Odyssey’s Bridge Deck Strenghtening


Thumk—thunk, Craig Bumgarner, Service Manager at Zahniser’s Marina tapped the underside of our bridge deck for what was going to be its third repair.  Thunk—thumk, he was using sophisticated equipment to sound the area under the forward berth–his pocketknife and his ears.  It all sounded the same to me until Craig pointed out there was a difference: an ‘m’ and a ‘n’ sound difference.

Core sample cofirms honeycomb is not attached to Nida-core skin

Later he confirmed his findings by having a core sample removed from the hull.  The inner Nida-Core skin had de laminated from the honeycomb interior structure. The I-beam strength of two fiberglass skins laminated to the honeycomb structure that separates them was compromised and lost all its strength.  Waves hitting the underside of the bridge deck flexed the deck inward causing the gelcoat to craze.  Inside as the bridge deck flexed inward it pushed the face board for the bookcase up breaking it free from bookcase.  The flexing had also popped the screws holding the forward berth board free from the supports underneath.  The defective Nida-core area was most of the hull area under the forward berth.

Craig opened his penknife and poked it into the anchor well drain at a 45 degree angle.  The blade easily penetrated what on closer inspection was totally exposed honeycomb structure with traces of what had been a thin gel coat covering.  “That’s not good.” Craig said and went on to explain the tech doing the repair would use a tool that resembled an Allen head wrench chucked in a drill to relieve the interior. Then a piece of PVC pipe would be glassed in place to protect the honeycomb and eliminate water penetration into the honeycomb.   It was something that was missed during the last repair.

2005 gelcoat damage

In 2005 we found a section of bridge deck gelcoat had disappeared.  Closer analysis said we’d hit something hard; hard enough to cause a section of gelcoat to disappear and cause the surrounding area to craze.  We didn’t recall hitting anything and at the time had no awareness what such a hard hit might have done to the Nida-core structure.  We had the gelcoat repaired, a cosmetic fix without involving our insurance company since the repair was less than our deductible.

2007 2 Nida-core cracks

Gelcoat problems on the underside of the bridge deck showed up again in 2007.  At first it looked like a repeat of our 2005 problem.  Then we noticed that the outer Nida-core skin was cracked.  We got Boat US involved and opened up the entire area under the forward berth and bookcase.  To our horror we found the Nida-core skin was cracked in two different places.   The inner skin as cracked 6” behind the anchor well drain just behind the bookshelf face board.  The outer skin and gelcoat were cracked 18” aft of the anchor well drain.  There were serious structural issues.  This time there was no evidence that we’d hit anything.

2008 Area under bookcase after repairs

Externally the gelcoat was repaired.  Internally  sections of 2×4 were glassed over the area where the two cracks were located.  Three 8” sections of 2×6 were glassed to the forward bulkhead and to the bridge deck under the bookcase help provide more support to the bridge deck since the area had no internal reinforcement in the area where the cracks were located.  The support for the bookshelf face board was also glassed to bridge deck.

Now in 2009 when we opened the berth area for the third repair all the added pieces had broken free and has done nothing to stop the bridge deck from flexing.

The proposed fix took time to understand and accept.

Here’s what was done.

  1. The anchor well drain would be corrected as previously described.
  2. Crazed outer gelcoat would be removed and replaced.
  3. The 3 fore/aft Nida-core bridge deck supports would be removed.
  4. The inner Nida-core skin and the honeycomb structure would be ground out from the inside leaving only the outer Nida-core skin.
  5. A build up of 1’ square by 1” thick structural foam squares with 45 degree edges would be glassed in place to replace the Nida-core structure.  This would create the new bridge deck interior.  The glass separating each section provides I beam strengthening.
  6. 5 fore/aft supports replace the 3 removed.  These supports go all the way to the forward bulkhead and are a minimum of 6” tall at the forward bulkhead.  The previous 3 stopped 2’ short of the forward bulkhead and were mainly considered to be supports for the forward berth.
  7. Port/starboard cross supports a minimum of 6”  high are spaced about every 18” forming an “egg crate” structure to stiffen the bridge deck.
  8. The egg crate support structure raised the forward berth 6”
Anchor well drain with PVC pipe liner

Anchor well drain with PVC pipe liner

One hitch showed up.   Boat US Insurance rejected the plan adding the egg crate since they don’t pay for improvements.  Craig recalculated the estimate to just put the 3 fore/aft supports in place and boat US accepted the revised quote.  We paid for adding two additional fore/aft supports and the cross supports.  The good part, however, was that Boat US considered this claim to be a continuation of the repair made over the winter of 2007/8 and there was no deductible to pay this time.

Egg crate reinforcement of the bridge deck area

The work was completed over the winter of 2009/10.  We launched in the spring and after an extensive refit for other issues (see Spring Commissioning) we were under way again.  Our one short encounter with rough water slamming into the underside of the bridge deck was positive.  In previous encounters the berth could be felt moving as the underside of the bridge deck flexed.  That didn’t happen this time.

Additional views of the new bridge deck structure.  Click on pictures to enlarge.

Closer view showing the port/starboard support

Berth surface now extends under the bookshelf

Center berth panel removed for inspection


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3 Responses to “Odyssey’s Bridge Deck Strenghtening”

  1. Randy Blake Says:

    Interesting. I am considering purchasing a 2001 TC36. Is this a common problem with these boats or are you just special? Now, I am wondering if I can trust this boat. I would hate to have to go through this very expensive and time-consuming repair.

    • Don Says:

      Your question is one I’ve considered also. I think the original two repairs were not diagnosed correctly. The hull around the damaged area was never sounded. The same man did both repairs and he was unfamiliar with Nida-core; as was I regarding damage and repairing.

      When we got Boat US involved on the second repair the adjuster was very demanding, but he never asked to have the damaged and surrounding area sounded. After reviewing the repair history, the Boat US adjuster indicated Boat US considered the third repair to be a continuation of the second repair and waived the deductible.

      I’m also the publisher of owner manuals for the TC36 and TC44. I’ve had e-mail contact with many of the owners and none have had anything similar. We contacted Endeavour to discuss the planned repair. They agreed with the repair method and indicated this was to their knowledge this is the first problem of this kind.

      In retrospect I now think that the problem started with the first repair. Had we been more knowledgeable regarding Nida-core and checked more carefully for damage to the honeycomb to skin bond the following two repairs would have not been necessary.

      Don Kalen

  2. Randy Blake Says:

    If this was a problem with other boats, I think there would be more stories like yours, but I haven’t seen any. And since I’ve just purchased a TC36, I hope we’re both right!

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