Large solar array support beams

[s/v Jedi]

Originally Posted by CaptainRivet

Looks awesome.
Did you check if the holding points of the arch are up to the task? That angle from the end of the pannels till where the arch is mounted to deck are huge and the dingy hangs there too.
With crane factor of 6 additional i just think about the case when strong rain or alike fills dingy with water and then some stamping in the waves additionallywind forces, that puts huge forces and loads of >10t on the holding points.

The dinghy mostly hangs from a lifting arm that is hinged low on the arch, so that’s the load bearing point for the dinghy. Also, it doesn’t fill up with water because that drains out the bailer.

The main tubing of the arch is thick wall 1.5” diameter so it’s pretty strong. The secondary tubing is still 1.25” diameter and thick wall too. Half of the weight of the panels is 20” from the tipping point and the rest of the panels 55” opposite of that tipping point, a 2.75:1 arm. But then there’s the struts that are about 30” from the tipping point so the oanels only extend 25” from that.

[jcapo]

Originally Posted by Lee Jerry

(Why does the CF software rotate the photo?)

I found that images that are too large, for some value of large, wind up rotated.

[Chotu]

Originally Posted by jcapo

I found that images that are too large, for some value of large, wind up rotated.

I don’t know why I am replying to this after all of the interesting stuff Jedi wrote about, but I happened to see it today.

The forum doesn’t rotate the picture. Apple products use information encoded into the image to direct the phone on how to rotate and display the image.

The image is stored on your phone 90° out of whack but Apple knows to rotate it when it displays it in your photo album/library.

The sideways picture is exactly what you uploaded to the forum. However, without Apple‘s rotation information, it doesn’t get rotated when you look at it through the forum.

Basically it’s Apple‘s fault. Not the forum.

[jcapo]

Originally Posted by Chotu

Basically it’s Apple‘s fault. Not the forum.

Photos from an Android wind up rotated. Rotating the image with Gimp or Paint before uploading does not fix it. Reducing the size fixes it for me. YMMV

[Chotu]

Originally Posted by jcapo

Photos from an Android wind up rotated. Rotating the image with Gimp or Paint before uploading does not fix it. Reducing the size fixes it for me. YMMV

Really?? It didn’t used to be that way a few years ago.

I’m guessing you don’t have gimp on an android though. Are you saying you upload from all sorts of platforms and find the same behavior if it’s over a certain size?

Let us know what file size causes it to rotate when you get a chance

[s/v Jedi]

The rotation is a standard header field in the images. The forum software is a bit slow adapting to tech advances.

[sailingharry]

Originally Posted by s/v Jedi

The dinghy mostly hangs from a lifting arm that is hinged low on the arch.

Do you know who made the arch? My arch is the same, made by Klacko in Canada. it's unusual, and an awesome way to work it.

[s/v Jedi]

Originally Posted by sailingharry

Do you know who made the arch? My arch is the same, made by Klacko in Canada. it's unusual, and an awesome way to work it.

A shop run in Trinidad and Grenada by a German “Dietmar” who designed it and mostly welded by his protege from Trini everyone calls “South”.

We had it built in 2004.

Edit: picture added with Dietmar and South discussing adjustments on the swimming platform

[sailingharry]

Originally Posted by s/v Jedi

A shop run in Trinidad and Grenada by a German “Dietmar” who designed it and mostly welded by his protege from Trini everyone calls “South”.

We had it built in 2004.

For boats with a reverse transom (most, these days), the lifting arm puts the lift point way back over the dingy when it is down, but then moves the dink forward as it lifts, putting it "over" the transom. It also seems to allow us to put ours (and in pictures, yours) much higher off the water and waves than most.


But you already know this!

[s/v Jedi]

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

[Toccata]

That's been a huge project, and looks to be nicely executed.
190 posts later!
Just once more for dummies, (at the end of the project) why didn't you do the structure in SS and clamp it on if it needed to be removable?

[sailingharry]

Because it's ALWAYS more fun to play with Carbon!

[CaptainRivet]

Originally Posted by s/v Jedi

The dinghy mostly hangs from a lifting arm that is hinged low on the arch, so that’s the load bearing point for the dinghy. Also, it doesn’t fill up with water because that drains out the bailer

The main tubing of the arch is thick wall 1.5” diameter so it’s pretty strong. The secondary tubing is still 1.25” diameter and thick wall too. Half of the weight of the panels is 20” from the tipping point and the rest of the panels 55” opposite of that tipping point, a 2.75:1 arm. But then there’s the struts that are about 30” from the tipping point so the oanels only extend 25” from that.

If its raining strongly or a following wave gets in the bailer is by far to small and dingy will fill up..or you forget to pull the plug from the bailer...murphy is waiting...
Always calculate for the worst i was told by the naval architect who calculated the arch on my old ketch hanging over the stern like yours too.
Then add the overhang, weight itself form your cassette/panel setup plus wind pressure. Then add stamping in waves means crane factor 6x the load you calculated before...>10t can happen
Not doubting the tubes will hold, more the attachment points to the hull. Draw an imaginary line from attachment point to end of solar panel, how big is the angle from vertical? 60degrees?
I had 20cm x 30cm 5mm SS plate and chainplate per side with 6xM20 bolts attached to withstand the >10t forces and spread the load across deck/stern even with a 45 degrees 20cm long support to main tube to plate as i had around 55 degrees. Where the tube meets the plate is the point with the most load that gets spread by the plate its welded to.

[s/v Jedi]

Originally Posted by Toccata

That's been a huge project, and looks to be nicely executed.
190 posts later!
Just once more for dummies, (at the end of the project) why didn't you do the structure in SS and clamp it on if it needed to be removable?

Stainless steel would be too heavy when made strong enough for the overhang.

It turns out that these beams are stronger than required because I move the whole boat when I try to move them but the carbon fiber weighs so little that it isn’t a factor other than cost of materials.

[s/v Jedi]

Originally Posted by CaptainRivet

If its raining strongly or a following wave gets in the bailer is by far to small and dingy will fill up..or you forget to pull the plug from the bailer...murphy is waiting...
Always calculate for the worst i was told by the naval architect who calculated the arch on my old ketch hanging over the stern like yours too.
Then add the overhang, weight itself form your cassette/panel setup plus wind pressure. Then add stamping in waves means crane factor 6x the load you calculated before...>10t can happen
Not doubting the tubes will hold, more the attachment points to the hull. Draw an imaginary line from attachment point to end of solar panel, how big is the angle from vertical? 60degrees?
I had 20cm x 30cm 5mm SS plate and chainplate per side with 6xM20 bolts attached to withstand the >10t forces and spread the load across deck/stern even with a 45 degrees 20cm long support to main tube to plate as i had around 55 degrees. Where the tube meets the plate is the point with the most load that gets spread by the plate its welded to.

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