Recoating in Dynel

[Eliseviv]

Hi Peeps

The cat I'm repairing has quiet a few punctures in the outer skin and poor repairs from previous wounds, and I'm stripping the paint, then filling and fairing with epoxy, effectively reskining the whole hull with dynel. Dynel is a doddle to work with, but it offers no increased structural strength. Will stitched weaves applied after the event offer increased rigidity? My primary objective of the dynel is to apply a new surface for cosmetic and waterproofing the core, but if some structural rigidity can be superimposed on a 30year old eggshell that would be better than not!

Any ideas?

Cheers

Brett

[PAR]

If the knitted fabric is applied before the Dynel, then you'll gain stiffness and strength. If you apply the biax/triax over the Dynel, then you've apply a thin rigid and stiff fabric of a pretty flexible coating which will make the outer knitted skin fragile to say the least. The Dynel or better yet Xynole (twice as effective as Dynel) is best applied as the outer skin.

[Eliseviv]

G'Day PAR

Thanks for that bit of info and the appropriate generic/brand names for the sourcing!!

There is little doubt that the outer skin has suffered over the years, so a renewed outer rigid layer should give her a new lease on life as the inner skin looks visually sound. (with the foam core a completely unknown quantity.

Cheers

Brett

[PAR]

Do a complete "sounding" on your hull, looking for "dead" spots which will sound quite different and "dead" or dull, compared to the normal areas of the hull. This will give you an idea of the condition of the core/laminate interface and/or possible problem areas to inspect further.

What you need to decide is if the outer laminate is still well attached, just banged up or if it needs repairs and/or reinforcement and of course what kind of reinforcement. Assuming your outer skin is still well attached, does it need additional abrasion protection or more stiffness and penetration protection? Use the Dynel or Xynole fabrics for abrasion protection and knitted for strength and stiffness. If you want to kill two birds with one stone, then use 1708 (or other combo fabric) with the mat facing out. You'll have the biax on the inside, against the hull, where it can help stiffen and add to the laminate thickness, plus the outer mat will make a resin rich environment, to improve abrasion resistance. You can take this over the top, with fillers to top off the mat's weave, making a nearly bullet proof outer skin.

[Eliseviv]

G'Day PAR,

Whats the 1708 exactly? (Brand name, or generic name I can ask for in a Fibreglass shop), as that sounds exactly what Im after.

Ive gone over the hull pretty closely and below the waterline especially there is no damage to the outerskin and it seems pretty sound (no bubble, breaks etc). I will run around it with a rubber mallet however and see if I can find the dead spots you talk of.

Above the waterline at the fattest point and the height of floating jetties etc, its like a car thats spent its entire life at the bottom of the lowest car park in a shopping centre. Nothing bad, but a future source of problems if I dont shore it up.

So primarily Im after a new watertight seal(hence the dynel comment above) but if I can add a bit of stiffness with only a small penalty in weight, (What's sub 100KG in a 37' cat!?!) then Id rather a bit of renewed stiffness in the hull.

Cheers

Brett

[PAR]

1708 is a combination of a 'glass biax knitted fabric that is lightly stitched to a mat. In fact it's called "stitch mat" by some and in this case it's two layers of 8.5 ounce unidirectional fabric, stitched at 45/45 bias to each other and a .75 ounce mat.

Personally, I'm not uncomfortable with fairing and don't have issue with these kitted fabrics, but many do complain about having to fair them out. The light mat will help with print through and fill with resin to harden up the surface. If you go to a fiberglass supply store (Duckflat?) and ask for 1708, they'll know what you're talking about or type "1708 biax" into your search engine and see what you get.