Solar arch design

[Yngmar]

The weight to bear in total is just under 50 kg (solar panels seem to vary a lot in weight between manufacturers - probably due to different thickness of glass and aluminium frame). Plus my own slim frame (cough) will also occasionally need to stand on the two bottom "steps" to clean the bird droppings and such off the panels.

 

[TQA]

I have 3 x 135 w panels mounted on an arch. Note that it allows the panels to tilt to follow the sun. This is important if you want to maximise the output of the panels. I have nothing mounted over the panels to shade them. [ I can not believe the number of installations I see where all sorts of stuff is mounted above the panels. WHY ?

The panels are fitted to an ali frame which has pivots attached see pic.

View attachment 59979
The arch is made from 50 mm ali tube with a shiny silver finish [ anodizing ? ] It is 9 years old now and still in good shape. It is strong enough to lift the RIB and 18 hp OB at anchor. I do not use it as davits on passage, the RIB is on the foredeck then.

 

[neil1967]

It's worth noting that for a solar panel or two and maybe the odd antenna, there is no need for massive structures made from monster tubing. Looking at the pics in the post #15 link, the ones at the bottom, with a single "goalpost" would easily support a couple of 100w panels. Tube size would only need to be 1" x 1.6mm.

Paul, thats interesting - I'm also planning to build an arch for either one or two 200-250W panels, although I was thinking of a DIY build using fittings from seascrew or similar. I'm considering a single arch, suitably braced, using 30mm x 1.5mm thick stainless tube. Is this likely to be strong enough for one or both panels? Each panel is likely to be around 20Kg.

 

[ghostlymoron]

If you have enough deck area, consider using semi flex panels bolted or glued to the deck. Gantries make an elegant sail boat look like a Bahamian shark fisher. You may need more wattage to allow for inevitable shading but it's elegant and robust.

 

[TQA]

If you have enough deck area, consider using semi flex panels bolted or glued to the deck..

Semi flexible panels seem to have a short life ESPECIALLY if walked on. They often fail after a year and rarely make it past three years. I am sure this will trigger a bundle of reports on long lived semi flexible panels but all I can say is that they keep turning up in the dumpsters in the Caribbean.

 

[PaulRainbow]

Paul, thats interesting - I'm also planning to build an arch for either one or two 200-250W panels, although I was thinking of a DIY build using fittings from seascrew or similar. I'm considering a single arch, suitably braced, using 30mm x 1.5mm thick stainless tube. Is this likely to be strong enough for one or both panels? Each panel is likely to be around 20Kg.

I would have thought so. To bend 1" x 16g stainless tube the bender needs to be bolted to the floor and it needs a length of scaffold tube over the handle. My panel on the pushpit is 1" tube, it's been there since 2001.

https://goo.gl/photos/DYYojvskk6kaFtWH6

 

[PaulRainbow]

If you have enough deck area, consider using semi flex panels bolted or glued to the deck. Gantries make an elegant sail boat look like a Bahamian shark fisher. You may need more wattage to allow for inevitable shading but it's elegant and robust.

Semi flexible panels seem to have a short life ESPECIALLY if walked on. They often fail after a year and rarely make it past three years. I am sure this will trigger a bundle of reports on long lived semi flexible panels but all I can say is that they keep turning up in the dumpsters in the Caribbean.

I have two 30w flexible panels on the coachroof, mine are very good quality Solara panels and have been there since 2001. They are however, extremely inefficient due to shading. We've just had a week of very hot Sun and the most these panels have harvested is 30w, that was once, on one day. More typical would be mid 20w's. I don't think there is ever a time when at least some of does not have a shadow on them.

On the other hand, the 64w panel on the pushpit never has a shadow on it, that i've noticed. I can't give any figures for this panel as it is on a controller that doesn't log charging data, but the charging LED is on when the coachroof panel controller has shut down. I would say that 100w on a gantry would be worth 300w on the coachroof.

 

[dgadee]

I was thinking of a DIY build using fittings from seascrew or similar. I'm considering a single arch, suitably braced, using 30mm x 1.5mm thick stainless tube. Is this likely to be strong enough for one or both panels? Each panel is likely to be around 20Kg.

I put up an arch for a single panel made with these fittings - 1" tube and it's pretty stable (rear section fixed to deck and to pushpit). I got the bends put in by an engineer. Not sure all these vast welded structures you see are really needed.

 

[silver-fox]

I had an arch made 10 years ago for my Moody 425 out of 30mm stainless to a similar design to the one you are proposing . It stands 2 metres high, is raked back over the sugar scoop stern, but doesn't increase the LOA. It is bolted directly to aluminium toe rails and braced by SS tube welded to the existing pushpit.

It supports 2 solar panels (mounted on a tilting SS frame) each roughly 1000mm x 550mm and also a wind generator. I have also used it as dinghy davits. It supports my 18 stone bulk too!

Overall the design had been satisfactory and delivered the features I was looking for but the design did have one initial weakness in that it was easy to wobble from side to side. Clearly not a desirable feature when heeling at 20 degrees, close hauled and thumping into a head sea! If I was designing from scratch I would ensure greater stiffness by using 55mm dia tubing or tapering the gantry into a something nearer a A frame shape for greater rigidity

Given that it was already built and paid for, I braced the existing design with a couple of diagonal struts and that made it really solid.

As a footnote, once I realised I had a stability problem and as I was in a marina with maybe 800 boats in it, of which a fair number had gantries, I spend a half day walking round, checking other boats, and it is no exaggeration to say 90% of all gantries were not sufficiently rigid and could easily be wiggled from side to side!

 

[Yngmar]

Wobbling from side to side is a concern, that's what those dashed orange or blue lines in my sketch are about - either one of them could be used to brace it against wobble. Still waiting for the welder to have a proper look and let me know what he thinks, as he's designed and built far more of these things than I have. Would like to discuss integration into pushpit again, although the additional work for doing so may prove too costly.

 

[prv]

Speaking of which, should it even be made of stainless steel at all? I've seen a few made of aluminium, which is certainly good to keep the boat from getting too top heavy. But then how do you treat that to protect it so it won't all crumble to white dust in a few years and blow away?

Has your mast crumbled to white dust and blown away yet?

Pete

 

[dgadee]

As a footnote, once I realised I had a stability problem and as I was in a marina with maybe 800 boats in it, of which a fair number had gantries, I spend a half day walking round, checking other boats, and it is no exaggeration to say 90% of all gantries were not sufficiently rigid and could easily be wiggled from side to side!

I presume 100% of aeroplane wings wobble about, too. Would you want to add extra struts to them?

The fact that 90% wobble yet seem to do the job would suggest to me (someone, admittedly, who failed a mechanical structures exam many years ago) that overbuilding might not be necessary.

 

[Deleted member 36384]

I too have a centre cockpit and want to mount solar panels. My plans are for the future but I will fit a wind screen and hard top, take off the current Bimini and fit the solar panels to the hard top. My new radar will be mounted on a back stay support or a dog leg pole on the stern. You also have massive aft deck area that could be used to mount solar panels.

Personally, I think your design proposal detracts from your boat quite significantly.

 

[Yngmar]

Has your mast crumbled to white dust and blown away yet?

No, because it's anodized to protect it. To the best of my knowledge that's a treatment not easily available for a gantry due to its size and shape.

 

[TQA]

No, because it's anodized to protect it. To the best of my knowledge that's a treatment not easily available for a gantry due to its size and shape.

My ali arch is anodized [ I think ] and is still looking good at 8 - 9 years of marine use.

 

[Saguday]

If I were to add an arch it would probably be from these guys:

http://www.katomarine.com/sailarches.htm

We have their dinghy davits and radar pole and their stainless work is top class. I think their designs are excellent and do not seem as overwight and top heavy as many I've seen.

Probably too expensive for the UK now post-Brexit-vote but browse their site and check out their photo's there's plenty of ideas there.

 

[silver-fox]

I presume 100% of aeroplane wings wobble about, too. Would you want to add extra struts to them?

The fact that 90% wobble yet seem to do the job would suggest to me (someone, admittedly, who failed a mechanical structures exam many years ago) that overbuilding might not be necessary.

My concern was not about the movement so much as the increased loading that would take place as a result - in much the same way as you can have when the standing rigging is too slack.

My sampling of other boats didn't prove their designs were inadequate for their needs, but it did convince me they were inadequate for my needs. We do some fairly long trips and the weather can be variable. Many of the boats in that marina probably hadn't seen an F5 wind outside of the marina. Different strokes for different folks.