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gathem 23-04-2015 10:57

Advice for mounting 800W of solar panels?
I purchased 3 huge solar panels totaling 800W. Each panel is roughly the size of a standard sized refrigerator.

I've been thinking about how to go about mounting them. I want to mount them over the back section of the bimini. I am completely fine with it extending beyond the back of the boat. They would be a good 8' above the water line @ the top of the bimini.

I am really looking for tips on how to a frame for them, and mount it to the boat. If it helps, I have a full set of welding/metal working gear. I've considered just welding a frame together, and then having it hot dip galvanized/painted or chromed.

I've also considered buying a bunch of bimini hardware, and just bolting a frame together.

Here's a picture of the boat for reference:

a64pilot 23-04-2015 11:18

Re: Advice for mounting 800W of solar panels?
Start with a tower maybe and add onto that? Has to be strong as that is a lot of surface area, and I'd say make sure the panels are easily removable, in case it looks like really bad Wx, you can remove them

gunkylump 23-04-2015 11:38

Re: Advice for mounting 800W of solar panels?
We have 690 watts of solar power, but only two panels. We have them mounted on a stern arch, along with our radar and gps antennae.

If you build an arch, make sure that you incorporate the ability to adjust the panels to follow the sun. It will give you additional hours of sunlight on the panels. Wish I could add a pic, but I don't have any on this computer. Then again, if you go to our blog, there should be pics of the solar array there....


gunkylump 23-04-2015 11:48

Re: Advice for mounting 800W of solar panels?

You should be able to zoom in on the mounts

msponer 23-04-2015 15:11

Re: Advice for mounting 800W of solar panels?
2 Attachment(s)
We did this last year. We sketched a lot of designs, and felt the strongest and best looking way was to replace the existing bimini.

Our goals were:
- Strong (to leave the panels up in high winds, lean against as the boat heels, use as a handhold, and hang a hammock in the cockpit from)
- Not too ugly
- Not too heavy
- Waterproof

We looked at a lot of other boats and drew a lot of sketches. We felt that fewer poles at fewer different angles looks cleaner than all the V's and triangles one usually sees with fabric biminis that have been reinforced to add solar panels to. So this set the overall vibe that we started working with.

We sketched a lot and evolved it from there. We made it less boxy by making the front tubes parallel to the front of the pilothouse and the radar arch. We wanted the horizontal part to be stronger, but did not want to add the usual diagonal struts to do that. It looked cluttered whenever we drew them in. After a lot of talking we decided it looks better to add a second tube below the top tube, to make a 5" beam, instead of adding two or four additional 45 degree angles to split the unsupported length of the horizontal tubing. I think it worked, visually. But without diagonal struts racking would be a problem, so we made the front tubes farther apart. This then allowed us to cantilever the back third, leaving the back seat more open to climb into from the swim platform.

I'm still not sure how it looks. It feels less ugly than the previous bimini, which was made of more thinner tubes at haphazard angles. I like that it is super strong. And I love the 750 watts of solar -- we no longer think about electricity, at all, except to smile when it's 11am and our batteries are full.

Anyways, good luck. Draw and talk a lot... :)

leftbrainstuff 23-04-2015 15:32

Re: Advice for mounting 800W of solar panels?
Some good advice here.

Engineers rules include:

1) Triangles are the strongest, stiffest and lightest way to build a spaceframe (tube structure). Triangles convert all bending loads to tension and compression.
2) design for dynamic loads. 4g for structure, 10g for impacts. Wind loads can be substantial.
3) Something will always fail first. Design it to fail gracefully and give a visual indication. Like bending. The mounts should fail last.
4) It should look right. Rarely do you need to use tube greater than 1/1/4" SS on a monohull. A good looking spaceframe will take much more effort to build than something ugly.
5) round tube will always be lighter than square tube.
6) We want to minimise weight at the extremities and concentrate it near the center of the boat. This always gives us a better motion and reduces the stress on components.
7) Strain failures occur quickly and catastrophically. If you can hang off it and it flexes anywhere it us not stiff enough.

Anything other than tig welded polished 316L stainless will look non nautical. The naturally forming chromium oxide will look good forever.

Chroming of steel is not an option for sea water exposure. You need to copper coat, then nickel coat, then chrome and pilish at every step. Cheaper to use good stainless.

Aluminium is another option. Sizes will increase and polishing will scratch easily. If you can tolerate the look of naturally oxidised aluminium that is.

Sent from my SM-N900T using Cruisers Sailing Forum mobile app

Tayana42 23-04-2015 15:33

Re: Advice for mounting 800W of solar panels?
Gathem, your boat has a pointy back end like mine so I'll be very interested to see what you come up with. One thing to consider when you put the solar panels on the Bimini and further aft is do you still need to access your boom when it's centered, even for putting on the sail cover or getting at the shives for out haul or reefing lines?

S/V B'Shert

gathem 23-04-2015 15:47

Re: Advice for mounting 800W of solar panels?
My boom ends about one foot aft of the dodger, and I plan to keep the gap between the bimini and dodger not covered so I should be able to access the boom even when its straight back.

I'm still working out the sketches, but my thought is something like this:

I'd really like to be able to use the frame as davits as well so I was thinking of welding the whole thing together as opposed with buying bimini hardware.

SV Lift 23-04-2015 15:50

Re: Advice for mounting 800W of solar panels?
Completely agree the only way to go is a welded arch (316 stainless or aluminum). Added benefit is a place to add a radar or davits (not great with a pointy stern but beats having it stolen).

Looks like a single backstay, so you can put one on either side of it... I'm at a loss where you could fit a third one. Let us know!

gathem 23-04-2015 15:56

Re: Advice for mounting 800W of solar panels?
It is a single forestay. That's the plan for the two, and one panel perpendicular to the other two behind it.

GILow 23-04-2015 16:02

Re: Advice for mounting 800W of solar panels?
2 Attachment(s)
A fellow double-pointy boat. Lovely.

Here is how it was solved on ours. Hopefully this picture gives you some ideas. It's all pretty cluttered and these are the old panels which have gone now, replaced with 2 x 140 Watt cheapies. Anyway, this setup could easily take a pair of 200 watt panels, not quite to your level, but the concept should work if you expand it appropriately.

For the record, this rig has done the better part of 40,000 miles through SE Asia and around the East Coast of Australia, so it is stronger than it first appears. It makes use of very good engineering principles, and LeftBrainStuff's excellent engineering comments have some echoes in what was built here, back in the mid 80's. I'd be interested in his thoughts if he were to see it up close, but the remarks about gradual failure were particularly pertinent I felt.

Apologies for the weird camera lens, we had a photographer on board for the delivery trip and he took some pretty clever but mind bending photos. Some of them still give me mild headaches if I look at them too long.


gathem 23-04-2015 16:21

Re: Advice for mounting 800W of solar panels?
What do you (everyone) think of just buying some bimini hardware and making a simple frame, and then attaching 4 panels (2 on either side of the backstay)

It would push the panel array width to 12' 8" (exactly the beam of the boat)

Do you think there could ever be a risk of hitting a piling and ripping them off?

Obviously in this setup, I would have to do something else for davits

msponer 23-04-2015 16:23

Re: Advice for mounting 800W of solar panels?

Originally Posted by gathem (Post 1808440)
I'm still working out the sketches, but my thought is something like this:

The diagonal shouldn't push into the middle of the vertical tube. It will bow it forward unless there's another diagonal running forward from the vertical. It's better for it to go all the way down to the deck (or welded to the vertical close to the deck). Or to the stern pulpit.

The top end of the diagonal is ideally where you will lift the dinghy.

Be sure to leave a lot of room for your backstay to vibrate. We initially had ~1" of space between the solar bimini monstrosity and the split backstay, and our rigger balked at that. He said it would rub and be annoying. So we (expensively) recut and bent our half finished frame to give each backstay ~3" of space. Maybe someone here knows more and can tell you how much room the backstay needs to move. I still don't know if we actually needed more than 1".

Paul L 23-04-2015 17:28

Re: Advice for mounting 800W of solar panels?
Maybe you could build a smaller, more graceful arch with less windage and weight up high if you went with 2 hard panels and then mounted 2 smaller flex panels on your dodger.

Hawkeye 24-04-2015 08:02

Re: Advice for mounting 800W of solar panels?
I mounted 920 watts of solar panels on my boat, beginning with two 210 watt panels fashioned as a hardtop Bimini with a 9" blue Plexiglas strip in the middle to minimize main boom shadowing. These panels were 37.5 inches by 65 inches. Later on, I added two 250 watt panels, right over the top of the existing ones, which easily slid outboard while at anchor, and came right in while sailing. The wiring was as simple as two sets of panels in series, then connected in parallel at the Outback MPPT Solar Charge Controller. When the lower panels were covered, they simply stopped providing power, but did not hinder the top panels at all.

A system like this needs a proper battery bank if you expect to get the full benefit. On my boat, that meant twelve Lifeline GPL-31T - 2 volt deep cycle AGM batteries, connected as 2 12 volt 630 AH cells. One was always connected to the service panel while the other was connected to the solar charger. When the Inverter started whining about low voltage, they were switched. I could do everything at anchor, or under sail, that I could do plugged into shore power at the dock. Including hot water by electric water heater. No windmill to vibrate or split my skull, and no noisy, maintenance and fuel sucking genset.

The system worked so well it is off the boat (which is now for sale) and scheduled to be installed in my new travel trailer.

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