radar placement on roof

[chesapeake albin]

Hello,
sorry to bring this up again but I wanted to let everyone know what I am doing,

I decided to put the radar on a 10" tower on the front of the pilot house rather than the arch. After looking at this I feel it is the only way to get clear shot of the water in front of the boat.

I know a few of you have done the same with various radar masts,

Question: Did you reinforce the roof at all?
Have you had any problems with the weight of the mast wiggling loose and cracking the glass or leaking?

Thanks again
Travis,

[djpeewee]

Travis,

While the roof is strong, it is not very thick. There is a 1/2" balsa core that is sandwiched between two fiberglass skins which are about 1/8" thick at best. In addition to this, there is a head liner that is the interior ceiling of the pilot house. This is about 1/4" thick. Also, there is about a 1/4" air gap between the hard top and this head liner.

Skin
Balsa Core
Skin
Air gap
Head Liner

If you just bolt through all of these layers, including the air gap, I suspect you would have problems keeping the hardware tight without breaking through the fiberglass skin on the roof. Look at the handrails on the roof and you'll see that they probably have cracks around the mounting points. It's not a real good design to be bolting hardware through.

When we bought our 28TE a year ago the roof leaked from every hole. Especially the handrail mounting points. They dripped water off the acorn nuts into the pilot house every time it rained.

What I did to fix the handrails as well as for the new radar mast:

- Removed existing hardware and over drilled the holes to through all the layers.

- Dug out all of the balsa core I could reach inside the holes.

- Taped the holes off from inside the pilot house.

- Filled the holes with epoxy. (You have to do this in several pours with different consistencies to get it to flow out and fill the hollow areas, but not run out of the 1/4" air gap).

- Redrilled the mounting holes through the cured epoxy.

- Reinstalled the handrails and hardware using 3M 4000UV.

This creates a "column" of epoxy through all the layers that allows you to crank the hardware tight without breaking through the fiberglass skin. It also keeps water out of the balsa core should the sealant give out. I do this with all of the holes that penetrate the deck and have not had a single leak since. There are a number of Internet articles explaining similar techniques.

I think if you did this with your new radar mount you would be fine. You could always put a backing plate on the mount, but I still think it would be a good idea to add the epoxy for strength. One other thing you'll have to account for is the arch of the roof. It is not flat so you can't just mount a flat piece of gear to it without creating a shim or a curved base of some sort. Starboard works well for this.

Sorry for the long answer. I hope I addressed your questions.

Damon.

[Jeremyvmd]

Sue you say you overdrilled the holes how large did you make them? Like a few sizes or much larger?

[chesapeake albin]

drill the holes the right size ( but not through the last layer) and get a bent screw driver and scrap out the core, then fill with epoxy and then drill again.

What you you using to handle the arc of the roof?

[djpeewee]

As Travis mentions, normally you would redrill the holes the same size after epoxying. That way you can't see the ring of dried epoxy, which will yellow in the sun, around the hardware you are installing. You have that waterproof super strong doughnut of epoxy between the fiberglass skins and around your hardware though. The beauty of this technique is that even if your sealant lets go, the water cannot get past the epoxy and into the core. Here's a perfect diagram of the technique:

Technique-core.2686.jpg

Because I wanted that "column" of epoxy through all the layers of the hard top, and to be as strong as possible, I overdrilled them. (For reference, the compression strength of the epoxy is 11,500 psi). The original holes were 3/8" and I went up to 5/8". The epoxy wasn't going to show anyway because I was going to use fender washers on the mounting hardware for further support. The outer diameter of the fender washers is 1-1/2" so there is plenty of room for covering the ring of epoxy. Plus, I wanted to dig out as much core as possible to make that "doughnut" of epoxy as wide as I could. Screw drivers, picks, bent nails in a drill - all of these help dig the balsa out.

Here is a picture of the layers of the hardtop that I mentioned previously. These are the 1-1/2" plugs I removed for the cable access way through the hard top to the new radar mount.

Skin
Balsa Core
Skin
Air Gap
Head Liner

Core.jpg

Once all the holes were epoxied and drilled, I used hardware that was identical to what the factory used to mount the hand rails. In the photo below you can see the outer hardware is for the factory hand rail, and the ones near the dome light are what I added for the radar mast.

Ceiling.jpg

Also, when I put the hand rails back, I installed a fender washer on the outside, under the hand rail tube, to help reinforce the whole epoxy column thing.

Roof.jpg

Finally, I made basic wedge shaped shims for the radar mast to rest on and take up the arch of the roof. Kind of difficult to photograph. Because we designed our mast to be folding, the base is sort of a big box that's about 36" long and 18" wide. For smaller footprints you probably wouldn't want a gap under the base, but I wanted to be able to rinse and clean under the mount, so the only parts that touch the roof are the shims, which are about 2" wide. The mount straddles these.

top2.jpg

Top.jpg

Again, sorry for the long post. I guess that's what happens on a rainy day with gale force winds on the water.

Damon.

[Jeremyvmd]

I know usually you would drill the correct size, I was just wondering how large you overdriled yours out of curiosity. I want to redo my roof hardware as it isnleaking pretty good. Plus I don't like the idea of hardware going through core materiel. Wondering if it's worth over drilling it...

[djpeewee]

Jeremy,

Sorry for the TMI. No more pictures... I swear!

In normal circumstances you wouldn't over drill the holes. You would leave the holes in the skins the correct size and only dig out the core. I only over drilled because there were multiple layers, including an air gap, that needed to be spanned.

Damon.

[Pitou]

Another product to fill the drilled holes is West System 2 part epoxy called Six10. It's a cartridge that is used in a typical caulking gun. it's a lot easier and less messy than mixing a pot. I used this when installing my mast on the rooftop.

http://www.westsystem.com/ss/new-six10-epoxy-adhesive/

[Jeremyvmd]

I just saw that stuff and was gonna ask about it. Was planning on using it for my transducer where I dig out the core. Glad to hear it worked for u. I'll use it when I rebed my hand rails and when I mount my kayak carriers...

[djpeewee]

IMHO One of the greatest benefits of "regular" epoxy is that you can match the consistency of the mix to the task. If you need to wet out the inside of a hole, you mix neat (thin) epoxy so that it gets absorbed into the core material for better bonding and water proofing. If you need to fill a hole or bridge gaps you add filler to bring the epoxy to the consistency needed - syrup, mayonnaise, peanut butter, etc. You also choose the type of filler needed for the job - high strength, light weight, easy sanding, etc. In a lot of cases, you use a few different mixes to get the job done. I like to have control of the mix to ensure the best fit for the job. Having said that, anything from West System is good!

[djpeewee]

Jeremy, one other thing. If you are going to fill the transducer hole with epoxy of any type, be wary of the heat gain. I spoke with one of the engineers at West System and he indicated that amounts around 1/4 cup or greater, when in a contained mass, run the risk of spontaneously igniting the surrounding material. I mention this because I nearly had a meltdown when I did my transducer holes. They got real hot real quick and started smoking. They were hot enough that I couldn't put my hand on them. I threw a bag of ice cubes on them to cool them down. All ended up well, but it was a good thing I was paying attention and didn't walk away. The correct approach to this would be doing small pours, letting the heat dissipate, before the epoxy completely sets up.

[Jeremyvmd]

im not filling the transducer hole, i overdrilled the hole and the PO didnt take out the coring so I want to cut it back about 1/2" - 1"to protect the coring from potential water intrusion. Is that what your talking about or u mean filling them in to move the transducer elsewhere

I've experienced the same thing you did on my dads boat once so I know to watch out for it. Most people don't realize how exothermic the reaction can be!

[djpeewee]

Not moving the transducer - the existing hole.

Ideally you want to dig out the core, fill the hole with epoxy, and then drill a new hole through the epoxy for the transducer. Kind of like creating an epoxy plug.

[Jeremyvmd]

Yea I realise:/ I was gonna leave the epoxy proud then drill it back without actually filling the hole in completely. But we are Wayyy off topic now. Lol. Sorry to the OP

[djpeewee]

Hijacked for sure.