UK-Cherub Forum
Cherub Chat => Tech Chat => Topic started by: AJP on March 20, 2014, 10:56:33 PM
-
Hi
What is the best heat shrink tape for use on spars?
Also does anyone know where I can get an inspection hatch smaller than 4" orifice, ideally about 3"?
Cheers
Arthur
-
The last stuff I got was from here: http://www.easycomposites.co.uk/products/vacuum-bagging/composites-shrink-tape.aspx
It seems to work well.
It is worth testing a bit before you use it as sometimes only one side will release properly.
-
I am never that keen on heatshrink.
The level of consolidation that you get is not that great.
I much prefer using 50mm peel ply. You can wind it on really tight and get much better consolidation.
https://marineindustrial.co.uk/index.php/west-system-774-776-peel-ply-tape.html?___SID=U
Clive
-
Thanks guys, I shall try them both.
Cheers
Arthur
-
Clive,
I have always struggled to get consistent tension when winding peelply, so the tube ends up a bit bumpy. How do you recommend winding to keep everything neat?
-
Come to that I have the same problem with heat shrink tape. I ought to be modding a mast some time this spring, so tips for bagless consolidation would be welcome.
-
I have to say I have never tried heat shrink but I don't have any opinion over whether its better or worse than peel ply - its just that i've always had peel ply to hand and have not yet heard a good enough argument for going out and buying the heat shrink.
I have found 2 things help for avoiding the bumpyness: Having one person to operate the peel ply and getting at least one other pair of hands to hold the tube, ideally with the tube being rotated, and secondly letting the peel ply come off a roll rather than holding it directly.
-
I think the best method is Mr Angel.
If someone could look around the site and find the link to images of "turning machine and foot pedal" - I have text only access atm.
-
Clive,
I have always struggled to get consistent tension when winding peelply, so the tube ends up a bit bumpy. How do you recommend winding to keep everything neat?
Hi Phil,
It is certainly an issue.
To state the obvious for things that help:
We try to accurately double wrap.
We limit the max laminate thickness by doing multiple hits.
I am a great fan of getting it all really warm so that the resin viscosity is low and the peel ply can really pull down.
For mast manufacture we pre heat the resin and mandrel to 80C.
For repairs I use the heat gun and back off if the resin starts to boil or when I see smoke.
I always feel that even in the bumps there is significant pressure and consequent consolidation.
The dips show how much more it could be pulled down.
When Roger is making tubes he has a wall mounted high torque motor drive that makes it much easier to wind accurately with really high tension.
It is not unrealistic to get 50 ponds of tension in the peel ply doing it this way. On a 2" tube with a double overlap of 50mm peel ply that gives a consolidation pressure of 25PSI.
Heat shrink may give a pretty finish easily but I don't think that it really consolidates.
We broke the top mast on Subtle's Ctech just before Pwllheli and looking at the fracture it was clear that they had used prepreg with heatshrink. The fibres were not well bonded and this resulted in the compression failure when they buckled during a gybe.
Clive
-
I have used peal ply as Clive but then used heat shrink after that. it is important not to use too much resin as this stops both methods from consolidating properly. My technique overcomes working in an ambient temperature rather than a proper really warm workshop (as clive suggests.
I have found that putting lots of tension on peal ply can lead to it wrinkling and creating grooves in the surface of the finished product so carefully application is essential. I had a supply of good heat shrink which was very effective but used it up. I haven't got used to the new stuff but so far haven't found it as easy to work with.