Seaview Radar Mast Hinge Adapter - Mainship 350/390

Hi All,

Has anyone used the Seaview hinge adapter for the radar mast on their Mainship 350/390? If so, what did you have to do to make it work?

Have to get under Chicago bridge and a spot on the Erie Canal.

https://www.seaviewglobal.com/products/hinge-adapter?variant=12309268758626

Many thanks for any input.

I have one on my boat but i am not familiar with the main ship. Mine is set to bring everything rearward and the mast will hang from the hinge.

The base of my radar mast is 11" (round) and not sure I will be able to get it to work be taping into the Seaview adapter.
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If you are thinking of adapting the current mast base to the hinge that may not work well. I looked at the hinge online and it is not meant to take an entire mast but rather just the radar and a couple of very light add ons.

Cut the mast somewhere above the base plate and install the hinge there.
I did not use the hinge discussed but made my own of 1/2" alum, a piece of rod bored out to take a 1/2" diam. SS bolt. I also used four bolts to hold the hinge closed. You could substitute the hand knobs for nuts.

THen I took it all to my local welder.

My need was not bridge dodging but rather winter covers and maybe a boat shed another day.

I made it so the hinge is about 2 ft above the base plate which is permanently mounted to the deck.

That sounds like a good idea. If it's convenient, would you mind sharing a picture of your set up? Many thanks if you can.

I will have to take some of the hinge.

Here are some photos. It is down now and the winter cover is in place so I can't/won't lift it.

THe two plates are 1/2" thick, 8" long x 5" wide. I used 4x 3/8-16 SS bolts, Nysert nuts and washers to hold the hinged plates closed. I put it up and take it down one time each per year. The wooden crotch is to hold the radar antenna off the deck.

THe hinge is a piece of aluminum 1" diam. rod bored out to a hair more than the bolt diam. of 1/2". The bolt and the bore I lightly smeared silicone grease on so it wont freeze up.

I cut the plates so the tube passes through just a bit back of the mating surfaces so the plates will be tight to each other. The tube and plates are welded both sides. Any weld material on the inside was then smoothed off.

You may want to sort out a locking mechanism that is faster than the bolts.
Maybe instead of the simple holes Slot the holes and use large knobs with the bolts that can simply be slid into place and then tightened. If you go that route get a couple of extras for the just in cases. Water loves those kinds of things.

A couple of suggestions for handles/knobs are
Veritas, Car Lane, McMaster Carr

I did not depend upon the hinge itself to hold thing together which is why the 4 bolts, 2 on each side of the tube.



The last photo shows the mast but without the hinge which came the next year. You can see one plate between the exhaust stack and the radar mast for steadying. It works and well.

Don't know why the photos came out cockeyed. They aren't in my files.


I hope this helps.

Here is how the hinge is setup on my boat.

Our mast hinges about 2.5' up from the base and folds towards the stern.

There are many ways to arrange a hinge. You need to look at whether to hinge forward or rearward. In my case the hinge is not arranged strictly forward and aft. It is slightly , about 4o, aimed at the boat centre to clear contact with the bridge port inside. How to support the mast when down.

If you have a rail nearby and behind then arrange the hinge so the down mast uses the rail as the support. What else does it do such as Nav. Lgts, antennas, flag flying and so on.

I had none of that , my mast does not have to be arranged to be put up and down every trip but only once yearly.
My main concern was a sturdy mounting and hinge.
The raw aluminum in my case suited my boat along with the dry stack.

If your mast must be raised and lowered often for bridge clearance or shed/roof clearance then consider that maybe as the primary need.


So study all of them. Look around marinas and ask the owners if they are willing.
Decide what you need and find and talk to a fabricator. They may have some good ideas and suggestions.

Good luck