Hanse 418 - Glued in Keel grid repair (vid)

MiddayGun

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So we've all seen videos of inexperienced couples trying to repair the structural floor pans that are all the rage in cheaper production builders today. 
Well I actually just stumbled across this video of a professional repair being done at a yard in Stockholm. 

I've not finished it yet so don't know how good the finished product will be, but thought it might interest a few a people to see one of these done as a 'pro' job. (it looks expensive) 

Looks like its been heavily grounded as the keel can literally be pushed up into the hull at the aft end.




 

TwoLegged

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I think it generally totals boats because of the cost of repairing it.
It's the dark side of the glossy boat shows of the 20th century: most of the craft on display are built in a way which leads to the boat being a possible write-off after a relatively modest impact.

 

MiddayGun

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(it looks expensive) 

I think it generally totals boats because of the cost of repairing it.
Typical British understatement from me. 

Interesting that the yard chose to go with polyester for this repair, presumably partly from a cost side, and they laid the glass over a polyester adhesive, presumably for better mechanical bonding. Interested to see if the glass guys on here have a take on that. 

Also I wasn't aware before this video, just how poorly those liners are bonded in situ. 

 
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See Level

Working to overcome my inner peace
Looks like it's not Patrick's first keel grid job. ;)

Look at how clean it stayed.

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Zonker

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Can't say I agree with cutting up the grid. He might not know how it is built - and how he should taper out repair and rebuild it. I know in the Beneteaus they use unidirectional e-glass on the top flange of the grid. You cut that, you really need to replace it with uni, not just some biaxial or double bias.

Even though it costs more epoxy is just so much better for structural repairs. Compared to the cost of the boat, what's a thousand dollars extra for epoxy?

Be curious how many gallons of resin Expedition Evans used for their repairs. 

 

TwoLegged

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Can't say I agree with cutting up the grid. He might not know how it is built - and how he should taper out repair and rebuild it. I know in the Beneteaus they use unidirectional e-glass on the top flange of the grid. You cut that, you really need to replace it with uni, not just some biaxial or double bias.
I guess that the difference between a good repairer and a cowboy is that the good one gets all that structural data from the designer/builder, then has a structural engineer draw up the repair plan to exceed the strength of the original inadequate structure.

 

Sailabout

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I guess that the difference between a good repairer and a cowboy is that the good one gets all that structural data from the designer/builder, then has a structural engineer draw up the repair plan to exceed the strength of the original inadequate structure.
Yes but we all know Beneteau wont supply that data so a grounded Bene is a write off as its now un-insurable.
Been some threads on that....

Didnt see the part where the hull was ultra sonic tested so is there de-lamination in the hull that you cant see?

 
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TwoLegged

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Yes but we all know Beneteau wont supply that data so a grounded Bene is a write off as its now un-insurable.
Been some threads on that....
Ah, I missed that.  What a scummy practice.  It makes buying a Beneteau (new or used) into a massive risk.

Is Hanse any more forthcoming?

 

Zonker

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I didn't know that. Beneteau could have them sign a NDA if you really cared. 

To determine a laminate, in order of accuracy:

1)  If you can't get the information, just take an angle grinder with a 50 grit disc. SLOWLY take off the gelcoat. Note the type of glass in the top layer (probably 1-2 layers double bias). Slowly grind down each layer and note what is there. If you have an educated eye you can probably eyeball the weight of fabric. If it is like Beneteau it will be probably 2 layers x 450 double bias, several layers of 300-600 gram uni, and 2 or so more layers of double bias (the top flange). Bigger boats will have a few layers of double bias in the middle of the stack. Measure the total thickness too and compare that to publicly available data on laminate thickness.  Vectorply lists all their fabric thickness for open mold and vacuum bagged process.

Option 2)  Take that chunk the guy carved out. Separate the top flange from the side web. Burn the resin with a MAPP propane torch until it's all gone. Then carefully separate the layers, noting the orientation. You'll need an accurate digital scale accurate to 0.1 gram to determine the fabric weight. (disclaimer; I haven't done this but I think if done carefully you won't blow the fibers around and lose them. 

Option 3)  take it to a lab that does "Burnout tests". https://proboat.com/wp-content/uploads/2011/04/burnouttest125low.pdf 

For the amount you are in investing in a repair a few hundred $ in lab tests might be worth it.
 

You're not going to get a structural engineer to design a new laminate. Just recreate what was there, and maybe increase it a bit, depending on your skill level/if you are going to vacuum bag it because the originals might have been vacuum bagged. Maybe. If you just cut off the bottom of the grid tabs, and re-tape, I'd just skip bagging the new tabbing. Use generous scarf ratios; 20:1 or more and then you won't have to worry about them either.

 

Mudsailor

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Can't say I agree with cutting up the grid. He might not know how it is built - and how he should taper out repair and rebuild it. I know in the Beneteaus they use unidirectional e-glass on the top flange of the grid. You cut that, you really need to replace it with uni, not just some biaxial or double bias.

Even though it costs more epoxy is just so much better for structural repairs. Compared to the cost of the boat, what's a thousand dollars extra for epoxy?

Be curious how many gallons of resin Expedition Evans used for their repairs. 
Secondary bonding is really poor with polyester, especially the DCPD resins (I would assume) these guys use.  As Zooker says….epoxy seems a minor extra expense for a much better repair

 

toddster

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Well, if you’re a big company, cutting a few minor extra expenses on each job (but charging just as much for the job) adds up to a nice bonus for the executives at the end of the year.  

Now, for the advanced class, we’ll discuss “softening” the difference between direct and indirect expenses...

 

MiddayGun

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Well I finished it. (top tip, set the playback speed to 1.25 or 1.5 and pause at the more interesting bits)

I'm not sold on the whole polyester thing, but it does seem that the yard does a hell of a lot of these, and judging from the amount of laminate added it looks like they went for the belts & braces approach. 
image.png
 

 I know in the Beneteaus they use unidirectional e-glass on the top flange of the grid. You cut that, you really need to replace it with uni, not just some biaxial or double bias.

Even though it costs more epoxy is just so much better for structural repairs. Compared to the cost of the boat, what's a thousand dollars extra for epoxy?
I'm guessing the uni across the top must be fairly common? I got the lay up scedule for my boat from the designer and the tops of the floors have 4 layers of 600gsm UR before the last finish layer of CSM. 

One thing I saw he did was using a polyester bonding paste from Crestafix to help with adhesion for the first layer of matt, Have you heard of that practice before @Zonker?

 

Sailabout

Super Anarchist
Ah, I missed that.  What a scummy practice.  It makes buying a Beneteau (new or used) into a massive risk.

Is Hanse any more forthcoming?
Couldnt say but Hanse's model is you never speak to the factory the dealer does everything?

I can see why the insurance industry wants the manufacturer to be involved in the repair as when the keel falls off its tends to kill people and we now have a history where poorly repaired grounding damage has failed and killed people.
My guess in these cases is  the extent of the damage was never properly determined so there was a smaller repair than required done?
Putting the same glass back and doing a poly over poly repair is weaker than the original is that an issue?
Where is the science to say how much extra poly to make an existing poly layup as good as it was before?

Should the insurance industry say a grounding repair must be done using epoxy? Where are the manufactures putting their engineering skills on the line here to give repairers advice?

If the grid has cracked should the whole grid be cut out and factory sends you a new one?

I am not sure that ultra sonic testing of laminates is an absolute science?

In my other life I race powerboats, plenty of people buy old boats and go fast and there have been some spectacular structural failures as clearly the slamming effect over years delamed the boat but you cannot see it even in hulls where the inside is left un coated just for that purpose. ( and save weight)

Does a grounding do the same damage as years of go fast slamming?

 
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Zonker

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I'm guessing the uni across the top must be fairly common?
Likely - but no direct knowledge.

sing a polyester bonding paste from Crestafix
Odd. Not sure why that would be any different than mat + laminating resin. Maybe just to fill in lumpy bits at the edge of the grid.

Where is the science to say how much extra poly to make an existing poly layup as good as it was before?
"Eh that looks about right"

Should the insurance industry say a grounding repair must be done using epoxy?
The insurance industry is remarkable in it's lack of knowledge of boats. They are $$ people. As long as the cost of claims << amount of premiums they probably don't care if you fix it with cardboard and it's deratives! 

If the grid has cracked should the whole grid be cut out and factory sends you a new one?
Probably that does mean a total scrapping of the vessel because you have to remove engine and much of the interior. The labour hours would eat up the cost of the vessel. I think a decent repair can be done in-situ. I do think vessel builders should provide repairers the laminate schedule of the existing grid. It's not really top secret.

They will not want to design a repair for you, because each damage is going to be different and you can't necessarily see all that has failed.

Even if they went back to laminating individual transverses of plywood and tabbing them in, the damage would be similar (cracked transverses and broken tabbing) and you'd have to grind back the tabbing and replace the transverse.

I am not sure that ultra sonic testing of laminates is an absolute science?
It's not what I would use. Think of ultrasonics as like a depth sounder. It sends out a beam, hits something and reports back the depth. In a metal you're looking for hidden cracks. If the metal is 1cm thick and the ultrasonic shows a spike at 0.4cm, then you have *something* there. 

With a laminate, each layer is a little discontinuity - and thus may reflect the beam. I don't know how much ultrasonics are used in composite NDT.

Thermal imaging is more common and does a good job of revealing defects.

Does a grounding do the same damage as years of go fast slamming?
Not quite. A grounding is one big spike. Years of go fast slamming is cummulative damage (micro cracking of the resin) and is more fatigue related and probably over a wider area. Unless you go over a monster wave that is much bigger than the powerboat is designed do. Then it's a big spike

 

SloopJonB

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Well I finished it. (top tip, set the playback speed to 1.25 or 1.5 and pause at the more interesting bits)

I'm not sold on the whole polyester thing, but it does seem that the yard does a hell of a lot of these, and judging from the amount of laminate added it looks like they went for the belts & braces approach. 
View attachment 446561
 
Wow - nice work. That looks like it came out of a mould.

 




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