STRONGBACK DISCUSSION etc.

[ebb]

C'227,
Nice to see those two compared in drawings with each other like that. Thanks.

You are correct on all points.
I've gone on about this subject adnauseum elsewhere. But suffice to say that in the Ariel the bulkhead is part of the mast support system. There are the two posts that define the doorway - they go down to the hull above the turn of the bilge (screwed to the plywood bulkhead.)
There are two cross braces on the Vberth side also screwed to the bulkhead that terminate on the Vberth plywood tops. And two more vertical braces that support the end of compression beam at the coachroof sides - also terminating on the Vberth. Across the top the compression beam is also screwed to the bulkhead. And held in place thru the top by two bronze #14s or #16s coming thru the mast pad, thru the composite deck, and into the beam.* All structural wood was white oak.

The plywood bulkhead in A338 is really two halves with a filler across the top of the doorway and a filler across at the step up into the V-berth stateroom. There is no work done by either of these fillers. (FYI A338 has since been remodeled to remove the doorway.)

The plywood "bulkhead" is tabbed to the hull ONLY
and not to the under deck or the coachroof sides or overhead.
Only the hull. And not across where one might expect a 'floor' to be in a wood boat - per your question.
Originally the space between the bulkhead and the liner was stuffed with a factory supplied fabric covered foam tape.

The compression beam load is ultimately taken to the hull via the half bulkheads (let's call them) on either side of the doorway. The compression beam is not supported in the center between the door posts. The door posts therefore are dual compression posts if you look at it that way. But they bear on the hull incidentally. In an upgrade a wider bearing pad would be cut in under these posts.
__________________________________________________ ____________________________________
*ANY upgrade or remodel imco, if you are working from the original Pearson model,
should have all dimensional wood members GLUED and screwed to the plywood at the very least.
But the Pearson model is very flawed.

[bill@ariel231]

A couple of points from an A-231 perspective:

"The manual (pg 23)shows diagonal supports, but does not show how they terminate on the lower end. Is there any additional structure not pictured in the drawings? "

Construction detail from A-231: A-231's diagonals terminate at the surface of the vee berth.


"The plywood "bulkhead" is tabbed to the hull ONLY and not to the under deck or the coachroof sides or overhead."

Construction detail from A-231: the original mast beam was buttered to the overhead with thicked polyester (the ubiquitous blue stuff). I did the same with thickened epoxy when i replaced the beam.

[Scott Galloway]

As a result of a bridge vs. mast accident resulting from a crew malfunction related to tabernacle operations in 2004 I needed to do some repairs to my mast base support system on my 1965 Pearson Ariel. For a more detailed discussion of this repair with photo documentation, please see my Ariel web page:

http://www.solopublications.com/sailarir.htm

Although like many other Ariel owners, I wanted my main bulkhead to be a strong as possible, it is worthy of note that after forty years of successive owners riding a Pearson Ariel hard and putting it away wet caused no visible deformation of the strong back as of the autumn of 2004.

I removed the Formica on the aft side of the strong back and sanded both sides of the strongback. I chased a few cracks and voids, but those led led me to workmanship and assembly issues that resulted during construction forty years ago when my boat was built.

I filled a few voids and strengthened a few areas. The bulkhead and strong back have served three owners well over the years. My somewhat destructive examination continued to show virtually no bulkhead damage Both professionals with whom I consulted did not feel that through bolting steel plates on either side of the strong back would be the best solution to strengthening the mast support system. In my boat there was no evidence of sagging in the strong back.

Once the teak doorframe was removed, it was apparent that the horizontal beam above the door was level. One of the vertical frame members was actually vertical, but the other is not, so that the door opening is a lopsided trapezoid. Since the plywood opening is cut this way and there is no separation from the hull on either side or underneath, I must conclude that this “as built”, rather than “as failed”.

Although the Main-salon-side plywood bulkhead panel was not glassed to the cabin liner, I could see over this panel to what appears to be a glassed seam between the strong back and the deck. This seam was solid and there was no indication of sagging or separation. The area above the plywood on the Main Salon side of the bulkhead looked fresh and solid. I came to the same conclusion by looking at the seam between the strong back and the underside of the deck from the V Berth side. Removal of the paint from the strong back confirmed that conclusion.

The cracks that I chased and the voids that I discovered were probably left by the builders (the failure to wet out tabs holding key braces in place, voids in the fiberglass, (the use of AC plywood with significant internal voids, etc.). So I would have to say that my boat might have been both hastily built, but it was also overbuilt. The Pearson Ariel is sort of like a Sherman tank built by the low bidder. This is one strong boat, albeit one built somewhat strangely in places.

Because it is conventional wisdom to strengthen the strong back, I contracted for reinforcement by a professional. My contractor installed unidirectional cloth and triaxial cloth. This was glassed onto the bulkhead and strong back in a sufficient number of layers to reinforce the strong back/bulkhead without drilling holes through it or installing steel reinforcement plates as have been used on some Ariels. This solution provided for the strong back to be glassed to the underside of the deck forward of the bulkhead and to the cabin liner aft of the bulkhead. When repairing the top deck, the new top laminate, bottom laminate, core, and cabin liner were reconstructed as an integral unit. Thus the strong back, cabin liner and deck now function as an integral unit. Thus there is no longer a void above the plywood section of the main bulkhead on the main salon side. This void was originally filled by that strange foamy wire-reinforced trim piece. That piece was glued into the void above the plywood. Those little wires are sharp and hard to remove.

The longer bolts in the mast base that had been inserted in the foreword two holes were seriously bent as a result of the mast vs. bridge accident. The bolt holes for these bolt were directly above and ran through the stong back. They penetrated the strong back directly above the doorframe. Their securing nuts were captive inside the beam. Inspection holes were provided by the manufacturer in the bottom of the beam. Those holes were drilled completely through the teak door fame as well. The beam prevented the lower portion of the bolts from bending. In the accident, the bolts were pulled upward. The bends in the bolts occurred at the very top of the bolts. The angle of the force of the impact pulled the longer forward bolts upward, and the shorter aft bolts downward as the mast step plate rotated aftwards into the deck upon impact with the bridge. This effectively crushed the deck beneath the mast step. This entire area was rebuilt as an integral unit, and the forward boltholes were relocated.

The cabin liner in the main salon was obviously distressed as can be seen in the images on my above referenced web page. Less severe distress was evident in the forward salon, but some cracking in the lower laminate occurred.

The shorter bolts were driven down through the cabin liner causing the liner to crack and shatter.

The cracks in the bottom laminate were removed by grinding, as was the paint on the central section of the strong back.

Multiple layers of vinyl ester resin and fabric were added to the damaged area and to the strong back to tie the deck section to and reinforce the strong back. Again there was no damage to the strong back due either to the accident or to cumulative stress to this area.

The application of glass to both sides of the strong back and to the deck sections forward and aft of the strong back created a very strong integral structure to support the mast.

The strong back area (both sides and bottom) was reinforced with multiple layers of vinyl ester saturated fabric including unidirectional cloth and x mat.

The lamination extending from the cabin liner aft of the bulkhead around the strong back to the lower deck laminate in the V Berth area is continuous and seamless. The seam between the remaining Formica and the original gelcoat cabin liner and deck section was sealed with 3M 5200 and topped with a bead of 3M 5200.

I know that all of the above is counter to the prevailing discussion on this page. My point in adding this post is to indicate to those who may be interested that solutions are available other than the removal of their strong backs or installing often unsightly and always conspicuous steel plates on the bulkhead. The choice is a matter of approach to solving a real or assumed need to strengthen the mast support system. Regardless of what is done to this area, the cored deck section beneath the mast as installed is a vulnerable area for compression. Creating an integral unit (deck, cabin liner, and strongback) in my opinion solves this problem.

[ebb]

GREAT forensics, Scott.
Love this kind of attention we give the ole girls.

Those extra laminations sound like a real good solution to making the whole strongback/bulkhead and mastload area as rigid and immovable as possible.

Think of you as in the restoration camp of Ariel upgrades. You are careful to honor the original intent of the designer/architect....whot's his name?

Many owners will want to see photos of your work. I know I'd like to see how the glassing went.
And the final result!

[Ebb has his caveats:
All rain water intrusions from the deck thru the repair area have to be completely sealed, ie bolts, screws, chainplates, electrical holes.
There should be no standing fresh water possible inside the mast. Don't want any water getting inside the new skin.

It sounds like you had the beam incorporated into the new interior skin reinforcement.
If you have an original oak strongback and it is now covered you might get away with it because of its age.
New oak won't accept regular polyester imco. I haven't worked with epoxy modified polyester.
But, as you know, if you laminated over everything (ply bulkhead - strongback - overhead) you are now getting the whole area into sharing the support of the mast load.

For DIYs: Styrene is a dangerous volatile component of vinylester. You ought to wear an appropriate canister mask for interior work and keep the boat clear of heavier-than-air fumes with forced air.
Imco vinylester should only be used by pros.
The right epoxy is much more user friendly and does a better job of gluing dissimilar materials together.

It must have been a difficult job of work - especially the prep and overhead work - and all the corners that had to be turned with wet Xmatt - would like a peek.]

[Scott Galloway]

Ebb,

Thanks for the comments. I am definately in the restoration camp, but I am also in the "publish all approaches to commonly shared problems" camp. A multiplicity of approaches is what keeps this site interesting. Fortunately Ariel owners tend to stay that way for awhile, so we can all check back in later to see how some of these innovative ideas and retrofit solutions work and whether or not they hold up over time. I am eager to see your boat splash down. You have incorporated a number of innovative features in your Ariel. I look forward to reading about your sea trials, etc.

Peeks are easy. Just come down to Santa Cruz for a sail. As for photos of the repair, I referred above to my Ariel Structural retrofit page:

http://www.solopublications.com/sailarir.htm

There are photos aplenty there of this specific issue and other retrofit work I did in 2004. Most of what I did was restoration-oriented rather than redesign-oriented. One thing I didn't do that I would do if I had the mast off the boat again (and I am not eager to do that again) would be to put a tricolor LED light at the masthead. I didn't want the weight of a traditional tricolor light and weight of the requisite traditional wiring that high up the mast.

As to the hard work of building an integral void-less structural unit from my existing (undamaged) oak strong back, the deck, and the cabin liner beneath the mast step, the design and execution of that task was done under contract in my slip here in Santa Cruz by a professional who used vinyl ester resin and all sorts of modern glass fabric as described above to complete the job. So no polyester resin was used. Epoxy has its merits, and I have used it on other projects, but gelcoat doesn't stick to epoxy.

I was fortunate to have insurance coverage to cover the repair of the accident damage in this case and a skilled professional friend who was willing to take on the repair job on my little boat. This repair and new standing rigging were provided under contract. In the end I believe that my boat is now stronger than it was when it was built, and certainly it is stronger than it was before the accident. All other work on the restoration of my Ariel both in and out of water I did personally over the period 2001 to 2004.

And in the spirit of innovation, I have also documented my development of a sheet-to-tiller self-steering system for my Ariel on the following web page:

http://www.solopublications.com/sailariq.htm

That page, completed in 2005, has full documentation of the concept, design and execution with many photos of the self-steering gears working under sail. The design and application of the self steering gears on that page are based on the pioneering work of John Letcher as documented in his book, Self Steering for Sailing Craft International Marine Publishing Company, 1974; and some sketches and suggestions included in Tony Heisel's book, A Manual of Single Handed Sailing Arco Publishing Inc., 1981. I also relied heavily on the on-line resources including the pages produced by John Ward and Al Gunther.

I single hand a lot, and the Ariel Self-steering gears that I developed have greatly increased my range and endurance under sail. Certainly they have increased my enjoyment and comfort.

[ebb]

Scott,
By the way GELCOAT does stick to EPOXY.

The epoxy must be carefully measured and mixed. Must be fully cured. Must be NO BLUSH.
My specs would say: 100% solids - 1 to 1 or 1 to 2 parts premium epoxy, so that there is no solvent out gassing to mess with the polyester.
Then it should be sanded with 60 grit.

Gelcoat will stick to epoxy.
But why would you want to use gelcoat over perfectly good epoxy?

[Scott Galloway]

Well you must mix up a better batch of epoxy that I ever have. Also my recollection is that I have read in some marine publication that the bond between epoxy and gelcoat is not a secure one. Can't say that I recall where I read that exactly. The previous owner of my boat drilled a few holes and filled them with epoxy. Gelcoat stuck to that for awhile. I removed a spinnaker pole holder and filled those holes with epoxy as well and ditto for the failure of those bonds in time.

I mixed my batches of epoxy as per the West System's instructions. All of the epoxy that I have covered with gelcoat was cured and sanded before the application of the gelcoat, but I have no idea at this point what the ratio of resin to catalyst was, since that was a number of years ago. The epoxied areas were very small in relation to the areas to which I applied the gelcoat. If it works for you, that's cool, but my few experiences with gelcoat to epoxy bonds have not been 100% positive.

The reason that I use gelcoat is that my boat has, as did all Ariels, a gelcoat skin on top of the fiberglass deck molding. I applied a new coat of gelcoat in several areas where the original coat was worn or where holes had been drilled and filled, or where stress or impact cracks were evident. I like gelcoat. It's pretty stuff if you apply it correctly, and it looks and lasts better than LPU. As to epoxy being a safe product to use, the safety of all marine products in my opinion is a matter of mythology, unless of course you are applying steamed white rice to nori, in which case only the raw fish that you apply afterwards is potentially toxic.

[carl291]

Sometimes I wonder if making one area super stiff (strong back area) is wise in a vessel that is constantly flexing and subject to so many outside forces.
My judgment is based on a tractor trailer truck that I had lenghtened the frame 30 " to install a larger sleeper. The frame rails cross members were C shaped steel, in my wisdom for improvement I used square tubing for extra support. This move stiffened the frame but after a period the truck suffered from cracked frame rails before and after the square cross members. After two attempts at repair that failed, I decided to go back and use the C shaped crossmembers, at this point I never had another frame fracture. What I learned from this was every componet has to work (move) together. Granted frame rails are parallell and the curvature of a hull and deck by nature spreads out a loading force
After 50 years of sailing, these boats are still floating, I don't thnk there has been any reports of a mast pushing through the deck on an Ariel or a Commander mast pushing through the keel.
I may be ignorant on boat construction but I would think short of total interior reconstruction (ie. Ebb) repairing water damage and worker screw ups and short cuts, the Alberg design is pretty sound, even when confronting bridges.
Hey, I'm just saying

[ebb]

Carl, this is a great point for discussion.
On boats I think naval architects and engineers are still out to lunch on the subject. Look at the constant breakdowns of the sleds in the Volvo Ocean Race and the repairs modern frp boats have to their hulls and decks.

I think FLEX came down to us from wooden boats, which are but bundles of mechanically connected pieces. Might say that the massively built clipper ships were very flexible - and while that may have saved them in heavy going - it may also have numbered their days.

I see the mighty oak vs the flexible sapling metaphor - but not sure how that relates to our A/Cs. Anything I propose comes from observation and reading, no formal training.

BUT, I think our boats have survived BECAUSE they were overbuilt and because they are STIFF.
We have exceptionally full and fair curves in the hull with no flats. The deck/cockpit mold also has curves in the flat appearing sections. As you know Ariels and Commanders have a pasted together BUTT JOINED DECK TO HULL SEAM. I don't know about other Pearson's of the time, but we might be the only class of boat that was put together this way. Lighter buillt engineered (chinsy) boats have serious problems with their hull to deck join - even if flanged, glued and screwed together.

And yet this seam which was pierced with screws from the s.s half round trim has never had an issue of actually coming apart. And I think that is because the boat AS A TORSION BEAM does not twist much. Given imco the seemingly casual way the bulkheads were put in this is pretty amazing.
I could be very wrong obviously. Somebody with a sailing Ariel can check this out by tying two lengths of string in an X from corner to corner in the cabin. If the tension is about even you might test any twist to the boat when close hauled by observing if one string or the other sags on a point sail.

Assuming this is a valid test, right? The boat might get more bent punching through heavy seas.


Because our four decade old boats began life in the beginning of the FIBERGLASS revolution Pearson got away with things modern boats have learned not to do. Engineers still push the envelope - usually for speed, and they don't ever think longevity.
While modern boats still manage to forget: stringers should never just stop but continue to the bow and stern. (Not done in the Ariel.)
Bulkheads (which are what helps keep a glass boat from twisting) should be attached to the hull and deck top-bottom-sides. (Not done in the Ariel.)
Bulkheads should not bear on the hull or deck without spreading the point load with wide fillets and tabbing. Thinner hulled modern boats float bulkheads
and attach them only from the sides - like a C-channel.

Carl, is your arguement that the funky way our boats were put together actually is the reason they lasted so long?

Even the A/C "over-built" hull showed the stress points. I know I found them when I faired the topsides prior to painting. The brown fairing compound in minor depressions on the old white gelcoat made a topo map of interior structures influencing the hull laminate.


I believe it is the nature of monocque construction to attain its integrity from having a stiff skin. Except maybe for ferro and steel the concept in fiberglass has its problems. Maybe a talented designer like C.A. takes that into account so that flex is factored into a plastic sailboat. The interior structure would take that into account.
But for the tabbing in of the accommodation settees and berths, I don't see that either the designer or manufacturer paid particular attention to hull-flex in my Ariel.

Ebb is certainly on record here concerning the support system under the mast.
I believe any flex here was due to corner-cutting and selling price. There cannot be flex here!

Don't know really to what extent the pros went to inside Scott's Ariel to tie the compression beam to the deck and to the bulkhead. In my mind's eye I see what I would have done. I believe the mast foundation should not move, ever. Any flex should certainly be in the rig. And setting up tensions in the rig would benefit hugely from an immovable base. We are talking about this single bulkhead. To spread the mast point load the cabin arch it stands on cannot be compromised. So arguably preserving that arch by almost any means is the right thing to do.


Now, Ebb, doing what he did: taking out most of this extremely important bearing and anti-torsion bulkhead, may be really asking for trouble. I'm depending on the overbuilt hull (which turns out in this later built hull, A338, is not so over-built) to stay out of trouble. Taking out the bulkhead and introducing FLEX could be my monkey. I'm tabbing in ALL my furniture, and call these panels: web frames. I feel that enough of them will nearly cancel out the torsion flex of the hull. Could be wrong. Like you say, Carl, trying to cancel out the natural flex of a fiberglass boat could be not only wrong but impossible.

On this score, I believe the lead ballast should be immobilized in the keel. That amount of weight concentrated in that one area in a relatively thin skinned vessel could out flex the innate stiffness of the monoque concept.


I've witnessed a couple earthquakes here in California.
I sat through one with a cup of tea in hand, actually enjoying the time of day and the landscape. I saw EVERYTHING in or on the landscape turn into waves: the solid ground, the porch I was sitting on, the house, the trees. Everything became plastic or liquid. Can't recall if the cup in my hand had the wave going through it.

Why couldn't a similar thing happen to a sailboat. Who's to say unknown vibrations can't happen to a vessel in water? So engineering gibberish and web frames will mean nothing when the boat turns to rubber. And it all becomes a wave form, including the skipper.