems to be the answer) . I will probably attempt this over the weekend assuming my package arrives by Friday.

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chrismp
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Re: Round Top skis 19/20

Post by chrismp »

Sounds like a plan! The important thing is to fill those small gaps from the bottom up. If you don't do that the epoxy might just stay on top of the gap and not fill it due to its surface tension.

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