Pallet Strapping reinforcement - RC Groups
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Dec 01, 2013, 03:55 AM
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davereap's Avatar
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Pallet Strapping reinforcement


This is not a new idea, but I thought it deserves its own thread...

The poly strapping used to bind items to pallets for shipping makes a good , much cheaper alternative to using CF for stiffening and strengthening foam..
You glue one length of strapping along the spar line, that's the thickest part of the wing, using a good amount of UHU por and then mirror it with another length below..
strap//foam//strap when doing a KF type wing put the strap along the step line..
The thicker the wing the more effective this method, so for KF designs with two or more layers it works very well..


It comes up used on a number of threads

https://www.rcgroups.com/forums/show...ostcount=11245 for the description
the pictures below were from this post.... thanks to pardshaw for the pictures
Last edited by davereap; Aug 16, 2017 at 03:50 AM.
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Dec 01, 2013, 04:05 AM
All can fly...Launch stronger!
ttersu's Avatar
Good idea! It would be usefull for gliders's wings
Dec 01, 2013, 04:08 AM
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davereap's Avatar
The above test was using depron..

I have just used it on an EPP model with similar results...

what I did notice is that when I first glued on the wing it still flexed easily... So I used a heat shrinking iron at 105 degrees to make the bond stronger and drive off any solvents remaining in the glue .
I left it overnight and found it vastly improved the next morning.. all nice and stiff..
Dec 01, 2013, 04:10 AM
All can fly...Launch stronger!
ttersu's Avatar
Thank
Dec 01, 2013, 04:24 AM
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davereap's Avatar
why use strapping??? its cheap and it works... cost is always a main factor..

well its cheap....
one ebay seller has short lengths at 4.50 for 50M and that's expensive when you can get 2000M for about 20....

it works its both stiff and light in weight
Make a foam sandwich and its stiffer than if you use a single 3mmx0.5mm flat CF spar but heavier..2.5gms for a single 3mmx0.5 vs 6gms
or 5gms for the 3mmx1mm CF flat vs 6gms for the strapping
however compared to a 1M x3mm rod which weighs 10gms it only weighs 6gms for the 2x1M lengths of strapping needed
Dec 01, 2013, 04:29 AM
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davereap's Avatar
performance ...stiffness gained....

The strapping works on EPP , and that's a soft flexible foam that has to be reinforced using something or it flops too much when its at any length such as wing span...

Note... as the foam sandwich gets thicker the stiffness increases....
.... as the foam gets denser... ie EPP to depron.. the stiffness increases
.... so a wood core is likely to be even stronger...

foam thickness..... its worth using strapping on 6mm thick or more ...on 3mm CF is likely to be the best bet...

Ive just made some big glider wings at 15mm thick and used 6mm CF tube as spars... two lengths were needed.. that's 13 for the two spars... so for a one piece wing I am sure that a couple of lengths of the strap would have made as good a job for stiffening the wing
however I am unsure how I could have made the centre join my wing having two halves has tubes for a joiner rod fitted to the CF at the centre
Last edited by davereap; Dec 01, 2013 at 04:38 AM.
Dec 01, 2013, 04:41 AM
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Dave

So per metre -
3mm x 0.5gm carbon fibre flat weighs 2.5gms,
3mm x 1mm carbon fibre flat weighs 5gms,
strapping on both sides of the surface (2 lengths of 1 metre) weighs 6gms total,
3mm carbon fibre rod weighs 10gms.

I wonder what the adhesive weights do to these comparatives as the strapping has a lot more surface area.

In your heat film iron at 105 degrees C comment which adhesive were you using. I am guessing one that the heat reactivated and which your iron made bond better.
Last edited by ChrisE; Dec 01, 2013 at 06:25 AM.
Dec 01, 2013, 07:51 AM
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davereap's Avatar
those weights are accurate, except the pallet strapping is 6.2gms rather than 6....I did a recheck...I use one of those tiny scales for the job...
for glue I use UHU por for just about everything..
The hot iron also flattens the epp which helps it bond ..
the weight is there , but I've never measured how much I add ..it gets applied as thin as possible usually by finger tip on epp or by credit card on depron..
the strapping is wider 12mm so yes it must use more adhesive..= more weight...
I use uhu when I glue in CF flats ...
round rods get even more of the glue and sometimes more is used or cool melt to fill any gaps from my poor cuts
Last edited by davereap; Dec 01, 2013 at 07:58 AM.
Dec 01, 2013, 02:26 PM
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IAFoamie's Avatar
Hello
The strapping is free if you go to a Grocery store or Clothing store where boxes come in all the time.Just ask someone who works there. It may be bent and only 18 to 30 inchs lengths without the bends. Bigger the box longer usable length. I think if you sandwich it ir will work very well vertical in a spar. Just my 2 cents.
IAFoamie
Dec 01, 2013, 07:43 PM
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propjobbill's Avatar
I have turned the strap on its side, cut aslot into the wingand glued it in the foam. it makes a very stiff wing. Because it is vertical and glue to both sides it makes the wing super stiff plus adds airfoil to top and bottom if you center it out.

I won't be able to take a picture to show what I mean for about 1 month. Ihave often used a slin slice of fur strip. Cut 1/16" thick out of 3/4" board for 30" legnth it weights about 1/2 ounce or less but super strong, your wing wont flex.
Dec 02, 2013, 04:48 AM
Registered User
Quote:
Originally Posted by propjobbill
I have turned the strap on its side, cut aslot into the wingand glued it in the foam. it makes a very stiff wing. Because it is vertical and glue to both sides it makes the wing super stiff plus adds airfoil to top and bottom if you center it out.

I won't be able to take a picture to show what I mean for about 1 month. Ihave often used a slin slice of fur strip. Cut 1/16" thick out of 3/4" board for 30" legnth it weights about 1/2 ounce or less but super strong, your wing wont flex.
There is a persuasive argument here that the strapping on the surface is better:
https://www.rcgroups.com/forums/show...ostcount=11259
Dec 02, 2013, 05:38 AM
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davereap's Avatar
On its side is fine as well.. top and bottom doesn't need cuts..

worth a note is that EPP is a poor surface to glue to, I find it needs more glue for a good result, whatever you are sticking to it..... while depron is ok..
So its worth checking your EPP laminations every now and again, just run over with a hot iron to make sure they are fixed, as I suspect constant stressing in the long term will lead to the strips popping away

It will be worth a couple of more scientific trials on positioning to see actual results number wise...

Ive got no numbers as yet, but the EPP model I made can be picked up fine at the wing tip it takes the weight of the whole model with just a small bend.. when a similar wing sheet without strapping, without the ailerons cut out , without the body , just gets a worse of a bend on...
Last edited by davereap; Dec 02, 2013 at 05:52 AM.
Dec 02, 2013, 06:55 AM
Registered User
Quote:
Originally Posted by propjobbill
i have turned the strap on its side, cut aslot into the wingand glued it in the foam. It makes a very stiff wing. Because it is vertical and glue to both sides it makes the wing super stiff plus adds airfoil to top and bottom if you center it out.

I won't be able to take a picture to show what i mean for about 1 month. Ihave often used a slin slice of fur strip. Cut 1/16" thick out of 3/4" board for 30" legnth it weights about 1/2 ounce or less but super strong, your wing wont flex.
this!!!
Im going to try it out on the next armin wing.
Lighter and stronger....

I know for a fact laminating 3 sheets of DTF with paper and stacking it vertical is plenty strong.
Strong enough to allow me to remove all the paper to the rest of the wing.
Lite and strong.

Holy wow DAvereap...I think you solve some of my problems on certain wing rib construction designs.
Im having a spiritual awakeing moment. Light bulb going off in my brain.lol
Last edited by smcx66; Dec 02, 2013 at 07:08 AM.
Dec 02, 2013, 02:26 PM
Altitude is my friend...
Depronicus's Avatar
I'm sure this technique works well, but it looks like a lot of work to get it applied. There's another way to go that has to be a lot easier. Use this particular clear packaging tape:

Scotch Heavy-Duty Shipping Tape

I haven't found an equal to it yet. It's thick, super-strong, and highly resistant to stretching. The adhesive sticks to all foams really well. One layer works great, and if you apply two layers on both sides of 6mm Depron, it feels almost like a piece of aluminum plate.
Dec 02, 2013, 02:34 PM
Registered User
Quote:
Originally Posted by Depronicus
I'm sure this technique works well, but it looks like a lot of work to get it applied. There's another way to go that has to be a lot easier. Use this particular clear packaging tape:

Scotch Heavy-Duty Shipping Tape

I haven't found an equal to it yet. It's thick, super-strong, and highly resistant to stretching. The adhesive sticks to all foams really well. One layer works great, and if you apply two layers on both sides of 6mm Depron, it feels almost like a piece of aluminum plate.
Is it UV stable? ie does it rot with sunlight?~~~~~~H


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