Gelcoat pressure(?) indentation

After a light coming together with a mast a couple of weeks ago, one of my hulls has a longitudinal wavey pressure indentation about 3 feet long and half an inch wide. It appears to be a pressure mark rather than scraped/scratched - or so it seems to me - still mirror smooth. It's obviously not invaisive damage but looks ugly - and looks impossible to fill because it's so shallow - probably about .5mm, if that. To rectify would I have to make it deeper and then fill or is there some magic wand I can wave...? It's an Auscat Mk5 Flyer made from carbon -> kevlar -> gelcoat. In fact I keep noticing pressure marks all over the hulls which surprises me; I never noticed such marks on my Dart 18...

You can fill it with a filler. Bondo brand filler is widely available in the US (used predominantly in the automotive industry) .. but they do make a marine version of it (although I'm not sure if the "marine" version actually has anything extra in it other than cost). The Bondo brand fillers are based on a polyester resin - so they work just great with gel coats. They even have a light weight version - thought I haven't used the light weight stuff for anything other than r/c boat repair.

Basically you fill in the void with the bondo and sand it smooth (see the other thread about long boards). Spray gelcoat on top, sand, wetsand, polish, and buff and the indentation is gone.

This was a nasty delaminated spot with a big rock dragging dent next to it - I had to reglass the delaminated spot and fill around it to get things smooth again. More during last March at http://www.teamseacats.com/2006/03/




not wetsanded yet:

Colin,



This is because the A is built as a foam sandwich with carbon on each side of foam. The dar is just a layer of glass/epoxy/gelcoat to keep the water out.

Give the side of a Dart a firm tap and it either moves and pops back, or breaks

Give the side of a foam sandwich boat a firm tap (not suggesting you do) and you get a "dimple" as the foam compresses and then does not return to it's old shape.

You can fill the bash you have with any filler, but make sure the area is very clean first and rough it up slightly so it sticks properly.

Thanks Jake and Simon. The full extent of my repair toolbox is currently a tube of this:-

http://marinestore.co.uk/page/mrst/PROD/plastic-padding-products-isopon/MD350009

Re foam: of course; I forgot about the foam! Nomex I think.

Well first your going to need the exact color Gel.

Because the the area is so shallow I would try just building the area up by spraying Gel and then sanding. It could also be done by adding a thickener to the gel and spreading it over the area then sanding.

If you haven't done any repairs with Gelcoat this may not be a good place to start. You might want to pratice on something else first or have someone that knows do it and hopefully you could be there to gain some experience.

OK, thanks Mike.

Colin

If you want to find someone local (ish) to do the repair then Jo Lines near Bristol comes highly recommended. One word of caution, I'm told AHPC use a 'special' gelcoat on the Capricorn which apparently is very difficult to match and considerably more expensive than normal - not sure if the same applies to your A. Hope that you are still enjoying it, Nacra 140 now at a new home in Rutland and it's berth taken by a Capricorn.

Adrian.

Jake/Mike

What sprayer type and nozzle size are you using? I know you thin the gelcoat with some styrene, but how thick do you spray?

First things first. Leave the dent alone if it is only .5 mm deep. Not worth fixing. A cats are lightly skinned boats, so they will surely dent if you smack em hard enough. as far as repairs go, I would not trust a normal fiberglass guy repairing them. Find out who repairs high tech dingys if you are going to do it. the gelcoat on an A is very thin and easy to sand through.
If you want to try a repair, first try heating the area gently with a heat gun. You may sucessfully make the foam core pop back to the original thickness. I have made several dents disapear by doing this.

good luck,
Eric

Hi Adrian,

Thanks for the info. I did wonder what GBR 6 was; I had visions of you trying to explain away four boats to your other half... <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />

Thanks Eric; sounds like good advice given my skiil level...

I found a similar indentation on the inside of my 2006 hobie 16.Not sure how it got there.Only explanation I can think of is from the Tiger Trax cat wheels.I am going to give the heat gun a try.Any added advice(i.e how long,how close,will a hair dryer on high work)

Careful with the heat...the foam will melt too. I know I've been showing a lot of pictures lately - but I've been through a lot of headache with this stuff. I had previously been working in some cold weather (40F) and using a heat lamp to keep any glasswork warm. We got a warm snap the next day and I walked away and left the heat lamp on a fresh repair - it was too close given the warm sunshine and overheated the foam resulting in a much larger repair afterwards.

Jay,
I went to home depot and bought the gravity feed gun they had. About $60.00. It doesn't take that much styrene to get it to spray..

I think if you don't get it hotter then you can touch the surface with your bare hand you are ok. Try a little heat, look at it, try a little more. I don't know how well this will work on a H-16 the skins are much thicker thne on the A so heat might not do anything. If you are carefull though it can't hurt.
Eric

good luck

Thanks for the tip, Mike. I've been sweating over that potential purchase for a while. I know there are different nozzle sizes, but I can fiddle with them to get the right one for each job size.

Most of my repairs have been small, not much more than dollar bill size. But, should I feel the need to "Pimp my Ride", a spray gun and/or airbrush gun may come in handy.

I just used some polyester filler new to me- "New Bondo"- which is UV activated! No MEK eroxide catalyst needed. It goes off really quick`in the sun- like 5 minutes. Useful for the beach? And no diatomaceous earth in it anymore- apparently just fumed silica gel. Just a quick swipe, and its in place- one hopes, because it starts getting lumpy right away.