Stern core replacement. Help

[LegacyT]

So I thought my Boat was pretty solid... I was working to seal up some former trim tab holes that someone made at some point... Port side went great. nice sharp sound when tapping with a screwdriver Then moved over to starboard started tapping and surprise :facepalm:. most of the coring is a dark brown mushy mess and soaked with water. So I started cutting away and its all pretty much bunk. from the outside of the stern inwards its 1/4 glass, 1/2" balsa and 1/8" glass. the coring extendeds 2" from the side of the hull to the transom and 2" from the hull/deck joint to 5" below the .floor but not all the way to the bottom of the hull. How do I go about fixing this? There are no stress cracks in the glass inside or on the gelcoat outside. Can I glass layers in instead of replacing coring? I really dont want to be putting in more wood.. heres a picture if it helps

 

[Silly Seville]

Re: Stern core replacement. Help

What you need is an entire transom replacement. And I would expect that your stringers are probably wasted as well. There is a wealth of information on this site how to proceed. I highly recommend you search for Frisco Jarrett. He is a master of restoration!

 

[captmello]

Re: Stern core replacement. Help

Can you post some better pics? Hard to tell what I'm looking at. Also a pic or two of the transom from the outside so others can see how the stern looks. I think you have a similar transom setup as me, where the hull extends past the center transom on both sides and is concave at the stern. I can kind of see it in your signature.

The coring on mine goes up the concave portion of the hull on both sides, and I'm pretty sure its structural. The coring is not tied into the transom wood at all. the transom plywood is just in the center section of the rear of the hull.

 

[Woodonglass]

Re: Stern core replacement. Help

More Inside/Outside pics will be necessary in order for the members to be able to SEE what you see and offer good advice. I searched the forum and did not find any other boats like yours that have done restorations as a reference. Based on your description, I'd agree with what's been previously stated and say you're in for a transom replacement which will be quite a bit of work on this boat. You will need to remove the engine and outdrive and then cut away the inner glass layer and remove all the rotted wood and replace it and then re-glass it all to the hull. This is all "do-able" by the "DIY'er" and we'll be here to guide and instruct you with all the details, if you're willing to do the work. It's itchy work but most find it to be rewarding.

 

[tpenfield]

Re: Stern core replacement. Help

Yup, more & better pictures would help.

They key is to find and remove the full extent of what is rotten. So, that may take you on a journey through the transom and possibly into the stringers. Sure, you could try to just patch things up, but you are best served to understand just how far the transom issues go.

 

[LegacyT]

Re: Stern core replacement. Help

Here are some more pics:



The plywood transom is separated from the rest of the coring. I plan to tackle that as well its not bad of shape but might as well. I've been reading Dave Gerrs book The elements of boat strength. Looking at solid glass from all of the calculations it seems like 7/16 of solid Glass would work instead of coring thats on paper but in reality I dont know... I'm trying to avoid re coring it as its a very awkward area and would mean separting the hull and deck to really get in there and do a quality job. I just dont have the means or space to do that kind of work. I wonder if they went overboard with all the structure in there since it was mush and theres no sign of fatigue in the structure from it being compromised...

 

[Woodonglass]

Re: Stern core replacement. Help

Based on these latest pics, this appears to be a pretty straight forward repair to me. Not to bad of a job either. Have you core sampled your motor mounts and stringers yet?

 

[LegacyT]

Re: Stern core replacement. Help

Yeah mounts and 3' of the stringers were redone 2 years ago all due to an old half *** patch repair of some trim tab holes the boat used to have. I'm pretty sure this is the result of those holes as well but since the core was in a separate layup the guy never did it...

 

[Woodonglass]

Re: Stern core replacement. Help

Sooo... is the Transom Wood (where the outdrive mounts) all good? Is it just the surrounding "Core" stuff that is soggy and bad?

 

[LegacyT]

Re: Stern core replacement. Help

The transom is actually mostly solid except for the bottom 2-3" where it's softer but not rotten out. I'm thinking of maybe laying up 3 layers of woven roving with epoxy directly onto the old glass where the the coring used to be. Does that sound reasonable?