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Initiate
      
Group: Basic Members
Last Login: Thursday, December 04, 2008 12:49 AM
Posts: 2,
Visits: 23
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| So, just spent a whole day better spent revising rebuilding my shield, after it shattered at yesterday's training. I'd originally made it out of 4mm plywood. This stuff was very flexible, as the grain of the outer sheets ran across the breadth of the shield, rather than up and down (the shield is eliptical, 36" high by 24", plus 3" to both dimensions after the foam is added). I thought this would be better, as it'd bend more before it broke, rather than being too stiff and snapping rather than bending. I also screwed a very thick piece of plywood to the back of the shield (at least a centimetre thick), big enough to reinforce the area where the arm straps were going to be placed (20"x7"). I then put two layers of 0.8mm foam (from a camping matt) on the front, and one on the back, with a 1.5" overlap around the edges. Finally, I used washers to screw some thick, padded webbing to the arm support, wide enough so that after a whole day of holdin the shield bare-armed, I didn't have a single mark or rub (insert annoying smilie face here). Anyhow, when I looked at the shield this morning, I was aghast to find that it had fractured. And by fractured, I mean that around two edges of the arm support, the 4mm plywood had shattered. It hadn't split, either, it had simply broken. Needless to say, I was a bit miffed, but I decided to try and fix it, rather than give up on a decent shield shape that had given me loads of protection. There was a big piece of clear, plastic roof plastic stuff in the garage, which we had used to put the roof on our conservatory. Looking at it, I found it was thick, strong and flexible enough to withstand a few blows: it was certainly tougher than the crap I'd bought for £5 from B&Q. So I used the origianl piece of ply for the template, cut the plastic to shape, and spent about an hour screwing the arm support back in. Hopefully, this one will stand up to the punishment coming to it. Another thing I learned was about attaching foam to the shield itself. For the first iteration of the shield, I crossed the centre of the shield with double-sided sticky tape, and used "Impact-Adhesive" (a special evo-stick brand which apparently stands up well to a beating) in the quarters of the shield. When I was pulling the foam off today, however, I found that the impact adhesive barely held the smooth surface of the foam, and that the sticky tape bonded it like super glue. As such, this time around, I've decided to use only the tape, putting it all around the edge of the shield in thin strips, and then using small squares of it on the main surface. I'm yet to finish, but so far it seems to have had a much better effect. It'll mean I won't be able to recycle the foam again if this version goes to pot, but it should hold the foam better, and will mean no waiting around for hours for anything to dry. Plus, it's less messy and easier to apply. So in summary (as this has been a longer and more narrative post than I anticipated), if you're building a cored shield for an LT event, make sure you use the right material for the core (as 4mm ply just didn't cut it, and I doubt 3mm would either, despite what has been suggested elsewhere. 6mm might do, or 4mm with the grain running the right way) and use double-sided sticky tape for large-surface-adhesion to foam. It's cheaper, easier and quicker. Finally, I'd also suggest having a rummage around in your shed/garage/store room and seeing if you have anything suitable before going off to buy stuff, as I've spent much more money than I needed to to get this shield to work.
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Heroic Knight
      
Group: Eos Staff
Last Login: Thursday, December 11, 2008 10:58 PM
Posts: 119,
Visits: 278
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i also suggest training withthe shield first ... before you take it to an event... aint that right rohgan :p
-Jay
LT- Vastya
EOS- Achmed the dead NPC
)J(
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Knight
      
Group: Basic Members
Last Login: Monday, February 19, 2007 10:14 AM
Posts: 55,
Visits: 681
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With respect and in addition to what is said above.
To any prospective shield maker:
Use ply in preference to other sheet woods (as opposed to chip & mdf) as it gives you the best properties of strength vs weight. A thickness of 8-12mm will give you the strength you will need for all by the longest shields. If weight is a major consideration the cut weight reducing holes from the middle of each shield
quarter.
For thicker ply the visible gain is less relevant as the component sheets of wood are laminated at 90 degree variations, with thin ply however there will likely be a prevalent grain alignment, this should be parallel with the longest dimension of the shield.
If you add a strengthening/thickening bar like described above increased durability can be achieved by making the bar curved or of irregular width as this will stop the bar edge acting as a 'knife-blade' for forces acting on the shield. In the example above the grain and bar-edge also run parallel which will help to produce the undesirable results covered above.
If you believe that your shield is going to get really wet (as opposed to a bit of rain), it maybe worth investing in marine-grade ply as it has better water resisting properties. Regular ply can delaminate if exposed to the elements too much, although with that said I have never had a problem.
Although I have never used tape for this purpose I find that in most cases the lifetime of tape to be shorter than that of glues. Tape will age badly and become tacky weakening the bond, glue will generally remain adhesive, this can take several years however so should only be a consideration for those building shield with a long working life. To use impact adhesive on foam it's best rough up the sticking surfaces of both materials, coarse sandpaper wrapped around a 3"x3" section is what I use, this allows the glues to permeate a surface and produce a secure bond. I would likely advise double-sided-tape for a new-builder as it will be far easier to handle and less messy than the solvent fun that impact adhesives can be.
NB - as an aside, younger hobbyist may have problems purchasing impact adhesives as their sales are currently becoming more restricted due to naughty solvent abusing types.
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and Minimeister
      
Group: Basic Members
Last Login: Sunday, April 06, 2008 8:31 AM
Posts: 960,
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Knight
      
Group: Basic Members
Last Login: Monday, February 19, 2007 10:14 AM
Posts: 55,
Visits: 681
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Coffmeister,
I'll post my answer to that as a new thread, to keep this one shield related.
-H
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Initiate
      
Group: Basic Members
Last Login: Sunday, February 03, 2008 5:37 PM
Posts: 1,
Visits: 7
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| Thank you for those tips Holme. I have a question about how to make a handle for my shield though: I understand that LT will no longer pass metal handles as safe, so I have been looking for alternatives. I am building the shield around a wooden core, and I was after a handgrip/forearm strap arrangement. Can anyone suggest a lightweight solution? Also, how thick would the foam on the front need to be? Thanks in advance Andy
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