Section 8 - maple pine build

[SHIF]

...I thought of maybe going back to a full wrap but doing it in a different way. Run a metal edge along the running length of the ski, then bend a separate edge for the tip area. Have them meet just after the tip starts to bend up. So you'd have 3 pieces, 1 for the tip and 2 for the running length. I'll go back and look at the skis I did full wraps on. I know bending for the tip is a PITA. I may still have the problem of the metal edge pulling away...

I've done this, 3-piece full wrap. Actually a 4-piece wrap. You have to make more edge joints doing this but the results are better. Especially if you smash your skis into a tree head-on. Not having an edge joint at the ski tip is more durable.

Are you fully annealing the steel edges where you wish to make tight radius bends? Get them orange-hot with a propane torch, let them cool, clean off the soot, then make easy bends by hand.

BTW, those top sheets look awesome!

[Richuk]

Where's the applause smiley when you need it!

[skidesmond]

Thanks! I rubbed out the poly w/ 0000 steel wool and flooring paste wax. Gonna hate when I get the first chip in them. But what the hell.

When I was doing full wraps I wasn't using any heat, just a cold bend. I didn't like the seam at the very tip where the 2 edges meet. Never really came out cleanly so I went to 3/4 wrap. I have scraps of edges, FG and a defective wood core left over so I'm gonna be doing some experimenting w/ 3/4 wrap and 3 piece method.

[MontuckyMadman]

Talked to a guy making skis for 15 years and he calls the problem you guys talk about, edge fall.

I have had it on some pairs and not on others. Doesn't seem consistent. I thought it was a pressure problem in those areas. I fixed my pressure distribution and the problem persisted but was less noticeable.

Of course every pair I make is different so consistency is a problem.


He said he prebends the edge/base upwards so the base and edge combo is already in that shape when he lays up his skis.

I have not seen any layup vids where the 3/4 wrap edge/base is prebent in the tip and tail upwards to form the rise.

Iggy how you prevent this?


He also uses plumbing heat tape on his cassettes on the bottom only to cook the skis to 180 in 20 min. Sounds ghetto but he's made hundreds if not thousands of pairs. Just goes to show there's about a million ways to skin a cat.

[iggyskier]

Some companies prebend edges, others don't. I personally find we get MUCH better results from not prebending them. If there is any kink or anything at all in a prebent, it can easily translate to a finished product.

Other companies don't have issues with prebending though.....so definitely multiple ways to do this. Personally, it is an extra step before layup and really just added busy work.

One tip is to make sure you have adequate space in the tips to allow for the hose to expand into the space. That might not make complete sense....but if you have you top mold too tight in the tips and tails, you can actually get a ski that pinches in the mold, preventing a 3/4" wrapped edge from getting a good meet with the base material. This can result in a gap between the edge and rest of the ski, essentially creating a ski with separating edges right out of the press.

By giving the hose enough room to fully curve and expand, you get much better pressure and avoid "edge fails", as was stated above.

Hope that helps.

[Richuk]

Avoid the pinch and use teflon - www.toastabags.com. It's crazy I know, but its works.

[MontuckyMadman]

Avoid the pinch and use teflon - www.toastabags.com. It's crazy I know, but its works.

That link is no good. Takes me here http://www.123-reg.co.uk/
meh?
http://shop.toastabags.com/

Wow iggy you are awesome you must read every forum thread everywhere.

I feel like I have that problem licked and my top mold is about 1.5 inches smaller length wise than the actual curve in the bottom mold.

But you maybe right.

I feel like I get great compression with no pinch but my press is super tight fit so maybe I need the slide effect from teflon perhaps.

[Richuk]

That's the one! ... links!?! You can probably get them locally.

I used them when I noticed that the tips were the last thing to be compressed.

[skidesmond]

I know what you mean about the hose bending into the mold. I had previous problems where the hose wasn't bending in tight enough. This time I slid back the top mold until the hose got good compression into the tip and tail. Ran a few dry run tests (w/o a layup), seemed ok.

So tell me more about this teflon bag. How do you use it? Where do you place it in the press?

[Richuk]

Thought this would help. I'm using the teflon sheet - the thicker the better. So it's mold, teflon, heater, cassette, heater, insulation, cat track, insulation, then hose ... not overly complicated at all!





The sheet is placed between the tip mold and the heater. I make sure it sits over the rear of the mold so the cassette and heater remains free to move.

I suspect I still need to sort out the tip mold and increase the curvature but I've just emptied the garage of mdf dust! So for the time being adding a drop more epoxy has given good results. Shout if you want the photo's posted.

Photobucket will re-size shortly

[skidesmond]

thanks for the photo. I'll give it a try, but honestly I don't understand how it works, but if it does it does.

[Alex13]

What's the theory behind the teflon sheet? I'm not sure I follow the reason for it, i.e. how it prevents "edge fall".

[MontuckyMadman]

so after going through this in my head a few times, its a pinching problem when initial pressure is generated.

the bladder pinches the base at the tip either on the base itself or on the cassette. This stops adequate pressure from being distributed to the end of the edge where it meets the base. It basically creates a small span that you probably cant see and prevents the base from meeting completely hard against the mold and pressure is not as great in that area.

This is why its inconsistent for me when I press. Sometimes it all lays flat and smooth and sometimes it doesn't.

The teflon allows more sliding and movement so everything lays smooth in there. This also explains why my rise is not quite as high as my mold.

Very subtle stuff we are getting at here.

Right track?

[Richuk]

MM, that's definitely the long and short of it ... I hope you don't mind the following comments:

'the bladder pinches the base at the tip either on the base itself or on the cassette', depending on the length of the ski within the cassette, my cassette is a bit longer and naturally I didn't want to cut it, so the ends gets pinned/pinched by the hose before it has a chance to sit in the mold correctly. I looked at changing the upper tip mold, but I didn't get better results when I added a few wedged between the track and top tip mold. I did reduce the height of the bottom tip mold, which increased gap between bottom tip mold and hose.

'It basically creates a small span that you probably cant see', you'll see the span effect when you press, it being the last area to be pushed into the tip mold.

'The teflon allows more sliding and movement so everything lays smooth in there', it's a good fix, but I suspect your results will vary depending on how your mold and hose fit together. Someone with a tight and consistent gap, tip through to tall, may need to apply pressure more slowly to increase the opportunity for the teflon to work - perhaps, no point going super slow.

He's a photo of the results (still working on these)... you can see a big band of black (rubber shear layer coming through) all the way round the tip. It deals with the pinch Alex, I am hoping it helps when pressing a 3/4 wrap. The second photo shows a better result from my previous attempts - a nice curve to the base around the tip, as per the mold. Fingers crossed, this decreases the potential for delamination.





SD, apologies, hope you don't mind the info on your log. Feel free to draw on my wall

[skidesmond]

RichUK, No problem. The more info the better. btw- that looks like a perfect bend. Nice work.

Montucky/RichUK - I think you may have something here. I had to mull it over for a while but now that I can picture what you're saying I think that is the problem. It's possible the hieght of the mold was just a bit too high and the cat track or hose was pressing on the top of the mold and bending the base and/or mold.

One problem w/ past builds was my curvature and hieght of the tips have been too low. On this one the curvature and hieght of the tip came out perfect. But I may have had the mold up a little to high.

But I think my cat track might have something to do with it too. The hose is inflating and looks like it's filling the tip area fine. But I think the individual boards in the cat track may be a bit to wide and not getting even pressure down into the tip area AND the mold may be too thin and could be causing a bend. I can also see a very slight crease across the tip that just happens to be where the metal edge ends.

See pic. Notice the slight crease across the tip. I think this might be cause be the cat track. (btw- I haven't cleaned the base yet. Still have time before the snow flies)


(my dog Ruby had to get in the pic)





I've been meaning to make a new cat track anyway and I think this gives me more reason. I just read a post where Vinman uses a thinner width material for the tip and tail section to get in tighter.