Composite Beams

[Thom delForge]

If any one was interested in an alternative material approach to wood beams -- I would happy discussing the idea. After having sever rot problems the second time with the beams on my Tiki 31. I decided to not use timber the third time. Actually, the second time was a pretty thorough going over -- and still rot crept through. After settling on alternative materials -- the choices I had where aluminum or composite. Since I have little experience with aluminum fabrication, composite was my choice. To simplify the design I decided to use the same dimensions as the original beams -- using close cell foam as a core shape (2"). The flange ('I' beam design) I am using four 1" x 1" pultruded fiberglass tubes glued to the core and then glass and epoxy wrap. I attached a few photos of process -- at each lashing point the beams have been filled and wrapped with several layers of 18 oz. bi-directional cloth. Under the mast steps I laminated several layers of carbon cloth and structural webs. At this point the beams are weighing in at about 40 pounds -- when totally finished I suspect I will be looking at about 45 pounds. Anecdotally, I suspect these to be at least as strong as the timber beams. I am still amazed at their lightness. Hopefully I will finish the work next month. As for mounting the different components -- through drilling will have fiberglass tubes epoxied in and neoprene tubing rubber sleeves to minimize chafing of rope.

[Thom delForge]

Still working .... but the beams are looking good. My marina is in the process of being foreclosed on -- I think, so I am looking to find a new place to set up shop while I figure what is next. So close ....

T

[Eric Harris]

Hello Thom

I am new to the forum but have been reading your threads with interest. I bought Tiki 31 (#97), sailed her from Cape Infanta (Southern tip of africa) to my home in East London (400m east.) Sailed around a bit and then put her on the hard for 'maintenance'. That was a while ago!

I have had to almost completely rebuild the beams! Finding timber has been difficult and the process is very time consuming as you know. Your composite beams look a much better solution. I was hoping you would say a bit more about the actual lay-up you used on the beams. I know people are often reluctant to do this because of the perceived responsibility but I would be very grateful. while I dont know much about the structural features of beams I have fixed and worked on plenty of surfboards, surf-skis and yachts to feel like I can lay up a composite if I am told the specs. I have tried to get wharram to sell me plans for a composite beam but have had no response.

I look forward to your response.

P.S. Ever though of dong the masts the same way?

Eric

[Ann and Neville Clement]

Keeping the boat light weight is important, but the crossbeam construction is the last place we would consider experimenting with. Chris White is another well respected multihull designer and he says to make the crossbeams strong even if it means throwing the beer overboard to save weight.

Wharram crossbeams may be excessively strong or even excessively heavy, but offshore in a Force 10 storm with a nearby weather buoy measuring 32 foot waves and higher with 55 knots of wind sustained, we were glad to have all that reliable and well tested strength aboard with us for the two and a half days we were hove to between Madiera and Canaries. We had no damage at all.

We wish you the best of luck.

Ann and Nev

[Thom delForge]

Funny thing happened from the way to this forum -- I thought I had responded back regarding Ann and Nev's comment on my composite beams -- my reply seems to have disappeared? I take their concern with great respect for their opinion. I do; however, think these beams are much stronger than the original wood beams. They are certainly more expensive (but rebuilding the my wood beams twice has a price as well). There is also a slightly greater flex, due to the material. I have overbuilt these beams for the reasons Ann and Nev suggest. The design is similar to a truss. I used the same overall dimensions and form plus two layers of 17 oz. bio-directional glass cloth with 9 oz. gussets at all joints. Additional wraps of 17 oz. at all lashing points. These are pretty tough -- but weigh no more than 60 lb.

[Eric Harris]

Thank you both for the responses. I am also very concerned about strength but do think that well designed composite should be as strong as the per plans timber version. My rebuild is close to finished now so it will be timber for the moment. I plan to build new composite ones (after more research) slowly once the boat os floating on her keels again.

I really appreciate your willingness to share the details Thom, details are hard to get on the forums. Now I can research and calculate for myself from a good starting point. Have you had a chance to put the beams through their paces yet? How do they perform?

Thanks for the comments and inspiration - folks like yourselves keep the dream and energy up.

eric

[Jesse Walker]

Hi Eric. I live in SA aswell and am very keen on Wharram's. I'm in PE, is there any chance if I am up that way that I could look at your boat, i would really like to see a tiki 31. Wharram's are hard to find in SA, or maybe I have just been looking in the wrong places.

Eric Harris said:

Hello Thom

I am new to the forum but have been reading your threads with interest. I bought Tiki 31 (#97), sailed her from Cape Infanta (Southern tip of africa) to my home in East London (400m east.) Sailed around a bit and then put her on the hard for 'maintenance'. That was a while ago!

I have had to almost completely rebuild the beams! Finding timber has been difficult and the process is very time consuming as you know. Your composite beams look a much better solution. I was hoping you would say a bit more about the actual lay-up you used on the beams. I know people are often reluctant to do this because of the perceived responsibility but I would be very grateful. while I dont know much about the structural features of beams I have fixed and worked on plenty of surfboards, surf-skis and yachts to feel like I can lay up a composite if I am told the specs. I have tried to get wharram to sell me plans for a composite beam but have had no response.

I look forward to your response.

P.S. Ever though of dong the masts the same way?

Eric

[Eric Harris]

Hi Jesse

No problem - she is in pieces at the moment but you are welcome to have a look. I am in Chintsa East, about 30km North of East London. I work offshore so I am not always around but drop me a line if you are going to be in the area.

Lots of wharrams in Durban and Richards Bay by the way. DOnt know if you are supposed to hand out personal contact details on the forum so will watch the thread. Off to Qatar tomorrow, back in about 10 days to two weeks.

Eric

Jesse Walker said:

Hi Eric. I live in SA aswell and am very keen on Wharram's. I'm in PE, is there any chance if I am up that way that I could look at your boat, i would really like to see a tiki 31. Wharram's are hard to find in SA, or maybe I have just been looking in the wrong places.

Eric Harris said:

Hello Thom

I am new to the forum but have been reading your threads with interest. I bought Tiki 31 (#97), sailed her from Cape Infanta (Southern tip of africa) to my home in East London (400m east.) Sailed around a bit and then put her on the hard for 'maintenance'. That was a while ago!

I have had to almost completely rebuild the beams! Finding timber has been difficult and the process is very time consuming as you know. Your composite beams look a much better solution. I was hoping you would say a bit more about the actual lay-up you used on the beams. I know people are often reluctant to do this because of the perceived responsibility but I would be very grateful. while I dont know much about the structural features of beams I have fixed and worked on plenty of surfboards, surf-skis and yachts to feel like I can lay up a composite if I am told the specs. I have tried to get wharram to sell me plans for a composite beam but have had no response.

I look forward to your response.

P.S. Ever though of dong the masts the same way?

Eric

[boatsmith]

Our last three boats have been built with composite beams. They are lighter than the wooden beams and will never rot. I believe they are at least as strong as the wooden beams , but I have not had them engineered. These have been for the Tiki 8ms(26'). When we put composite beams on a a larger boat I will have an engineer run the calcs and verify that my scantlings are in order. Here are some photos of the beams being built. They are made of Divinycell foam and the tops and bottoms have two layers of 3/4 oz CSM, a layer of 24 oz unidirectional glass fibers and a layer of 10 oz biaxial carbon. The fwd and aft faces have twice this. Then we laminate on flanges to support the cockpit and deck.

[Lee Dilkes]

Hi all,
I'm about to start a Tiki 26 and am quite taken by the idea of composite beams.
Have been working professionally with glass and timber boats for years so would love to see more detail.

Cheers
Lee