Mast Intrusion
Right on Bill!
Shouldn't have to add anything except to emphasize this: Remember, there are four things that could be happening to the support beam.
1) It could have contracted rot through the electric wire hole and can no longer hold its curved shape. (338's beam was bandsawn white oak and showed no rot.) White oak doesn't like to rot.
2) The composite sandwich of the molded roof could be deteriorating because the core balsa is rotting from water entering the same wire hole. It compresses under the mast when there is no support inside.
3) The wood parts all together may have 'settled' and moved a little over the decades.
[This was 338's main problem when first tackled. I thought the beam had gone bad - but when taken out was perfectly OK] The composite core had some deterioration but imco the actual problem was the mast's irresistible force down on the beam and the beam not able to keep its original position.
Forensics conclude that since NONE of the parts (beam, angled braces that terminate on the V-berth tops, doorway framing) were glued to the plywood bulkhead but just mechanically screwed on... it all over time had gotten tired making it easy for the mast to compress it. While the mast contributes constant pressure, I'd guess that sailing the boat compounds the downward pressures.
The bulkhead upon which the strongback system is dependent is only 3/4" exterior fir plywood* that is tabbed to the boat ONLY at the hull under the deck. The whole top with the significant doorway cutout is free to move.
(With the exception of the two lags that hold the step in place that go through the deck into the top of the beam. And maybe the uppers' chain plates held by the deck!)
4) Constant downward pressure of the mast and step on the coach roof causes the beam to deflect, or to appear to deflect. The white oak beam is only 4 feet long - and if it's healthy no way in hell or high water will it flex. You might find deterioration of the fir plywood right next to it but the beam will be fine. (This is a guess -ANYTHING is possible.)
The round wood laminated step outside might also be deteriorating.
338's is still going strong.
Problems seen at the beam inside (the trim of the doorway sagging is common) could be one or a combination of these symptoms. Examine the parts and with what other Ariel skippers have found figure out what might be going on.
Imco if you are going to really fix this common aging problem you have to make sure that the coach roof under the mast can never deflect, never flatten, and always keep its original molded shape.
As Bill suggests all the interior structure under the mast should be renovated into a monocoque, a glued and screwed structure with the bulkhead tabbed everywhere, all round, to the boat. (Naturally, you won't tab onto the cabin liner!)
The upper shrouds thru-deck chainplates would also benefit from a more secure bulkhead. The ply where the uppers' chainplates come thru the deck no doubt is also deteriorating from water leaking in. Check this also.
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DOUBLE BULKHEAD idea for the traditional interior.
* A better structure would be to add another 3/4" ply bulkhead to the V-berth side of the beam and braces. Make it into a kind of a boxed truss. The all important 'compression' beam would then be supported on both sides and transformed into a true bridge.
Instead of it all cantilevered off the one wall - which is the problem.
Movement of all structural pieces would be locked forever between the bulkheads and all downward force from the mast taken evenly to the hull by both bulkheads. NOTHING COULD MOVE. The mast load would have a wider 'point load' spread on the hull - where a single loaded bulkhead often deforms a glass hull. It's the hull that takes all of the mast load.
Could scroll openings into the new bulkhead (maybe now even both) to gain back some lost space and keep closed areas ventilated.
This begs the question: why go to the trouble adding a whole bulkhead when a large one piece GUSSET that spans the whole doorway on the V-berth side MIGHT get the stiffness and immobility needed?
The original Pearson SO-CALLED bulkhead that the compression beam is sort of attached to is actually in THREE pieces: the two major pieces on either side of the doorway and a FILLER piece over the door that the door trim hides.**
(This is another unacceptable (imco) cheat on the part of Pearson because it don't add a MODICUM of support for the mast beam.)
It would have been much more shippy if the doorway had been top rounded like the Brits did in the Contessa 26 creating more truss and panel support for the beam. But then the carpentry trim and the door would have been beyond the capabilities of Pearson carpenters - would have had to be out-sourced and added another $200 to the price of an Ariel.
Instead of a complete second bulkhead:
Adding a crosspiece that goes completely across & down a little ways ( or even to the V-berths) is something to consider. Especially if you are racing your Ariel. Also if the bulkhead is being redone by, say, the removal of the disgusting imitation wood formica on the accommodation side - a cross TIE of plywood or mahogany across the top could be added on this side as well that would provide extra support for the beam. Glue and screw.
After the space above the beam has been addressed and filled or shimmed, adding a one piece gusset over the door in the V-berth that fits the coach-roof curve AND a side to side cross-tie in the cabin would stabilize the compression problem imco.
[It's my opinion that a metal strap across the top of the doorway does not fully solve the compression beam sagging problem.]
Point is
there are any number of fixes possible.
Even for a completely altered interior:
1) Water intrusion HAS to be fixed.
2) Rot has to be removed and fixed. Especially in the composite. It's pretty easy. 338 now is solid stitched mat and epoxy instead of balsa.
3) Coachroof must be full rounded, fully restored or fully upgraded.
It gets tremendous strength by being a true arch. If flattened, stress is concentrated right under the mast instead of the point load being spread to the curve of the arch. The beam inside is meant to preserve the coach-roof arc. The mast load should be held by the whole beam - not just the middle.
Wires should probably exit the side of the mast a half a foot or more above the deck and enter the interior thru one or more thru-deck glands near the mast. Thru-holes from the mast interior should be sealed off. It's no place for a hole because there is no access to a problem there.
OK, got carried away again!!!!! Apologies
I AM just throwing logs on the fire for discussion.
Wouldn't it be great if a concensus could be reached here?
that would provide an easy, satisfying and strong fix that ANYBODY with a new Ariel could use to repair the MAST SUPPORT BEAM PROBLEM./././
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**This major fumble was left out of Everett's biography.
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