DIY stern mount for radar?

[bobmcd625]

Late last year I purchased a B&G Zeus 2 MFD and a Simrad 3G radar kit. I have successfully installed the MFD, along with wind, water, VHF and Triton displays. Now it's time to get the radar on board. I have decided to go for a stern mounted pole and have seen several ready-made kits (ScanStrut, for example) which look very nice, but wow...not cheap. I wonder if any of you in this august group have fabricated such a pole mount from scratch. The commercial poles are aluminum about 8 ft tall with a deck mount and two lateral supports. This does not seem beyond the wit of a metal fabricator to put together. Anyone done this?
Thanks in advance

[Steadman Uhlich]

Originally Posted by bobmcd625

Late last year I purchased a B&G Zeus 2 MFD and a Simrad 3G radar kit. I have successfully installed the MFD, along with wind, water, VHF and Triton displays. Now it's time to get the radar on board. I have decided to go for a stern mounted pole and have seen several ready-made kits (ScanStrut, for example) which look very nice, but wow...not cheap. I wonder if any of you in this august group have fabricated such a pole mount from scratch. The commercial poles are aluminum about 8 ft tall with a deck mount and two lateral supports. This does not seem beyond the wit of a metal fabricator to put together. Anyone done this?
Thanks in advance

I recently sailed with Boston Blackie (a CF member) on his admirably "tricked out" J-42. One of the things he did to modify his boat was the addition of a very sturdy RADAR pole on the aft deck. What made it sturdy was the 5" or so diameter of the tube, and that he inserted a matrix of wood into the center, with holes for the cables. In addition, the pole went through the deck to the hull level, where it was attached with epoxy and mat, forming a very strong bond to the hull in the lazarette area. This supported a larger RADAR dome. He told me that he had earlier had a more typical deck mounted SS pole, but it was wobbly and he much preferred this new pole he fabricated. If you send him a PM, and request info on it, I think he would be happy to tell you about his design and construction of his DIY pole.

[bobmcd625]

Excellent advice. Many thanks, Steady Hand...

[UNCIVILIZED]

I've made a lot of comments & suggestions on DIY mounts, & enhancements there on in the past. So you'll likely find'em if you use my handle plus appropriate topic headers in the search engines.

IMO basic pole OEM/off the shelf mounts are a bit flimsy, & while they can be braced, you can also guy them. Much like a mast, including adding spreaders. To include building them from old spar sections, spin poles, & even broken carbon spars, spin poles & such. For example, on Bruce Schwab's Ocean Planet, his "pole" was a carbon composite, stayed, semi-wing section. Which is easy enough to see in pics of the boat online.

Also, prior to building, give a good amount of thought to how you'll gimball things or set up the mount so that you can cant the dome to match your average angle of heel. Which, of course if you gimball it, that's even more weight up high. Not a problem if it's planned for from the outset, but if not, then your mount will be even more whippy.

You can also mast mount, particularly if the dome is protected from flailing sails.

And I concur with running the pole for the unit through the deck, & securing it at it's base to the hull. As keel stepped masts are much stonger & stiffer than deck stepped masts of the same diameter. See "End Fixity" in books on rigging, such as those by Brion Toss. Ditto his writings on spar design & construction. One key point of which is that the stiffness of panel lengths is a to the 4th equation, as in one notch above a cubed one. So the shorter the unsupported panels in any "spar" the better, within reason. Which is why you see so many sets of spreaders on racing boat rigs.

The other thing is that many folks seem to be fixated on using stainless poles for radar mounts, which really just adds to the weight up high faster than it does to the mount's stiffness. More or less, stiffness goes up with the cube of diameter of thickness (diameter). So given that aluminum's density is 30% of stainless, it's a no brainer. And carbon's yet better, it's just not as much of a fan of being drilled, etc. But in an overbuilt "tube"...


Also keep in mind that radar, like viewing things through binos, is affected by a boat's rolling, as well as height of "eye". So more weight up high = more rolling overall. And if you've ever been up the mast, especially at sea, you understand how this motion gets magnified the higher up you go. Although the higher up you are, the further you can see. So don't buy a unit with a (theoretical) 50nm range, & expect it to perform well if the dome is only 10' off of the water.
Not to mention all of the EM radiation it'll be pinging the crew with if mounted that low.

PS: There are backstay radar mounts, including gimballed ones. Can't say as to how good that is for the rigging wire though.

[Steadman Uhlich]

UNCIVILIZED brings up several good points and tips (as usual).

Boston Blackie's RADAR Pole was made of a light material, reinforced inside by the wood matrix he built of wood staves in a circular pattern.

Also, he had his radome mounted on a gimbal that was very effective. He used a gimbal mount typically seen on a backstay, but modified it to mount to the top of the pole. It worked well. I think his radome was about 24" diameter Furuno.

[gamayun]

I have this set up on my boat with 4G radar mounted on the pole that goes through a wood block and down through the stern to a FG tube at the aft cockpit locker of the boat. I do need to install guys to make it bomb proof, but I've been offshore in 15' seas and 30 knots of wind and it holds just fine as is. I've researched the radar coverage and it picks up what you need far enough away when it's about 15' above the waterline. I can post some pictures, if you like, when I get back to the boat on Tuesday. It's pretty simple. I also don't think a Gimbal mount is necessary. The radar reflector is attached to the pole, too.

[GILow]

Ours is about 8 feet tall and made from a section of old aluminium mast.

But, being a canoe stern, it sort of makes sense at the (other) pointy end of the boat.

It is cleverly integrated with the davits AND holds up the wind generator, so it is serving a number of functions.

Best photo I could find was this one...

[bobmcd625]

Good stuff from you all. Many thanks. I was only surprised by the feeling that the pole should go through the deck and be grounded on the hull. I would have thought that a base plate firmly anchored to the deck would be fine provided that lateral support (2D) to the rails is provided. Gimbled must be beneficial even if not absolutely essential.
Now to look for a discarded spinnaker pole!

[Davidhoy]

Have you thought about installing an arch instead of a pole? Not only can you then mount your radar on top, but it's also useful for mounting solar panels, VHF and GPS antennas, hoisting a dinghy, etc. I'm in the process of mounting one on the stern of my boat, using a kit from FishOnSports. Now, I realize that not everyone likes the aesthetics of an arch, and they are not suitable for all boats, but one might be an option for you, and they can be quite reasonably priced.

As you can see from the photo, in my case the arch is not out of place with the large hard-top bimini I already have. The arch is not fully secured yet, just held up with the mizzen halyard while I get it adjusted just right.

-David

[Matsubob]

I have just made a mount for my radar for FREE, out of the front section of the tower on a derelict ski boat. We cut the stainless tubing with a grinder, then welded angleiron to make a base and the width fit the top brackets of the davits on the stern, making an "arch". The front of the tower had a slight "rake", making a gentle angle on the stern of my 30 footer. Just an idea, that didn't cost anything but the longer SS bolts to reach through the angle iron and the brackers on the Edson Davits. This is much more sturdy than a single pole and doesn't need any support; it also makes a good brace between the two davits. This puts the radar about 12 feet above the water and is fine for close maneuvering. The broadband radar unit doesn't emit dangerous rays, so can be mounted anywhere.

[capt jgw]

Originally Posted by bobmcd625

Good stuff from you all. Many thanks. I was only surprised by the feeling that the pole should go through the deck and be grounded on the hull. I would have thought that a base plate firmly anchored to the deck would be fine provided that lateral support (2D) to the rails is provided. Gimbled must be beneficial even if not absolutely essential.
Now to look for a discarded spinnaker pole!

Metal dealers will have aluminum and SS tubing in many sizes and wall thicknesses. SS is pricey but aluminum is fairly cheap. Any spin pole that someone threw away is going to be badly beat up, if it broke it's likely no longer long enough.
A friend of mine built a wind gen pole from aluminum pipe, with a deck base and two tabs for braces welded on. Had a local shop do the welding and the braces were standard bimini tubes and fittings. I think he had about $200 in it.

[Captndave1]

I built my own backstay mount complete with swivel for under $200. for my Garmin radar, works great

[W3GAC]

Yes, I added a home brew radar pole. Pretty easy if you have a welder that can do aluminum. Got him to weld the flat mounting plated on top of the 3" dia aluminum pole. The plate pattern was traced from bottom of radar (or if you have their pattern so much the better... but not critical. I actual added to the trace two bulges on either side (port- Starboard) to add GPS and second VHF antenna. The braces can be made using standard stainless hardware for railings/ Bimini. Took about two days on and off after got mast back from welder. Oh yes, bottom of mast to deck (or stern) was a simple U - bent heavy aluminum plate welder bent for me with 'axial' bolt drilled through sides of U and through the mast and 'swivel' bottom hole drilled and on through deck (or stern). The U axle and swivel bolt allow 3 axises mounting which I found was needed since nothing on a boat deck or stern is vertical or level. Total cost was still $350 ish. Good luck

[bobmcd625]

Originally Posted by W3GAC

Yes, I added a home brew radar pole. Pretty easy if you have a welder that can do aluminum. Got him to weld the flat mounting plated on top of the 3" dia aluminum pole. The plate pattern was traced from bottom of radar (or if you have their pattern so much the better... but not critical. I actual added to the trace two bulges on either side (port- Starboard) to add GPS and second VHF antenna. The braces can be made using standard stainless hardware for railings/ Bimini. Took about two days on and off after got mast back from welder. Oh yes, bottom of mast to deck (or stern) was a simple U - bent heavy aluminum plate welder bent for me with 'axial' bolt drilled through sides of U and through the mast and 'swivel' bottom hole drilled and on through deck (or stern). The U axle and swivel bolt allow 3 axises mounting which I found was needed since nothing on a boat deck or stern is vertical or level. Total cost was still $350 ish. Good luck

Thanks for that. Clever U-joint. Sounds perfect. Did you paint the aluminum pole?

[Qayaq]

I made mine from Bimini and balustrade fittings and lengths of 316 stainless tube(not pipe). Didnt have access to a welder at the time so it's all Bolted and riveted together. Pretty happy with it and managed to make it in the cockpit. 1" tube for supports and 2" for the pole. I also found bolt on pipe supports/hangers that are used in factories, could only get them in 304 but they haven't corroded yet so I used those to tie into the Pushpit for added support. Through bolted a balustrade fitting through the coaming for the bottom of the pole.It has a T piece above the radar for AIS and bullet aerials. Radars about 13/14 ft above the waterline and seems to work fine, it's on a leveler as there was one on the boat. Next time I would weld it, and probably will on some of this one when I bump into a welder. Good luck with yours