Large solar array support beams

[s/v Jedi]

Originally Posted by s/v Jedi

I would almost forget to post the first time we deployed the array

For reference: the dinghy hanging underneath is a Highfield Classic 340 so 3.40 meters or 11 feet.

Each panel is 44” wide and we have some spacing in between, making the total span 180”, 15 feet or 4.5 meters.

[sailingharry]

The good news is that after 196 posts, we are done with this thread. The bad news is that it has been a wonderful thread, with lots of good stuff and not too many derails!


Seriously, it's been a great thread and the result is amazing.

[RaymondR]

Originally Posted by s/v Jedi

I would almost forget to post the first time we deployed the array

That's a very nice looking job Jedi and I'm particularly impressed with your beam fabrication. Congratulations mate.

[CaptainRivet]

Thanks for detailed answer Jedi.
Yes I don‘t know your boat and only saw the 2 photos you posted. Couldn’t see all what you described.
You clearly thought this through and know what it takes.
I just repeated what the naval engineer told me how he calculated all the loads on my old ketch’s arch. I just brought up what most people forget and you too, the crane factor:
You have your load after pivot point with 192kg and now you sail close haul against short waves then the crane factor of 6 applies to this 192kg means 6x192kg= 1,2t in worst case… ok it’s not the full 192kg (but maybe 120kg of it but that difference is another safety margin I was told) and your are still safe as I can see from your numbers. Sounded logic to me but I am no naval engineer, I just noted the main things down to learn and repeat them here.
Add to this your classic 340 which is another 70kg, I had and have the Ultralight 340 which is 43kg…you are still good and this is the extreme but by not so much margin anymore.

The bailer is about 15mm in diameter and identical in classic and UL….good to know it can do 1500l in 20min, didn‘t assume that. I had it actually in a Harbour some leaves got into dingy and blocked the open bailer so it filled up half till I realized.
Just sharing my experiences and know how I got taught here too.
Which nick has Lee cherry?
don‘t have access to the naval engineer anymore and I am designing a new solar arch for my cat too and would need some help with calculations and checks on mine.

Originally Posted by s/v Jedi

I don’t think you realize what kind of boat this is, how much engineering went in and what my sailing/cruising experience is.

First, the arch doesn’t overhang the stern. You think the stern is where the deck ends, but you don’t realize that there’s a ladder down to a swimming platform before you get to the stern. The stainless steel ladder construction part of the arch, which is the load bearing part, attaches down further aft.

The angled part you talk about is the single tube, not the ladder construction, which comes forward for fore-aft support and integrates with the pushpit where it replaces the aft stanchions. This is not the load bearing part.

The arch was engineered to the level that you can hoist the boat with it. This wasn’t an “arch in a box” Internet special, it was custom designed and fabricated by a German engineer, college teacher.

This boat itself was designed by Steve Dashew, a living legend for offshore boat design. When we tested behavior with the stern facing 6 meter high waves while stationary (no forward motion) some 20cm water came onto the swimming platform which is 10 cm above water and there was some splash against the stern. It took 4 of the biggest waves to put a single drop onto the aft deck. The dinghy is still one meter higher than the aft deck, more than two meters above water. It doesn’t get pooped by waves because a wave can roll over the decks without touching the dinghy.

Also, we have spent 20 years in the tropics with this boat. If there is tropical downpours then I can assure you that we have experienced the worst of them. My record of catching rain water is 1,500 liters in 20 minutes and that’s after loosing at least half to spilling as my hose diameters were not large enough for the volume.
Even during those downpours the dinghy doesn’t get flooded and the bailer easily gets rid of the water. You clearly don’t have this experience because then you would know that these downpours can put a lot of water in a dinghy that’s in the water with closed bailer, but it doesn’t even fill it up so the bailer easily handles the amount.
And now the biggest flaw in your reasoning: we don’t even have to open the bailer with the dinghy hoisted up because it stays dry under the solar array.

We carefully designed the structure for holding the panels. The process is documented here on the forum with great help from Lee Jerry who designed the carbon fiber layup schedule and ran the numbers.

When we look at the overhang, you must first define where the downforce is… which is the pivot point on which the array balances. As the only attachments are at the ends of the panels, half the weight is carried by each end. The inward end is 20” past the pivot point (the ladder arch welded part) and the outward end is 55” past the pivot point. This is a 1:2.75 ratio.

The weight of the cassette is only 4kg per rail so 8 total. The panels are 23kg each so 92kg. The slides are heavy too, 18kg total. The beams that carry this are 8kg each so 24kg total.

So we have 8+92+18+24= 142kg or 71kg for each end. Due to the moment of the arm, the aft end puts a force of 2.75 x 71 = 195kg down while the inboard end is just 71 so we have to counter 195-71=124kg. This is distributed over three beams so it’s about 40kg per beam. The lashings at the inboard end are more than 2 tons strength after a 4:1 safety factor. They will hold the 40kg, even during shock loads.

After building this and getting a feel for the results, I may do it differently next time. I would probably only use two beams and make the cassette rails stronger to carry the center. The reason is that I see the center beam provides less support because the arch gives a little in the center while it doesn’t at the ends.

I am considering larger panels in the future, moving these four panels to our second array over the bridge deck. This is why the beams are longer than needed. When that time comes, I may eliminate the center beam, put the other two a little closer together and design a stronger cassette to support the center.

What is interesting is how the loading changes as the array is deployed vs stored. When deployed the center beam does not get any load at all because each outer beam balances two panels. When stored the center beam carries half the weight and the outer beams only 25% each. In reality the center beam doesn’t move down when the panels are stored while I could pull it down by hand relatively easy. The reason is that the cassette distributes the load as it. Is very stiff by itself and greatly reinforced by the heavy slides that are bolted to it, so most of the forces are carried by the outer beams anyway.

And then we added the struts to support the beams. They aren’t even needed as the math above shows, but they support the beams at around 30” beyond the pivot point, leaving only 25” overhang to the aft rail of the cassette.

While mounting these (no pictures unfortunately) we first drilled and tapped the inward end so they are attached with two M5 machine screws to the lower tube of the ladder of the arch. Then I temporarily lashed the aft cassette rail to the beams, attached a halyard to that and put tension on until I visually saw the aft end lift a bit. Then we attached the 8” long mounting pads of the struts with 1.25” wide VHB tape and two lashings around the beams, each lashing rated for 1,170kg strength after a 4:1 safety factor.

There is one more support that I add, which is to support the aft end in the horizontal plane, which becomes important when heeling. As it is, this support is provided by the beams and by the two fixed panels. I don’t like to see the panels experience any of that load, so I add two Dyneema diagonal stays underneath the array. We do the same with the dinghy and it’s very effective.

I will keep updating this thread as we gain more experience

[RaymondR]

When you cannot make it strong enough for some reason, designing in "preferred failure modes" can be an effective strategy.

[s/v Jedi]

Originally Posted by CaptainRivet

Thanks for detailed answer Jedi.
Yes I don‘t know your boat and only saw the 2 photos you posted. Couldn’t see all what you described.
You clearly thought this through and know what it takes.
I just repeated what the naval engineer told me how he calculated all the loads on my old ketch’s arch. I just brought up what most people forget and you too, the crane factor:
You have your load after pivot point with 192kg and now you sail close haul against short waves then the crane factor of 6 applies to this 192kg means 6x192kg= 1,2t in worst case… ok it’s not the full 192kg (but maybe 120kg of it but that difference is another safety margin I was told) and your are still safe as I can see from your numbers. Sounded logic to me but I am no naval engineer, I just noted the main things down to learn and repeat them here.
Add to this your classic 340 which is another 70kg, I had and have the Ultralight 340 which is 43kg…you are still good and this is the extreme but by not so much margin anymore.

The bailer is about 15mm in diameter and identical in classic and UL….good to know it can do 1500l in 20min, didn‘t assume that. I had it actually in a Harbour some leaves got into dingy and blocked the open bailer so it filled up half till I realized.
Just sharing my experiences and know how I got taught here too.
Which nick has Lee cherry?
don‘t have access to the naval engineer anymore and I am designing a new solar arch for my cat too and would need some help with calculations and checks on mine.

It is 71kg, not 192kg. The 192kg is including the crane factor you talk about. I call it the moment of 2.75:1 as calculated.

Lee Jerry is in this thread, send him a pm

[Aspen22]

Originally Posted by s/v Jedi

I would almost forget to post the first time we deployed the array

How are the slides holding up and working after a year in the saltwater environment? I'm debating between something like your design and those slide or a much more expensive design similar to SailLife's slide out design.

[s/v Jedi]

Originally Posted by Aspen22

How are the slides holding up and working after a year in the saltwater environment? I'm debating between something like your design and those slide or a much more expensive design similar to SailLife's slide out design.

I am utterly surprised that there is not a speck of corrosion.

The intermediate slider part isn’t sliding as smoothly so I will be spraying it with Boeshield T9 soon.

I think the corrosion protection these slides come with is better than most anticipated.

Edit: that said, I am working on other methods for sliding… I want to try to have the aft end of the panels freely overhanging like I had with the fixed array. This requires a slide underneath the panels plus an innovative way to mount the fixed panels overhead, butI think it’s possible:-)

[Aspen22]

Originally Posted by s/v Jedi

I am utterly surprised that there is not a speck of corrosion.

The intermediate slider part isn’t sliding as smoothly so I will be spraying it with Boeshield T9 soon.

I think the corrosion protection these slides come with is better than most anticipated.

Edit: that said, I am working on other methods for sliding… I want to try to have the aft end of the panels freely overhanging like I had with the fixed array. This requires a slide underneath the panels plus an innovative way to mount the fixed panels overhead, butI think it’s possible:-)

Thanks! Its nice to hear corrosion resistance is better than expected! I was pricing out stainless tube here in the US, and holy molly, i can almost buy a brand new 4-6kw GenSet for the labor and material cost alone not including the panels... I already have an arch. Just need to solar panels mounts/supports and slides. Its Wild..

[s/v Jedi]

Happy update: today Jedi produced 10kWh of solar power! The new array did more than 8kWh

[RaymondR]

You can buy SS cam rollers and SS C section can be made by taking sections out of one side of RHS and SHS SS tube.

[Pete7]

Originally Posted by Aspen22

I was pricing out stainless tube here in the US, and holy molly, i can almost buy a brand new 4-6kw GenSet for the labor and material cost alone not including the panels... I already have an arch. Just need to solar panels mounts/supports and slides. Its Wild..

The price of stainless has jumped alarmingly over the past couple of years. We have definitely noticed it this side of the pond too

[s/v Jedi]

Originally Posted by RaymondR

You can buy SS cam rollers and SS C section can be made by taking sections out of one side of RHS and SHS SS tube.

Please explain what you mean. I don’t even know what the abbreviations mean…

[CaptainRivet]

Originally Posted by Pete7

The price of stainless has jumped alarmingly over the past couple of years. We have definitely noticed it this side of the pond too

Yes thats the case, prices significantly up for 304 SS and the quality you get is worse. Reason is inflation and higher energy costs everywhere, also in China where a big part of the SS is produced

[CaptainRivet]

Originally Posted by s/v Jedi

Happy update: today Jedi produced 10kWh of solar power! The new array did more than 8kWh

So thats 2kw per 550W Renogy panel, looks like they are well made.
Any idea who is the original manufacturer as renogy just buys them branded from the real manufacturer. They don't sell them over here in Europe you only get 220W bifacial.