79SN Rebuild

I, and many others here, have used US Composites with good results.

Glass CC's were built with polyester resin until 1989. They were built with vinylester from '89-92 (AME4000). Since then, theyve used a vinyl/epoxy blend (AME5000).

Epoxy is the best of the 3 types- it does not absorb water. It is also the strongest, and its easiest to work with (easy to get proper mix ratio between resin and hardener, very low on fumes, no need to add wax to get it to cure, etc). Polyester is the low end in all these regards, vinyl splits the difference between the 2. Pricing per gallon is in the $30 range for poly, $40 for vinyl and $50 for epoxy. For a manufacturer, the difference in cost is significant when youre building a lot of boats (which is why most are built with poly). For a single boat rebuild, the cost difference for the small amount of resin required (10-15 gallons) is only a few hundred bucks... so it seems most people are willing to spend a little extra for the "good stuff" if theyre going to be investing 200+ hrs in labor for such a project.

David, From what I remember when doing the research for my 79 sn rebuild, is that polyester is hydroscopic. Water will penetrate it. I used epoxy and was pleased with the results. I'm sure some of the experts will chime in. I am just a hobbyist but I hope that this helps. Monty

Dbat 79SN wrote: I'm just about finished cutting and fitting the new stringers and wat to start priming them with CPES. I can't find any coverage area on any of the websites that sell CPES. Can anyone give me a clue as to how much I need to order to prime the primary and secondary stingers?

Dave,
Have you been looking at the existing threads on stringer replacements? they are an excellent source for what's needed. The big variable will be the moisture content of the wood you are using. What is it? have you checked it with the moisture meter??? The drier it is, the more CPES is sucked in!!

seems that two gallons is about where most guys end up. That left me some do to the inspection panel in the back and the wood pieces up under the bow, I used every drop.

well, coverage depends on what soaks in. I think its maybe a little under a gallon for stringers? Are you doing a wood floor? because mine was like 2 gallons for everything.

Tim - Careful posting shop pictures on the web -- I know that would get me fired from my job.

BuffaloBFN wrote: Nice break-down Tim; almost sounds like it came from someone who's worked with it before? What's your tech 411 on talc?

Yeah, just a little bit. 10+ years of composite experience for DAL. Guess if they go belly up I can get a job in Orlando building boats. Built up an air/oil seal just yesterday.

Guess I need to start taking pics of all this stuff. I'll have to post pictures of a acoustic liner that I repaired but first had to pull parts of 'Tweety' out of.

Here's the scoop on:

Talc - an inexpensive filler used to extend resin and reduce shrinkage. Talc is a component in many fillers and faring compounds imparting excellent sanding properties where weight is not an issue.

I do have a confession though...I'm not that techno savy when it comes to definitions. I do know the uses of each and why you use one or the other but cheated when it comes to short descriptions. Here's the link where I got the info:

Resin Fillers and their descriptions of use.

FYI for you guy's that are doing stringer jobs and don't know:

Cab o Sil - fumed silica, used for altering the properties of resin to change thixotropy, add viscosity or increase bond strength. Use to prevent draining from glue joints or on vertical surfaces. Use in combination with other fillers to improve working properties and minimize draining with polyester and epoxy resins. Use with resin or gel coat to make a patching paste or putty.

Milled Fibers - fine powdered glass fiber used as a reinforcement to increase mechanical strengths of resins. Add to fillets for increased strength. Use when laminating to fill tight radius.

Microspheres/ Microballons - use to extend resin, to reduce weight, shrinkage and sanding effort. Use to fill laminate weave, as a fairing compound and for making fillets.

We use all three at the 'Big D' with Microballons probably what we use the most of. We use a resin mixed with 22% ratio of Microballons for a rubstrip on an air oil seal that is attached to the main rotor shaft on a CFM -56 motor. Needless to say it's pretty tuff stuff.

** post edit** Resin and Microballoon mixtures are also used to pot replacement honeycomb core into a damaged portion of aircraft panels, fairings, cowlings etc. It's a normal Boeing repair so if we're using it to fix panels that go over 400 mph I'd say its pretty safe to use to bond stringers to a boat.

Dbat 79SN wrote: Thanks. Couple more questions: Has anyone used LVL lumber instead of douglas fir for the stringers? The secondary stringer was made of 3/4", can 1 1/2" be used there just like the main stringer?

Dave,
Yes, LVL is an alternate and in fact we have a member who has done it. There's a complete thread with pictures on it. I recommended it and he tried it. It came out great. Don't worry about the secondaries and having to use doug Fir. They are not the main structure so you can use some decent 3/4 pine of any species. Just make sure you CPES all the wood.

Try the advanced search feature. (over 6 months old) If you can't find it, I'll see if I can. Sometimes the key words can be tricky.

'Peanut butter' is epoxy resin thickened with a solid like cabosil or milled fiberglass. It is just a filler to create a radius.

4.5" Angle grinder with a diamond wheel will take care of most of your cuts. DO yourself a favor first though and gut the boat. Take everything you can out of it but the gauges unless they are not working. You cant cut the whole floor up until the engine is out. My cables were all pretty new so I coiled the controller cables and electric cable up, zip tied them together and hung them from the shifter. I completely pulled the steering system though. The floor cut pics start here in my thread to get an idea what its like.

Just depends on how much spare time and energy you have. I spent the better part of 2 1/2 days a week starting in August and did a floorless water test at the end of November! Then I took my time for 4 months doing the last 40 or so hours in my garage.

Rebuilding these old boats is a huge undertaking just because of the time thats required to get it all done. I believe someone else added up how many hours its taken for them to finish there boat was like 200hrs. so far i believe i have 24hrs invested with plenty more to go. But best of luck to you!

Dave,
The real trick is to see how much of the wood is not there around the battery box. About right in that area where your wood is gone, my wood was a tad bit better. But once i went forward from that point there was nothing solid!

All ive got to say is pick the engine and start cutting out the floor!

Nick