Radar - Pole mount

[wizard]

Having bought a Raymarine C70 and 18" Radome at the SBS which has now been delivered I have the problem of making up a pole ( preferably stainless ) to support the raydome at the pushpit ( I certainly don't want a scanstrut at approx £500 -how can it cost approx 75% of a C70 display !!! )

So, has anyone out there been through this exercise and what problems did you encounter, what advice about design, pitfalls etc

All advice and reccomendations gratefully received.

 

[pvb]

You'll know by now that the radome is a fairly heavy chunk of kit, so the pole obviously needs to be quite strong. Most custom-built stainless steel poles are too slender, in my opinion - I'm sure they're strong enough, but they look "wrong". Don't automatically assume that the pushpit can be a fixing for the pole; in many cases it won't offer enough rigidity. Ideally, try to arrange the base fitting so the cable can go straight down into the boat, rather than needing to exit the pole and go through a separate deck gland. Consider incorporating provision for mounting GPS or other antennae on the pole. Make sure the mounting platform for the radome doesn't obstruct the radome's drain tube.

 

[chriscallender]

I made one up for about £20-£30, its not too hard to do if you can weld stainless. As far as the design is concerned, all you really need is to weld a flat plate to take the radome on the top of the pipe tubing, and attach some cross braces about half way up the pole that go down to the deck. I seem to remember also seeing a pole that was set up like a minature mast with some wire stays but I would probably just go for two stainless tubes as the bracing, one to hold it fore/aft and one across the way. I actually used the existing pushput on the boat as the cross bracing but that part really depends on the boat. One little trick I came up with was to use some stantion base fitting at the bottom of the pole (make sure its stainless and not ally) to the boat. Same idea could probably be used for the cross braces as well if you can get some angled stantion bases. Then just bolt it to the boat with appropriate reinforcement on the inside. I used 1" outside diameter tubing for the pole I think with 3mm wall thickness. However with the benefit of hindsight I would probably use a bigger diameter tube for the main pole and make the whole thing beefier, 2" tubing is probably more appropriate. However that might mean that you might need to make up and weld on your own deck plate rather than using the stantion base.


Height of the pole is something of a compromise - as high as possible to get it away from frying you & your crew and to get as good a range as possible, but not so high that it starts becoming a silly looking thing and becomes very hard to brace.

In terms of making it, I made it with a MIG welder and an angle grinder with a stainless cutting disc, not too hard if you've got that gear. I got most of the bits cut to size anyway by getting the stainless from Metal Supermarkets. Don't do any cutting with anything that will contaminate the stainless eg a hacksaw

If you don't own a welder and aren't reasonably used to welding then its probably a trip to your local stainless steel fabricator but I would guess that this kind of thing can still be made up professionally for much less than £500.

If you do weld it yourself then its necessary to pickle the welds once you have done them (basically involves putting some very nasty acids on them to get rid of the welding residue). I had some pickling paste anyway from other jobs but a tub of this is about £50 on its own so not really worth buying just for this job.


Hope this helps. It all depends on whether you have the gear to do the welding really.

Chris

 

[Swagman]

Fitted the same gear last year and wanted a clean look plus a bit more.

So had a 60mm tube custom made with a top plate to take the randome, two horns to take GPS and Navtex aerials, and a pole gantry which could be removed easily but when needed, allow me to haul outboard etc from the lazerette and drop down to waiting dinghy.

They fabricated it with a plate at deck level and the tube went on down below to be fixed at its base. Very rigid - and looks good.

It cost me £350 installed - done by a Lymington firm - and IMHO much better value than 'standard' options.

If you wish me to dig out name etc PM direct.

Cheers
JOHN

 

[Richard_M]

pm'd you

 

[srm]

I was faced with the same situation 3 years ago when purchasing my current boat, only needed the radar fitted in a hurry for the trip home (single handed).

I opted for the taller Scanstrut option and was severely surprised at the price but went ahead due to pressure of time. Its a substantial piece of kit and was easy to install - about one day with 2 of us. On the other hand if you have all winter a custom designed unit could well be a better option.

As mentioned by pvb the scanner is heavy and will exert high loads at the end of your pole due to the motion of the vessel which could lead to fatigue failure. Many years ago I lost a group of antenna over the side which had been mounted on an aluminium pole on the pushpit due to metal fatigue from a couple of seasons offshore sailing.

 

[Steve_N]

I made my own SS pole for my previous boat, and am about to embark upon the same exercise for the current one. I used a fairly slender 1.5" round tube with a simple plate for the radome welded on top. This was braced to the top bar of the pushpit, and then 2 struts led to the existing pushpit bases where they were attached right to the base of the downtube with SS clips. Rather than trying to engineer some kind of baseplate that fit the sloping, convex deck I simply cut a 1.5" core, dropped the pole through and glassed it under the deck and at the contact point with the hull beneath. The cable went down the tube. I think that my rational at the time was that this 1.5" core was the only drilling/cutting required and could be easily repaired and repainted with deck paint should I wish to remove the pole and take it to the next boat. But of course I never did..

Athough very slender it had ample strength and rigidity.

There are a couple of pictures which just about show the pole here:
Pic 1
Pic 2

 

[chriscallender]

Hi

One other thing I just remembered, I attached a couple of right angle pieces of SS on the bottom of the plate that the radar mounts on, running from the front to the back of the plate on either side of the pole. The idea was to stiffen the plate and I also felt that it would strengthen the pole attachment. This may not be too important a part of the design (especially if you go with the suggestion that others made here to use a bigger pole diameter).

Another thing I remembered, watch out for the plate warping when you weld it onto the top of the post.

I can't really find a good photo of what I made just now but if you want I'll take a few next time I'm down at the boat (maybe this weekend?).

Chris

 

[Swagman]

Richard - did not get a pm - please try again.

JOHN

 

[John_Clarke]

I made my pole out of 75mm diameter aluminium tube 5 mm thick and (like Swagman I think) took it through the deck and down to a sleeve glassed to the hull below; there is also a sleeve glassed beneath the deck. It is 2 m tall above deck and about 1 m below deck level.

The pole is very stiff and needs no struts so it looks neat (unfortunately no photos of it to show you). The top plate is made of 10 mm thick epoxy/glass laminate and incorporates a sleeve to fit the pole and a bracket to the rear which I use as a single davit for the Avon dinghy - this work very well with the line lead via a cheek block at the base of the pole to a sheet winch to hoist it; the stern navigation light also mounts on the rear bracket. There is a side arm for antennae – GPS and emergency VHF. There is an Index Marine deck gland to take the cables into the pole and hence below decks.

The whole thing is painted with etching primer, epoxy undercoat, and Brightside (should have used 2 pack polyurethane for abrasion resistance). The work involved was significant – at least 100 hours and the cost of materials probably about £150 – makes Scanstrut look good value – but I am delighted with the end result.

The C series radar overlaid on the plotter is very good – without the overlay it would take me far to long to understand the radar image; MARPA makes tracking targets fun. The display is mounted in the cockpit so we can relate what we see to the radar image. Was also useful for inshore pilotage to confirm that the charts/GPS were accurate – when the radar image of rocks and islands overlaid precisely on the chart at 1/8 NM scale. We used this going into tight anchorages on the West Coast of Scotland.

 

[wizard]

Thanks to everyone for your help and advice it has given me plenty of thought prior to undertaking the project which I now think is very feasible -the consensus for through the deck for stability is probably the most important point along with the cable entry.

 

[kengill]

We used the pre-fitted pole that came with the boat - Its called a mast!

Fitted the tri and the non-directional VHF aerial at the same time.

Whatever you do make sure its fitted to the starboard side of the cockpit so that its possible to do a high wire landing from a helicopter. A port side fitting emasculates the diver.
Fair winds,
Ken

 

[John_Clarke]

Agree with you. I put mine about 100 mm to starboard of the centreline to clear the backstay fitting. It looks more balanced near the centreline and is safe from damage from harbour walls or high sided vessels which might bump it if too near the stern quarter.

Another point - make sure the height is above the level of the boom to avoid reflections from it.

 

[Sans Bateau]

Dont forget keep the Port side clear, just in case you have to invite a winchman aboard /forums/images/graemlins/blush.gif

 

[sailorman]

theres one on the "for sale" section on the forum