Large solar array support beams

[s/v Jedi]

Originally Posted by team karst

Sorry; can't believe plywood is in the discussion. I bought a sportfish one time that had freshly made plywood cored fiberglass flooring for the marlin tower. Within a year of exposure, I knew that someday I had to rebuild them. Yep, barely 2 years from layout, they exploded with rot. I replaced with 1" what I though was WesCore (?) and one layer biax top and bottom. This flooring was supported by Al angle shapes in a 3 x 6' rectangle, and two of those side by side. I also made a deck walkway about 5' long and 12" wide, supported ONLY on its long side/ends. Same technique, only I used Divinycell H60 (the green one) for coring. It supported even a 300# crew member. The panel weighed 5 to 10 lbs. edit: I did have a 4" vertical thin blade on bottom side to reduce deflection..
Not certain if I used 2x or 1x on the biax. Seemed like new a decade later, always exposed to SF weather. NO plywood in the rain. Hard to imagine how to keep out water....

We will see but I am 100% sure because this isn’t a floor; these are carbon fiber epoxy composite cantilevered beams with zero skin penetrations. Moisture simply can’t get in. On the choice for douglas fir, Google tells me:

Douglas fir is a traditional boat building timber as it comes in long lengths and sometimes can be virtually knot free. It is very strong for its weight and is therefore used for both heavy constructional purposes as well as being suitable for masts and spars.

[s/v Jedi]

Originally Posted by Senojev

Did you notice that the sliders you linked to were just galvanized steel? In a saltwater environment, they will not hold up beyond a few months. If you search, you can find full 316 SS full extension sliders. Not cheap but will last.

Yes, I did notice Can you post a link to the sliders you found? Note that I need 44” or longer ones.

I do believe I will get many years of service out of these, because all the exterior surfaces will be coated either with paint or a tape (need to isolate different metals) and the interior bearings and bearing races I will regularly address with rinsing and Boeshield T9.

I have similar sliders in use inside the boat for the past 4 years and they look like new without any additional measures.

I looked at aluminum sliders but the shipping coasts alone were $700, then they were twice as thick and cost $350 each ($700 per pair).

[s/v Jedi]

I just checked materials I already have at hand and was happy to find 16’ of 50” wide 1708 which is enough for the beams and the cassettes.

This material is a 17 ounce 45/45 degree non-woven fiberglass biaxial on top of an 8 ounce random strand mat and all that stitched together. It is used for the core of the beam (in between the plywood layers) as well as for the skin of the angle profiles that form the panel cassettes.

There’s also a 2” wide woven 6 ounce tape that I use for covering the edges (or tabbing light parts). This is cheap off Amazon and works very well.

For epoxy resin I am using the good old 5:1 resin with slow cure hardener. At the moment I use Totalboat because it comes in plastic containers that don’t rust.

I will be painting these parts with Awlgrip. Grey 545 primer and original black topcoat. I still don’t understand why people use clearcoat on carbon fiber.

[Lee Jerry]

Originally Posted by s/v Jedi

After a glorious Atlantic crossing aboard the Queen Mary II, we arrived back in Florida yesterday and this project is on

I'd like to hear more about this.

Have you done other cruises, and if so, how did this compare?

We've done three cruises post-Covid on two different lines (not Cunard), and would have to say that the quality of both the food and the service has dropped, substantially in some cases. Can you confirm that too?

Also, just fyi, one of ours was an east-bound trans-Atlantic (re-positioning), FL to Italy. The time changes were much more tiring than we expected. Not sure it was better than flying in that respect. Losing an hour 2 out of 3 nights repeatedly really messed with our sleep schedule.

Originally Posted by s/v Jedi

After actually ordering materials, this is the revised plan;

The beams will be 210cm long which is just under 7’. It will have a composite plywood (need one sheet $113.-) with fiberglass core and carbon fiber skin.

Core: I have selected a 3/4” thick marine grade Douglas Fir plywood and 1708 fiberglass. There are three layers of plywood with two layers of 1708 in between. I plan to use some locating dowels so that things don’t shift during clamping it all down with epoxy resin.
I will first wet out the fiberglass (on plastic) and plywood surfaces, then add a little microfiber filler to add some glue to the plywood surfaces so any imperfections are filled. Then put it all together, insert locating dowels and clamp down.

The four long side corners get a 1/2” radius roundover to help the carbon fiber conform to the shape. I will keep the core long so I can cut it to exact size, getting rid of the carbon edges etc.

This core will have at least 3 times the shear strength of a Coosa Board core. The Douglas Fir alone is 2.5 times as strong as the Coosa Board.

After all the cutting, milling and sanding, I plan to seal the core with the penetrating epoxy, then sand any pooling epoxy off after cure.

With these three cores I will do a first fitting aboard so see where the struts end up, which angle these make with the beam etc. This allows me to make the fiberglass blocks that help mount the beams.

Carbon fiber skin: the supplier I used didn’t have the 12 ounce unidirectional I wanted, but did have nice 9 ounce, 12” wide unidirectional. This means I need ine additional layer, resulting in the following schedule:

1. 203gsm plain weave (one cloth piece per layer)
2. 203gsm plain weave (one piece per layer)
3. 193gsm biaxial 45/45 (single piece for two layers)
4. 305gsm unidirectional top and bottom only
5. 193gsm biaxial 45/45 (same piece as layer 3)
6. 305gsm unidirectional top and bottom only
7. 203gsm plain weave (single piece for two layers)
8. 305gsm unidirectional top and bottom only
9. 203gsm plain weave (same piece as layer 7)

Total 1,198gsm sides and 2,113gsm top and bottom.

I will make a jig to turn the core like a rotisserie, which I can use both for carbon fiber layup as well as the paint job.

Sounds like you have things well in hand. And you already know this, but a couple comments on the highlighted items, which may have been a little ambiguous:

For the first two, primary bonds are better than secondary bonds. If you can, wet out and glue only the flat mating surfaces of the core only and let cure and described, leaving the outer surfaces "dry." You could then do your fitting (or use a separate template). I would then put in your jig and wet out the outer surfaces (with a microfiber step if required) and complete the entire carbon fabrication in one continuous process if possible.

Of course you will finish off with some type of end caps to fully encapsulate the core.

[s/v Jedi]

Originally Posted by Lee Jerry

I'd like to hear more about this.

Have you done other cruises, and if so, how did this compare?

We've done three cruises post-Covid on two different lines (not Cunard), and would have to say that the quality of both the food and the service has dropped, substantially in some cases. Can you confirm that too?

Also, just fyi, one of ours was an east-bound trans-Atlantic (re-positioning), FL to Italy. The time changes were much more tiring than we expected. Not sure it was better than flying in that respect. Losing an hour 2 out of 3 nights repeatedly really messed with our sleep schedule.

Sounds like you have things well in hand. And you already know this, but a couple comments on the highlighted items, which may have been a little ambiguous:

For the first two, primary bonds are better than secondary bonds. If you can, wet out and glue only the flat mating surfaces of the core only and let cure and described, leaving the outer surfaces "dry." You could then do your fitting (or use a separate template). I would then put in your jig and wet out the outer surfaces (with a microfiber step if required) and complete the entire carbon fabrication in one continuous process if possible.

Of course you will finish off with some type of end caps to fully encapsulate the core.

We only do Atlantic crossings and have done so many that I lost count years ago. I like Cunard best, especially the west bound in January that sets of their world cruises as they stop Transatlantic service due to inclement weather. We get on in Southampton and off in Ft Lauderdale, a car drive away from our boat in Canaveral. Service aboard the QM2 isn’t as good as before Covid but it beats everything I know of in the US. Very good, but you must select late seating for dinner. We also ask for English and American people at a 6-person table. Best thing is the people you meet with those filters set , very different than all other ships.

We also like Holland America Line. We went from Ft Lauderdale to Rotterdam on our Eastbound crossing (we use ships rather than planes whenever we can). Of course we’re Dutch so we appreciate many of the Dutch things aboard as well as many Dutch passengers, a bunch of which we know and meet again and again aboard the m/s Rotterdam
What sets HAL apart is their BB King Blues cafe and their Rolling Stones rock lounge. Every night.
I prefer open seating with HAL and ask for large shared tables.

With late seating and time changes during the night we find it very good, of course west bound better than eastbound.

Both these ships now have Starlink which is nice.

I just cut the Douglas Fir plywood for the core. Smells nice :-) I will laminate the three pieces with 1708 biaxial fiberglass in between to improve shear strength like CoosaBoard does. After full cure I will cut these cores height to twice the thickness, for which I have enough material as everything is cut a little larger. I will also cut the lengths to 7’6” to get clean ends for the jig and to stay within the 8’ length of the flat and level bench I have. The carbon fiber won’t go all the way to the ends so I have room to write markers etc. during the layup.

I decided again to not vacuum bag because of the jig which allows easy wrapping so I’ll use peel ply, some absorbing paper, then that wrapping plastic for packaging to clamp it down. All the epoxy and carbon will go on in one operation, will be exciting but we have done so much fiberglass work that I’m confident. Slow hardener and air conditioning also helps haha.

Attached a picture of $600 worth of carbon fiber materials

[s/v Jedi]

Finished cutting the plywood for the three cores. Marked and clamped them, then drilled 1/4” holes near the ends for a locating dowel. These ends are later cut off.
I ended up with one piece that had a repair on the face side so quality is only so-so for a marine plywood but overall I’m very happy with it and that one board goes into the center so that’s fine. With tax I had to pay $120 for that one sheet of plywood lol

Now it’s cutting fiberglass for this composite core. I should be gluing and clamping hopefully the first one today

[s/v Jedi]

6x 1708 fiberglass 7-1/2’ x 6” wide for the laminations… done!

I can still move my fingers because of using the electric shears instead of manual. This 17 ounce biax is sturdy!

[s/v Jedi]

First core laminated. I had forgotten how difficult 1708 wets out. I bet the second one will be quicker.

I used TotalBoat 5:1 epoxy with slow hardener and their pump set, using a total of 24 pumps for this. As visible in the picture, a bunch of resin is squeezed out during clamping and two pumps are in the roller so 20 pumps left in the laminate.

The alignment dowels were the best thing, it was so easy to clamp this.

Tomorrow I will put the beam on a sled for the table saw to get the first clean edge, then turn around and cut the other edge, then chop off the ends, use the router with round-over bit to round the four long corners then end with gluing up the second beam.

I used a West System epoxy roller cover, cut in half because it’s too big for these beams, as well as an aluminum finned roller for squeezing air and excess resin out.

[s/v Jedi]

All cleaned up, cut to size and ran the router with 1/2” radius roundover bit along the edges.

The thickness of three layers plywood with fiberglass in between came to exactly 60mm which was totally unexpected. The detail picture shows the fiberglass layers in between the plywood.

The height was cut to 120mm and now I only have to cut a piece of each end off to make it exactly 7-1/2 feet long for the rotisserie jig for wrapping the carbon fiber on.

I plan to glue up the second one this afternoon.

[s/v Jedi]

This morning the second core was cured. I switched to the assembly table in the “dust free” garage as it became available. Again lots of excess resin but I needed the amount for properly wetting out the fiberglass so I don’t really see it as waste.

The excess fiberglass sticking out is for multiple reasons: the cut edge can fray a bit so you make sure it isn’t on the piece you laminate. Also, the cut edge will never lay flat so you don’t want to use it anyway. Last but not least, it is supposed to hold the excess resin that is squeezed out but obviously I had too much squeeze out for that to be 100% successful.

Note that the plywood strips are also wider than what I need. From each side more than 1/4” needs to be cut off, which eliminates the edges and all the mess in one go.

Today will be easy as I only laminate the third beam so I can do the cuts on the table saw for both beams, minimizing the saw adjustments.

[s/v Jedi]

Here’s how we use the sled on the table saw. This replaces a jointer for which I have no room and also I use this for scarf jointing long boards. It’s just two pieces of plywood screwed together in an angle, but it’s straight.

The fence on the saw is set so that the sled fits in between exactly. Now the piece that needs a clean, straight edge is put on top sticking out what you want cut off. Then I screw it down at both ends where also the positioning dowels are visible and what will be cut off later.

With the first beam I popped the 20A breaker so now I am running it through twice with the blade cutting through one fiberglass layer per pass. This isn’t the sharpest blade because the fiberglass ruins blades quick and when a woodworking blade dulls a bit, it becomes a fiberglass blade

I use a clamp halfway to keep things tight as I don’t want any screws there. I simply remove it while sawing. We use a roller stand to carry the sled beyond the table saw.

After this you have a straight side so you can cut the other side without the sled.

[s/v Jedi]

Test results are in. The core weighs 8.8kg for a 210cm length.

With free overhang of 1 meter and the weight 15cm from the end, which is about where the aft end of our panels will rest, we found only 0.1mm deflection with 10kg weight and 0.4mm with 25kg weight. I couldn’t find anything suitable to hang off it for 30kg but this is more than enough testing for the core alone. Let’s say we have 0.5mm deflection with just the core, which is amazing. That Douglas Fir in combination with the 1708 fiberglass as a laminate is a beast.

So I expect zero deflection with the finished beams for static load and only a couple mm with dynamic loading when we’re sailing. When it is rough weather, the solar panels will be in a stored position, which reduces loading dramatically and reduces size to half.

[s/v Jedi]

After some work on building the cassettes for the panels that go on top of the beams, we finished the final prep of the beam cores before wrapping them in carbon fiber.

We put the sides that we added penetrating epoxy to in order to stabilize the wood, through the thickness planer, then some sanding before I took the router along the roundover corners once more. This worked perfectly, no splintering at all and the cores are ready. Dimensions didn’t change significantly, about 3/64”

[s/v Jedi]

The rotisserie jig is finished and we’re ready to start cutting the carbon fiber!

[s/v Jedi]

Cutting carbon fiber. 18 pieces of uni-directional, long live electric scissors