As published in Australian Amateur Boatbuilder - #86 Apr/May/June 2015
If you are like me and think sanding sucks, then peelply is a brilliant product that will save you heaps of time and money. Like all things involving boat building / restoration, there is a degree of technique and I recommend you have a play with Peelply on a scrap piece of timber or something not critical before using it on your pride and joy. The worst thing I have seen is when someone put the Peelply over their wetted out fibreglass and then proceeded to remove it while the fibreglass was still wet.
Oh! What a mess.
The use of Peelply in the fibreglassing process is important in ensuring the optimum fabric to resin ratio. For all those chasing lightweight construction it is the best way to achieve a good finish as the closely woven nylon or polyester fabric to which epoxy will not adhere. Do not go to a fabric shop and buy any old nylon or polyester as it does not work as it needs to be 100% polyester and very tightly woven and it is not normally used in dressmaking. I have heard the tales of woe from some who have tried and failed miserably.
Peelply is applied as the last layer of the sheathing process or the last layer applied in a single day. When applied, the Peelply fabric will allow the excess resin to draw through and ensure the fibreglass will be in full contact with the underlying laminate. This is achieved by using a Fibreglass Roller to push the Peelply evenly onto the fabric forcing the excess resin through the weave and also aids in spreading the fabric / resin evenly across the surface, especially where there are overlaps in the fibreglass cloth. Using a stippling action with a brush works well on small areas such as fillets when the tape has been applied.
The other accepted method of filling the weave in the fibreglass cloth is to let the saturation layer of resin go almost green so the glass cannot float and then apply a filling layer of Epoxy Resin over the top. This method does not ensure the correct resin fabric ratio and then there is the sanding. Also, it adds unnecessary weight if you are chasing a lightweight finish.
The additional cost of using Peelply is far outweighed by the reduced labour & consumables involved in sanding a cured epoxy coated surface. Remember, sanding sucks and any opportunity to save on this thankless task is a bonus.
Figure 1 – Prototype Canoe with Peelply applied
The Peelply can remain on the surface for lengthy periods as it will still pull off easily, thus protecting the epoxy / fibreglass sheathing. The idea is to remove Peelply just before the application of subsequent coatings to prevent surface contamination. Lay out the Peelply on the epoxy / glass surface, then use a Fibreglass Roller and / or squeegee starting from one end and push the Peelply evenly onto the wet out fibreglass as this helps to expel all air. Using a stippling action with a brush works well on small areas such as taping Stitch N Glue joints as shown in Figure 2.
Figure 2 – Stitch N Glue joints with Peelply applied
There will probably be enough excess epoxy in the laminate to thoroughly wet-out the Peelply, if not, it is probably because the resin has started to gel or you need to add a bit more resin when wetting out. If this happens, leave the dry areas as you will make a mess when trying to lift it to add more resin. Hence, the comment previously to practice on a scrap of plywood or off cut of your job before “going to town” on your pride N Joy. This is important, as I have seen issues with a customer’s Huon Pine strip planking practice piece where it was so oil rich, as the strips were freshly cut from a slab, as a result the oil was reacting with several brands of epoxy causing a horrible orange colour.
For the novice there is good advice on how to fibreglass using Bote Cote Epoxy Resin in the “Boat Building with Bote Cote” Book in the very good section on laminating fibreglass. Overlap the peel ply at joints as shown in all Figures, leaving a dry edge to facilitate easy removal.
Figure 3 – Peelply applied to Cosy Aircraft components
- When glassing compound shapes such as canoe/Kayak Hulls; wet out approximately one (1) metre at a time for the final coat of Epoxy. Tear the Peelply into strips approx. 300mm wide and overlap as per Figure 1. This eliminates creasing & epoxy gelling before the Peelply is wetted out.
- Do not use too much epoxy resin as it will be wasted & can cause the Peelply to bury itself at the joints.
Why use Peelply?
The major advantages of using Peelply are;
- To ensure the epoxy/glass sheathing is evenly consolidated as more pressure can be applied without disturbing the fabric.
(ii) Excess epoxy is brought to the surface and is removed from the laminate minimising weight and maximising strength.
(iii) The fibreglass is pressed down onto the substrate, thereby preventing the fabric from floating.
(iv) When the Peelply is removed the textured surface will need minimal to no sanding, thus allowing further layers of glass/epoxy, fairing compounds or coatings to be applied straight over the previous layer of dried fibreglass.
(v) Overlap joints, and taped edges on fillets are feathered out by using Peelply leaving a nicely finished edge.
(vi) A significant saving in consumables & time sanding before the next step.
(vii) For you thrill seekers insisting on using old technology epoxy; it is an easy way to remove Amine Blush as it will be pulled away with the Peelply.
I know a boat builder who uses peelply when coating timber & plywood surfaces with Bote Cote after the last coat as it saves him sanding and usually a better finish.
I use it when doing osmosis and other fibreglass repairs as it keeps glass on a vertical surface inplace and minimises slumping as shown in Figure 4. After grinding out the damaged area and using 265 gram Double Bias cloth to repair the craters, I then mix some sanding filler with leftover resin to an extremely thick mix and trowel over the surface to overfill the repaired area. I then apply Peelply patches and smooth out with a fibreglass roller with the result being a slightly overfilled surface and a light sand to achieve an easy to finish result.
Figure 4 – Peelply applied to Osmosis Repair
Now go and have a play and you wil l wonder why you were not using Peelply years ago. Besides that, anything that saves sanding is a bonus.
If you have any other Tips N Tricks with using Peelply I would love to hear them as it all helps with people making life easier for repairing, restoring and building their latest project.