Large solar array support beams

[s/v Jedi]

I am designing cassettes that hold two large solar panels (think 2 x 1 meter panels) with one panel fixed on top and one sliding panel below. These would come to around 50kg weight so a hefty cassette.

I will build two of these and mount them on the arch we have on the stern. Of the 2 meter length, 1.5 meter would be unsupported overhang, so this requires strong supports that would appear much like the horizontal part of davits, except with a 2 meter length.

Attached my initial sketches for the cassettes as well as the supports. My arch has three stainless steel tubes to mount the supports to. I am planning to use Dyneema lashings for mounting the supports to the arch, as well as the cassettes to the supports.

The cassettes would basically be angle profiles made from something like 1/2” Coosa board with fiberglass skins. The solar panels themselves connects these angle profiles, so the two supports that carry this also form a constructional part of the cassettes.

I have zero experience with designing such composite supports for the weight they need to carry. My initial idea is to use a 1” foam core with 1/4” plywood skins and add enough carbon fiber to make it plenty strong enough with a large safety factor.

I think the plywood skins may be silly and probably it’s better to use 1.5” foam core with just carbon fiber skins.

With two beams for each cassette and the cassette weighing 50kg, each beam would carry 12.5kg at the very end plus 12.5kg at the inboard end that has direct support from the arch.

Of course I will test for strength but I hope to make that just for proving everything is correct, not so much for experimenting. Is there someone who knows how to calculate a carbon fiber layup schedule to bring the strength to these requirements?

The panels I’m looking at are 440W each, so a cassette would be 880W and with two of them we get 1.75kW. This all replaces an array of three similar panels that was taken out by hurricane Ian, so this must be much stronger.

[Lee Jerry]

OK, I'll go first I guess. I didn't really follow the details of your plan so may end up with more questions than answers, but here goes...

Originally Posted by s/v Jedi

I am designing cassettes that hold two large solar panels (think 2 x 1 meter panels) with one panel fixed on top and one sliding panel below. These would come to around 50kg weight so a hefty cassette.

Why cassettes and why does one have to slide? This will really complicate the structure. It would be much easier (and cheaper and lighter) to just build a platform to attach the panels to. The sliding will really add to it. See next.

I will build two of these and mount them on the arch we have on the stern. Of the 2 meter length, 1.5 meter would be unsupported overhang, so this requires strong supports that would appear much like the horizontal part of davits, except with a 2 meter length.

If there are only two panels, each 2m x 1m, why not orient them transversally next to each other? This would make a 4m x 1m planform rather than 2m x 2m. Should fit rather easily on your boat. Then the overhang off the arch would only be ~0.5m. Again, would make a much simpler mounting system.

Attached my initial sketches for the cassettes as well as the supports. My arch has three stainless steel tubes to mount the supports to. I am planning to use Dyneema lashings for mounting the supports to the arch, as well as the cassettes to the supports.

The cassettes would basically be angle profiles made from something like 1/2” Coosa board with fiberglass skins. The solar panels themselves connects these angle profiles, so the two supports that carry this also form a constructional part of the cassettes.

I have zero experience with designing such composite supports for the weight they need to carry. My initial idea is to use a 1” foam core with 1/4” plywood skins and add enough carbon fiber to make it plenty strong enough with a large safety factor.

I think the plywood skins may be silly and probably it’s better to use 1.5” foam core with just carbon fiber skins.

There are many things here, but I'll only address a few now (and maybe the others go away or answer themselves).

Angles are probably not the best section to use, but there are other issues first before further discussion.

I wouldn't think of Coosa board as a normal core material, but maybe that's just me.

You talk about fiberglass in some places and carbon in others; are you planning on using both materials or just using the terms interchangeably? They're very different with very different properties. I would think you'd pick one and use throughout (but not necessarily).

FRP (of GRP) is usually comprised of a core (often foam or wood) covered by a skin (often fiberglass or carbon). So foam, plywood and carbon together would be unusual, and I don't see the benefit.

With two beams for each cassette and the cassette weighing 50kg, each beam would carry 12.5kg at the very end plus 12.5kg at the inboard end that has direct support from the arch.

Weight is only one load case, and probably not the most demanding one. And your reactions are both wrong and incomplete. This is a cantilevered beam.

The inboard end of the "beam" has to support the entire weight, so 25kg each side in your example (not just 12.5kg). The outboard end "sort of" supports 0 and "sort of" supports 12.5kg (depending on our nomenclature and how it is finally attached). But the inboard end also has to support a bending moment due to the overhang. This would be ~25kg-m each side. This gets superimposed with the weight reaction, and the "beam" has to support all of it. Note that this moment is significantly reduced with the transverse orientation mentioned above.

In addition, the weight needs to have an acceleration factor included due to vessel motions. For the stern, 2 is probably adequate (for the bow I'd go 3). Therefore, double all of the above numbers.

And, as previously mentioned, the wind forces will probably be higher. 4m^2 is a pretty large sail (or wing) area regardless of the shape. Beating into 30kt, with ~40kt over the deck (plus puffs), heeled over and exposing the panels, for just one example. And this is before we talk about the hurricane. I'll leave it there for now as I think that gives you the idea.

There may be other load case to consider, too. For example, can someone grab the panels (from a step or swim platform or other vessel) and induce forces into the system? Or is it too high?

Of course I will test for strength but I hope to make that just for proving everything is correct, not so much for experimenting. Is there someone who knows how to calculate a carbon fiber layup schedule to bring the strength to these requirements?

The panels I’m looking at are 440W each, so a cassette would be 880W and with two of them we get 1.75kW. This all replaces an array of three similar panels that was taken out by hurricane Ian, so this must be much stronger.

I'm probably missing something, or several things, but it seems like you're making this more complicated than necessary with the sliding and the orientation (especially the sliding). So maybe more info would help.

[s/v Jedi]

Originally Posted by Lee Jerry

OK, I'll go first I guess. I didn't really follow the details of your plan so may end up with more questions than answers, but here goes...

Why cassettes and why does one have to slide? This will really complicate the structure. It would be much easier (and cheaper and lighter) to just build a platform to attach the panels to. The sliding will really add to it. See next.

There isn’t enough room for four panels in a row. Like I wrote, I had three panels before and with close quarter maneuvering, it is risky with high pilings or a wall like in a lock.

So I want to be able to go down to two panels for offshore sailing and maneuvering, while having four panels at anchor.

My stern is only 3 meters wide.

If there are only two panels, each 2m x 1m, why not orient them transversally next to each other? This would make a 4m x 1m planform rather than 2m x 2m. Should fit rather easily on your boat. Then the overhang off the arch would only be ~0.5m. Again, would make a much simpler mounting system.

Because that would make it 4 meters wide which is not possible.

Angles are probably not the best section to use, but there are other issues first before further discussion.

Angles give me the vertical surface to mount the panels and sliders, plus the horizontal underside to provide strength and for lashing them onto the supports.

I wouldn't think of Coosa board as a normal core material, but maybe that's just me.

Coosa is listed as a core material for high load applications. It is a fiber reinforced foam.

You talk about fiberglass in some places and carbon in others; are you planning on using both materials or just using the terms interchangeably? They're very different with very different properties. I would think you'd pick one and use throughout (but not necessarily)

I only use carbon where it’s additional stiffness makes a difference.

FRP (of GRP) is usually comprised of a core (often foam or wood) covered by a skin (often fiberglass or carbon). So foam, plywood and carbon together would be unusual, and I don't see the benefit.

I’m not sure why I think of using plywood. I can buy plywood with a balsa or foam core so it’s not unusual, but I think it gives me a good pattern to hold shape, use for guiding a router, help with rounding over the corners etc.

Weight is only one load case, and probably not the most demanding one. And your reactions are both wrong and incomplete. This is a cantilevered beam.

The inboard end of the "beam" has to support the entire weight, so 25kg each side in your example (not just 12.5kg). The outboard end "sort of" supports 0 and "sort of" supports 12.5kg (depending on our nomenclature and how it is finally attached). But the inboard end also has to support a bending moment due to the overhang. This would be ~25kg-m each side. This gets superimposed with the weight reaction, and the "beam" has to support all of it. Note that this moment is significantly reduced with the transverse orientation mentioned above.

I don’t think so. The cassette weighs 50kg and rests on the supports at the ends, so that is 25kg per end but there are two support beams so it is 12.5kg per beam.

The inboard end is pushed down by the cassette onto the arch tubing, so it’s just in compression. The outboard end tries to tilt the support and hinge it around the upper outward tube of the arch, lifting it from the inboard end and pushing it against the lower third tube which is functioning like the attachment point for a supporting strut.

In addition, the weight needs to have an acceleration factor included due to vessel motions. For the stern, 2 is probably adequate (for the bow I'd go 3). Therefore, double all of the above numbers.

Yes, this is what I meant with “safety factor”

And, as previously mentioned, the wind forces will probably be higher. 4m^2 is a pretty large sail (or wing) area regardless of the shape. Beating into 30kt, with ~40kt over the deck (plus puffs), heeled over and exposing the panels, for just one example. And this is before we talk about the hurricane. I'll leave it there for now as I think that gives you the idea.

I have sailed for two years with a 6 m2 surface formed by three panels, as well as ride out hurricane Isaias with it without any trouble.

There may be other load case to consider, too. For example, can someone grab the panels (from a step or swim platform or other vessel) and induce forces into the system? Or is it too high?

Yes, too high.

I'm probably missing something, or several things, but it seems like you're making this more complicated than necessary with the sliding and the orientation (especially the sliding). So maybe more info would help.

The sliding mechanism isn’t more complicated as a drawer, but yes it is more complicated than just slapping panels on. We have had panels slapped on this arch for the past 18 years and I simply want four panels here while being able to slide two panels in to make it twice as small.

The info I am looking for isn’t to talk me into a different setup, but rather info like how many layers of carbon fiber would be required to mount this etc.

[Chotu]

These cantilever support arms are actually not that different from the davit we did in another thread for my boat. Remember that one?

I used a 4"x 4" square premade frp tube with 1/4" wall thickness.

it has absolutely no problem holding up my dinghy with outboard attached, fully fueled, heavy security chain to lock up the dinghy when ashore in there. All of the things you are supposed to have in there. Groceries. And a bicycle. Or a dinghy full of water.

so likely you are over building it.

but what I can say about the composite part of it is yes. I wouldn’t bother with the plywood. Instead just use biaxial on that face. on the top face of the support arm you could use a Triaxial or alternate biaxial and some Uni fibers.

If you think about the square tube I am using for a very similar application, but one that carries even more weight than you are suggesting, a 1/4" composite buildup and air is all that's supporting it.

if you are looking to keep it light weight but overbuilt for a margin of safety, I would do this:

Foam core
1/4" biax buildup on both vertical faces
1/4" triax (or biax/uni alternating) buildup on the upper horizontal face
1/4" biax buildup on the lower horizontal face

That would have the same structural integrity that I have that is currently carrying many times the weight.

if you want to make it more appropriate for the weight you are supporting, 3/16". And if you are doing it in racing mode where it might break?, 1/8"

remember the stiffness will come from the distance these faces are apart from each other. So it comes from the thickness and dimensions of the foam.

[anotherT34C]

Not having studied your setup, how about having two panels swing out from underneath, rather than slide out? Swing out possibly allows you to angle to the sun.

[wholybee]

I really like the idea of the setup. I can't give an knowledgeable opinion on construction strength etc., but I think what you have drawn seems more than strong enough.

I think selection of sliders that are robust enough will be the most difficult part, but I guess you have already found some.

[Lee Jerry]

Originally Posted by s/v Jedi

There isn’t enough room for four panels in a row. Like I wrote, I had three panels before and with close quarter maneuvering, it is risky with high pilings or a wall like in a lock.

So I want to be able to go down to two panels for offshore sailing and maneuvering, while having four panels at anchor.

My stern is only 3 meters wide.


Because that would make it 4 meters wide which is not possible.

OK, it's your boat and project. Still not clear on the dimensions though; is 2m x 1m the size of each cassette or each solar panel? If the latter, does that mean each cassette is 2m x 2m, and when the lower one is deployed the planform is 2m x 4m?

Out of curiosity, do you have a dinghy hanging from this arch?

Angles give me the vertical surface to mount the panels and sliders, plus the horizontal underside to provide strength and for lashing them onto the supports.

Angles on their own don't provide good section modulus. Some better options (probably in order) are channel, I-beam and RHS (rectangular hollow section), like Chotu used (and let me preemptively say a square is a rectangle). They all provide the same vertical and horizontal surfaces you need.

Coosa is listed as a core material for high load applications. It is a fiber reinforced foam.

Sorry, my bad, I was thinking star board.

I only use carbon where it’s additional stiffness makes a difference.

And that will make a noticeable difference in the support beams?

What about to the weight of the cassette (and subsequent reaction loads) if used there?

I’m not sure why I think of using plywood. I can buy plywood with a balsa or foam core so it’s not unusual, but I think it gives me a good pattern to hold shape, use for guiding a router, help with rounding over the corners etc.

Cored plywood for light bulkheads and cabinetry is a different application. (If that is the type of material you are referencing.) I still don't see why you'd do that here.

I don’t think so. The cassette weighs 50kg and rests on the supports at the ends, so that is 25kg per end but there are two support beams so it is 12.5kg per beam.

The inboard end is pushed down by the cassette onto the arch tubing, so it’s just in compression. The outboard end tries to tilt the support and hinge it around the upper outward tube of the arch, lifting it from the inboard end and pushing it against the lower third tube which is functioning like the attachment point for a supporting strut.

A sketch of your arch would be useful; not sure what/where the third tube is.

Referring to the force between one support beam and the arch, the net vertical force at the "end" of the beam that is reacted by the arch is 25kg (as you've described it), not 12.5kg. Otherwise the support beam would fall down. If the beam is hinging around the outward (aft?) tube 0.5m from the inboard (forward?) tube and the beam is 2m long (giving the 1.5m overhang you mention), the reaction on the arch outboard tube is 50kg upward (i.e. in compression) and the reaction at the inboard tube is 25 kg downward (i.e. in tension), and the net force is 25kg upward to support the weight of the cassette. (Again, not knowing the role of the third tube. And ignoring the weight of the beam itself. And...)

Yes, this is what I meant with “safety factor”

OK, but not really the same thing (IMHO). The dynamic factor relates to (gives you) the actual load. (Yes, 2 may be conservative and you could argue for another, lower value; but not the point.) "Factor of safety" relates to how close to the yield stress limit you want to design to (for a number of reasons). But you can mash everything up into one "fudge factor" if you want.

I have sailed for two years with a 6 m2 surface formed by three panels, as well as ride out hurricane Isaias with it without any trouble.

But not hurricane Ian, apparently...

And you said it needs to be stronger than that previous one, but how strong was it?

Yes, too high.

Maybe for someone to grab, but not for other concerns. Otherwise you wouldn't need to slide it out of the way at times.

The sliding mechanism isn’t more complicated as a drawer, but yes it is more complicated than just slapping panels on. We have had panels slapped on this arch for the past 18 years and I simply want four panels here while being able to slide two panels in to make it twice as small.

The info I am looking for isn’t to talk me into a different setup, but rather info like how many layers of carbon fiber would be required to mount this etc.

While you provided more info upfront than many when they ask similar type questions, I was just looking for more details and background. That process may involve explaining some of your decisions or considering alternatives. If that's too much to ask, then the best answer I can give you is "42."

[RaymondR]

Use aluminium sections and paint it. Small SS cam rollers on the corner of the sliding panel.

[s/v Jedi]

Originally Posted by Chotu

These cantilever support arms are actually not that different from the davit we did in another thread for my boat. Remember that one?

I used a 4"x 4" square premade frp tube with 1/4" wall thickness.

it has absolutely no problem holding up my dinghy with outboard attached, fully fueled, heavy security chain to lock up the dinghy when ashore in there. All of the things you are supposed to have in there. Groceries. And a bicycle. Or a dinghy full of water.

so likely you are over building it.

but what I can say about the composite part of it is yes. I wouldn’t bother with the plywood. Instead just use biaxial on that face. on the top face of the support arm you could use a Triaxial or alternate biaxial and some Uni fibers.

If you think about the square tube I am using for a very similar application, but one that carries even more weight than you are suggesting, a 1/4" composite buildup and air is all that's supporting it.

if you are looking to keep it light weight but overbuilt for a margin of safety, I would do this:

Foam core
1/4" biax buildup on both vertical faces
1/4" triax (or biax/uni alternating) buildup on the upper horizontal face
1/4" biax buildup on the lower horizontal face

That would have the same structural integrity that I have that is currently carrying many times the weight.

if you want to make it more appropriate for the weight you are supporting, 3/16". And if you are doing it in racing mode where it might break?, 1/8"

remember the stiffness will come from the distance these faces are apart from each other. So it comes from the thickness and dimensions of the foam.

I don’t remember the free span of your davits but I think most davits are shorter. I also wonder how you fastened them.

I am considering the use of carbon fiber to reduce weight as much as possible because the weight of the supports may be higher than what they carry. Also, by using a shape as on my sketch, I can create a much higher (7-8”) laminate at the base and I hope to have it end as low as 2” at the tip.
Compared to the tubular aluminum frame I had before, this replaces the struts I used then to form the triangle structure.

Unless I find some good data on laminate strength and stiffness, I will probably end up finding out by testing this in my workshop. When it fails it will be a costly test though…

[s/v Jedi]

Originally Posted by anotherT34C

Not having studied your setup, how about having two panels swing out from underneath, rather than slide out? Swing out possibly allows you to angle to the sun.

I have considered many designs, including swing out The one that intrigued me most is two cassettes that sit over a center panel and switch up, aside and down like a toolbox opens, exposing three panels, then doing the slide-outs to make it 5. The problem is that these panels are so big and heavy and overhanging the water so mostly out of reach, that you simply lack the means to make it move like that, and I don’t want any pneumatics etc. to make it work.

Also, for swing-out from underneath, you can’t mount it on top of something anymore.

[s/v Jedi]

Originally Posted by wholybee

I really like the idea of the setup. I can't give an knowledgeable opinion on construction strength etc., but I think what you have drawn seems more than strong enough.

I think selection of sliders that are robust enough will be the most difficult part, but I guess you have already found some.

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.

[s/v Jedi]

Originally Posted by Lee Jerry

OK, it's your boat and project. Still not clear on the dimensions though; is 2m x 1m the size of each cassette or each solar panel? If the latter, does that mean each cassette is 2m x 2m, and when the lower one is deployed the planform is 2m x 4m?

Yes, it sure is my boat and project, you got that right

The panels are 1x2 meter (all of them are in that range, have you not used them?) and the cassettes are 1x2 meter plus the little extra for the angle profiles, slider and filler pieces. With the sliding panel deployed, it becomes 2x2 meters, even a little more because I plan to use 44” sliders. With two cassettes, the array will be 2x2 meters retracted and 4x2 meters when deployed.
My old array was fixed 3x2 meters.

Out of curiosity, do you have a dinghy hanging from this arch?

Yes, see pictures attached.

Angles on their own don't provide good section modulus. Some better options (probably in order) are channel, I-beam and RHS (rectangular hollow section), like Chotu used (and let me preemptively say a square is a rectangle). They all provide the same vertical and horizontal surfaces you need.

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.

Cored plywood for light bulkheads and cabinetry is a different application. (If that is the type of material you are referencing.) I still don't see why you'd do that here.

Like I explained: to act as a guide for a router and support the round-over edges instead of them being foam. I would add to that, that even though not comparable to carbon fiber, they still act as a reinforcement. Many boat hulls use plywood stringers, as do surf boards.

A sketch of your arch would be useful; not sure what/where the third tube is.

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.

Referring to the force between one support beam and the arch, the net vertical force at the "end" of the beam that is reacted by the arch is 25kg (as you've described it), not 12.5kg. Otherwise the support beam would fall down. If the beam is hinging around the outward (aft?) tube 0.5m from the inboard (forward?) tube and the beam is 2m long (giving the 1.5m overhang you mention), the reaction on the arch outboard tube is 50kg upward (i.e. in compression) and the reaction at the inboard tube is 25 kg downward (i.e. in tension), and the net force is 25kg upward to support the weight of the cassette. (Again, not knowing the role of the third tube. And ignoring the weight of the beam itself. And...)

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.

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.

OK, but not really the same thing (IMHO). The dynamic factor relates to (gives you) the actual load. (Yes, 2 may be conservative and you could argue for another, lower value; but not the point.) "Factor of safety" relates to how close to the yield stress limit you want to design to (for a number of reasons). But you can mash everything up into one "fudge factor" if you want.

I agree. I am an EE with only limited training on mechanical engineering so Ijust try to explain things without knowing the correct terms. Also, English is not my first language.

But not hurricane Ian, apparently... And you said it needs to be stronger than that previous one, but how strong was it?

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.

Maybe for someone to grab, but not for other concerns. Otherwise you wouldn't need to slide it out of the way at times.

Like I explained, the worry is high vertical pilings or seawalls like in a lock. It is impossible to make it strong enough for dealing with a collision with one of those, which is why I want to retract the outer panels during close quarter maneuvers, as well as offshore passages.

While you provided more info upfront than many when they ask similar type questions, I was just looking for more details and background. That process may involve explaining some of your decisions or considering alternatives. If that's too much to ask, then the best answer I can give you is "42."

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.

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.

Also, the reason that I can’t fit four panels permanently is that they would stick out… I am a monohull and a narrow one at that, so I don’t have the luxury of a wide beam that the catamarans have. Like I explained, even three panels can easily get me into trouble as was a cause for concern over the years I had that.

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

[s/v Jedi]

Originally Posted by RaymondR

Use aluminium sections and paint it. Small SS cam rollers on the corner of the sliding panel.

My previous array used an aluminum frame to carry the panels. I used anodized tubing but the fittings were not anodized and I’m afraid paint wouldn’t stay nice for very long on the parts that were not anodized.

Also, the heavy aluminum fittings were ripped apart by the storm. See attached image.

[Chotu]

Originally Posted by s/v Jedi

I don’t remember the free span of your davits but I think most davits are shorter. I also wonder how you fastened them.

I am considering the use of carbon fiber to reduce weight as much as possible because the weight of the supports may be higher than what they carry. Also, by using a shape as on my sketch, I can create a much higher (7-8”) laminate at the base and I hope to have it end as low as 2” at the tip.
Compared to the tubular aluminum frame I had before, this replaces the struts I used then to form the triangle structure.

Unless I find some good data on laminate strength and stiffness, I will probably end up finding out by testing this in my workshop. When it fails it will be a costly test though…

Actually, the unsupported part of my cantilever davits are very close to the same length.

In addition, all of the weight is at a point at the very end hanging below them. Much more weight than you are supporting. Your weight is spread out as it is a panel (I think). Mine is a larger point load at the very end of the davit.

In my case, just to reduce the amount of fiberglassing chemical work, I attached them by through bolting and using fiberglass backing plates or doublers.

Vertical stiffness comes from the distance between the upper face and lower face of these support arms you are building. horizontal stiffness comes from the distance between the faces on each side of the support. So, the foam thickness is what dictates the stiffness. at least up until the point where carbon starts giving way. also, carbon is a bit stiffer than glass. That’s something to keep in mind. it has less give overall

I was trying to find direct substitutions for you regarding the laminate thickness but I was unable because I just don’t have enough time this morning to put into it. It’s quite a bit of research online to do that.

But if you can translate from my glass figures to carbon, you have this made. Because you have real world testing already going on. Quarter inch laminate thickness will definitely work if glass. You just have to translate that to carbon somehow.

[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