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

[Andy Best-Dunkley]

You might be right about the time the information about epoxy/glass composite took to filter out to the building community, but I do clearly remember one of the first Pahi 42 builders using epoxy, and of course the Tiki 21 was always designed for epoxy construction. I think Wharrams always made allowances for people to use different materials and construction methods - for example some materials are very expensive in certain parts of the world.

I don't have personal experience of bad/good support from "the firm" as I haven't needed so much, but it is worth remembering that JW's philosophy was originally to design for the ordinary, unskilled person to build a boat and sail the oceans. So the way the plans are drawn is meant to help facilitate this. Woods, who also worked for Wharram for a time, took the same approach with more conventional/modern hull forms. Most of the other multihull designers are drawing for professional builders, so the plans are often not so complete, and so the builders still need to get lots of personal updates and corrections from the designers. I think JWD would reckon on giving _some_ personal consultancy to builders who've purchased plans, but you have to think how much you've paid, what you are getting out of the deal - they are trying to make a living after all. Of course if there is a real problem with the design then that should be corrected as quickly as possible - but if Hanneke and James are away sailing somewhere it's not going to happen!

[stella]

No further comment,dismantling at low tide for boom-truck.

Pahi 31 beams, sold as "guaranteed" by French chantier naval, in court as of now.

[Roger]

Sorry, that is a sad sight.

About beams in general, the alu beams on Little Cat are an interesting option. They are extremely rigid yet light (carry with with one hand). They are also to plan - just with welded alu pieces instead of wood! They seem as tough as nails with no apparent downside (yet?). The catch is it may be expensive to pay a pro to weld the pieces together.

[Galway Bay]

Stella - this is very serious. How old are those beams ? It is like Deja-Vu - exactly like my beams. Mine were only 7yrs. Like many sailors, I suppose to some extent I took some of the blame on my own shoulders ... you know the kind of thing " why did I not paint more often etc."

[Thom delForge]

There should be some engineered specs. on the limits of these structural 'I' beams.  Personally I would rather see rectilinear tubes of sufficient dimensions.   Pultruded structural shapes differ depending of cross section, resin type and reinforcing medium. I am sure that structural analysis would be able to determine the correct  size. 

The beans I built are a combination of four pultruded 1" x 1" tubes laminated to a nonstructural foam core (the shape was to act as an armature for three layers of 17 oz. bidirectional glass with all tubes glass reinforced fillets.  Without sophisticated testing means -- I error-ed on over building (so far there seems no sign of any distortion).  The cambered shape is an important element as the timber beans.  In addition all my deck components fit as original. 

I hope to be at the Hui-Wharram in May -- check with Hui-Wharram in user groups on Wharram Builders web site.  I will repost address soon.

[Thom delForge]

Here it is -- http://wharrambuilders.ning.com/group/hui-wharram-florida Hope to see you all there.

[Thom delForge]

Galway Bay said:

Stella - this is very serious. How old are those beams ? It is like Deja-Vu - exactly like my beams. Mine were only 7yrs. Like many sailors, I suppose to some extent I took some of the blame on my own shoulders ... you know the kind of thing " why did I not paint more often etc."

[Thom delForge]

Plastic is the way to go.  I did consider aluminum -- but my learning curve for TIG was a little steep.  I had thought about designing a webbed beam consistent with the shape of the original timber beans (I did the same with the composite beams).

Windchime (David & Nielia Coe's old Nari) in the process of being rebuilt after nearly 20 years her steel beams were done.  Jim Beyer has been in charge of the refitting -- I will suggest he post a few photos of his progress.  Looks to be an excellent job.   

[Andy Best-Dunkley]

This is a really interesting conversation - seems just about every type of material and construction has been tried for the beams: wood - laminate, ply I-beam, aluminium, steel, foam + glass/epoxy. It would be really interesting to compile a side by side comparison of the pros and cons of each. And of course, all the different ways of attaching the beams to the hulls, various lashing methods, etc.

[Thom delForge]

Perhaps the only way to do a comparison would be to have an engineer model the different systems with known constants.  

[Andy Best-Dunkley]

I don't have direct experience with engineer calculations, but multihull and rigging "experts" that I have talked to have always been totally frightened off by the flexi-lashing systems on Wharram designs. I think it makes it almost impossible to make accurate calculations - or...?

I was thinking of a compilation of peoples' long term experiences with the various materials - how quickly rot set in and where, what works well, etc. I'd also like to hear experiences of those who have converted to fixed, rigid beams. I'd be somewhat tempted by this if/when I replace all my beams, but I presume it requires also a lot of strengthening of the hulls around the beam areas.

[Thom delForge]

The flexible beam connections is one of the major design features of Wharram's designs.  All the way back to the Classic Designs they have always been able to flex, a little.  Remember what all the 'real' yachtsmen and women (mostly men) had to say about multihulls?  I think it should be obvious by now that James Wharram has been pretty conservative in terms of design.  Safety has always been on top of his design requirements.