Composite Beams

[Thom delForge]

I will be interesting to see if these beams are strong enough -- I am not an engineer; however, I believe my beams are as strong or perhaps stronger than my original beams.  I decided to build my composite units to the same dimension as the timber.  Using four pultruded square 1/8" wall tubes laminated to a foam core (non-structural) shaped to match the original dimension.  I also laminated diagonal components to form a 'web truss' within the beams.  At the mast step additional pultrusions were laminated to the center of the beams to distribute any load.  I then began laminating two layers of 17 oz. bidirectional glass cloth on the entire outside Extra layers on all tube connections, and then several layers at around the lashing positions.  I feel that has more than made up the structural equivalent of the wooden units.  All in all they seem quite stiff, although I know they will have a slight degree of flex -- being encapsulated as they are I don't have any doubts at to their strength.  These too are over built -- just in composite.   

My plans now call for finishing all the 'mods' this winter and possibly sailing to Key West by winter -- ambitious perhaps, but getting close.

Thom

[stella]

hi!

I like the composite beam idea. Are they still holding up? How would you strat a full hull around the shape fo a Pahi. Any suggestions for plastic battens and bulkheads?

[Thom delForge]

My beams are exactly as I installed them nearly 2 1/2 years ago.  They turned out to be about half the weight of timber.  I could have made them lighter, but I decided to err on the conservative side.

T

[stella]

thanks for your reply. Gald to hear that. When my project of a full plastic Wharram becomes definite, I'd be gratefull for more photos of the building and more instructions.

[Thom delForge]

Sure.



stella said:

thanks for your reply. Gald to hear that. When my project of a full plastic Wharram becomes definite, I'd be gratefull for more photos of the building and more instructions.

[Galway Bay]

Permalink Reply by Patrick John McGrath 11 hours ago

I have been concerned with the fact that there have been a lot of crossbeam failures over the years, mainly with the classic designs.  The problem seemed to not with the original design, but with the incompetence of in- experienced  builders who constructed unsafe beams because of their ignorance of basic beam structures.

One such boat, an ORO, was built by a carpenter who should have known better. He laminated the beams up from 3M lengths butted together. Worked alright until he got into the choppy seas around the Bahamas and the beams started un- ravelling, finally ending in the hulls coming apart. The boat was only saved by the rigging holding the two hulls  from wandering away from each other, and the boat was salvaged.  

Another builder, of a Tehini, wanted to put a modern Bermuda rig on his boat, which of course required the mast to be supported by the centre of the main beam. He took the advice of a civil engineer and used steel I beams,(RSJs), for the crossarms. The beams were strong and light, and being of I section had a degree of flexability. They were bolted by the flanges to reinforced areas of the gunnels, and were completely success ful, holding the boat together when they grounded on a sandbar on a falling tide on the East Coast seaway. They completed a trip around the Bahamas and returned to Toronto in time for the first world multihull symposium where Wharram actually sailed on the boat and approved of the system

PATRICK -I think you probably intended to post here so I took the liberty of copy / pasting .

On my travels on the West Coast I meet a man who previously sailed a Tane. He tells the story of how when James Wharram tried to sail the Round Britain Race in his Tehini [ 51ft ] he was forced to abandon the race after only about 400 nm due to beam failures. Coming ashore in quiet Achill island [ still beautiful ] my friend built for / with them THREE NEW BEAMS before they could put to sea again.

This is hardly a case of amateur incompetence or modification.

My own beams built carefully to plan failed after 7 yrs. One failed at sea 200 nm from home.

Only now with this site is there some where to say this. Much or most of what we "Know" about Wharrams is just advertising.

[allan poulter]

Has anyone has a look at this product for beams? http://www.usplastic.com/catalog/item.aspx?itemid=23006&catid=561

[Robert Hughes]

Looking at this link I'd suggest being very careful.  The tolerances they quote are very slack, +/- 10% on thickness and +/- 5% on width and depth.  Fine in the building industry but doesn't inspire confidence in their quality control if you're engineering something like a seagoing boat.  Couldn't see anything about the type or orientation of the glass used, or the stiffness or strength.  If I wanted a ready-made material for beams I'd go for aluminium extrusions of the type used in yacht masts (or carbon fibre if I had unlimited money!).  The quality control is high and the physical properties exactly known and consistent.

Before I came back to boats I spent a few years messing around with microlight aeroplanes ("ultralights" if you speak American).  They originally developed from people sticking motors onto hang gliders.  I heard that back in the early days some folks found a "really good" cheap source of aluminium tube - the poles used for mounting TV aerials.  What they didn't consider was the spec of the aluminium used, and some people ended up dead.

Whatever you use for beams, make sure it's either properly engineered or extensively tested, or preferably both.  In aviation they have it easier than we do in one sense, because the loadings are easier to predict than for our sort of boats, so we have to include big safety margins.  Here's a picture of one of the tests on a small wing:

If I ever need to build new beams for my Tiki I'll try something like hanging a car from them!

allan poulter said:

Has anyone has a look at this product for beams? http://www.usplastic.com/catalog/item.aspx?itemid=23006&catid=561

[Galway Bay]

In case my post on the older beams is causing concern to our more modern sailors I have no reports of failure in TIKI style beams. I use timber I beams now.

Why Wharram stuck to the old beams so long I cannot say, but I believe it was a mistake.

They were also the last designers that I know of to use Epoxy. Dick Newick's proa Cheers [ my favourite boat of all time ] was Epoxy / ply in 1964. I myself have used stitch'n glue since 1966. When I was building in late '80's Wharrams were still recommending polyester resin and resorcinol glue. Only with the TIKI 21 in 1991 did they accept stitch-n-glue and Epoxy resin. I had to do a major rebuild some years ago most of which would never have been necessary had the boat been built with epoxy as just about every other designer recommended.

[Andy Best-Dunkley]

Hi, Galway Bay - I think you are out by about 10 years in Wharrams' uptake of epoxy. I worked for them in Milford Haven during 1982, when the Tiki 21 had just won the Cruising World award, and I also helped to build the first Pahi 24 (I think it was 24'...or 26?) We were certainly using epoxy for that - stich n glue with epoxy fillets. I believe they continued to recommend either polyester resins and resorcinol glue as well as epoxy for some time, most likely due to cost of use for home builders. A well-built boat with either should last. Many boats (such as my own, which was completed in 1986, not by me) will be using both resorcinol and epoxy due to the long time-span of the construction.

Returning to the beams discussion - I agree that the original beam design is not the greatest. I have repaired 3 of my beams and replaced the forth. I asked Hanneke about using the "new" Tiki style I-beams, but she said that these are longer than the original Pahi 42 design, and require changes to the hulls at the lashing points. As my "building" window each year is very limited I don't want to radically change the hulls, and need to work on one beam at a time. For my replacement beam I used a ready laminated pine beam (used for construction here in Finland), reshaped and laminated with glass/epoxy. They are designed to withstand moisture even without the glass and paint on top. I am sure that the industrial wood lamination, even if not designed for boat construction, will be stronger than anything I could achieve...at least that is my belief! So far it seems to be working well. I intend to replace the other three at some point.

If anyone has experience of using the I-beams on a Pahi 42 I'd be glad to hear how it went, especially if you retro-fitted an existing boat. It seems very difficult to get any advice on beam construction for Wharram style multihulls due to the flexible mountings - all other multihull "experts" totally don't get it, and it is very difficult to actually calculate what the stresses will be (or so it seems). This is why James' mantra of make it doubly safe and strong was the way to go back then.

[Patrick John McGrath]

Andy Said :- 

Andy said:- Hi, Galway Bay - I think you are out by about 10 years in Wharrams' uptake of epoxy. I worked for them in Milford Haven during 1982, when the Tiki 21 had just won the Cruising World award, and I also helped to build the first Pahi 24 (I think it was 24'...or 26?) We were certainly using epoxy for that - stich n glue with epoxy fillets. I believe they continued to recommend either polyester resins and resorcinol glue as well as epoxy for some time, most likely due to cost of use for home builders. A well-built boat with either should last. Many boats (such as my own, which was completed in 1986, not by me) will be using both resorcinol and epoxy due to the long time-span of the construction.

Yes, I remember Wharram was still using stiff cloth bonded on with resorcinol glue for quite awhile before he took up epoxy/glass coating. The first boat built and coated with Epoxy I recall, was a Tehini built in Toronto for a movie producer, using Bote-Cote epoxy.   Wharram eventually started using WEST epoxy much later.

[Galway Bay]

Andy - I think perhaps you had the advantage of being at the coal - face, so to speak and the message took some time to filter out to us in the 'boonies. Even then unless you were building a Tiki the message seemed to be that Epoxy Could be substituted not that it Should be. The whole Epoxy thing could fill a thread of it's own. For instance a good sheath in Polyester has to be so much heavier [ mine is about x 3 times as heavy ] that I see no saving. Likewise inside the boat I find x 2 coats of epoxy is cheaper and better than alu. wood primer.

As to the beams I have since received a fuller report on James' difficulties in the Round Britain Race from a second source. I find some of the details even more alarming and upsetting than the original account.

Mostly I am struck by the fact that this is the first time I have seen any of this aired in public. Any previous accounts were always brushed aside by blaming the builder for poor construction, modifications etc. Or this is how I remember it. I certainly [ like the T 38 mast-step issue ] do not remember Wharrams discussing the issue in an open fashion.

I must confess to having a love - hate relationship with Wharram. Or perhaps more accurately with the operation of Wharram Inc. or Wharram Ltd. as the very few times I have met him he was always charming and helpful.

On the one hand the boats are just so beautiful that I must go back to craft like the Bluenose Schooners to find comparisons. On the other hand my experience of building to plan was that I did not get the very best advice. Mostly what I did not get was an open forum where known problems could be discussed so that the builder could make an educated decision on possible changes.

[Armin Foell]

But now, glad as we are, we have such forum!

Cheers, Armin

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