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Thread: STRONGBACK DISCUSSION etc.

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  1. #1
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    STRONGBACK DISCUSSION etc.

    113 needs a new beam and since Ebb has broke the mold I think we're going to laminate a new beam similar to his. Fortunately for me, I have a friend that is well versed in the ways of wood. He's laminated everything from fishing nets to display cases to full blown foot bridges. He also finds my anxiety regarding this piece humorous. To him it's just another arc, but as we all know it's the backbone of our beloved little craft. So we've done some research and mixed his experience with a little nautical input. Here is where it has to end up. One of the previous owners did a repair(hack) job on the area NEAR the mast step but not really. As far as I can tell all they did was cut out the cabin liner in that area cut through the inner skin and then glue it back in completely cockeyed and unfair. Off by a strong 3/16" Not to mention that the inner skin is still mobile under the step. So we'll put in our strongback and main bulkhead first and then go topside and finish the job.
    p.s. I know-I know the plywood head liner doesn't look original. But it's stuck really well to the fiberglass so we'll deal with it. Actually it may facilitate in adding handholds forward.
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  2. #2
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    Gettin Jiggy with it

    This is what we're going to use to make our strongback. Well, most of it at least. Made from scap wood that has acumulated over the years. I traced the radius onto the jig base from a pattern made from 113's cabin top. The pattern was exact-so it included all the waves and woobees. Then I faired line to give a smooth arc the was the best fit at the twelve contact points of the jig knowing that some of the strongback will need to be ground away and some spots may need to be filled when jacked into place. Then I built up the two by four blocks along that line. The blocks on the ends of the arc are just stop blocks to keep the plys from running wild. They are in the same plane or angle as the sides of the coach roof but they are 3/8" wider so we can shape the ends of the strongback to a smooth edge. The greatest unsupported span of our strongback will be 24" so I'm opting for a slimmer, trimmer beam than Ebb. I'm planning for 2 3/4" wide by 3 1/2" tall. The four pieces of wood spanning the blocks are 2 3/4" off of the jig surface and are there to keep the plys from slipping off eack other when pressure is applied with the clamps. They are pre-drilled and mounted with screws so they will be removed to allow the glued plys to be introduced to the jig, then replaced and 'snugged' as needed when the cranking starts. It all sounds straight forward doesn't it? Wish us luck or send beer!
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  3. #3
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    338 sends LUCK!

  4. #4
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    Senor Ebb -

    Par for your course, the work is excellent and shows much thought and even more labor! The 1/2 solid dodger - great idea, will have to ponder that one. I have been planning to build (make?) a firehose-frame dodger, a la Yves Gelinas on "Jean-du-Sud" . Combining the two ideas deserves some consideration...

    Anywho, I've begun (de)construction belowdecks. After dropping the mast this past Sunday, I decided to go ahead with the strongback modification while it is down, and before I put it back up.

    The past couple of days I've been battling a head cold, but today I got fed up with just lying around feeling ill, and took out my aggression on the strongback and bulkhead. The strongback is now lying on the cockpit seat, and the bulkhead is cut away to within 2" of the top of the standard locker countertops. The "main cabin" is now open to the v-berth, and it really makes a difference in how the interior "feels"!!! I love it, it's like the boat is bigger already. Hopefully by the end of the week/early next, I'll begin reconstruction of the structural components I've removed. I'll be posting pics in my Gallery thread soon...

    So anyway, I have a question for you concerning your strongback -

    Basically - What are it's dimensions? That's to say: How many inches thick is it in its vertical and horizontal cross section? I'm trying to get an idea of what I'm seeing back on page 1 of this thread, and in the latest pics...

    I've decided to go with a wide, low-profile design for the strongback, about 2" 'thick', and 8" wide (or more - I'll be removing some of the headliner to do this). Reasoning: keep the interior as visually open as possible, while making sure that my non-engineered solution is far and away stronger than what was in this boat for 40 years (which was surprisingly slapdash, once I could see it upon tearing it apart). I think it'll be all composite, glass and foam, mostly glass.

    I drew a line onto the bulkhead and s/b before tearing it apart, to get an idea of how much space that was, and I think it'll be sufficient for getting the material I need in there. Yours looks to be about the same size as the strongback which was original - is this so? Thanks!
    Kurt - Ariel #422 Katie Marie
    --------------------------------------------------
    sailFar.net
    Small boats, long distances...

  5. #5
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    Hey Kurt, excellent!
    Did I miss what wood you will use for the compression beam?
    Depends on where the struts, the verticals are going. All the way to the cabin side (as 338) or are you keeping the forward stateroom, and will have a doorway?

    Could guess that if you were going with the doorway 2 X 8 would be OK. In white oak. Wider apart and deflection could be a factor. I would go to 2 1/2" And I might think to lag in a piece of 5/16" steel on edge - cut exactly to the arc of the cabin roof - as insurance. There is a problem with this if you are laminating: your lags are going into the lams which spoils their integrity.

    There is good reason why beams are usually deeper rather than flat. You know you'd have a superior beam if you put the 8" on edge. I think 338's is like 2 3/4 X 5. With smaller section plain whiteoak struts on the sides, at the ends of the beam.

    Maybe you could weld up a 2 X 8 s.s. arc as a 'C' channel. That might work good. No wood, just steel. Very good, if you through bolted across the cabin top the whole length.
    Don't think I'd do away with some kind of verticals going down to the berths.
    Theoretically any arch can't deflect if its ends cannot move. On the Triton site at least one guy assured his cabin arc by fabricating a curved athwartship mast base - thrubolted with the beam, no doubt.


    At the end of the cabinsole where the V-berth deck rises -right there at the doorway in the bulkhead - I've glued in at 2'' thick mahogany 'floor'* (crosspiece) and I will be doubling that (and maybe a bit more) thinking that I may have to put a compression pole in because the beam is not adequate. They naturally end where the original settees rise. With a pad on them and the pieces fitting well andthe remaining pieces of the old bulkhead tabbed in solid they may spread the load of the mast over the keel well enough. I've heard that poles are great to grab onto below. Imagine a well rehearsed two handed 180 swing from a crouch to a 360 landing on the Airhead...

    White oak is not a wood for gluing. Tannins mean the resorcinol won't work. Can't remember about brown glue (the powdered stuff} but white oak? don't think so. There are enough complaints about Gorilla urethane glue to keep me off it. No 'soft' glue will hold stress lamination. And epoxy requires a glue line. Might talk with Smith & Co. about their epoxy AllWoodGlue.

    If the beam appeared to be molded into the cabin, not featured, but was disappeared, nicely rounded, into the cabin painting scheme, I bet you could go deeper on the beam scantling and be positive (almost) that the mast would stay out of the accommodation. Incorporating a number of fastenings thru the lamination might insure the mast won't crack it and delaminate. Be cool if you could carve the beam out of a curved branch. Indeed, if you rounded the bottom, curved it like a branch you'd gain more strength without it being obvious.

    Interesting problem.

    Epoxy has to have a glue line. In curved lams prebending by steaming would allow gluing without force. If your lams are thin and easy to bend (1/8"), and if you have the time: gluing up a few at a time, letting them get hard, and continuing with a few more, etc could work. Gluing a bundle of wood together under stress is not correct anyway. The piece will want to straighten itself out (flatten) which is not what we want to happen - so why build it in?
    Wide lams may be difficult to set up a jig and to clamp. But the beam is pretty small. Gluing the beam to the boat would add strength and solidity.
    Screws could be used to hold lams together while gluing and backed out after set. I have a bunch of 1/4" luan 1 1/2" squares with a hole in the middle. Drive them in with a grabber to tighten up pieces, get a bulge out.

    I think you have to give attention to supporting the full width of the 8" beam with 8" wide verticals. Gotta support the beam!

    Go for it!

    __________________________________________________ ________________________________
    *floors connect ribs together over the keel in traditional wood boats. Each pair of ribs, port and starboard, would have a floor, each floor fastened to the keel. Snobby using a term like that in a lit'l ole plastic Ariel. oh well...
    Last edited by ebb; 08-16-2006 at 11:49 PM.

  6. #6
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    Included is a quicky graphic* I did up to illustrate my current thinking. I'm with you on the stiffener thinking: Since the vertical component of an I-beam is what makes it resistant to downward bending, I have been trying to figure the best way to incorporate that into a 2" thick structure which could resist the compression forces put on it by the mast. I've ruled out wood, because I think that in what I'm going to do it will only add extra weight, w/out adding any extra strength. I'll be relying on glass for strength. Too bad, I like the look of wood! But it will be elsewhere in the cabin, so...

    In a nutshell, to build the beam: Lay up the glass onto a sheet of 3/4" thick foam (one side at a time), putting a total of 1/8" thickness glass on each side of the foam. This can be done with the foam in a horizontal position, making it easy to control wetting out, and to control alignment of the glass fibers in the cloth to achieve maximum strength in the finished beam. Once both sides are glassed and cured, carefully cut the 1" thick individual "slices" of the beam to a template taken directly from the hull, then bond the 'slices' to each other. After the slices are assembled into a unit, glass on the outer layers (top and bottom skins of beam).

    When this entire beam assembly is cured, it gets bonded into/under the deck, bedded in glass and "ebb's mishmash" , drawn up into place with screws and/or bolts until cured. Use more mishmash to filet the edges of the beam to the deck for smooth transitions, and then, last, laminate on a final overskin of glass.

    I plan to put 2 vertical stainless poles in place where the old doorframe verts were, they should give additional support and handholds. I 'mocked this up' yesterday to see how they would look visually, and they don't detract from the 'open' feeling the cabin has with most of the bulkhead removed (which I am loving!). At the bottom, they will tie in to reinforced floors similar to what you have done.

    Whatcha think?


    *(((As I was just making the graphic, the thought came to mind: "Hey, there's also the space between deck skins which could be incorporated!". Hmmm - doing so would give structure which would not protrude down into cabin space (good!), but it would involve much more work - remove outer deck skin once new beam was in place, build structure in where the current balsa core is, then replace deck skin. An idea which deserves further thought, and which someone else might be able to use at some point, so I've included it...)))
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    Kurt - Ariel #422 Katie Marie
    --------------------------------------------------
    sailFar.net
    Small boats, long distances...

  7. #7
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    note to all 'beam' builders out there....Plywood is VERY strong when on edge (vertically).4 layers of 3/8th ply would give GREAT strength as long as the bottom edge was 'trimmed' out with wood so as to keep it from deflecting for/aft under load. I know little about boatbuilding,but in home building we often use plywood as an additional laminate when building a beam to increase the compression strength. WAY stronger than conventional wood.

  8. #8
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    Frank -

    I assume that is so because the wood fibers run in different directions in a ply? (as opposed to the same direction in a normal piece of wood.)

    I'd considered using plywood in this manner, but thought I might get a stiffer vertical with the glass 'ribs' like in the graphic.

    So - I could do the beam then with 14-16 'slices' of 1/2' ply, bonded together with a couple layers of 6 oz cloth between each, make it 1 3/4" thick in the vertical dimension, and cap it with 1/4" of glass...? All this would get the same final treatment - completely encapsulated and bonded to the underside of the deck, as noted above.

    It might be quicker to do that way. One thing I liked about all-composite, though, was no worries about water penetration. Could take care of that with much care in sealing things up I guess...
    Kurt - Ariel #422 Katie Marie
    --------------------------------------------------
    sailFar.net
    Small boats, long distances...

  9. #9
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    beamish ramblings

    Indeed. I do like the multiple I-Beam composite, great graphic. It's an engineering challenge! EG how thick do you make the webs? The more you think about it the more feasible it becomes.

    The verticle supports inside, two placed about where the original doorway is, should do it. Could also buildup wide pads on the beam to spread the 'point load' of the supports.

    Mike Goodwin introduced us to maranti "Aquaply" and "Hydroply" which are superior in every way to American fir - that stuff would make a good arch - ala Frank's post. Thanks, buddy! 3/8" of maranti equals 3/4" american fir. I would not use FinnPly. Would caution that cutting the 2" wide curved pieces out and gluing those together side to side to get your width is not such a good idea. There still will be flex don't you think? Could you put it on the floor and jump on it??? Even with the extra wide width I think there is not enuf 'meat' in 2 inches. Would like to debate this. I'd be happier with 2 1/2". Plus the two columns inside. As you know it's imco. Frank, though, of course meant bending 1/4" over a form and gluing up a 2, er, 2 1/2" stack! Only with meranti.

    A composit structure composed of two skins separated by foam, endgrain balsa, honeycomb -essentially a nonstructural filler - will be stiffer than a solid lay up. Also lighter of course. But we can't forget that the load on the beam is concentrated in one place. Spreading out that point load is very important. Correct?

    What we learned about an unrestored Ariel with a flattened cabin-crown under the mast is that the original Pearson structure (beam, strut braces and bulkhead) while funky was still working and in good shape. (On 338 anyway.) The structure had probably 'settled' or shrunk over the decades allowing the rigging to pull down on the mast. That is, it was more of a result of aging materials rather than the weight of the mast, or rot. After the two screws that hold the round wood maststep to the beam inside were removed, the composite cabin top popped back up to it's original crown!! Or pretty close to it - how about that?? That's the challenge confronting the renovator. We need to make some structure that will not move over time. This time. Or one that can be adjusted up when needed. I'll take the immovable, with some redundancy built in. And everything GLUED IN. We live in the age of incredible glue.

    If one had the time, testing various structural ideas would be revealing. We'd need the various arcs and a carjack and some sort of meter. But doing this in the imagination is a good alternative. One can 'see' the various ideas and how they might be expected to react to a carjack (or an unmetered jumping attack by a twohundredfifty pounder wearing Redwings!) trying to straighten them out.

    I'm oldfashioned and think solid heavy oak will do. But a well thought out composit of carbon fiber and the best epoxy would be much lighter and more in keeping with the technologic advances of this era......... Would be a curious jig to come up with! Vacuum bagging, anyone?

    The load on the compression beam is constant - and no doubt there'll be times when sailing that the load exceeds the norm, would be constant AND 'pumping.'

    Gotta go to work


    __________________________________________________ ______________________________
    (Supposed to be working...) How about bent square (rectangular) steel tube? Easy to get the arc done. Get the best curve, weld four of them togther side to side. Fill the odd angles and spaces up top with epoxy mix using the beam with a film release. Take it down. Then glue it back up with rubber. No?

    Might get a clear span out of that one. And however the supports go, they also could be the same tube all welded together. There's that old problem of what the finish will be: chromium oxide? Wait a dang minit... Use the best quatity iron (the other steel) tube and get it galvanized. No stinkun chromium oxide and no sticky epoxy!!!
    Last edited by ebb; 08-17-2006 at 10:19 PM.

  10. #10
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    Been thinking on this, and will be until I start doing something about it...

    I took Franks post to mean that the ply - used as a stiffener - would be *on edge* (its laminates placed in a vertical orientation, like end-grain balsa). Each individual layer of wood being, in effect, the vertical component of an "I" beam. The fibers of the wood in the ply would be more-or-less vertical if it were installed that way. Laminated together flat the fibers would be horizontal, and function more like a leaf spring, right? Seems like that would be so...

    Point loading: Exactly - I'm thinking "wide" in order to spread the point load of the mast base out.

    The mast base pad on Katie measures a bit over 7.5" in diameter, but this sat on only a total (strongback + bulkhead edge) of 3.5" of structural support from belowdecks. (Not to mention that someone at the factory neglected to install the diagonal braces on this particular Ariel...) By making the beam 8" wide, I should see a lot more support from below.

    I saw a different reaction than what you did when the deck was relieved of the mast burden. Mine has remained in the same slightly depressed shape, it didn't spring back up like yours did. I likely had more compression, due to my missing diagonal braces, though. In fact, I see evidence under the side decks that they flexed to a point which caused minor cracking - zoiks! So I am very much interested in spreading the load as far and as wide as I can, so that more of the deck/hull structure shares the burden.

    I've given a lot of thought to different metal tubings as a brace. The ultimate would be 2" aluminum round tube, bent and welded in a shape just like that of the underdeck and hull shape, clear down and around. It would be as light as possible, very stiff and structurally strong, I think you could even do away with the entire bulkhead if you wanted, and it would look nicely "techno". It would not be cheap, however - I'd have to sell both CrewDogs and at least 1 kidney to be able to afford that! I think that if you welded up several square tubes, bent to fit the underdeck curve, you wouldn't need to fill them with anything other than some type of anticorrosive agent. But that would be complex, probably not cheap, and probably heavier than a wood or composite beam. Perhaps an I-beam made of flat plate, the top of it curved to mate the underdeck would work well, and be fairly easy and cheapest for a welder to make up. Maybe a wide box-shape, something like that. I don't weld, though, so someone else will have to pursue that route...

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

    This weekend, I am going to take some scrap ply that I have - it's 1/2" or 5/8" - and rip it into 2" wide strips, then screw them together to make a 6-8" wide "test beam" - no curve, just a flat piece as long as the strongback will be. I'll put it up on some bricks or something, and jump up and down on it, maybe jack up my Toyota and set it down on it, see if I can destructively test it to get an idea of how strong such a construct might be. Kinda like that TV show.

    If it proves strong enough, then next week I'll make one to fit the boat, tab it in similar to how the original strongback was tabbed (quick and easy), and then get some galvy pipe to support it with from belowdecks. At that point I'll be able to put the mast back up for some testing. It won't be hard to remove if it:

    a) either doesn't work, or

    b)works great, and just needs to be put it in properly - bedded in mishmash and glassed all over.
    Kurt - Ariel #422 Katie Marie
    --------------------------------------------------
    sailFar.net
    Small boats, long distances...

  11. #11
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    mast support beam

    The beam in 198 has a very slight bow in it, barely noticeable when eyeballed, and less than an eighth inch at the corners when measured with a straight edge, is that enough to worry about or should I do some refurb on it?

    Did search, but while info on swapping and re-enforcing it was abundant, I couldn't find anything to indicate what was acceptable.

    Also, are replacement lenses available for the stern light? mine has everything but the lense itself, looked at the other lights, and it's the same style (hemisphere about 1-1.25" diameter) the light's in good shape except for the missing lense so would prefer finding a lense if possible.

    Thanks
    Ken.

  12. #12
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    Search on "strongback" for answers. Manual has complete discussion.

    Sea Dog makes 1" replacement globes that fit the Pearson hardware. Plastic, however, not glass. Cheap, so you can purchase extras . . .

  13. #13
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    compression beam possible quick fix.

    Hope that 'Bill Ariel 231' will post here. He is more practical and less wordy than I.

    The support beam has a bow in it, of course, that more or less conforms to the curve of the coach roof. The support beam supports the composite fiberglass/balsa laminate that the mast step and mast sits on.

    I believe that over time there is natural settling and shrinking that happens even though the wood of the beam is still in good condition. If you have opening across the top it may merely be a condition of age. Even bad original fitting that has opened even more.

    Test the beam for soft spots especially in the center. If you have rot, that is a more complicated problem. It's another diagnosis. A repair such as described below cannot be fudged on a rotton beam. Replacement.
    Check the curve of the roof outside to see if the mast rigging has pulled the mast into the roof any. Flattened it.
    Because the navigation wires (used to) go into the interior through a hole under the hollow of the mast, rain water may have rotted the balsa under the mast-step in the composite. Check the roof if there is a slightly more localized depression. Needs to be fixed.
    The coach roof should have a fair curve to it. Anything else requires a change in plan.

    If you are lucky to have the mast sitting on a nice round cabin roof without any flattening (you may be the first!) then you can go about finding a way to fill the narrow space between the beam and the coach roof inside.

    When you decide to go full monte on this fix, you remove the deck mast step by taking out the two 1/4" (#16) bronze flat-head lags that clamp it to the beam inside. Could be problem. When mine came out on 338 the cabin roof nearly returned to its original molded curve. And the narrow space inside opened up considerably more.

    Pearson fudged the fit when assembling the Ariel as they used the mast support beam to clamp in the forward end of the cabin liner. That means that any fix cannot be attempted from the cabin - but from the V-berth area. It also supposes that the beam didn't fit quite as snug as it was supposed to. The beam may be tight against the liner on plywood bulkhead side but not quite so tight on the V-berth side.

    You cannot fix the space problem with the mast rigged and pushing down on the roof. You can fix it when you RETURN THE COACH ROOF TO ITS ORIGINAL MOLDED CURVE by temporarily relieving all the pressures on it. The mast has to be taken down.


    The coach roof has some rounded dimensions that isn't really compatible with flat carpentry.
    Look at the problem with a few options in mind. You could for example bandsaw and shape to fit a single piece of wood that you glue into the space. That's the best way.

    One uncommon way to consider.
    Clean, scrape and remove paint, silicone snot, fillers that are in and around the space. You are working from the V-berth side. And you are deciding what you can do that will keep the roof totally supported.

    I have had success using wood filler pieces and epoxy mishmash (laminating epoxy, fumed silica as thickener, and 1/4" chopped fiberglass strand) a kind of hairy pudding.
    Wet the inside area with plain mixed epoxy and wipe it up best you can. Use terry toweling pieces stapled to thin battens. Get this 'primer/bond coat' dry as you can after wetting so that your mishmash won't mix with it and loosen and sag out of the joint.
    Slide your wood filler pieces in slathered with gobs of pudding. You will have done a dry run so you know they fit good and where. The more wood, the less expensive glue. Longer pieces might even add a little strength to the beam.
    Make sure you are stuffing the cavity all across the top.* You may be using some shim/wedges to get a tired coach roof to curve back properly - no forcing - you don't want to put anything under tension here - it will pull apart later - just enough.
    I would shim the coach up using the beam in the center if necessary. Or prop the coach roof fair next to the beam with some 1X2 or 2X2 from the berth or sole. They'll be in the way, tho.
    You might have a special shim or two that can be left epoxied in there. Use durable woods like fir and mahogany. Don't leave anything sticking out.
    Once it's gooped and filled, take paper towels and remove any squeeze out and runs.
    Clean up with alcohol so that there is minimal sanding prep for the next step.
    This is a quick and dirty fix that allows the carpentry to be kept in place. It will only work if your diagnoses was correct.
    Assumes that your beam and bulkhead are in good shape. That the composite under the mast is also OK. And the mast step itself.
    It can be done this way, but I don't really recommend it. I would do a classic reconstruction if warrented - and do it right.
    __________________________________________________ ________________________________________
    * To control the extent of epoxy being pushed into and through the joint (the juices may run down the cabin side of the beam and bond the cabin door trim )- use cheap polyethylene foam 'backer rod' from your concrete store in the back of the space (seen from the V-berth). It isn't hard rod, it's soft yet firm foam you can stuff into tight places to create a dam. When you push in the wood filler pieces, you want the epoxy pudding to kind of billow out. There's going to be a little waste.
    __________________________________________________ ________________________________________


    BUT it's hard to know exactly what you got there without some photos. Good luck.
    Last edited by ebb; 10-01-2008 at 08:02 AM.

  14. #14
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    Ken

    I agree photos would help here. It sounds like a couple things may be going on here. I recommend a through check of the beam, the columns that support it and the deck core directly below the mast step.

    Beam: is the beam compressed in the middle where it has been drilled out for fasteners and wiring? (mine was) Is it compressed where it crosses the columns at the passageway? It is supported by roughly a 2x2 at that point. Are there any tell tale fractures across the grain in either area? The only way to tell is to grind off the paint to see. If the beam has a small depression where it meets the column (or none), and there are no cracks and no rot then Ebb’s epoxy fix will work just fine.

    If there are cracks or signs of Rot… reach for the Sawzall. The Beam is held in place with 3 to 4 wood screws (port and stbd) installed from the cabin side (hidden by the formica). I elected to cut them flush on the vee berth side. Making a new beam is easy if you have a band saw, not much harder with a recip saw and an angle grinder. If there is any doubt about the beam, it is worth the piece of mind to change it. Although the deck beam doesn’t look like it can take it, the design load for the mast step is often a high fraction of the boat’s displacement. (refer to Brian Toss’ book for the test case at 45 degrees heel on a boat’s standing rigging). In Periwinkle’s case (A-231) the beam had both rot and a fracture in the middle of the beam. The replacement was a white oak beam glued up from two planks, rough cut to a paper template of the old beam and trimmed to fit with a grinder. My replacement beam is now screwed in place with wood screws thru the bulkhead at the original factory location. Installation of the beam followed Ebb’s suggestion with the beam buttered in thickened epoxy before final assembly. One alteration I made from the factory install was to relocate the mast wiring to a tube on the stbd side of the mast mast step. After fabricating a new mast beam I couldn’t bring myself to drill a big hole in the middle of it for a wire chase.

    Columns: Compression at the top is possible, but I haven’t seen it or any photo’s of pearson tritons and ariels with that symptom. See if there is any rot top or bottom that might indicate the column and the bulkhead moving down. This would be bad but again there is easy access on the vee-berth side to affect a repair.

    Deck: While you are there, make sure the deck under the mast step doesn’t need to be recored. I’ve pulled my mast step twice. Once for the restoration and again when the deck core under the mast step failed. I believe the deck directly under the mast step should be solid ‘glass (or at least plywood). The original Balsa on mine was both crushed and wet when I opened the deck after 4 years of service. No issues since replacing the core with glass for a couple inches around the mast step. I recommend checking the deck core while all of this work is in progress because this is an easy extra step while the mast step is out.

    Good luck
    bill@ariel231
    Last edited by bill@ariel231; 09-30-2008 at 05:36 PM.

  15. #15
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    Wink 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.


    __________________________________________________ __________________________________________
    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./././
    __________________________________________________ ___________________________________________
    **This major fumble was left out of Everett's biography.
    Last edited by ebb; 10-04-2008 at 04:18 PM.

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