Do I glass stringers before bedding them?

[Benny O]

I'm in the midst of a rotten floor replacement on my 1976 Sea Ray 20' Cuddy Cabin and have a quick question: Do I need to resin and fiberglass the plywood I'm using for the new stringers before I bed them to the hull? Or should I just place them unsealed into the peanut butter I'm using to bed them in place and glass over the stringers?

I've followed a bunch of forum threads about this topic and have yet to find a clear answer.

I'm using poly resin and cabosil with chop strand fibers as my peanut butter.

Also, just so I'm clear: after I removed all the decking and stringers and used a grinder to get down to the hull, I roughed and scuffed the remaining hull to get the top coat of resin off, as I read in numerous forum suggestions. Should I lay CSM and woven glass, or would one layer of CSM over the entire hull do the trick? I don't need to grind the existing fiberglass down to the bare hull, do I? (please say I don't have to keep grinding...).

Any advice on these questions is much appreciated, thanks.

 

[gonzo]

You need to remove the gelcoat if there is any. Otherwise, roughing the surface is fine. Are you planning of laminating over the entire hull? It is only necessary to laminate the stringers and enough to tab them to the hull and transom. What weight and type of fiberglass are you using. Woven (roving) is hard to wet and keep tight on corners. A biaixal with mat (like 1708) would be much easier. However, many of those early boats had mat only and it works well.

 

[Benny O]

I wasn't planning on glassing the entire hull. Hoping not to, actually, since the existing coat is still in great shape. So you're saying I should laminate the stringers separately (around all the edges) and then bed them to the hull and transom? Then glass over the bedded stringers to the hull?

I believe I'm using 1oz CSM and 6oz roving cloth, with 18oz biaxial to tab the deck to the hull. I think. I'm new to all of this. I thought one of those that I ordered was 1708.

Thanks for the quick reply -

 

[tpenfield]

Either way is OK . . .

You could put the stringers in dry, pre-soak them with resin and then immediately glass over them and tab them to the hull. As Gonzo mentioned getting the glass to go around the edges/top of the stringers may be a challenge. I often use thin plastic sheeting (i.e. drop cloth) over the glass at corners/edges to keep the glass/resin tight while it cures.

An extra layer of glass (CSM) over the other freshly ground area would be fine too.

Post some pics when you can . . .

 

[gonzo]

Usually the stringers are bedded on polyester putty or two layers of mat wet with resin. Then the whole thins is fiberglassed over in one shot. It may be necessary to add a brace of something else to hold them in place until the resin cures.

 

[Benny O]

Either way is OK . . .

You could put the stringers in dry, pre-soak them with resin and then immediately glass over them and tab them to the hull. As Gonzo mentioned getting the glass to go around the edges/top of the stringers may be a challenge. I often use thin plastic sheeting (i.e. drop cloth) over the glass at corners/edges to keep the glass/resin tight while it cures.

I'm curious how you use the drop cloth to keep the glass/resin tight while curing, tpenfield. Do you put it over the wet glass and clamp it on or something? Then peel off after cured?

I saw one video where the guy actually stapled the glass to the edges right at the top of the stringer to keep them in place after placing it dry on a resin-soaked stringer, then glassed over from there. I was thinking of doing something along those lines, but I hate to put staples into the wood if not necessary.

I'm actually heading out to the boat today to bed the stringers in - I'll snap some pics and post later. Thanks so much for the advice.

 

[Benny O]

Usually the stringers are bedded on polyester putty or two layers of mat wet with resin. Then the whole thins is fiberglassed over in one shot. It may be necessary to add a brace of something else to hold them in place until the resin cures.

Yeah, I hear that on the brace. We're rigging up a couple of braces to keep them straight up and down while curing. Fun project, now that I'm finished with all the nasty demo and grinding!

 

[tpenfield]

I'm curious how you use the drop cloth to keep the glass/resin tight while curing, tpenfield. Do you put it over the wet glass and clamp it on or something? Then peel off after cured?

I saw one video where the guy actually stapled the glass to the edges right at the top of the stringer to keep them in place after placing it dry on a resin-soaked stringer, then glassed over from there. I was thinking of doing something along those lines, but I hate to put staples into the wood if not necessary.

I'm actually heading out to the boat today to bed the stringers in - I'll snap some pics and post later. Thanks so much for the advice.

Usually the plastic drop cloth (sheeting) will stick to the resin. So you start on one side of the stringer about 1/2 way up and then go up and over the stringer to about 1/2 down the other side. Smooth out and air bubbles and it will usually stick until cured. Comes right off after that. I have seen folks use some clamps as well, at the top portion of the stringers, if the cloth was rather stiff.

 

[freddyj]

Usually the plastic drop cloth (sheeting) will stick to the resin. So you start on one side of the stringer about 1/2 way up and then go up and over the stringer to about 1/2 down the other side. Smooth out and air bubbles and it will usually stick until cured. Comes right off after that. I have seen folks use some clamps as well, at the top portion of the stringers, if the cloth was rather stiff.

I've done it this way also. Works well, keeps air out.