This is a duplicate post of the one I just put up on the SO37 arch. Seems like a lot of people have the same questions.
This is going to be long but I have put all the photos up in the cloud with a link for anyone who wants to look at them
Things to mount on arch
Background – My arch was fabricated and installed by Kato in 2007. It is made from 316 SS, which I would highly recommend, because it will not develop rust stains in salt water. It does not have the extra strengthening pieces that they offer. This might be something to consider, but I don’t think I have ever needed them.
I had a full cockpit enclosure installed right after the arch. The canvas maker decided to mount the SS bows for the enclosure independently of the arch, on the tubing for the stern pulpit. The aft bow of the bimini support runs parallel to the fwd tube of the arch, but the side curtains are draped down inside the arch tubes to snaps on the side of the cockpit. This gives a space between the side drape panels and the arch, and then between the arch and the pulpit rails. I still have the original pulpit, with a mounting pad for the outboard engine. It sits outside the enclosure on the pad when it is not sitting on the dinghy. If we are not out in the ocean, the dinghy (Caribe c9x), with the outboard (Yamaha 9) are together, hanging from the arch. The dinghy is tied in place outside the back panels of the enclosure to the pulpit tubing, which is also outside the enclosure.
You have to remove the tubs in the aft quarters of the boat to get the arch installed. The one on the stbd side holds the gas bottles, while the other one provides access to the top of the original liferaft locker, or a genset (in my case). The tubs are simply glued in place, and you can find the seam by carefully probing around the edge with a pointed knife. I have re-sealed the gas locker because if you don’t, you can get rain leakage into the aft cabin. The port side tub is not sealed so that I can get to the shore power connector and the genset from the inside. I can also get to the top of the steering quadrant, to the windmill and solar panel electronics, wiring, and controls, and over the top of the quadrant to the space under the tub on the stbd side. There is a gas drain hose from the stbd tub to the stern of the boat which has to be cut to get the tub out. I will see if I have any photos of the underside of the arch. I know that I can get an easy photo of the port side, but not sure about the stbd side.
I have put a bunch of photos up in the cloud here, if you want to see how it all fits together.
drive.google.com/drive/folders/1UjSuTbpN5SeEI5HO2hXzEuSsPNNZB4ad?usp=share_linkForgive me for having a lot of canvas photos here - I am going to have to have the zippers replaced, and wanted something to show to the canvas maker. But the cats should be amusing.
1. Dinghy – perhaps use rotating tubular bow to hold dinghy. Must measure dinghy support points and ensure that dinghy will not scrape back of boat as it is hauled. Use 3/8” lines for dinghy tackle and engine hoist tackle. 5/16” is hard on hands. Some people haul the dinghy up to the top of the arch or davits, but I prefer to haul it up to the level of the stern pulpit and tie it off there to the pulpit. Have to run diagonal lines from dinghy to boat cleats. This also provides a good stable work platform to do maintenance on the windmill, solar panels, and other equipment, if needed. I also like to be able to climb up the arch to deal with the windmill. I just have to remember not to leave any tools or parts on the solar panels, because they will inevitably end up being sacrificed to King Neptune. <g>
2. Windmill – I have 1 , but also have an extra mount on the other side of the arch that I would like to use for Starlink antenna. It is the same as the windmill mount, but currently blanked off.
3. Solar panels – several. Need wiring holes large enough for large wiring.
4. AIS antenna – Best to install 1” riser in middle of arch, away from windmill and any other antennas. AIS requires its own, dedicated VHF antenna and GPS.
5. AIS GPS puck on 1” riser
6. Dinghy Engine hoist – want to be able to use both inside and outside the arch. Might be best to have BOTH inside and outside mounting points that can use the same hoist arm. Make sure it is mounted where it can easily lift and deploy the engine on to the dinghy, and bring it to the stern rail for mounting engine on stern rail. This will be needed if dinghy has to go forward for offshore passage. It would be nice if the hoist could lift the engine off the dinghy and place it on the dock alongside the boat this might require a very long arm.
7. Mounting rings and cleats for hoists. I only have one cleat on each side, which is not really enough. I really need another one for the hoist.
8. Mounting point and wiring access for WiFI antenna – 1” riser – I am currently using the mount for the hoist, but this is not optimal.
9. Mounting point and wiring access for SSB radio antenna. Antenna cannot run inside arch – must be supported outside arch, about 6 inches, with standoffs. Mount can be a simple ring, with line to top of mast. Measure antenna to match most used frequencies. Need a good antenna box inside boat.
10. Mounting/attachment points for stowage of SCUBA tanks. I originally had 2 tanks, but now have only 1. They fit very nicely sitting on the stern rails, wedged between the pulpit and the arch.
11. Move stern nav light from back of boat to top of arch. Make sure visibility is not impaired by any equipment.
12. Overhead light on arch – switch on engine panel. I don’t use this much, but it seemed like a good idea at the time.
13. Horn mount – horn button on engine panel. I have the horn, but haven’t gotten around to mounting it. Kato makes some clamp rings for stuff like this that would be perfect.
14. Attachment points to stow extra/docklines - install 3 extra rings on each side of arch. I currently just use the horizontal members on the arch, but they block the view, and are really too large for this. Maybe a simple line would work, too.
15. Mount for Starlink antenna and wiring access – can use windmill mount, if you don’t mount 2
16. Make the arch separate from canvas enclosure arch. Best to have the enclosure separate from the arch so that you can mount a bicycle and SCUBA tanks outside the enclosure. It does make line handling to the stern cleats more difficult, as well as attaching the shore power cable.
17. Leave room between arch and the bow for the enclosure and the stern pulpit for bicycle stowage on the deck, between the enclosure and the arch
You also might want to include mounting of the solar panels on top of your bimini, but that would make it a LOT more complicated to dismount the bimini when you have to change something like the zippers, or need to strip the boat for a hurricane or the winter.