jreisberg

Keel bulb repair on a Pogo2 MiniTransat. Any ideas?

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Noticed some cracks in the paint on the bulb. One piece looked like it had a deep crack. Got my knife in there and popped out a few chunks. The lead keel appears to be encased in epoxy, in some areas very thick. No filler. Very brittle, although the bulb shouldn't experience any stress.

 

Any ideas on a repair? Seems like the thick epoxy casing adds only a little weight and a lot of drag. Wondering about removing all epoxy from lead bulb and rebuilding with a lot less thickness. Seems like patching only the areas that have lost bond with the lead is a fool's errand.

 

Thoughts?

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Are you free to modify the bulb within the series class or does it have to remain a Group Finot Pogo2 to a "class rule"?Under the fairing, you may find a fairly irregular bulb any you only see the "worst" part. Pull off all the fairing and you are faced with designing a new bulb profile.

 

I'd start with contacting Group Finot and asking how why the bulb got such a thick fairing coat. Could be the bulb started life narrower in the aft section and drag was reduced somewhat by lengthening it and making the aft part fatter.

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Are you free to modify the bulb within the series class or does it have to remain a Group Finot Pogo2 to a "class rule"?Under the fairing, you may find a fairly irregular bulb any you only see the "worst" part. Pull off all the fairing and you are faced with designing a new bulb profile.

 

I'd start with contacting Group Finot and asking how why the bulb got such a thick fairing coat. Could be the bulb started life narrower in the aft section and drag was reduced somewhat by lengthening it and making the aft part fatter.

The boat was built in California. I understand that the casting resin was applied using a mold, which would seem to suggest that the lead bulb is uniform.

 

There's no Classe Mini sailing in the U.S., and I'm happy to modify the bulb to prevent further issues like this. I know others have had difficulty reaching out to Pogo in the past about build issues. But I might check with Groupe Finot. Thanks.

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I'd do something like this:

  1. Remove the loose fairing. Don't go overboard unless you plan to make templates and have experience making symmetry where there is none.
  2. Prep the exposed lead with very course (#36) on a DA or grinder
  3. Use interprotect 2000 or equivalent to seal it up
  4. Get some small stainless flat head sheet metal screws and drive them into the lead. 3/16" x 1/4" long, available in boxes of 100 at McMaster Carr. Use a lot of them. The heads will stand proud and provide excellent retention for fairing.
  5. Fill with your favorite thickened epoxy
  6. Fair until you're happy
  7. Go sailing

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That is not how Pogo2 bulbs in Europe were done IIRC. Much less skin.

So find the US builder for info. Groupe Finot would not know shit about it, other then their original drawing.

 

use the intact side to get some cardboard cut outs with the profile.

Hammer all of, and see what you have got.

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molded with liquid resin and no glass reinforcement. repair and go sailing. could even re bond the old pieces on and fair and go sailing. if you want a bigger project, prep and glass over bulb and fair. I you want a stupid lot of work then hammer it all off only to see that you have a lead bulb under the filler and you should have never done that and that you just lost a whole sailing season.

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I'd take off all the filler fair the lead. Add a thinew layer of fairing if you need it. Paint with ip2000. Then what ever af you need. Should take you about 20 hours to have a faster and smaller bulb.

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I'd take off all the filler fair the lead. Add a thinew layer of fairing if you need it. Paint with ip2000. Then what ever af you need. Should take you about 20 hours to have a faster and smaller bulb.

20 hours . don't make me laugh you will have 20 man hours in the project just in getting the boat positioned so the lightweight lead keel is hanging so you can do the work. and that is one of my favorite things to do, laying on the ground under a 1000 lbs of lead filling and sanding to a perfect shape. The lead under the filler is no way fair and this is why the bulb was molded to a fair shape around the lead. no one that has ever done the fairing on a bulb is going to recommend starting over if it is not necessary.

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I'm surprised by the amount of filler, but not surprised it is breaking off. Unless it is structural filler, it is usually recommended for it to be no thicker than about 1/4".

 

Although the bulb may not be stressed structurally, it can still be subject to thermal stresses, which can be far greater than structural ones.

 

My thinking is that a patch type repair may work in the short term - but you will not have solved the problem causing this in the first place and the problem will return eventually - probably sooner rather than later.

 

If it were me, I would do what Irish Rover suggests - but that's just me.

 

Edit: also agree with Overbored that it will likely take a lot more than 20 hours to do the job properly.

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I worked on a 9000# bulb last year. We moved over 800# of lead. Cut the nose off, added a shoe, stripped off the fairing, rough shaped with a power planer, hit with 36grit, faired it and painted. This keel would be small potatoes.

 

Perfection will get in the way of excellence.

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I worked on a 9000# bulb last year. We moved over 800# of lead. Cut the nose off, added a shoe, stripped off the fairing, rough shaped with a power planer, hit with 36grit, faired it and painted. This keel would be small potatoes.

 

Perfection will get in the way of excellence.

Love all the tips, guys. Priority number one is to go sailing. I like the idea of removing portions that have poor or no bonding to the lead, and using sheet metal screws to provide additional structural support (like steel rods in concrete). That said, I also like the idea of not having so much damn casing. A project for another season.

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I like the idea of just repairing the areas that definitely need it, and keep the job relatively small. My wife and I completely stripped and refaired a fin keel a couple of years ago, and it's not a fun process (although the result was awesome).

 

When it comes to fairing onto the lead, here is the method that was taught to me by someone who used to work for Gugeon Brothers and literally wrote their manual on how to fair a keel:

 

- Scuff up the bare lead with sand paper du jour (i.e., 60 or 80 grit). Wear appropriate PPE and practice good hygiene for working with lead.

 

- Apply one coat of neat (no filler) West Systems to all of the lead surfaces.

 

- Use 60 or 80-grit wet sand paper to wet sand the epoxy before it cures. This allows the epoxy to create a chemical bond with un-oxidized lead surfaces (the sandpaper is scraping into the lead, which is still encapsulated in the wet epoxy).

 

- Once it goes tacky, start applying West Systems thickened with fairing compound (peanut butter consistency that doesn't sag) to get one solid coat of fairing over all the lead surfaces. Even if this takes a while and the neat epoxy doesn't still feel tacky, you still get a good chemical bond to the first layer of neat epoxy as long as the fairing compound is applied during this initial working session/shift, since it takes ~24 hours for cross-linking to complete.

 

- The idea is that you get a chemical bond of epoxy to unoxedized lead, then another chemical bond of fairing compound to epoxy. All other layers of fairing compound have primarily a physical bond to the previous layer of fairing compound.

 

- After this, wait at least 24 hours (allow the fairing compound to cure), then sand to desired profile (80-grit, longboard, etc.), and then apply the next layer of fairing compound. It helps to use pigment to dye successive layers of fairing compound different colors to get a good 3-d view of where your highs and lows are as you build up and sand down.

 

- I really liked using two metal trowels - one large one (~2 feet long) in my left hand to use as a "pallet" for the fairing compound, and a smaller one in my right hand to apply fairing compound to the keel. The metal is easy to clean as long as you wipe it with acetone ASAP. Some people use a notched trowel for the first coat to build up thickness, then smooth over that with a smooth trowel. If you do that, I would recommend adding the second "smoothing" coat just after the first coat sets up, but on the same day as the first coat, to avoid having to deal with removal of the amine blush that develops upon final cure. The notched trowel might be particularly effective on the curved surfaces of a bulb, where it can be difficult to get substantial buildup while maintaining a decent shape.

 

- Use a batten or thin strip of wood to test the profile of the shape as you're sanding. It's easy to spot lows and highs. Or use a flashlight in the dark. Also, your hands don't lie. You can detect small inconsistencies pretty easily.

 

- Once complete, coat with 5-7 coats of Interlux Interprotect 2000e to seal it all in (best is to use alternating grey and white coats to ensure complete coverage), then apply bottom paint du jour.

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Ok.  So, after much contemplation, all of the epoxy casing around the keel was removed.  The idea was that I didn't want to risk other areas of the epoxy casing becoming unbonded from the lead, requiring success repairs.

Once the epoxy casing was removed from the keel, we noticed a problem--the bulb was not square with the boat.  It was off by what appears to be 3/4".  Obviously this has ramifications for sailing, including different stabilities depending on tack.  Truth be told, however, I never was able to discern differences between the sailing characteristics of the boat on port versus starboard sufficient to identify an imbalance in the keel bulb alignment as the cause.

So now the issue becomes, what to do?  The two options that are on the table are (1) fair/reshape the lead bulb to achieve symmetry and skim coat; or (2) obtain the mold that was used to encase the misaligned keel and ensure that at least the water flow across the bulb is identical depending on tack.  

Submitting to the Court of Public Opinion--any thoughts?

Thanks,
Josh

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Buy a cheap power planer and have at bringing the big side down to small side to square it up. You will have a lighter bulb, but it only really make a differnce at high angles of heel.  Or buy a 1/2sheet of lead and glue it on to the small side and re shape from there.

 Lead is easy to fair. Just wear a good respirator. 

We removed 275# in one day with a power planer to this bulb.  In total we had close to 900# in lead chips that came off via a power planer, ok maybe it was two power planers, one died. This keel was also 3/4" out of square when we started. It was hard work but totally doable. IMG_0693.thumb.JPG.6ddb86094f77a6d0813d65066a458439.JPG

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On 6/6/2017 at 11:42 PM, jreisberg said:

Ok.  So, after much contemplation, all of the epoxy casing around the keel was removed.  The idea was that I didn't want to risk other areas of the epoxy casing becoming unbonded from the lead, requiring success repairs.

Once the epoxy casing was removed from the keel, we noticed a problem--the bulb was not square with the boat.  It was off by what appears to be 3/4".  Obviously this has ramifications for sailing, including different stabilities depending on tack.  Truth be told, however, I never was able to discern differences between the sailing characteristics of the boat on port versus starboard sufficient to identify an imbalance in the keel bulb alignment as the cause.

So now the issue becomes, what to do?  The two options that are on the table are (1) fair/reshape the lead bulb to achieve symmetry and skim coat; or (2) obtain the mold that was used to encase the misaligned keel and ensure that at least the water flow across the bulb is identical depending on tack.  

Submitting to the Court of Public Opinion--any thoughts?

Thanks,
Josh

IMG_2078.JPG.jpg

IMG_2071.JPG.jpg

Just saw this - the laser what did you use to get that?  thanks much

Tom

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Sue the keel foundry.

Then live with the asymmetry unless you are racing at a high level

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1 hour ago, SloopJonB said:

Sue the keel foundry.

Then live with the asymmetry unless you are racing at a high level

I hope you're kidding SJB - Good luck in suing a French company.

Also, all the bog may have been intended to properly "align" the bulb - so would it be considered a defect?  IDK -  I'm also not a lawyer (obviously).

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Yes I was.

I forgot the sarcasm font again.

Not about the asymmetry though - I can't see a small variation in a torpedo shape having much or any effect on a keels lift and it would be a brute of a job to correct it.

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if i was to play peter perfect, i'd have a new bulb made.

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On 17-4-2017 at 4:31 AM, jreisberg said:

The boat was built in California

From one lase line you never can deduct a warped bulb.

When same moulds were used in France they were right.

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