Mast conduit--is it worth the effort?

[nestorph]

I have my mast down (Islander 30 Bahama) and have a number of maintenance and upgrade projects on the list before she goes in the water. I came across an excerpt from Don Casey's book that described a method of installing a conduit inside the mast using sealant or adhesive to secure the conduit against the inside. This prompted several questions:

• What size conduit is typical? I was thinking 1-inch
• What type of sealant or adhesive would be able to hold the conduit? We're talking at least 40 feet!
• Would the adhesive really be able to sustain a drill coming through the mast and into the conduit without it being pulled away from the mast?
• Is this whole exercise even worth the effort?

I appreciate any and all opinions.

 

[AXEL]

Why are you thinking of putting a conduit in your mast? Is it to run electrical wires? If so, I used the nylon tie wrap method. I located 6" (or 8") nylon tie wraps every foot or so around the cables all the way up. Obvioulsly you have to have the cable harness out of the mast. Do not cut the ties wraps. They will support the harness all the way up so no slapping wires inside the mast. Way easier than trying to attach a conduit.

 

[Skipper]

I'll tackle the last question, with an alternate installation idea I've been considering for mine.

I thought it would be worth it to install conduit, only to silence the wire-banging, when I 1st started sailing the boat. The halyards run outside the mast.

It's been 3 years now, and I realized that I can't hear the banging anymore. I've become accustomed, like my grandfather who could no longer get to sleep after his noisy mechanical clock stopped working. He'd fallen asleep to the noise for 20 years, and the subsequent silence was deafening.

Anyway, if given the opportunity (IE: mast down), I'd probably look at conduit. My idea is to attach the wires to the outside of the conduit or rod, then adhere it to the inside of the mast. This would eliminate having to drill through the conduit at the steaming light, and having to pull the wires through the conduit. I'm no expert on this type of installation, I only have ideas, so would have a conversation with the pros when I'm ready.

A properly secured conduit can be drilled through. Or, you could measure and pre-drill. Also, you'll have to consider conduit material for adhesion, corrosion properties, and longevity. I'd think non-metallic would be worth looking at, if it's specific to the application.

 

[tommays]

I put mine in following knotheads advise and it was not that hard

You drill one tiny hole to use a coat hanger/hook to hold it in place while you drill and pop rivet the conduit

I was able to do a careful hole for the steaming light /deck light fixture wires after the install and it worked out

I use 3/4 ? cant remember and wish I had gone one size bigger as between the 5 wire cable for the lights and the coax cable it was fairly tight

When you done you just pop rivet in the few extra holes


I did use goop to hold my J24 mast wires after I painted the mast and while it did work I would NOT do that again

 

[centerline]

ive used the tie wrap method, and would again... in my opinion, conduit is unnecessary and not worth the hassle.
if your only thought is to quiet the tinging noise, the nylon ties are cheaper, easier to work with (now and later), require NO maintenance, and will never come loose by accident and cause a worse sound than before.... and they are lighter.
as for wire support, the condiut does nothing to add vertical support. that has to be done with a strain relief cable, if its even required on your boat. usually if the installation of the wires have been bundled correctly and secured well at the top of the mast, the wires are strong enough to support their own weight for at least 50ft or so...

BUT, if your wires come out of the coachroof under the mast, then a short piece of conduit to make that transition would be a much better way than the option my boat, and probably most boats, has.
on my boat the wires are all bundled together and then about two caulking tubes of sealant has been applied around them and then glued and sealed to the coachroof to shed the water so it doesnt enter the boat. I think with an 18inch piece of conduit the job would have been better, stonger, easier to work, during the install and now, and cheaper.... sealant would still be needed but not as much.
as it is, its going to be a pain to add another coax or wire down thru the roof from the mast....

 

[Ron20324]

I can't help but wonder, if you pop-rivet a PVC (or whatever type) conduit, wouldn't it be prone to breakage when the mast bends in any direction? Particulary those with backstay adjusters.

 

[cjm1]

I have this thing of drilling holes in a mast. I replaced a damaged wood mast with an aluminum spar off a Sabre 38 with exterior halyards and internal electrical mast lighting and no antenna. The mast is 53 Ft (5" x 9") with some original internal foam blocks inside (not sure how many but guessing 5). I made a conduit out of regular 10 Ft PVC tubing (in this case 5 of them glued together) and fitted a wood pointed tip to the end and pushed it thru. No ties but I may have anchored the top and bottom with silicone to the side of the mast. It is 3/4 In and only carries the antenna wire but could carry more mast head wires if needed. No noise or movement and has been in place 20 years.

 

[Tim R.]

I can't help but wonder, if you pop-rivet a PVC (or whatever type) conduit, wouldn't it be prone to breakage when the mast bends in any direction? Particulary those with backstay adjusters.

PVC electrical conduit is very flexible. The bend is not enough to cause an issue.

To the OP: If your mast extrusion is completely smooth on the inside this is typically the way to install a conduit. If your extrusion has any "T"s on the inside like mine then you can split the conduit and run it up the ridge.

I have installed conduit in both kinds of extrusions.

The rivet method I had the mast down on sawhorses. I removed the top cap and used a 16' length of 1/3 strapping(working from each end) with a couple small blocks of wood on the end to hold the conduit in place while drilling and riveting(1/8" aluminum). The conduit was laid on the bottom of the mast and I drilled up from below. I pre-installed some pull strings for the whole length and some just to the steaming light exit. You can pre-wire but you have to be very careful not to drill so deep to damage the wiring.

 

[Tricia]

Do the rivet ends inside the conduit chafe...

...the cable insulation? I've only ever done the wire tie method and it's worked well for me.

 

[Scott T-Bird]

I think a 3/4" conduit would be fine. I have wiring for lights, COAX and cable for the wind instrument. Before selecting, run some wiring thru some short pieces and make up your mind just by sampling.

My mast had the conduit installed originally with gray conduit (electrical?). After 20 years it was very brittle and the pvc broke free at several rivets so it was loose. I replaced the conduit in kind, realizing it isn't going to last for life. Aluminum pop rivets will work fine, no worries. I wouldn't use glue, that would leave a mess when somebody eventually has to replace the conduit. It is exposed to weather so it isn't going to last forever.

I think it is a much better solution than a loose bundle of wires, but I'll acknowledge that it is a matter of personal preference. I don't like the idea of the halyards tangling with the ties, but I suppose that isn't really an issue.

My conduit is secured to the leading edge of the mast, which has caused some interference when installing hardware on the leading edge for spinnaker gear, but the conduit is flexible and was basically moved out of the way without disrupting the rivet pattern.

BTW, I wondered why there was a pair of holes at every other location! I used Tim's method and installed it with no fuss. I recommend running a string thru initially so that you can fish the wires after drilling.

 

[shemandr]

If I had a choice between conduit or none - I would take the conduit. I think I would just like to have my halyards running as free as possible without possible crossing over wires or vice versa. I always found it hard to tell if wires and halyards were really not crossed with the mast on saw horses. Maybe I had bad technique. Nevertheless, I don't want my halyards binding at all.
As far as getting used to slapping wires in the mast - I didn't and the Mrs. certainly didn't. Maybe you've heard the rule vis-a-vie wives, which goes something like "If I'm not sleeping neither are you."

 

[TLW]

Many of you will find that your mast sections have a "T" or "C" shaped part of the extrusion that accepts a PVC conduit and holds it in place for the entire length of the conduit. Isomat, Sparcraft, Spartan, the MORC Sections from Dwyer, some Kenyon extrusions accept the conduit. With the "T" shape, the PVC tube must be split, cut, over its entire length to slide onto the "T." Also, using two lengths of PVC, one following the other, leaves access to steaming light wires at the appropriate place on the mast.

The section below has two "T"s in the forward part of the extrusion.

 

[Scott T-Bird]

That makes some sense to have the conduit offset from the center to allow room for spinnaker hardware in front. My mast section is Kenyon MORC 4060, but it doesn't have those extrusions. It does seem to have a shape that allows the conduit to be offset slightly, though.

 

[TLW]

Interesting! The MORC sections from Dwyer Mast do have the "T" extruded with the mast section. I thought the Dwyer sections were the same s the old Kenyon spars. I see that some Kenyon spars listed as MORC sections do not have the typical "foil" shaped design. The Dwyer sections have similar numbers - 460 rather than 4060, etc. Not sure what the history is here.

 

[Anonymous 121765]

My 1980 C30 was not made in an era of Quality Control in boat building.

My wiring cables would slap back & forth while sailing & on the hook.
My halyards all ran on the outside only adding to the slapping.

The last time I dropped the stick, I not only added a conduit tube, but also modified the mast to run all interior halyards. Also, it's a great time to inspect & changeout any hardware & attachments.

Best decision I ever made to stop the annoying "Clang & slapping."

CR