87 Sun Sport Overhaul

[NeilMcg]

Mike,
Ok will do on your suggestion.


Okie,
All that rotted wood is from the rear seat area, and there is clearly visible bad wood under the fuel tank.

This leads to my first 2 big question regarding stringers and Floors:

1. What is the true dope on Polyester vs. Epoxy Resin?

2. Since I'll coat the wood thoroughly, then glass, then re-apply, is there any real-world difference in what wood I use?

[rludtke]

Polyester resins are most likely the resin used in the original boat build. When bonding new polyester to old, the bond is primarily a mechanical bond, not quite as strong a joint as the original chemically bonded original laminants.

Epoxy creates a chemical bond even when bonding new to old (or secondary bond), and will be equally as strong as original laminants (primary bond). Epoxy will secondary bond well to polyester, but the opposite isn't usually true.

Epoxy is much more viscous (resists pouring) than polyester.

As for wood choice: A single layer of glass laminated to the wood with resin will not add much, if any strenght. It will help the wood resist moisture, and make it more durable. Therefore, the strength of the stringer or floor or whatever you are building will come from the wood selected. Hardwood, or several layers of marine plywood are the typical choices for stringers and other structural members. Obviously marine ply is the best chioce for the floors. If the wood components are to be laminated, one could argue that Marine grade might be overkill. Exterior grade plus the fiberglass will probably give more than enough years of service.

No doubt you have noticed the soft wood (the back seat for instance) the manufacturer selected to save money, and it lasted a long time.

[Okie Boarder]

Rick nailed it. I would add that many of the boat building forums will provide a lot of information. Quite a few of those guys use Douglas Fir. If you can get that in your area, that would be a good choice.

The one thing to remember is that you have the chance to use a little better materials and methods than the factory did over 20 years ago, so you should expect it will last a little longer. Completely covering and coating wood, using products like CPES, using epoxy all add longevity to the build. But, you need to ensure you are sticking within the constraints of your budget.

[NeilMcg]

Rick,
Thanks for the help,
I've gone dizzy on the poly vs. epoxy debate, but have decided to go with epoxy to save my sanity, if not my wallet.

Some more questions if you don't mind:
1. Once everything is torn out of the hull, should I sand and apply a coat of resin before doing anything, or just clean thoroughly?

2. How much resin should I expect to use (Stringers,floor and, if recommended, the hull?)

3. Is there a difference in epoxy quality (West systems, TAP, or the dreaded Home Depot?)
Thanks

[rludtke]

I have not done a stringer repair/replace job, but I have built and repaired numerous composite kit airplanes.

The preperatory steps for a secondary bond using either epoxy or polyester is to mechanicaly clean (abrade with course paper), and then chemically clean (scrub/wipe with acetone), immediatly prior to laminating. Its generally good to brush a light coat of resin over area before placing the fabric.

Some times I pre-wet the fabric laminations over a plastic sheet on a flat table, and then walk the stack-up over to the project and flop them all into position, and remove the plastic. This can be a real time saver, especially if the shape is complicated.

I don't know about the quantities needed, but others have posted here about their stringer jobs and should know. I am not really sure if resin brands make a big difference. I would expect the cheapest resin you could find would still give you good service life. You are going to buy this stuff by the gallons, so the price will add up. I am not familiar with Home Depot resin, but if it is the cheapest, I would consider using it. My guess however, is that a composite distributer will have better retail prices.

[Okie Boarder]

1. Plan to do lots of grinding. You want to get down past the layers of glass and resin they used to attach to the hull and be to the layer that is the atual hull. As Rick stated, wiping with acetone prior to laminating is a good idea. You'll be bonding the stringers to the hull first with thickened resin (most likely) prior to lamination over the tops or tabbing along the bottoms.

2. I would plan for somewhere in the neighborhood of 20 gallons. You might use more or less depending on methods, total laminations and amount of bedding material you have to use.

3. I've read a lot about this. Some guys swear by certain brands, but most don't see the value in some of the expensive ones, like West. Check out US Composites. They have good products and pretty much the best prices your going to find. Nearly half the price of West.

I agree with Rick's suggestion of laying layers out on a table first. Whether you are going to mostly tab, then wrap or just wrap, wetting out the layers of fabric you are using is much easier on a horizontal surface. It will be a lot like handling a wet noodle to put them on and it takes some getting used to.

[sybrmike]

I second the others...

Mechanincally abrade (grind/sand) the surface you're bonding to. It doesn't have to be perfectly flat and smooth, but bumps and ridges will pevent the cloth from laying down without air bubbles. Vacuum up the dust, then wipe with acetone prior to wetting out with resin. It's a trial and error feel type thing as to how much resin to put down and prewet the cloth with. Use the least amount of resin possible to fully wet the cloth. Too much resin actually weakens the layup and the waste can add $ up quickly. Squeegies are a great way to force out the extra resin. You can push it up into needed areas until it starts to "kick" and no longer wets out the cloth. Wipe and remove as much excess resin as you can on each layup before it sets - a lot easier than grinding it out after it's cured.

Around 20 gal of resin sounds about right - but you're mileage may vary. I used a bit more, but on a bigger Saltare.

US Composites makes good stuff & prices are about as good as it gets - used them for years.

[NeilMcg]

It's been a few months since I started this project and I finally have time to start up again. I just got back dropping off all the uphostery and he said that he'll need 33 sq. yards of material! That sounded like quite a lot. Any thoughts?

[mapleleaf]

He's prolly not too far off, sorry to say it!, I remember being somewhere between 20 an 30 on my Conbrio. Be happy someone's doing it for you, it's not an easy job!!!

[NeilMcg]

Thanks Maple. I'm relieved to know that even though its a bit of a suprise, I now know I'm not getting taken. Thanks for the reply. Looking at @ $2,200-2,500 as an estimate, which includes some woodwork for the rotten areas of the bowrider section and rear bench.