bertram31.com

Guys,
I can need your help badly! I went to drop my boat in the water yesterday and when they lifted it off its blocks I noticed a small drip. When I looked closer I saw a cracked keel! The keel was crushed flat where it rested on the block and there was a crack all the way through the thickness of the hull. Upon close examination it appears that this area may have been repaired in the past (but not in my 15 years of ownership). You can see a smoother finish of the glass on the inside of the hull and you can see a faint print bleed through on the outside of the hull in the damaged area. I am not sure what the outline of the two rings in the photos is because they were not done by me.

I believe my fiber-glassing skills are up to the task at hand of repair, however, I need the best advice on how to go about making the repair. I am thinking of making a form on the outside of the hull and doing the repair from the inside. I know it is easier to lay the glass from the top as gravity is your friend that way. I am looking for advice for layup schedule, etc. All work will be done with epoxy. I plan to grind back to good solid fiberglass at a 12:1 angle. If you fellows know a better approach, please share. Any other advice is much appreciated. Thanks as always.
Here are some photos:

Vince, looks like old transducer through hulls that someone repaired. Tough second guessing what was done in the past, grind away till you get to good green glass, white is bad. Taper it back like you said make a plywood support with wax paper and start the repair working mostly on the inside then feather a couple layers on the outside, you don't want hydro peel on the outside. Capt Pats link to strut repair is a wealth of knowledge. I went all epoxy on my repair.BH

The hole is scarfed by using a high speed grinder with a 36 grit disk. The scarfing is much deeper on the interior of the hull and is carried down to a knife edge. (Full Tip)

Thanks guys for the heads up on the "hydro-peel".

Another question: would some extra multiple layers of 1708 bi axial work or do I need that 32 oz. woven in the matrix?

Vince

Vince,

All 1708 except for a couple of top layers of 1 1/2 oz matt if wanted...

that crack almost looks like the shape of a dunnage block. lift failure, and no one said anything at the yard?

Thanks Capt. Patrick!

Eric, yes the damage is the shape of the block. The yard is very "concerned" that they did something wrong. They pulled their records show that this is how the boat has been blocked for the last 15 years that I've owned her. They emphasized that repeatedly. I tend to think that it is more a combination of things . I think that the previous repair was not done properly. It's almost as if the 'v' portion of the keel was hollow. Also, we had unusually cold weather this winter and I think water got in that area and helped crack the hull. They are working with me and helping me out with the repair by moving the boat on the blocks, resetting, etc. and no additional storage fees, etc. I am happy with that.

I will post some photos of the repair.

Vince

Fiberglass cloth will "telegraph" it's "weave" through the gelcoat... That's why manufacturers lay a layer of fiberglass mat against the gelcoat before they lay fiberglass cloth...

Your last picture (see the area I highlighted with the red rectangle) shows a very clear case of such "telegraphing"...



My suspicion is that there's a prior repair in that area... That repair may be less then good...

I agree Navatech. That's what I noticed. Also, look at the shiny surface of the interior. That's another clue to a repair job. The yard has been good about the whole incident.

Vince

Vince Luciani wrote:Also, look at the shiny surface of the interior.

Way to much resin... That is indeed another clue... Of course, there's also the pretty dry cloth to the top right of the two circles... Bertram weren't always that good with their laying up of the fiberglass but they were never that bad...

Frankly, I would consider taking out the old repair in total... Your biggest problem with that is the close proximity to the strut's base plate... Unless there's enough "good" hull to connect to you might be looking at a repair section that starts outboard of the strut base plates...

Navatech,

My damaged area is up by the forward bilge pump, not near the struts at all. However, I will certainly heed you advice when I start my grinding.
Thanks,

Vince

Vince Luciani wrote:My damaged area is up by the forward bilge pump, not near the struts at all.

On second thought (and review of the picture), I have no idea why I thought that plate with the bolts was the inboard part of the strut...

Vince Luciani wrote:However, I will certainly heed you advice when I start my grinding.

Gutting out the currently damaged area and the adjacent previously (and questionably) repaired area is definitely going to increase the scope (and effort/cost) of the repair job... However, it WILL be a complete and proper repair job rather then a mostly cosmetic repair... If I were you, that's what I would do... A proper repair!...

That's the second 31 I've seen fail at that spot.
Thruhull unbonded?
Slow weeping thru hull?

JP,
I noticed that the grounding on my garboard plug is gone. I intend to replace the grounding to the plug. The thru-hull had a little electrolysis but I wire brushed it and it appears OK.

I started my prep work last night and cut out some fiberglass from the affected area. You can see a couple of things in the attached photos. When I removed a section of fiberglass (it was taken from the centerline of the keel), the pieces de-laminated very easily. Also, it appears that only mat was used in this area. I don’t see any evidence of biaxial cloth. Is that normal? The ease of which it delaminated is making me think that freeze-thaw damage is part of the issue here also.

All the pieces removed had the green color that is found throughout the rest of the boat. This is making me tend to believe that there was not a repair. I am thinking that it would have to be a coincidence that the repair was made with the same green resin.

Vince Luciani wrote:When I removed a section of fiberglass (it was taken from the centerline of the keel), the pieces de-laminated very easily.

NOT a good sign...

Vince Luciani wrote:Also, it appears that only mat was used in this area. I don’t see any evidence of biaxial cloth. Is that normal?

Definitely NOT normal for new boat construction... Mat has its uses but offers very negligible structural strength!... One of the reasons the "El-Cheapo" "chopper gun" boats of the 60's and 70's are pretty much extinct today...

Vince Luciani wrote:The ease of which it delaminated is making me think that freeze-thaw damage is part of the issue here also.

I can't state categorically that you're wrong but I doubt it... Mat has pretty much no structural strength... As for the easy delimitation, it could be due to improper resin mixing, application and/or surface preparation... Furthermore, resin is known to have low adhesive capabilities... There's a reason it's advisable to do such repairs with epoxy rather then resin...

Vince Luciani wrote:All the pieces removed had the green color that is found throughout the rest of the boat. This is making me tend to believe that there was not a repair. I am thinking that it would have to be a coincidence that the repair was made with the same green resin.

Or, it was a coverup attempt!... It's not that difficult to get a close enough match of the tint... Resin is clear... You add some green pigmentation and you get green resin...

Vince,
It looks like someone did a transducer hole repair. The picture off the bottom shows the bottom paint, the original white gel coat, the boat cloth skin , heavy mat green glass and a grey colored filler which is not original to the boat, When you start grinding go at least 12" from the crack in each direction so you get a good dish effect. Also the drain plug fitting looks like it has been weeping, fix that also. I always moved the keel blocks either forward or aft every year, just to make sure the load was spread out and keel blocks did not cause hull compression. The sections you took out, appear to have a lot of white dry glass, which indicate glass failure due to either an accident or keel block compression. Good luck with the repairs.

Vince,
I stated that the grey area was foreign to the bottom, I meant the off white color which looks like some type of epoxy filler, the grey appears to be the barrier coating on the entire bottom.
Pete Fallon

Pete,

Thanks for the observations and advice. I made the repairs and have posted some photos below. I intend to smooth the finish a bit. I will post some photos of the outside when I get a chance. I am very confident in the strength of this repair. I have 11 layers of 1708 in the crux of the keel. I built the thickness up on the inside of the hull so I have a little high spot there. I hear your comment about moving the blocks every year, but I am thinking that I have a lot of confidence in the repair area so I was going to block it at that point in the future. It is thicker in my repair area than the rest of the hull.