Classic Dan Arena

[David55cobra]

I have finally fallen victim to a fiberglass hull after over 40 years of working on the older Chris Crafts..... finally, a fiberglass hull with lines that make my heart race ! I suppose it had to happen sooner or later.
The boat itself is listed as a 20 ft runabout, built somewhere around 1973. It has a 300hp chevy inboard/outboard drivetrain at the moment. The tough question is how practical is it to replace all the stringers, floorboards, and transom. I'm assuming that the transom is a fiberglass/plywood/fiberglass composite - knocking my knuckles on the back produces a rather hollow sound anywhere other than around the edges of the transom, so I assume its all rotten inside. The floor is completely gone, and the fiberglass around the longitudinal stringers is partially stripped off exposing lots of rotten wood. When I sight down the outside/bottom of the hull lengthwise, it is slightly concave back in the last ten feet, but I'm assuming that this is caused by the boat sitting on the wrong trailor with completely broken and improper bunks for support.
Having no experience with fiberglass boats, I'm assuming that the process would be to pull the engine/outdrive ( thats the easy part), strip the interior of the hull out, support the hull properly and try to get it back to its proper lines, then somehow cut out the transome plywood, replace and re-glass that in, then replace the stringers and floor supports. Sound about right? What I dont know is the following:
If the transom has plywood inside, do I attack and replace it from the inside by cutting the inside layer of glass loose at the outer edges?
When replacing stringers, what is involved in bonding them to the inner hull, and what would be the best core material inside the fiberglass cloth ?
As usual, the best question is the last one - is this boat worth saving, and is it actually do-able ? Old boats are always a labor of love, so once you've fallen in love with it, its always worth doing if you have the time and money,,, but, with my almost total lack of experience working with fiberglass, is it REALLY worth doing ?
My personal opinion is that, IF it is worth doing, do I want to keep the old volvo IO drive, or convert it to a v-drive and re-balance the center of gravity?
Lots of questions just to get started, I know ! Any helpfull advise is greatly appreciated !

[LMB]

Restoring a boat is never practical, but it is worth doing when you have some sort of affection for the craft involved. It will take a ton of work, but still siginficantly less than a full on restoration of a wood hull. I run a fiberglass repair business and I've restored several boats. More recently, a 20footer fitting a similar description. On that job I used over 45 gallons of resin and about 600 man hours. It is dirty, difficult and health hazardous work, however with proper planning and precautions can give very rewarding results. Expect it to take three times longer than planned. Same is true for costs. Based on my experience I would estimate anywhere from 400 to 1000 man hours for a turn key job. Theres a lot of resources on-line, I would research material choices thoroughly before beginning. Resin choice, and thorough knowledge on using it will be key and could save you a lot of trouble. I would be most concerned about the hull bottom having lost shape. Make sure that is correctable first. The glass could have stretched and be difficult to get back straight. Any "hook" in the hull bottom could be a major performance problem. Replace transom from the inside, since you'll be in there anyway. Wood cores are cost effective choices but you might consider foam cores as well. Wood is fine when prepared and glassed properly. I also like the dense foams like Penske board. They handle more like wood and give some structural integrity over they lighter stuff. Do the structural rebuild one step at a time. Start, by correcting hull shape and supporting properly, then replace the transom, then each stringer and bulk head one at a time. Get a general idea first and then focus on the details of each phase. Keeps it manageable. Once you get into it we can focus on specifics. You'll get a broad range of advice though, so be prepared to figure out what works for you.

[David55cobra]

Thanks for the reply. I posted another letter with more questions - probably typical for something new - it concerns construction of the stringers - do they need to be solid wood, or could they be a composit of strips glued/bonded together. I have seen this done with cabintop frames that were weak, and it looked like a very good solution to the problem - I think they were thin strips of pine and epoxy glued in place to retain the shape of the cabin top. My thinking here is that if the hull wants to vibrate and absorb shocks, would epoxy laminated stringers eventually shatter? Might something like 3M5200 be a better choice ?

[LMB]

I wouldn't get too creative on a structural repair. See whats in place for stringers now. If the boat has typical wood core fiberglass, I would recore the original layout with wood or an appropriate foam core material. Only make changes to the orignal design to the extent you need better fit or have an obvious flaw in the original design. Extra glass work is o.k. too but you don't want to go overboard. Some measures for below deck drainage and addition of floatation foam would be other prudent considerations. Laminating you own core material would be o.k. but likely unneccessary. Sometimes you need a scarf joint to get the full legnth on a stringer, but I doubt it will be necessary on a 20' boat. Stick with a laminating resin ( epoxy or vinyletser would be good choices ). An appropriate stringer layout will be stiff/tough enough not to worry about shattering. 5200 is a great product, but if you need secondary bonding of structural component there are other choices that may be more appropriate. Just depends on the situation.