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Old 19-01-2020, 21:48   #16
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Re: Mast-mounting radar

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Originally Posted by a64pilot View Post
I believe a mast is in compression and therefore holes aren’t as big a problem, however smoothing out the edges of the holes with sandpaper etc will go a long way towards preventing cracks.
Just like the serrations on a candy bar wrapper, a hole with nicks on it has stress risers and you can be sure where the crack will start.
A tremendous number of boats are out there without cleaned up holes, it’s just good practice is all.
Besides it will help prevent chaffing of the wires.


A mast is in compression and bending, even if you are not intentionally trying to bend it.
Holes are best in the sides of the mast, preferably near spreaders or intermediate shrouds.
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Old 19-01-2020, 22:17   #17
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Re: Mast-mounting radar

Don Dodd’s in Modern Seamanship recommended a radar antenna height of 16-32’ above water, minimum 12’ above highest deck you could stand on.

The minimums had to do with safety due to irradiation, especially the eyes and that you weren’t going to see anything closer than 75’ due to pulse length which translates into 16’ vertical.
32’ was not a hard maximum but more the point he drew a line on diminishing returns. You could bump it to 50’ but that only adds 2nm miles to the radar horizon.

In total he recommended a 24nm range model or less, wasn’t much point in longer ranges since you could no mount the antenna high enough to get that range on anything floating. For high terrestrial returns or returns from weather 24nm or longer might be useful but probably not.
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Old 20-01-2020, 01:24   #18
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Re: Mast-mounting radar

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Originally Posted by Adelie View Post
Don Dodd’s in Modern Seamanship recommended a radar antenna height of 16-32’ above water, minimum 12’ above highest deck you could stand on.

The minimums had to do with safety due to irradiation, especially the eyes and that you weren’t going to see anything closer than 75’ due to pulse length which translates into 16’ vertical.
32’ was not a hard maximum but more the point he drew a line on diminishing returns. You could bump it to 50’ but that only adds 2nm miles to the radar horizon.

In total he recommended a 24nm range model or less, wasn’t much point in longer ranges since you could no mount the antenna high enough to get that range on anything floating. For high terrestrial returns or returns from weather 24nm or longer might be useful but probably not.

If I remember correctly...regulation for the oceanic racers is radar to be mounted a minimum of 3.5 meters above sea level
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Old 20-01-2020, 03:38   #19
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Re: Mast-mounting radar

Quote:
Originally Posted by Adelie View Post
A mast is in compression and bending, even if you are not intentionally trying to bend it.
Holes are best in the sides of the mast, preferably near spreaders or intermediate shrouds.
I respectfully think you are over analyzing. How many masts have failed at or because of the radar mount?

Since the mast creates a blind-spot and the profile of the side of the mast is much larger than the profile of the front, placing the radar array to the side gives a larger blind spot. IMHO, even if the blind spot is to my starboard (stand on) side, it is still less desirable than having the blind spot to my stern.
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Old 20-01-2020, 07:57   #20
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Re: Mast-mounting radar

I was just going off what I read, I'd seen multiple sources say ideally you want the radar 12' off the waterline, which I thought was awfully low (I have 5 ft of freeboard already, that could get knocked around by my headsail pretty badly)... looks like I should do some more research on that...
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Old 24-01-2020, 18:00   #21
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Re: Mast-mounting radar

I mounted a new broadband on my mast last year.
Mine is mounted about 18 feet off the water, it hasn't happened it close range performance.
On my B&G the plugs were small enough not to require a large hole.
The one thing I'd like to change is the mount. I had a boat prior to this one that had a swivelling mount, it kept the radar parallel to the earth.
When heeled over with a fixed mount I get sea clutter on the low side and reduced range. On the high side it's just the opposite, I can't anything up close. Fortunately I can still see distant squalls at a decent range but not so good on the low side.
One of the reasons I bought broadband was the ability to see squalls in more detail. On that level it was a worthwhile investment.
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Old 24-01-2020, 18:23   #22
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Re: Mast-mounting radar

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I mounted a new broadband on my mast last year.
Mine is mounted about 18 feet off the water, it hasn't happened it close range performance.
On my B&G the plugs were small enough not to require a large hole.
The one thing I'd like to change is the mount. I had a boat prior to this one that had a swivelling mount, it kept the radar parallel to the earth.
When heeled over with a fixed mount I get sea clutter on the low side and reduced range. On the high side it's just the opposite, I can't anything up close. Fortunately I can still see distant squalls at a decent range but not so good on the low side.
One of the reasons I bought broadband was the ability to see squalls in more detail. On that level it was a worthwhile investment.

I have sailed with both gimbaled and fixed mast mounted radar

I can’t see any difference in performance

With a fixed radar I have seen sea turtle backs, seal herds, ice blocks, ship wakes , long line bouys...

Gimballed may provide more performance ..it definitely is more fragile and more expensive
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Old 25-01-2020, 21:05   #23
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Re: Mast-mounting radar

Already have the radar and mount and just need to mount it just above the first spreader along with a deck light, so very relevant thread.
An additional question is what to use for the mount, drill and tap for screws or just rivets? Will use tefgel but not sure which way to go?
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Old 25-01-2020, 21:58   #24
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Re: Mast-mounting radar

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Originally Posted by jeff356 View Post
Already have the radar and mount and just need to mount it just above the first spreader along with a deck light, so very relevant thread.
An additional question is what to use for the mount, drill and tap for screws or just rivets? Will use tefgel but not sure which way to go?
Jeff
I suggest rivets. Screws can vibrate loose.

Tefgel is a greasy product. I had a boom gooseneck get very loose when the bolts backed out due to Tefgel. Tefgel works good with rivets. For bolts I prefer Duralac but it can be difficult to find. Duralac hardens up, Tefgel stays greasy.

Almost 30 years ago I used rivets to attach a Radar bracket to my mast. The mast has been repainted twice and the Radar replaced once but I am still using the original bracket held in place with the original rivets.
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Old 26-01-2020, 01:19   #25
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Re: Mast-mounting radar

Our Raymarine Quantum 2 had wireless, we had the cable too, but gave the wirless a try. It has been good, so we just ran power cable.

Just above first spreader, with scanstruct mount and radar protector bar.

Been pretty happy with it. We will loose a small channel buoy about 5-10 from boat.
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