To wedge, or not to wedge, that is the question? - The Hull Truth

PugtSounDav · 07-22-2007, 03:21 AM

I'm installing a Garmin GMR41 RADAR for navigation and primarily collision avoidance.
I'm confident that this RADAR will depict the shorelines, small islands, and other boats.
But, what I'm really concerned with, is spotting logs and crab-pot buoys at close range.
We have alot of these floating around the Puget Sound!!!

Garmin says that the GMR41 has a 25 degree wide (vertical) beam width:
(thats 12.5 degrees above and 12.5 degrees below the horizon).
But, my boat tilts upward somewhat at any speed above idle.

Would installing a 4 degree down wedge actually improve my ability to spot small objects on the surface???
Hoping to get some practical experience from any THT-ers out there using a wedge under their RADAR.

Thanx, Dave.

Glen E · 07-22-2007, 09:14 AM

I have mounted a 40 and 41 with and without a wedge - no major diff - I took the wedge off....

SeaSwirler23 · 07-22-2007, 09:28 AM

Depends on the boat/radar's attitude when you are off plane. You figure you need it most in poor/low visibility when, if you have a brain, you aren't bombing along at 40 in theory, and the boat probably isn't going to be planing. If your radar is going to be shooting up and out off plane, add a wedge to bring her back down a bit. Just my .02.

Stu_ny · 07-22-2007, 08:56 PM

I had the same question a few months ago and went with the wedge. No idea if it would have worked fine without it, but I am very happy with the performance of my radar with it. One thing I noticed last week when having to navigate a long trip through heavy fog in the ocean though, was that there were a lot of times when the boat was "driving up" the back side of a swell and radar targets would "disapear" for a second and then "reapear" as I came back down. It occured to me that the extra 4 degress probably helped me see the targets longer than if I didn't have the wedge.

thataway · 07-22-2007, 10:02 PM

I have never used a wedge and try and mount the radar so that is is parallel with the horizon when the boat is at slow speed. But, you are not going to see logs, and probably not see crab pot floats. I have seen some crab pot floats with mini aluminum radar reflectors.
If you think about what range you will be using--that is 3 miles, occasionally maybe a mile plus or minus. You will be going at displacement speeds in minimum visability.

07-23-2007, 07:24 AM

Mine is on an adjustable platform. I had it adjusted so it was parallel at a moderate to fast troll (bow up). At the dock it appeared to be lookingb into the water so I decided to go almost to level at the dock. Reception turned terrible and I realigned to the original downward angle. Furuno 1732 on a 30' Grady.

starrfish · 07-23-2007, 07:50 AM

the narrow beam width on my open array was greatly improved with the wedge so i would go with it.. possibly try a few shingle shims for a quick test on a calm day.. then decide.

surfcaster51 · 07-23-2007, 09:03 AM

I have a GMR 18 installed on a seaview mount with a 4 degree wedge. I am more concerned with what is in front of me then what is behind me. Even with the 5 degree V beam with the gain turned up to 70% and scaled to 3/4 miles or less It will clearly mark lobster pots out to at least a 1000' and as close as 30' and allow me to navigate thru them.

marinerjoe · 07-23-2007, 01:08 PM

On my last boat (Wellcraft 290 Coastal), I had the 24" RADOME mounted on a downward angle towards the bow. Since I sold it over a year ago, the new owner did not use the boat but two or three times, and when I last saw the boat, the antenna was gone.

He told me that with the downward angle on the antenna, the drain tube in the rear did not drain water. He fired up the system (which had gome unused for MANY months) and fired the antenna.

I agree with the posters that say to have a wedge aiming the antenna down towards the bow. The moral of this story with my old boat is to use your boat as often as you can. And make sure that the antenna is not full of water before you power it up.

Joe

DogTired · 07-23-2007, 06:19 PM

Avoiding Crab pots with radar?

I have to laugh out loud at that!

This captain has had too many bloody mary's and apparently can't see any further than his bow!

He is tracking wave runners as well?

griffgil1 · 07-31-2007, 04:12 AM

Just a thought:

Anyone know anything about the new "patrick" radar mount? It's pretty new, and not well known. You can adjust the angle of your radar from the helm via a switch. Uses a trim tab actuator/piston. Pretty cool in theory, but can't find anyone using it for first hand info. Check it out at thepatricklevel.com I am thinking of getting this for a R.M. 4' array, but don't know enough about it. Seems to be the endall/beall of radar mounting!- if it is built well and has longevity.

arizona · 07-31-2007, 11:19 AM

Don't forget that radar has a minimum distance of about 125'.

NWfisher · 08-04-2007, 03:35 PM

One thing I rarely (if ever) see mentioned about wedges is the raising of the radar beam aft and above the heads of us humans. Radar exposure is harmful, especially so close to the dome. I used a wedge and a mount high enough that the radar beam at its minimum downward angle of 12.5 degrees would be above my head (6 foor 4) while standing at any point on the aft deck. A few measurements and a little trig showed how high the radar had to be to shoot over my head. The radar works well in all directions and is safe for anyone on the aft deck and the radar turned on.