Keel to Hull Flexing Issue, Comments invited!

[TomandKarens34]

There may-in-fact be no real answer to this situation. There is clearly some flexing going on where the keel is flared into the hull. I have a 1979 Irwin 34 Citation. They are lightly built and flexible anyway. Therefore the hull has a somewhat shorter life expectancy due to the extra amplitude of the flex cycles. Compounding this is the method of attachment. Clearly, from the photos I hope to post, the keel is semi-encapsulated. As I have been unable to find a single keel bolt, it may be hung by fiberglass only. Cutting up the cabin liner ( not recommended ) will have to be done to verify the absence of keel bolts, but so far, I have found none. The two cross members that can be seen across the bilge also seem too narrow to have bolts run through them.
Gel coat may also be complicating the analysis. It is quite thick in many places and crack repair is an on going process everywhere. Voids are common in the area where the stress cracks are occurring, where the keel fiberglass is lap jointed to the hull fiberglass. There is no blistering on the hull. The cracking is fairly consistent around the entire keel joint. [IMG][/IMG] The keel lead, by the way, is about 4 or 5 inches below the joint area, leaving a tiny area for the bilge. Old gel coat is known for being brittle, so perhaps I'm just picking nits here.[IMG][/IMG]
[IMG][IMG][/IMG][/IMG]
My thinking right now, is to find all the voids I can and fill them with new gel coat, then sand down and gel coat the entire joint. Follow up with epoxy barrier coat. Sail for a year, then re-asses the condition of the joint. I'd really appreciate some feedback on my plan. I have heard of Irwins dropping their keels, but these have been later models with bolted on keels and I have seen the '80 and '81 models in person and my keel is totally different from the later model setup, as far as I can see. A final repair might involve stripping out much of the cabin liner to get to the stringers and cross members to see if they've come away from the hull. Not a happy making plan. How about some opinions, guys ?

[sailingdog]

I'd point out that the cracking there really doesn't look like stress cracking... the cracks are generally more parallel in nature when you have a surface flexing.

I'd expect to see something more along the lines of this:



rather than what I'm seeing in your photos where the cracks are not really parallel in nature:



The cracks there may just be due to the gelcoat being applied too thickly, which you say is an issue on this boat.

[hellosailor]

Doesn't look like stress cracking, it looks like someone used filler or perhaps barrier coating at some time, and it was improperly applied and is now simply lifting in patches.

And you won't be filling anything with gel coat, that's totally the wrong material for this type of repair. The folks at West Systems (Gougeon Bros.) make some fine products and they'll give you free tech support if you give them a call. No requirement to buy their products first, although obviously that's the goal.

[TomandKarens34]

Maybe this is just the ancient repair done when the boat was cleaned up after the hull mold was removed ???

[RichH]

Without actually seeing this and without actual survey//testing of a 'coupon sample' of the laminate schedules in a mechanics lab. .... 0142.jpg picture by akint - Photobucket .... looks quite 'ominous' and should cause great concern until the actual cause of the apparent *delamination* is verified .... more so if this condition is on both sides of keel.

Irwin boats of the era were 'notorious' for FRG lay-up errors in construction ... principally very resin-starved matting layers (matting is the 'cushion layer' between the gelcoat and the structural roving); matting and gelcoat provide nil structural carrying capacity. This typical 'dry-matt' condition led to water absorption problems that generated quite severe 'osmotic blisters', and other problems, etc. That the 'suspect area' in the pic is 'so uniform' should give high suspicion that at the worst case there is delamination going on but since this is in or adjacent to a curved section (actual turn of the keel 'root') I would think that simple percussion with a phenolic hammer isnt going to tell one very much. Whether the suspected delamination is in the cosmetic-matting/gel layer (high probability due to Irwin 'history' - but trivial/unimportant re: 'structure') or deeper down in the structural roving (less probability - highly serious), I think HAS TO BE ascertained because this zone is in a potential very high stress area - for safety reasons.

Since you are Maine, and with LOTS of 'savvy' boat and fiberglass 'artists', I strongly recommend hiring one (seek out a 'reknown' artist) and suggest some small/localized 'destructive testing' with a 'localized/small 'peel' with hammer and small sharp chisel, etc. to find out exactly WHERE and in WHAT LAYER the potential delamination is occurring. If its solely gelcoat then simply forget it; If matting layer, then 'how deep'; If roving then you have a potential 'major/severe problem'. With hiring an 'artist' to do the small scale assay, you are paying for 'expertise and knowledge'.

The 'uniformity' (squarishness) of the zone, I think, is 'the clue' to a OEM laminate lay-up error.
Back in the 'old days' the lay-up crew would stop at the end of the day and restart in the morning .... and the previous layup would cure in the meantime affording poor chance of the successive lay-up to adequately bond to the new. If they stopped on Friday PM and restarted on Monday AM the mal-bonding between the laminate layers would be 'much much worse'. FWIW - Modern high-quality boats are laid-up in a single continuous process to avoid mal-bonding between the laminate layers - there is no start/stop any time during the lay-up ... until done.

That this zone is only 4-5" wide and is 'squarish', Id be suspicious that this is a matting layer failure (exacerbated by hull flex at the keel root) and can easily be 'peeled' back to taper slightly into the surrounding area. (Dont even think about 'grinding or disc- sanding' this zone by hand' as a DIY if you want this area 'fair'). Hey, its winter time and peeling crews are always looking for work in the winter - a 'time availability' fixed contract would be cheaper, and certainly you wouldnt need to peel the entire hull, just the 'zone' and tapered into the adjacent area for a 'worst case'. If youre handly, you could do the rest of the repair with heavy epoxy cloth (forget using matting and gel for underwater surfaces) ... somewhat backbreaking working upside-down but not tooo expensive as a DIY.

The above describes a 'worst case' scenario .... get an 'FRG artist' (not a "surveyor") to make the initial determination. A hammer and small sharp chisel on a very small section is going to give you your answer of how serious or not this 'actually' is. My 'bet' is that the a small section of the matting layer 'went' due to 'lay-up' error.

hope this helps. ;-)

[TomandKarens34]

Rich ! Thank you so much for your perspective on this issue. I appreciate your time in replying to my thread very much. Because I always use fiberglass cloth for repairs, it didn't occur to me I was looking at a matt lay up. Once you include the random directional fibers of matt, into the picture, the curly cue nature of the cracking suddenly makes sense. I will do an inspection in the bilge tomorrow and see what I can see. I think it has been painted so there might not be obvious damage that a simple visual inspection would reveal.
What I'm getting from your reply, is that it is a matt layer failure that has multiple possible causes. That without an artist with experience, on site, the actual extent of the damage will remain undetermined. The best case is that the matt failed because it could not flex with the roving glass. Worst case is there is a failure with the bond between the roving and the keel, and it will take a more experienced eye that my own to resole this. I concur. Have to find one !

[sailingdog]

Umm...that was Rich, not Jeff...

Originally Posted by TomandKarens34

Jeff ! Thank you so much for your perspective on this issue. I appreciate your time in replying to my thread very much. Because I always use fiberglass cloth for repairs, it didn't occur to me I was looking at a matt lay up. Once you include the random directional fibers of matt, into the picture, the curly cue nature of the cracking suddenly makes sense. I will do an inspection in the bilge tomorrow and see what I can see. I think it has been painted so there might not be obvious damage that a simple visual inspection would reveal.
What I'm getting from your reply, is that it is a matt layer failure that has multiple possible causes. That without an artist with experience, on site, the actual extent of the damage will remain undetermined. The best case is that the matt failed because it could not flex with the roving glass. Worst case is there is a failure with the bond between the roving and the keel, and it will take a more experienced eye that my own to resole this. I concur. Have to find one !

[TomandKarens34]

Oppps ! ( Hits forehead with hand ) Gosh, that's so 57ish. ! Sorry Rich !

[sailingdog]

Originally Posted by TomandKarens34

Oppps ! ( Hits forehead with hand ) Gosh, that's so 57ish. ! Sorry Rich !

LOL...just thought I'd mention it.

[sailingfool]

It looks to me like the keel/hull joint was patched, then covered with gelcoat. The gelcoat is failing, as mentioned its not a good idea. The could be a problem underneath, or it might just be faring material. Which would be my bet.

sure, get some expert advice...