Large solar array support beams

[s/v Jedi]

Originally Posted by 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

Hi Phil, I went with aluminium the last time and it failed. It was rather big and heavy duty and ai wouldn’t want bigger components. For stainless steel, we are in the process of trying to get rid of it as much as possible… plus and I am ashamed to say this… I can’t weld. In the army, my instructor took the stick welder out of my hands and told me never to touch one again

I also found that I can make anything out of composite and make it as however strong it needs to be. My last project was our boom gallows, for which I did a 20mm solid glass layup and it went smooth as if I make such things all the time

The foam for the supporting beams/davits: these do not get any metal fasteners. They are shaped to engage three stainless steel tubes from my arch and will fasten to them with Dyneema lashings. One calculation I did manage to do was the static load on the most heavily loaded lashing and that is 75kg. I will use 1/8” diameter Spyderline for these and one wrap holds a full ton so no worries there.

Then the cassettes that mount on top will be mounted with these lashings as well.

Then for the cassettes, I think the word “cassettes” is too big, because it’s just two angle profile end rails with nothing but the solar panels in between, so alignment is automatically perfect. The only thing that must be really precise is the spacers for the top panel, which must be exactly as thick as the sliders for the bottom panel.
For mounting the sliders, I could use screws into the fiberglass skin and Coosa core (Coosa will hold screws) but will probably use flathead machine screws with hex drive going through the rails from the outside, with regular nuts and high strength thread locker on the inside. This allows me to use long screws for the top panel that fasten the panel as well as the spacer, and short ones to mount the sliders…. which will probably need to be cut to length after fastening to not interfere with the mechanism.

I could easily make the cassettes with aluminum angle profile and even have some 1/4” thick at hand, but it isn’t anodized and I know it’s gonna be a problem to keep paint on it with the fasteners etc.

For the sliders, you can not achieve full extension with 2-part sliders. It really isn’t easy to make these, but someone just posted a source for corrosion-free full extension sliders that are available long enough so I think that one is tackled

[s/v Jedi]

Originally Posted by Lee Jerry

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.

I agree that they are all stronger, but they don’t work well in this application because the cassettes need to mount on top of the beams, while the whole underside is a moving part, leaving only the very inboard and outboard sides to attach them. If that is the vertical side of the angle, then the horizontal side can go underneath the sliding part and the only piece sticking out is the thickness of the vertical part of the angle.

If I take a square tube, the whole tube sticks out. If I take an I-beam, the top flange will shade the top panel and half of the top and bottom flanges stick out.

Channel… half an I-beam so all of it sticking out or shading the top panel depending on how you mount it.

I really don’t understand why you focus so much on these end rails of the cassettes… they are low strength, simple and I have no questions about their construction because I made similar parts many times before, with much higher loads too.

[s/v Jedi]

Originally Posted by Lee Jerry

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.

We’re talking about different things. You mean the compression force at the hinge point, which is 25% of the distance from the inboard end of the beam. This force doesn’t worry me one second because the only risk here is the 1.5” diameter tube crushing the laminate which is very easy to deal with, especially considering the strut to the 3rd tube will take a large portion of that force. On the previous construction I had to shorten the struts because they took all the force which I noticed when I could move the fitting on the upper tube side to side, showing that a perfect fit is needed to share the load.

It is the long arm to the outboard end that supports that 12.5kg that worries me, not just for strength but also deflection. I considered using aluminium T-slot 80/20 structural framing, which is anodized, and they provide a calculator that showed more deflection than I wanted, meaning I need the struts like the previous construction and there are no good fittings for mounting that.

To do any calculations on the shape I have in my sketch, I have to divide it into as many sections as possible and seeing the spreadsheets for that is a big turn-off. I’m not gonna go through that, so my new plan is to calculate for a straight rectangular profile cantilevered beam with a hinge point plus a strut of the same profile supporting it at 60% outboard. This is how the previous frame was.

I can cheat by comparing tensile strength and flex modulus with an aluminium beam that they provide calculators for.

Even though I am a lifetime behind mechanical engineers, I am learning a lot very quickly in this process. I am now considering longer slots cut into these beams to make it look more like that cantilevered beam with a supporting strut, because this allows me to get much more fibers in optimal orientation around the edges of those slots by using unidirectional carbon fiber tape all around it, instead of it being core material with just a skin with fibers not oriented very well.

My idea about the use of fiberglass in combination with carbon fiber: I can put a skin of 1708 on both sides of the foam core before even cutting it, giving me a nice base to work with and fibers in the diagonal directions. Also, when I finish with a layer of say 6-ounce cloth, I have isolated the carbon fiber, preventing corrosion where it will touch metals.
The 1708 will contribute strength and the 6-ounce cloth just a finish non-conducting surface.

My next step is coming up with more precise measurements, because the panels are actually a bit larger and the tubes of the arch are closer, but the panels can come forward of the arch a bit too and all the small differences can add up to significant numbers.

[s/v Jedi]

About the pictures of the previous array: they have the aft end of the panels hanging over freely beyond the aft end if the frame. This unsupported end is 40% of the length of the panel and it looks like impossible, especially when considering the manufacturer mounting and supporting frame requirements.

But looks are deceiving. When you check the picture where I test the attachment with U-bolts and King Starboard spacers I made, you will see bare aluminium inside the panel frame. This is actually a 3/16” thick, 1” x 1” aluminium angle profile running the full length of the panels, attached with aluminium rivets along the length. So there’s actually frame elements hidden from view inside the solar panel frame.

[s/v Jedi]

Originally Posted by 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.

It really upsets me that I can’t weld. I am very proficient with soldering and am thinking of just buying a portable TIG welder and start practicing.

But even then, I still need to find a good anodizing service and the last time I tried, I didn’t even get replies to my inquiries… I’m afraid I’m gonna skip aluminum this time… except for the sliders

[s/v Jedi]

Originally Posted by Joli

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

https://dragonplate.com/

Yes, they are the goto site when I think of carbon fiber frames. Do you know the YoungBarnacles YouTube channel? That guy is a carbon fiber expert and I believe he built his solar frame out of those tubes. Small and light ones too!

But for connecting them he is basically wrapping the joints with carbon fiber tape to make it all one part. Like welding.

I have considered a square tube from them as a reinforcing part, but with the laminating I’m gonna do anyway, I think it won’t contribute enough for the added cost.

[s/v Jedi]

We’re currently traveling and I’m in a very different time zone than normally, so it takes a while for me to respond

[s/v Jedi]

Notice: attached picture for entertainment purposes only

It starts looking like a rifle… I swear, it’s purely accidental

I changed it into a hook model to engage the three tubes from the arch a bit smarter… or so I think. The three tubes are pictured on the left as the three circles.

Also, it now shows the cassette with two panels mounted on top with two angle profiles. The lower panel has sliders and the upper one has spacers for a fixed mount.

Also, it shows the Dyneema lashings. The angle profiles will have two holes where they cross a support beam that can’t be seen in this drawing. At the inboard end, the support beam has a vertical slot that the lashing can go through and on the outboard end the lashing simply goes around the beam.

The three tubes have lashings as well to secure the beam in place. I intend to use Spyderline 1/8” diameter for the lashings which is a Dyneema core with polyester cover.

I also show a diagonal slot that kind of reveals the support strut of the beam. The reason for this slot is to hang things from
Also, I can use unidirectional carbon fiber to line the edge of the opening with so that I get more fibers in the optimal direction, aligned with the strut.

To mount the beams I would point the barrel up and hook around the inboard tube of the arch, then lower the barrel to engage the other two tubes, which form the strongest part of the arch (they have a web of connecting struts between them and go all along the arch, down to the transom).

The reason for the height of the beam above the arch is to create enough distance to the lower third tube of the arch so that the strut gets a better angle. I have not yet decided on this height.

The difficulty will be getting the dimensions around the tubes right. I guess it’s a matter of making sure there is enough room for fibers and then adding until I get a tight fit.

[s/v Jedi]

And these are the panels I’m gonna try to source:

https://www.aptossolar.com/wp-conten...heet_21023.pdf

Edit: these are bifacial and this array has the potential to output 2,288W of power when the two sliding panels are deployed and the dinghy is out of the way. 1,760W with only the tops exposed and 880W in retracted, stored configuration.

My first array on that arch was 220W and I installed that one in 2004 :-)

[AKA-None]

Use multiple wheels per side so it doesn’t get jacked up

[BG305]

Originally Posted by s/v Jedi

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!

NP, i was looking at the one with locks.

https://gsf-promounts.com/product/co...-pair-pricing/

[s/v Jedi]

Originally Posted by BG305

NP, i was looking at the one with locks.

https://gsf-promounts.com/product/co...-pair-pricing/

I’m afraid I can’t reach the unlock handles….

[s/v Jedi]

Here is a picture of one of the many RV’s with sliding panels. You can see the yellow unlock handles, which will be out of reach for me…

[Lee Jerry]

Originally Posted by s/v Jedi

We’re talking about different things. You mean the compression force at the hinge point, which is 25% of the distance from the inboard end of the beam. This force doesn’t worry me one second because the only risk here is the 1.5” diameter tube crushing the laminate which is very easy to deal with, especially considering the strut to the 3rd tube will take a large portion of that force. On the previous construction I had to shorten the struts because they took all the force which I noticed when I could move the fitting on the upper tube side to side, showing that a perfect fit is needed to share the load.

It's that (strength of beam i.w.o. the arch tube), but also a little more than that too. It actually affects the reactions (shear and bending moment) along the entire beam, and therefore the required strength of it. But it does seem we are now together on my page (although I still don't know what page you were on before, but that's OK).

But these are only the loads when the slider is stowed. When it is extended, another moment is induced on the cassette end rail (which was one reason I'm concerned about its strength / stiffness) which then gets transferred to the support beams through said end rails - down on the outboard and up on the inboard. Therefore, the outboard beam will see increased load and the inboard will be reduced. This should be fairly obvious since the configuration is changing from the two panels being supported centered between the two beams to one panel still supported by both beams and the other one being completely supported by only the one (outboard) beam. It seems like this is going to be a significant increase in load to that beam (like around 1.5x), but I haven't run any numbers yet to confirm (I'm just typing as I go here, hopefully not saying something too embarrassingly off).

It is the long arm to the outboard end that supports that 12.5kg that worries me, not just for strength but also deflection. I considered using aluminium T-slot 80/20 structural framing, which is anodized, and they provide a calculator that showed more deflection than I wanted, meaning I need the struts like the previous construction and there are no good fittings for mounting that.

To do any calculations on the shape I have in my sketch, I have to divide it into as many sections as possible and seeing the spreadsheets for that is a big turn-off. I’m not gonna go through that, so my new plan is to calculate for a straight rectangular profile cantilevered beam with a hinge point plus a strut of the same profile supporting it at 60% outboard. This is how the previous frame was.

I can cheat by comparing tensile strength and flex modulus with an aluminium beam that they provide calculators for.

How much deflection was predicted? How much (little) do you want? And what were the inputs used to get there (beam shape, height, width, skin thickness, E)?

"As many sections as possible" seems rather excessive (unless that was just hyperbole). I'd think 5 or 6 would do fine, 3 or 4 may be enough. If this was entering into a website spreadsheet, then maybe a p.i.t.a. But if on your own comp software (Excel or whatever), then it shouldn't be that hard - cut, paste, change a few values and Bob's your uncle. Repeat a few times. (Or copy the sheet and update.) I can help with this analysis if you want to do it (I mean with the calcs, not just spreadsheet instruction).

My idea about the use of fiberglass in combination with carbon fiber: I can put a skin of 1708 on both sides of the foam core before even cutting it, giving me a nice base to work with and fibers in the diagonal directions. Also, when I finish with a layer of say 6-ounce cloth, I have isolated the carbon fiber, preventing corrosion where it will touch metals.
The 1708 will contribute strength and the 6-ounce cloth just a finish non-conducting surface.

I read it as you were going to "sandwich" carbon / glass / carbon / glass / ... some number of times. Don't do that. A finish layer is fine (but I wouldn't think necessary - the resin protects it unless ruptured; plus you'd lose that cool carbon look ).

My next step is coming up with more precise measurements, because the panels are actually a bit larger and the tubes of the arch are closer, but the panels can come forward of the arch a bit too and all the small differences can add up to significant numbers.

Yes, shifting the panels forward and reducing the overhang could help a lot.
(If you mean tubes are closer together than the 50 cm, that bad.)

[s/v Jedi]

For the 8020 website the calculator is here: https://8020.net/deflection-calculator

I checked for a single metric 4080 standard profile and got about 1.5” deflection.

A strut would fix that and they have nice variable angle fittings to connect the strut to the beam, but I see no good fittings to fasten beam and strut to the stainless steel tubes of the arch.