How TAFG is constructed - manufacturer's description

I'm a little way into a keel-strike repair of my boat and blogging about it here.

As this is a subject of general (and probably future owner) interest, I wanted to start a new forum thread. I e-mailed Gene Kohlman with a description of my problem and for any input on how the TAFG-hull bond is formed. I included a couple gory shots of my keel strike. Gene e-mailed right back. Here is my e-mail and his response:

Subject: Question on TAFG construction

Hi Gene,

I hope you are doing well.

I had a quick question on how the Tri-Axial-Force-Grid in my boat is constructed and was hoping you could answer or put me in the right direction for information..

In early February I had the unfortunate experience of a hard-grounding keel strike. My fault - too close to the South Tower of the Golden Gate bridge. Mea culpa.

My boat (a 1990 32-200) did exactly what it was supposed to do in that it kept me safe. I really whacked the heck out of it. (Doing 6.5 knots, clipped the lowest 7" of my deep-draft keep, sent the boat into a nose dive.) I got it back to my slip in Sausalito and there was a mere trickle (quart per 24 hours) seeping in, probably via the keel bolts.

I have my boat hauled out at Ken Keefe's yard in Sausalito. The hull flexed somewhat and we are trying to determine the best way to diagnose areas that need repair.

My principal question is how the TAFG is bonded to the hull. I think the TAFG in my boat has a solid bottom that was then glued in to hull. Some other guys on the Ericson board said that the grid bottom is "open" and then tabbed into the hull with lapped fiberglass. My bilges have smooth corners and do not seem to be lapped between the TAFG and hull.

I am curious if you can shed any light.

Thank you in advance for any suggestions.

Tom Vilhauer

-------------------------------------------------

Hi Thomas,

I am so happy that you and others on the boat are safe. The TAFG was engineered for just that circumstance. We wanted to reduce the odds of an anomaly threatening the boat and crew.

I suspect you are right about the leak coming from the keel bolts. The bedding has likely lost its elasticity. I would suggest removing the keel to inspect the seating of the keel bolts.

The mast was also engineered to withstand the massive compression from a sudden stop. I know of a few Ericson’s racing with spinnaker that hit rocks when skippers took an aggressive line to gain an advantage. Same outcome as yours.

I do not think you need to be worried about the bonding of the TAFG to the hull. It fits so precisely and is so ridged that the keel bolts would hold it in place. In any event it is placed into the finished hull while the hull is in the mold. It is compression bonded in place with wet fiberglass strips between the horizonal flange contact points, the bilge area, and the hull. The hull is solid and locally reinforced with unidirectional roving at high stress areas. The perimeter of the open areas where you can see the hull are glass taped to the hull as well.

The brochure image you include below accurately describes the construction of the TAFG. It is all hand layup with Unidirectional roving in the tops of the beam about an inch think. The beam sides and bonding flanges are around ½ inch thick. The TAFG was co-engineered by our in house engineer Charlie Newman and David Pedrick of Pedrick Yacht Design.

I hope this info helps. So glad that everyone is well.

Follow up from Gene:

You are welcome. BTW, it would be worth inspecting the mast and shroud attachments and spreader roots and tips. The mast would have experienced severe compression loads.

Please say hello to Ken Keefe for my brother Don and me if you run across him in the yard. Your boat is in very good hands.

Makes me glad I bought an Ericson......

Somehow this important note should be archived for anyone having a future misfortune. Given this information I think doing much to assess and repair from the inside seems like a waste of time and money. One of the guys at my yard said these were built like tanks. I agree. You would have had a lot more serious damage with a built boat that uses the hull for basic structural strength.

Tom, if there was an Ericson 'award' for most helpful post in a long time... it would be yours!

No question that Ericsons are very stoutly built, but . . . for a hard grounding it would be prudent to ascertain the damage, if any, in the high stress areas. In this case, that would be the transverse TAFG beams & bonds near the leading and trailing edge of the keel. At the minimum, I think a good surveyor should do a thorough visual inspection (as a 32 owner myself, I know that's not so easy).

I'd also consider NDT (non-destructive testing), either ultrasound or thermal imaging. A good technician should be able to pinpoint any structural issues. I'd think KKMI would have some leads on this.

This unfortunate boater documented repair process under a similar situation on a Hanse 40' and what he learned about boat construction not in the brochure.

Roger said:

No question that Ericsons are very stoutly built, but . . . for a hard grounding it would be prudent to ascertain the damage, if any, in the high stress areas. In this case, that would be the transverse TAFG beams & bonds near the leading and trailing edge of the keel. At the minimum, I think a good surveyor should do a thorough visual inspection (as a 32 owner myself, I know that's not so easy).

I'd also consider NDT (non-destructive testing), either ultrasound or thermal imaging. A good technician should be able to pinpoint any structural issues. I'd think KKMI would have some leads on this.

Click to expand...

I would be interested in what you would expect a surveyor to be able to discover without destructive effort. I confess to being less than impressed with the dozen or so surveys I have had on my boats over the last 40 years.

jtsai said:

This unfortunate boater documented repair process under a similar situation on a Hanse 40' and what he learned about boat construction not in the brochure.

Click to expand...

This is interesting and points out another diagnostic thing. This Hanse looks like it took a really big hit if all the furniture was dislodged and you wonder about the initial rigidity of the their grid. Would be interesting to know the details of the strikes and see the keel--was this boat hammered on a rock or did it have a forward strike?. I had the same result in my Tartan 37 hit--much of the furniture had been displaced by a quarter inch or so. Seems like this is an indicator of the amount of flex the whole boat had. I would find it hard to imagine having this happen to my 32-200 with the same hit. The massiveness of the TAFG just would not move that much as the floor timbers. It is interesting to see this guy tabbing everything to the hull---my guess is that, like Kolhman said of the Ericson TAFG--Hanse had origninally dropped the grid in the hull and depended on "wet" compression for bond. In my work with rebuilding a couple of boats, I would be very skeptical that this is much of a bond at all--this boat (think about the timing of catalysts) was not tabbed initially as they are doing in the rebuild. It is really nice to rebuild a boat much better than it came from the factory--and that is not hard with most production boats I have worked on. All us want our boats to be as perfect as they can be. But I think there is a bit of OCD here. Seems like on the internet you can find just about any level of workmanship you like held up as an example.

Not exactly related to the thread topic but I found the Baltic sailor's video interesting, particularly a few of the repair methods:

• Reattaching the keel with Sikaflex between the keel top and hull? While Sikaflex has some adhesive properties they should not be considered significant in a keel attachment strategy. This tells me the Sikaflex is to prevent water incursion while the bolts hold the keel loads. Back in the early 1970's I worked at Columbia/Coronado. The external keels were bedded to the hull in an epoxy-like material called Epi-Bond 150 A/B in addition to through-bolts. I remember one Columbia 34 that had the wrong keel attached, a standard draft instead of a shoal draft. The keel replacement began about a week after the wrong keel had been installed. They put the finished boat in the travelift slings, undid the bolts and lifted, jostled, hammered, Sawzalled, wedged and pried for a week before it finally came loose. That was the Epi-Bond alone holding it on.
• Re-bonding (aka tabbing) the grid back to the hull. I did not see or hear anywhere the 12:1 taper in grinding preparation to assure the repair reached deep into the original laminate rather than just the last layer. I realize there may not have been enough room in some of the tighter spaces but there was no mention of a taper anywhere.
• Difficulty working in tight spaces, particularly under the galley? If they thought grinding under there was difficult, just wait until they start bonding. For such a critical repair to be done the best it can be, the repair would benefit from the best access they can get so why not remove the galley cabinetry? Budget? Doesn't seem like budget is an issue.

There are numerous examples on Youtube of earnest people repairing keel-struck hulls. "Expedition Evans" and "Bums on a Boat" channels offer other perhaps amateur versions, if you can get through the cute-couple-ness of the videos.

I think these repairs are areas of work that are difficult to model. How do you know if your repair is good enough? Well, you go out and run into something and see if your boat sinks. Or you sail your boat and nothing terrible happens (unless it does). This is one reason I want professional help/execution, Don Casey DIY enthusiasm notwithstanding.

Re the Sikaflex vs. Epoxy, it seems like Kohlman was suggesting slight elasticity is appropriate. The keel-hull joint will presumably flex under load, more than the stainless steel keel bolts will, so perhaps some flexibility is in order.

Tom,

It seems like this accidental grounding is on its way to being the best thing ever for you.

You get the full value of the claim.

You get to drop the keel, inspect the bolts, and re-bed it (which I would have wanted to do anyway, and will make you sleep better on your way to Hawaii).

You get to know the guts of your boat a lot better than you did before.

Seems like a great outcome.

I still think those KKMI guys are bandits and you'd be better served going someplace else with this new information, but I presume it may be hard to change course now.

Rob

racushman said:

Tom,

It seems like this accidental grounding is on its way to being the best thing ever for you.

You get the full value of the claim.

You get to drop the keel, inspect the bolts, and re-bed it (which I would have wanted to do anyway, and will make you sleep better on your way to Hawaii).

You get to know the guts of your boat a lot better than you did before.

Seems like a great outcome.

I still think those KKMI guys are bandits and you'd be better served going someplace else with this new information, but I presume it may be hard to change course now.

Rob

Click to expand...

I don't want to project too much on the financial side yet, but I think it will work out okay.

As for switching yards, there are a lot of frictional costs with changing situations at this point (paying out KKMI, new haul elsewhere etc.).

The other consideration I have is resale. If I tell a potential buyer in 5-10 years that I had a grounding, but:

A- I had it fixed at the top-notch yard where they work on $2mm boats, or
B- I drove it over to Berkeley and this nice guy over there showed me how to to do the fiberglass

version A sells better to someone who has no idea about boats generally or my ability to fix them specifically. Maybe I sleep better too...

I sent this thread over to the ship wright doing our re-fit.
He has repaired damage like this, and said that he would drop the keel and if there is any damage to the laminate he would do the repair from the outside. i.e. grind and re-glass from the outside, as needed.
Given that EY bonded the internal grid with tabbing rather than depending on weak adhesives like Ben____tau, he has faith that the hull and grid will be OK.

Good luck on your repair, however you tackle it.

If I was buying a boat that had a major keel repair, I suppose the reputation of the yard might matter to me, but not as much as the fact that the PO had faith enough in the repair to take the boat to Hawaii afterwards.

I was watching (and somewhat cringing at) that video link. That owner has confused all production boats with his chosen brand, as tho they are all the same. Gak!

The takeaway is that even tho he plans to pay to have portions of his boat's grid re-attached by tabbing, he does not really understand why the original construction technique was so poor, i.e. he should have bought a better built boat in the first place.
While that would have cost more money up front, he would have saved even more money later by not having to expensively remedy the designed-in shortcuts.
(Sidebar: this is a brand of boat that we really liked when we toured a new one at the boat show Oakland in 2008. Sigh....)

He also was referring to thruhulls as "plastic" and was unsure about alternatives being brass or bronze. I wish he would have referred to the composite thruhulls as way different from the cast plastic parts you often see installed above the waterline on a million powerboats.

Another takeaway: most of the surviving builders of production sailboats have successfully bamboozled the marketplace into believing that their cheaply built boats are normal.

And then.... his references to a "kitchen" and "bathroom" and his incomplete understanding of poly and epoxy resins. (many modern poly resins are quite different in their properties compared to the older formulations, I understand).

Watching him criticize the hardened poly mush when pulls a chunk out from below the grid, and talk about how it all should flex instead was a little unreal too.

And, thanks for the link. Another Good reason to keep my present boat for a long time.

edit: the next video he blithely accepts the yard's explanation of why they have to use a lot of weaker mat. Evidently they did not want to vacuum down the layers of bi-ax, which would have conformed it to the shapes in the bilge OK. Laminating inside the stringer moldings was interesting, and yard guys must have had their reasons, altho I cannot imagine gaining much strength with pressing mat into those inside spaces.

goldenstate said:

I don't want to project too much on the financial side yet, but I think it will work out okay.

As for switching yards, there are a lot of frictional costs with changing situations at this point (paying out KKMI, new haul elsewhere etc.).

The other consideration I have is resale. If I tell a potential buyer in 5-10 years that I had a grounding, but:

A- I had it fixed at the top-notch yard where they work on $2mm boats, or
B- I drove it over to Berkeley and this nice guy over there showed me how to to do the fiberglass

version A sells better to someone who has no idea about boats generally or my ability to fix them specifically. Maybe I sleep better too...

Click to expand...

+1 for Ken's point about the surest sign a prospective buyer would have is an ocean voyage to hawaii and back

On the buyer disclosure point, I do not see a customary need to disclose damage history on a boat (unlike houses, or airplanes)... it's the surveyors job to find things not the owner's job to point things out. My current boat has clearly had some modest repairs over the years... judged NBD by the surveyor... and probably someone has driven her hard aground in the last 32 years, but no obvious areas of concern. Obviously if I thought there was a safety issue that needed to be fixed I would tell the buyer, but otherwise it's caveat emptor.

racushman said:

+1 for Ken's point about the surest sign a prospective buyer would have is an ocean voyage to hawaii and back

On the buyer disclosure point, I do not see a customary need to disclose damage history on a boat (unlike houses, or airplanes)... it's the surveyors job to find things not the owner's job to point things out. My current boat has clearly had some modest repairs over the years... judged NBD by the surveyor... and probably someone has driven her hard aground in the last 32 years, but no obvious areas of concern. Obviously if I thought there was a safety issue that needed to be fixed I would tell the buyer, but otherwise it's caveat emptor.

Click to expand...

I guess you could say it was a judgement call, but regardless I would venture that given my writing here and duplicated at my "public blog" www.sailboatrefit.com (which google says no one ever reads) there is more public documentation of my hull #915 than any other 32-200 in existence. I'd say it was poor form generally not to disclose it, and make me look like a dishonest knucklehead because the information is already out there...

Tom,

Don't know if you've seen this thread. A PM to any of the posters may provide some extra info.


If I had purchased the boat I saw (See post #3) and repaired the keel issue, when time for selling came I would have advertised that I had dropped the keel and checked out the bolts and re-bedded it. If asked details, I would provide all the info I had dug up. As a buyer of a forty year old boat, I would MUCH prefer to have a list of all the repaired items and know the status of them vs having no info at all and having to guess at the condition of all the unknowns.

Mark

Just my $.02 worth; get your rigging inspected after the boat is back in the water. Gene mentioned it earlier and it is a good idea. I've inspected quite a few rigs after hard groundings and found issues aloft on several of them.