Large solar array support beams

[s/v Jedi]

Originally Posted by Chotu

It’s pretty clear from your pictures that I just saw how the old ones broke.

first, these things are up in the air with nothing below them so they are acting as sails. Second, they are cantilevered sails. The force on those original brackets would be incredible in any kind of wind.

I can definitely see why you are doing the slider now. It will reduce the sail area.

maybe some flexible solar panels on a roller Furler? (A joke)

I think no matter what you do on this laminate the trickiest part is the mounting to that very narrow arch.

is there a way to use steel and reconfigure the top face of that arch in such a way that it will take the force of the solar panels?

I know you are not looking for other ideas but I thought I would just throw that one out there because that would be a foolproof way to do it. Then you could just mount the solar panels directly to stainless steel.

The laminate thicknesses I gave at 1/4 inch and the specifications for the type (biax and biax/uni) would work if glass. If you are using carbon, then all you need to do is find a translation between the two. Those don’t really exist but you might find enough examples that you can see a trend

The surface area is horizontal so actually the wind load is minimal unless it comes from a cat5 hurricane and manages to get under the panels from behind. Still, the dinghy would block most of that…

The top of the arch is easily strong enough to hold these support beams. I think one could lift the whole boat from this arch unless the whole aft end of the boat gets ripped off

For doing a test, I think that 3/16” glass would be enough. Carbon fiber gives some extra strength, but mostly extra stiffness in the range of 20%.
Uni directional carbon fiber would work very well on the top of the beams, which are in tension. I’m not so sure that it works as good in compression but will find out. They sell very nice uni directional tape 1.6” wide for surf board stringers which should work well.
Looks like I’m gonna do the testing on a bench, hanging weights off the tip of the beam

[ohdrinkboy]

I believe Mads on SailLife (youtube channel) built something similar for his solar array. You might want to check his video or contact him.

[wholybee]

Originally Posted by s/v Jedi

I would love to have been the one to come up with this but I think it has been the overland community who put these cassettes on the roof of their vehicles.

It is very easy to get the sliders. Here are the 44” sliders on my parts list: https://www.amazon.com/VADANIA-Drawe.../dp/B08147TPN2

I have used similar ones for our fridge and freezer boxes before and they come up to 500lbs capacity or even more.

"Alloy Steel"?
That might work in a fridge or freezer, but outside exposed to salt? Zinc plated probably? And the bearings bare steel? I would think these would require a lot of maintenance, spraying with fresh water, applying corrosion x, etc.

[BG305]

Originally Posted by ohdrinkboy

I believe Mads on SailLife (youtube channel) built something similar for his solar array. You might want to check his video or contact him.

I think i saw this one the other day on YouTube. I will see if i can find it in the history and post the link. Underway or in the marina he has them nested together and when he is at anchor they are spread out.

[s/v Jedi]

Originally Posted by ohdrinkboy

I believe Mads on SailLife (youtube channel) built something similar for his solar array. You might want to check his video or contact him.

Yes, but his setup is kind of a first generation for him and he is using small panels iirc. The sliding mechanism is very simple, just like a drawer. I can’t use the locking sliders because I can’t reach the handles to unlock but maybe if I hang some small pull-cords on them it would work. It adds to the complexity of the mechanism and I may just use a pin or lashing to hold them open/closed.

[s/v Jedi]

Originally Posted by wholybee

"Alloy Steel"?
That might work in a fridge or freezer, but outside exposed to salt? Zinc plated probably? And the bearings bare steel? I would think these would require a lot of maintenance, spraying with fresh water, applying corrosion x, etc.

The sliders are not stainless steel but they do have corrosion protection because they are designed for pull-outs in RV’s. I have these already in our motorhome for 8 years and they stay in remarkably good condition.
For use on a boat I spray them with Boeshield T9 which works very well on other plain steel items I used.

I’m not sure which sliders I linked to… it’s supposed to be the ones with pictures of RV’s.

[s/v Jedi]

I have been reading a lot and found that for the shape I am planning to use, it’s only possible to come to a prediction and actual testing will have to be done to confirm.

I also see that in the vertical surfaces, the center is neutral (not in tension and not in compression) and is often removed. I am now thinking to use narrow unidirectional tape and lay them along the lines that experience the larger forces. I will probably be using some fiberglass layers with carbon fiber tapes in between as reinforcements. This insulates the carbon fiber from any metals touching these supports to prevent corrosion.

It now occurs to me that this is a bit like how they make those “tape drive” sails.

Testing is gonna be fun… I will document this.

[markxengineerin]

I didn't read the whole thread, but I'd be very concerned about the slides surviving for very long, based on what happens to a bicycle left on deck. The bearings, sprockets, etc become salt encrusted, rusted, dried out and inoperable in short order, measured in days not years. The same bike on a RV roof would fare much better, so it's not a great comparison. I don't see a spray being effective in fixing the problem, or at the minimum, you'd be using a ton of it and very inconvenient and messy maintenance item.

I also have a goal of "slide out" solar panels to mount under the fixed 660 watts I have now on a narrow canoe stern, but I'm planning to use the flexible type for the ones that pivot /slide out, and a mechanism that doesn't need bearings because it's so light weight. Materials will be the conventional stainless steel, aluminum, fiberglass, carbon fiber- things that have some history of surviving on deck.

[BG305]

Originally Posted by s/v Jedi

I would love to have been the one to come up with this but I think it has been the overland community who put these cassettes on the roof of their vehicles.

It is very easy to get the sliders. Here are the 44” sliders on my parts list: https://www.amazon.com/VADANIA-Drawe.../dp/B08147TPN2

I have used similar ones for our fridge and freezer boxes before and they come up to 500lbs capacity or even more.

I was looking at this supplier for the sliders.

https://gsfslides.com/applications/m...non-corrosive/

[catsketcher]

Don't go composite,

Jedi - I wouldn't use foam in that situation. It looks like a high load case where you will be using lots of fastenings to mount your sliders. I don't know if Coosa board is dense enough to take the point load of fasteners without needing coring out and replacement with HD inserts.

I spent too much of my life building folding catamarans, with parts that pivot, swing and roll. I have a fore beam that is under load when retracting that uses rollers that are glassed in to the board the beam runs on. Your stainless system could easily have rollers attached with small lugs under your existing panels. The new panels (buy ones smaller than the existing ones) could have a piece of alloy RHS bolted on to the sides. There could be rollers at the outer edges of the existing frame (Pointing upwards) that take the downward loading of the panel RHS, especially as it extends.

Orientated sideways, I would bolt alloy C section. Two of these run right across the arch, the fore C open aft and the aft open forward. At the inner end of each panel an acetal wheel runs inside the C channel. You would need some extra bury so that the cantilverer is not excessive.

I would caution trying to make things roll out of composite. It becomes very tricky to get epoxy to align items perfectly. I have had better luck with using stock alloy sections. I think two alloy C channels facing sideways, a roller under the panel at the outer end and a larger roller inside the C channel at the panel's inner end would be easy to fabricate, cheaper by far, much quicker and slide very easily. My advice after making two composite folding cats - stay away from fine tolerance matching composite parts.

(Of course my solar arch is composite, but it doesn't slide)

cheers

Phil

[Lee Jerry]

Originally Posted by s/v Jedi

No, that wouldn’t work at all because only with angles can you make attachments underneath the sliding panel. The options you list add to the overall size of the construction because they go on the outside of the panels, adding to the 2-meter length.

Channel is essentially two angles, one on top of the other. No additional size at all.
I-beam is like four angles, would add a little bit (less than half of width).
RHS is four channels in a different arrangement, which would add size.

But all three are "better" shapes from a strength perspective.

The sketch of the support shows the three tubes and how it would attach to them. They even show the small holes to allow the Dyneema lashings to fasten it. The 3rd tube sits under the outboard/aft tube. See attached pictures.

There is a 4th tube but that is a moving part, namely the hoist arm of the dinghy and it comes up to just under this 3rd tube and it is the reason I can’t go lower for supports.

I see the three tubes in your sketch now.

Reading this, it feels like you turn things around. How can one support see 50kg when two supports together carry a 50kg load. The outboard tip of each support carries 12.5kg and the inboard (big) end of each support carries 12.5kg, for a total of 25kg per support.

With the hinge point at 50cm or 25% of the beam length, the force trying to turn around that hinge is 75% (18.75kg) of the total because the other 25% (6.25kg) is counterweight.

No. The beam is hinging (balancing) on the outboard arch support; the moments (not just force) on either side have to be equal. So although the weights at the ends are equal (12.5 kg) the distances are not. Therefore the reaction at the inboard arch has to pull down to make the (total) moment on that side equal the other side. This means 25 kg (@ 50cm) pulling down on the beam. The reaction at the outboard arch then has to push against all three of these forces (not just the two weights) and therefore is 50 kg.

I see how you describe the reaction forces on the arch tubes, but you are using numbers for two supports that carry the cassette added together, while I describe one support.
Also, you omit the third tube, which acts as the attachment point for the lower end of the support, like a strut. My previous array was carried by an aluminium frame and it had the struts attached there to form the triangle. Now with this design it becomes one part and a big portion of the weight is transferred to this 3rd tube, relieving compression force on the outboard (aft) tube.

No, I am talking about a single beam.

And yes, as I said I am ignoring the third tube for now. I don't think it will add as much as you think, but we can get into it in a bit if you want.

During hurricane Isaias we were anchored and experienced 70kts winds for sustained periods. During hurricane Ian we only saw 50kts winds, but we were hauled out, adding 2 meters height to the array and not turning with the bow towards the wind. We ended up with the wind coming from behind and up under the array. This caused heavy aluminum fittings to be torn apart until ripped all four aft attachments, resulting in the whole array turning over the two from supports and slamming upside down onto the mizzen boom.

My mistake was not even considering all this because the array did fine in all kinds of heavy weather or I could have prevented this with just two small Dyneema strap-down lines from the outboard corners down to the swimming platform. I won’t make that mistake again but I consider us very fortunate considering how many boats got totally destroyed by Ian and that the storm came right over us.

I find it...not sure what the best word is...ironic, humorous, frustrating, whatever, that you dismissed when I suggested that the wind loads were more demanding than the gravitational loads when your previous array was destroyed by wind. Also, if Chotu and I are saying the same / similar thing, then maybe there's something there.

Why the poke? I get the feeling you are here to entertain yourself rather than help me. If you would follow my posts here on CF you will find that I try to help as many members as I can for subjects I am knowledgeable. I have worked with fiberglass for 40 years incl. building my first sailboat, surf board etc. but never had to design a fiberglass layup schedule, which is why I made this post.

The poke was in response to what I perceived as a slight. If I misinterpreted that then I apologize. I try to help too, when I can. I think I can do that here, if you want.

I am not interested in comments like “use two panels instead of four” simply because I need four, not two, because if that would have been the case, I would have selected two panels, not four.

I didn't say that, or at least I didn't mean to. What I think I said (or meant to say) was use a 4m x 1m arrangement rather that 2m x 2m for the fixed panels. This was before you described your narrow beam at the stern.

Now I have no idea of your knowledge and if you even want to help me or are just fooling around making fun of me. I must say that I keep providing info as much for others that I hope will contribute, than I have hope it will trigger helpful info/data from you. I already told you that I have zero experience with designing layup schedules so there really is no need to establish your superiority on this subject other than overwhelming me/us with your expert data

I'm trying to help. You do not seem (to me) very receptive to it (from me).

The problem is that it is not as simple as just "designing a layup schedule." There are lots of variables, some of which I started to (try to) address, and some others we haven't even gotten to yet. The latter include things like shape and dimensions of the support beam, carbon you want to use (there are options, not all are equal) and the layup process you intend to use.

Originally Posted by s/v Jedi

The surface area is horizontal so actually the wind load is minimal unless it comes from a cat5 hurricane and manages to get under the panels from behind. Still, the dinghy would block most of that...

If you look at the first (of the four) picture you posted above, the one with the flag in it, you will see the wind getting under the panels.

(If I wanted to be snarky, I would point out that some of those horizontal surfaces are called "wings" and can lift planes into the air. But I don't want to antagonize, so I won't say that. )

Originally Posted by s/v Jedi

I have been reading a lot and found that for the shape I am planning to use, it’s only possible to come to a prediction and actual testing will have to be done to confirm.

I also see that in the vertical surfaces, the center is neutral (not in tension and not in compression) and is often removed. I am now thinking to use narrow unidirectional tape and lay them along the lines that experience the larger forces. I will probably be using some fiberglass layers with carbon fiber tapes in between as reinforcements. This insulates the carbon fiber from any metals touching these supports to prevent corrosion.

The web (vertical surfaces) is still needed for shear resistance (parallel to the horizontal faces or flanges). It is OK to put some (small) holes near the neutral axis.

I recommend against intermingly the glass and carbon. The stronger / stiffer carbon will be taking essentially all of the load any, with the glass providing very little, so just leave the glass out.

[RaymondR]

We're trying to save you from a world of misery with that sticky, yucky stuff Jedi.

The upper sketch is a side elevation of a cantilever beam fabricated from two C sections of 3mm aluminium sheet and bent up on a metal shop bender.

The lower RHS sketch is the end elevation of same showing the upper C section with the cam roller mounted sliding panel in red and the lower fixed panel (also in red) mounted in the lower C section (fixings and spacers not shown)

You could go 4 mm if you can find a shop with a bender that will handle it.

After tack welding the C sections together and drilling for all the fastenings you could give it a polish and have the two beams anodized.

[Joli]

Possibly reach out to Dragon Plate, they may be able to offer you guidance on your plans.

https://dragonplate.com/

[s/v Jedi]

Originally Posted by markxengineerin

I didn't read the whole thread, but I'd be very concerned about the slides surviving for very long, based on what happens to a bicycle left on deck. The bearings, sprockets, etc become salt encrusted, rusted, dried out and inoperable in short order, measured in days not years. The same bike on a RV roof would fare much better, so it's not a great comparison. I don't see a spray being effective in fixing the problem, or at the minimum, you'd be using a ton of it and very inconvenient and messy maintenance item.

I also have a goal of "slide out" solar panels to mount under the fixed 660 watts I have now on a narrow canoe stern, but I'm planning to use the flexible type for the ones that pivot /slide out, and a mechanism that doesn't need bearings because it's so light weight. Materials will be the conventional stainless steel, aluminum, fiberglass, carbon fiber- things that have some history of surviving on deck.

Yes, it will be a great experiment. When we were in Central America, we experienced a lot of salt buildup everywhere and I would have been very pessimistic as well, but now that we are in Florida and the Bahamas, salt buildup is non existent and I think we will be okay.

I also plan to build non-metal sliders, but I guess it’s gonna be up to me so it’ll take a while. It’s not easy to build full extension sliders, which requires three parts.

You can simply use plastic bearing balls; there is no need to use anything other than a high performance panel… why take all this trouble for a short lived panel when you worry about lifespan of sliders with a panel that lasts 20 years?!

[s/v Jedi]

Originally Posted by BG305

I was looking at this supplier for the sliders.

https://gsfslides.com/applications/m...non-corrosive/

Thank you, this is exactly what is needed. Here is a model that will work: https://gsf-promounts.com/product/ad...non-corrosive/

It is 30mm thick while the steel ones are only 19mm but I think that cassettes being 22mm longer is well worth it to get corrosion-free sliders. And they don’t break the bank!