Installing a radar arch

[rogerbum]

All,

I'm finally getting around to installing the radar arch that I bought at the factory garage sale in Jan and the used radar that I bought a month or two later. I've already positioned the arch where it needs to be and drilled the holes in the roof to attach the base of each leg to the roof. I've also done a test fit to see if the cable from my Furuno 1712 will fit through the currently existing hole in the cross member (it won't) and though the arch in general (it will fit through the tube but I am fairly certain it won't make the bend). Before I complete the installation, I have a few questions...

1) Since the cable won't make the bend in the radar arch, I am left with cutting a slot in the tubing just below the bend or on the corner at the top. I'm leaning towards cutting a long slot (2-3") just below the bend on the inside of the bend.
a) does this make sense or is there a better way?
b) How to cut a decent slot in the side of stainless steel tubing? I have a normal collection of tools but am not sure on how to approach this.
2) What should I use a sealant to seal the holes in the roof? I was planning on 5200 but recent posts from Bob Austin in another thread (vague memory) make me think maybe I should use a more standard silicone.
3) I am also thinking about spacing the bases a bit off the roof with perhaps a silicone pad that is slotted or even some stainless washers. The though is to leave room for water that condenses or otherwise finds it's way inside to escape. Another option is to drill a small hole through the tube at the low side of each support base. Again I have a vague recollection of someone complaining about water collecting inside the radar arch legs - comments, thoughts?
4) Any other gotcha's I should consider?

The radar arch was purchased as much for the radar as for the rocket launcher rod holders so the simpler PVC pipe mount that Bob Austin is fond of is not what I'm after. Advice on how to best install what I have would be much appreciated.

[drjohn71a]

Hey, Roger,

'Good to hear about the radar arch improvement. Here are some of my thoughts:

1 - It's difficult to cut cleanly into Stainless steel with ordinary tools - maybe grinder, but a plasma cutter is the best. Maybe some shop would consult and do the cuts. Do you have to cut into the arch? Could you just run the cable in a sheath outside the arch?

2 - I believe 4200, or silicone on non-submerged parts, is the sealant of choice on a removable item, but you're probably going to leave the arch in place a long time and 5200 is not too bad to get off a small flat area. They advise sealant only on the outside roof area so any moisture that gets thru that shows up in the cabin and you can fix the leak before wood damage occurs. Sealing the bottom could accumulate water.

3 - My arch has holes thru into the cabin at the leg bottoms. Anywater can leak thru that, I guess. You could line those holes with epoxy.

If you can, I'd mount it flat and sturdy on the roof with no overhangs for maximum strength. Is it too wide to fit that way?

Good Luck on the Mod' - I'm certain you'll get the info you need,

John

[thataway]

Basically I agree with Dr John. I am not a fan of silicone as a beding compound, but it can be a sealant (see below) The only place that Boat life Life Caulk (which is a combination silicone and urethane)--is when putting plastic items onto decks etc. Never under SS. Plain silicone has very few uses in the exterior of the boat.

I advocate coating the inside of the holes you have drilled with epoxy--best to route out the first 1/8 to 1/4" of the balsa core, and then fill this with thickened epoxy, then redrill the hole the size as the bolt. (No screws for radar arches!) The sealant of choice would be 5200. Secondary is 4200. If you can get the fittings in the tubing, then you should be able to get them around the bend. (Use the lubricant which is used for fishing wires in conduit (steel or PVC). You want to both push and pull. Secure the pulling "tape" around the cable exterior with tape, not to the radar fitting. (plus you probably will pull the cable up from the cabin which has not fitting on the end which attatches into the radar dome in the Furuno. Don't put a spacer or pull the arch off the top of the boat--bed it properly and leave it there.

If you seal the holes in the arch, and keep them under the SS tubing, there is little chance of getting water in the tubing. Now for sealing the hole where the various cables into the SS tubing--that may be a place for a good silicone sealant.

Roger, you don't like my commode flange fittings and PVC radar support? Wateproof, cheap and durable. We did this on a trawler about 8 yrs ago, and it is still working perfectly. That boat has done the loop plus--well over 20,000 miles. It all started when a visiting trawler owner couldn't find the proper tubing and fittings at our local metal scrap yard. I came up with the PVC pipe idea, and we developed it from there. Actually I started using the PVC pipe 4" 45 degree "el's" for holding wind instruments and speedo on racing boats back in the 60's...Some manufacture picked up on this and made the first pods...So it is not really a new idea.

Looking foreward to photos of the project as it evolves.

[rogerbum]

Thanks for the advice. The fitting will fit in the tube but it is about 1.5" long and won't clear the bends. I'm am also considering just running it on the outside of the tubing and then bringing it in under the side overhang of the roof. That would be easiest but not as aesthetically pleasing ( I mean if I ugly up my 22, I might as well buy a 29... )

I not criticizing your mount, it just doesn't have space for 4 rod holders on it.... I was just trying to cut-off others in advance who might suggest that I should solve my radar arch problem with a non-radar arch solution. I also know that I could entice (entrap) you into replying if I mentioned your mount and your advice is highly valued (pretty tricky, eh?).

So, I'll use 5200 to seal it. The roof, I believe is fiberglass coated plywood (not balsa core) - am I wrong on this? Either way, epoxy filling would be good. Do you have a recommended epoxy brand/type?

[thataway]

Roger,
I don't claim beauty and the whole Commode radar mounting is a great laugh for use--especially when folks ask us how they are made--now if you want the "improved model" with 8 PVC rod holders attatched, that can be arranged....

Roger, have you looked at fishing the radar end of the cable thru the tubing? As I recollect on the 1715(the 1712 was the predicessor) has a smaller diameter connector on the radar end of the cable. Even if you had to round some of the plastic fitting corners, it should fit into the tubing.

Although you could run the cable outside or cut the tubing with a grinder, I would really advise against that, unless it was the last resort. You can use a cable clam to give a water proof route thru the roof.

[starcrafttom]

roger. I had a hard time getting my cable thru the tube, both the bends and the slot at the radar. I had to cover the fitting with tape and form it in to a point. Then I taped it to a metal wiring tape thing( sorry cant remember the right name. ) its a stiff metal tape for pulling wire. If you need help I could come down this week and lend a hand after work.

[TyBoo]

[rogerbum]

[Not For Hire]

Hi Roger,

I have the low model arch. I installed the arch. One year later installed the radar. On the reinstall I removed the arch altogether to pull the bulky cables through and because it was leaking rain around one of the bases. I did push/pull the radar cable through the pipe with a nylon cord pulling and me pushing. I had the fitting taped, I had the various other wires running through the arch taped to the cable behind the fitting. When I then reinstalled the arch on its four feet I used 4200 caulk and I also put a disk of neoprene between the arch and roof and another disk between roof and backing plate. The neoprene compressed and with the new caulking = no leaks. Don't know how long it will last but so far so good. I got the neoprene by cutting up an old dive suit.

Regards to you and thanks for your past help,

Mark

[rogerbum]

A brief update:
1) Tyboo Mike is right of course the roof is simply fiberglass so no epoxy needed. If I had paid more attention while I was drilling, I would have known this.

2) I did manage to get the cable through the radar arch. Even the small end of the cable was too large to go through the round hole in the tubing and make the turn but after the encouragement of you all (a "Patrickism"), I decided that it likely would make the bends. Hence, I went out this AM with a dremel tool and 30 mins and 4 cutoff wheels later, enlarged the hole in the tubing to a nice slot through which I could get the connector. Just a little pushing, and the cable came through.

3) Tonight, I'll complete the job, I'll bed the feet in 5200 and run the wiring for the all around light down one leg and the radar down the other. The front two legs are in tubing with no holes in it, so I'll just seal them off with some 5200 when bedding the feet. I couldn't find stainless steel 1/4-20 bold that where short enough (need 5/8-3/4") so I'll have to cut some 1.25" ones down. Need to pick up a 1/4-20 dye tonight so I can be sure I don't bugger up (a "Tybooism") the threads too much. I think if I just put a nut on the end of bolt and use the cut-off wheel to cut flush with the nut, I'll be OK. Probably will go through another 4-6 cut-off disks, but there cheap and I have about 30 of 'em.

[drjohn71a]

Roger,

You could run a VHF antenna wire or two thru while you are at it. They put two on mine - one for VHF and one for FM.

Glad to hear you conquered the problem!!!

John

[Sea Wolf]

Rogerbum wrote (stuff clipped):

" I couldn't find stainless steel 1/4-20 bold that where short enough (need 5/8-3/4") so I'll have to cut some 1.25" ones down. Need to pick up a 1/4-20 dye tonight so I can be sure I don't bugger up (a "Tybooism") the threads too much. I think if I just put a nut on the end of bolt and use the cut-off wheel to cut flush with the nut, I'll be OK. Probably will go through another 4-6 cut-off disks, but there cheap and I have about 30 of 'em."

Cutting off bolts and machine screws needn't be too complicated. Here's a trick that so simple it evades discovery.

Take the longer than necessary bolt/screw and put a nut on it all the way up to the head or end of the threads.

Clamp the end to be cut off in the vice.

Cut off the bolt/screw where desired. Even a hacksaw is good here. No need for a precision tool.

Now go to a grinder and gently smooth off the end of the cut and round down the threads at the end at a 45 degree angle to provide a taper.

Now back the nut off the bolt/screw slowly over the end and the tapered threads several times to straighten them out.

This will eliminate the need for a die, and you won't have to buy dies for all the common thread patterns, although it's great to have a good tap and die set.

Incidently, you can get an inexpensive 60 piece tap and die set from Harbor Freight Tools for $21.95 HERE.

The T&D set can save you some money and time. We broke off the end of a $130 reverse cable on our jet ski the other day, and I was able to re-thread the end of the broken rod and add a barrel nut and some threaded stock and re-use the original cable: Savings: $128 + quite a bit of time!

Joe.

[Grumpy]

Roger,
If you are already going to the trouble of cutting bolts to the right length, I would suggest you fit a washer and a dome nut. It makes a nicer looking finish.
Merv

[McMike]

[Captains Cat]