Protecting royalite? Foam exposed

[Pea Pod]

I've exposed the foam on my royalite Spark by abrasion. Is this a concern? If so, what should I do to protect the exposed foam?

[DougB]

If it's actually into the foam then yes. You will want to patch that up! My old Ocoee was into the foam and became soft/delaminated quickly

[2opnboat]

G flex is the cure

[ezwater]

G-flex and glass cloth. Has to be something to keep abrasion and rock blows from chewing into the foam.

[pblanc]

I too would use G Flex, thickened with silica powder, to fill in the exposed foam core and build it up to flush with the adjacent hull, then use unthickened G Flex and cloth over the repair overlapping onto intact hull by about 2 inches.

Some have reported good results filling in the foam core with Gorilla Glue. I would still do a cloth repair over it.

[Pea Pod]

At present, there are a several small bits of foam exposed, about one-quarter the size of a US dime each. Are the previous suggestions still the best option here?

[Einar]

Agree on the g flex, had good results with it but i would expect that ti will abrade off and will have to be redone. It may craze and crack allowing water inward, I would consider keeping a small tube of silcone handy to give it a light flexible wipe. Whatever it takes to keep the water out. Eventually it will weaken and you will have to buy a new hull but you will be ready to move on anyways by then.

...and look like this.

[jknkboaters]

I too would use G Flex, thickened with silica powder, to fill in the exposed foam core and build it up to flush with the adjacent hull, then use unthickened G Flex and cloth over the repair overlapping onto intact hull by about 2 inches.

Some have reported good results filling in the foam core with Gorilla Glue. I would still do a cloth repair over it.

When you state use G-flex and cloth does that mean kevlar cloth or fiberglass cloth? or does it matter.

[pblanc]

I would use either fiberglass (6 oz/sq yd) or Dynel (5 oz/sq yd) on the hull exterior. For interior repairs I usually use 5 oz/sq yd aramid (Kevlar). G Flex should work fine to fill in the rather small defects where the solid stratum of ABS has been worn away to expose the foam core. But almost certainly, the solid ABS stratum on the exterior has been worn thin in the areas adjacent to the foam core. Sometimes you can identify the areas where the ABS solid layer has been thinned by pushing on it with your thumb. Thinned areas often feel soft, or spongy. I would cover any such areas with thickened G Flex (using colloidal silica powder or cab-o-sil as the thickening agent) then cover the whole thing with cloth.

[kayakbob1700]

I've made several repairs on an old shaman12 on the cracked stern. I ground open the cracks, filled with gflex and then applied glass patches on both inside and outside. The stern patching seems to be working quite well after several months of boating and banging down low water runs.

I now want to protect the bow and stern with grunch pads and have followed the topic in previous posts. However, I wonder whether it is better to just rough up the vinyl covering, or sand down to the ABS layer.

Also is it better to slightly flame the ABS or just gflex the dynal to the bow and stern?

Thanks for any help you may offer or advice.

Bob

[Roy]

I know it is too late in this case, but I would like to put in a vote for fixing abrasion problems when they first reach the ABS layer...well before the foam. Early patching makes the patching easier, cheaper, and longer lasting.

For Royalex hulls, I have had good results with System 3 epoxy resin...which I buy from Merton's Fiberglass. I am sure Gflex is great, too. Where I differ with many is, I use polyester cloth to make patches and skid plates for ABS canoes. I buy it from Sweet. You see, I want a patch which is quite flexible...this reduces de-lamination when "glued" to the quite-flexible Royalex. Epoxy/polyester cloth patches are the most flexible fiber-reinforced option. The PE cloth will fuzz when abraded, but that does not concern me.

PE cloth is cheap. It should not be creased in storage as wrinkles are hard to remove. Wrinkled chunks of cloth should not be used. You can use an iron to remove minor wrinkles.

For core replacement, I use mirco-ballons in epoxy...but, the Gorilla glue sounds even better.

You don't flame Royalex before epoxy. I don't know about Royalite. I would call Esquif and ask...I would also ask for their suggestion for an epoxy to do this work on Royalite.

Roy

[pblanc]

I've made several repairs on an old shaman12 on the cracked stern. I ground open the cracks, filled with gflex and then applied glass patches on both inside and outside. The stern patching seems to be working quite well after several months of boating and banging down low water runs.

I now want to protect the bow and stern with grunch pads and have followed the topic in previous posts. However, I wonder whether it is better to just rough up the vinyl covering, or sand down to the ABS layer.

Also is it better to slightly flame the ABS or just gflex the dynal to the bow and stern?

Thanks for any help you may offer or advice.

Bob

As to prepping ABS by flame oxidation with a propane torch, I have discussed this with the technical advisors at West Systems and was advised that they consider flame pretreatment "optional" for ABS. I have used G Flex and cloth (fiberglass, aramid, and Dynel) to repair quite a few boats now, and I only flame pretreated once. I have not had any problems with delamination of any type with G Flex so based on my personal experience, flame pretreatment appears unnecessary for ABS. It is absolutely critical for polyethylene.

But the adhesion data currently posted at the West site shows an improvement in tensile strength of G Flex bonds to ABS with flame preparation, so you might want to do it. Just keep the propane torch moving along at a good clip to avoid melting or deforming the foam core.

As for removing the vinyl layer or not, I have always sanded the vinyl very well and cleaned it with denatured alcohol but have not generally tried to remove all of the vinyl. In all cases the vinyl was partially gone in the area of the repair. Ezwater, who posts here quite a bit maintains it is best to remove the vinyl with a wood chisel to allow bonding directly to the ABS to prevent the potential for the vinyl to delaminate from the underlying ABS taking the repair with it. I do think that makes sense from a theoretical standpoint, but I have not usually done it and haven't had problems so it is up to you. If the vinyl comes up fairly easily without a lot of gouging of the ABS I would say do it but if it doesn't and you don't want to take the time and effort to sand or grind it off, don't sweat it.

I think the issue about choosing materials that are more flexible when repairing plastic is a good one. I strongly suspect, however, that the elasticity of the cloth used has a lot less influence on the overall flexibility of the repair than the elasticity of the cured epoxy does. I like using G Flex on Royalex for that reason. Cured G Flex has a much lower modulus of elasticity than cured 105/205-206 epoxy does. A lower modulus of elasticity means it is more flexible. The following table from West Systems shows that both the flexural and tensile modulus are lower (more flexible) for G Flex and the percent tensile elongation is greater meaning cured G Flex is better able to expand or shrink, and flex along with the underlying ABS so that there is less tendency for a stress riser to form at the margins of the repair:

http://www.westsystem.com/ss/typical-ph ... roperties/" onclick="window.open(this.href);return false;

[clt_capt]

PE cloth is cheap. It should not be creased in storage as wrinkles are hard to remove. Wrinkled chunks of cloth should not be used. You can use an iron to remove minor wrinkles.

Exactly - PE or Dynel are going to be more flexible than glass - and lower profile than kevlar felt. G-Flex is more flexible but more expensive than System 3 - but either will work just fine

[ezwater]

This is a shot of how a low angle chisel will lift the vinyl off the ABS. It takes advantage of the fact that the vinyl is soft, while the ABS is relatively hard. The chisel should be held at a low angle, and perhaps at a small angle relative to the direction of skimming.



On what cloth to use, I would still favor S-glass over polyester, because S-glass will result in a very resistant repair to compression forces. But I would be very interested in reports on performance of polyester.

[Roy]

"On what cloth to use, I would still favor S-glass over polyester, because S-glass will result in a very resistant repair to compression forces. But I would be very interested in reports on performance of polyester."



Like I said, I have repaired quite a number of Royalex canoes using epoxy/PE cloth. I used to work for an outfit which poled and hauled their well-loaded canoes up and down all sorts of shallow rivers, brooks, and streams.

I think in terms of compression/tension/shear while designing composite boat lay-ups, but I have never really worried about those attributes while patching Royalex. Over bare foam, I would generally use a 3- or 4-layer patch (the PE cloth Sweet sells). I would, of course, feather the edges of the patch to limit the delamination potential. I have had lots of long-lived patches. When the outer two layers of PE wears off, just lay down another two layers (before you wear through all the layers of PE).

If you catch the wear just as you hit the ABS layer, one or two layers of PE cloth will work well. I used to use five layers for skid plates; cut the cloth on the bias, and handle the cloth gently until it is wetted out or it will bias-flex all out of shape.

Roy