electrical wire fitting

[paulga]

what wire fitting do you use to channel wires through the helm station surface, if not using a Seaview Cable Seals?

it's for the electrical wires to the monitor of a backup camera system as shown below. or other instruments that tap into the buss bar inside the helm station.

the camera wires will pull along the passages under the seats up into the arch, then exit from the top of arch and routed to the corners of the sundeck roof where the two cameras are placed

 

[Comodave]

You can use a small clam shell vent to cover the hole and let the cables exit the bottom. You can caulk it or just orient it so water will not run under the clam shell. They come in a variety of sizes. I found this particular one on Amazon.

Perko 0315DP2STS Stainless Steel Clam Shell Ventilator -​

 

[Bmarler]

It would depend on where the monitor will be mounted. Dave’s suggestion of the clam shell is a good one as long as it’s protected from water spray.
Otherwise just google “marine cable gland” and pick something out that looks ok.

 

[Nick F]

You can use a small clam shell vent to cover the hole and let the cables exit the bottom. You can caulk it or just orient it so water will not run under the clam shell. They come in a variety of sizes. I found this particular one on Amazon.

Perko 0315DP2STS Stainless Steel Clam Shell Ventilator -​

Good solution if you are passing the cable through a vertical panel.

A couple of questions:
1 - Does the cable have a bigger diameter connector which must pass through the panel before you fit the "trim" piece?
2 - Are you looking for a watertight closure or are you just looking for cosmetic appearance of the exit point of the cable?

In my opinion, the best options will depend on the answers to these questions.

 

[paulga]

Good solution if you are passing the cable through a vertical panel.

A couple of questions:
1 - Does the cable have a bigger diameter connector which must pass through the panel before you fit the "trim" piece?
2 - Are you looking for a watertight closure or are you just looking for cosmetic appearance of the exit point of the cable?

In my opinion, the best options will depend on the answers to these questions.

the cable will be either a 16gauge two wire cable, or a universal 4 pin aviation video cable shown as below

it's more for a professional looking. the flybridge is fully enclosed by a hard top and ising glass so the helm station is not subject to weather

 

[Nick F]

Looks like Commodave's suggestion of a clamshell fitting is the best option. The connecor should pass through a 9/16" hole which would be easy to cover with a clamsheell.

An alternate fitting would be a simple rubber (or plastic) grommet. Cut the grommet in one place to flex it open and fit it around the cable and only insert the grommet into the panel after you pass the cable and connector through the panel.

 

[EngNate]

Look at snap-in bushings from Heyco Products. You have to glue them in thick panels. They come solid and split. Any major electronics supply.

Digi-Key Elect - Bushings

 

[IWAB]

Paluga, What cameras did you buy?

 

[paulga]

Paluga, What cameras did you buy?

I ordered an off brand wired 4 channel camera system from overseas
If you don't need split screen, this yakry 2 channel has good reviews. Their support team can send a second camera for free at request. They also have a 4 channel wireless model but I'm not confident about it staying connected. I have to pull electric wires to the cameras anyway.

 

[paulga]

Looks like Commodave's suggestion of a clamshell fitting is the best option. The connecor should pass through a 9/16" hole which would be easy to cover with a clamsheell.

An alternate fitting would be a simple rubber (or plastic) grommet. Cut the grommet in one place to flex it open and fit it around the cable and only insert the grommet into the panel after you pass the cable and connector through the panel.

I figured that having the hole on the topside of the control station, right behind the camera, would hide away more cables. It will be a 1" hole similar to below. Is this cored fiberglass? Its thickness is about quarter inch. 1" is the diameter of the widest part of the harness. After the entire harness channels through, the cable dia is a quarter inch.

@Nick F could you show me a rubber grommet that fits here to do a watertight seal?

 

[luna]

Given your dimensions of a 1" hole and a 1/4" cable, this should work. Note that the side entry of the cable keeps things neat.

Side Entry CableClam - Blue Sea Systems

Engineering high quality marine electrical components for safety, reliability and performance

www.bluesea.com

If you want/need to go bigger and chunkier with the cable perpendicular to the mounting surface, maybe this.

CableClam 1.40" - Blue Sea Systems

Engineering high quality marine electrical components for safety, reliability and performance

www.bluesea.com

Amazon or your favourite chandlery should have both.

 

[paulga]

Given your dimensions of a 1" hole and a 1/4" cable, this should work. Note that the side entry of the cable keeps things neat.

Side Entry CableClam - Blue Sea Systems

Engineering high quality marine electrical components for safety, reliability and performance

www.bluesea.com

If you want/need to go bigger and chunkier with the cable perpendicular to the mounting surface, maybe this.

CableClam 1.40" - Blue Sea Systems

Engineering high quality marine electrical components for safety, reliability and performance

www.bluesea.com

Amazon or your favourite chandlery should have both.

Thanks. Cableclam requires drilling holes for screws. A grommet to me is simpler to install and can also seal it, but I may not have found the buzzword to the correct link.

 

[Nick F]

I figured that having the hole on the topside of the control station, right behind the camera, would hide away more cables. It will be a 1" hole similar to below. Is this cored fiberglass? Its thickness is about quarter inch. 1" is the diameter of the widest part of the harness. After the entire harness channels through, the cable dia is a quarter inch.

@Nick F could you show me a rubber grommet that fits here to do a watertight seal?

View attachment 159694

Lots of grommets on Amazon - just type "grommets". However, a grommet will not be waterproof athough it would greatly reduce the quantity of water going through. Personally, I would use the clamshell type devices as suggested by Luna et al. You will have a more professional looking finish and the straight-through should be watertight. Whichever method you use, I recommend a "drip-loop" in the cable underneath the panel.

PS: you might have difficulty finding a grommet that will accommodate the thickness of the panel - they are most used for openings in sheet metal.

 

[paulga]

The general drill bit size guidelines do not apply to fiberglass. According to the drill bit size chart, 1/8" bit should be used for #8 screw on hard wood. But here on fiberglass, 1/8" hole runs too small. The screw does not go in without chipping the gelcoat.

Is there a separate chart for fiberglass?

 

[Bmarler]

You should use a small countersink before inserting the screw.
And I think a #8 screw is about .160 diameter. You could go up to a .135 hole.
Or, I have good luck using machine threads. Instead of a wood or metal screw, use an 8-32 instead.

 

[paulga]

You should use a small countersink before inserting the screw.
And I think a #8 screw is about .160 diameter. You could go up to a .135 hole.
Or, I have good luck using machine threads. Instead of a wood or metal screw, use an 8-32 instead.

Thanks. I recall last year one advice to do it was to make a larger hole, fill with thickened epoxy, then redrill after curing. Since the flybridge is fully enclosed, no need to do that way.

The next larger drill bit than 1/8" that I have is 9/64" or 0.14. I will try that with countersink.

There is a very thin milky coat on the underside, looks like it's the final coating in the lay up schedule. What material is this coat?

 

[Bmarler]

Hard to say what it is. Could be paint, could be gel coat. It’s a hidden surface, so just something to seal the surface.
If the .140 hole doesn’t hold the threads, you can fill it and do the 8-32 instead. I think it will though.

 

[paulga]

Hard to say what it is. Could be paint, could be gel coat. It’s a hidden surface, so just something to seal the surface.
If the .140 hole doesn’t hold the threads, you can fill it and do the 8-32 instead. I think it will though.

It's still very difficult to drive the screw in a 9/64" hole. The fiberglass was making crackling sound when the screw was driven. so I decided to switch to #8 machine screws.

The diameter of #8 machine screw is 0.16", I had to use a 5/32 bit, as the next larger bit in my tool set, 3/16, is too large. Then I tried enlarging the hole using the same 5/32 bit, but unfortunately chipped the gelcoat. Gelcoat is very fragile to this type of peripheral force.

The correct drill bit size for 0.16" is a #21or #20 drill bit. I don't have any filing tool or burr bit that fits. Other than buying the correct drill bit, are there alternative ways to enlarge the hole to 0.16"?

 

[luna]

I have never tried to have a machine screw cut threads in fibreglass. I doubt that it would work. What edge does the cutting? Stainless is pretty soft and galls easily.
Sounds like a disaster.

If you now have a 5/32" (0.156") diameter hole in the fibreglass that is around 5/16" thick and the head of a #10 machine screw will fit on whatever it is that you are trying to secure, buy a #10-24 tapered, spiral or straight fluted tap and a tap wrench if you don't have one and tap the threads into the hole in the fibreglass.

If you countersink the holes to a depth equal to the gelcoat thickness (0.030"+/-) it will make starting the tap easier and you should not chip the gelcoat.

Make sure that the tap is started parallel with the hole, go slow, 1/4 turn or less in, 3/4 turn out, until the tap is sticking out the backside of the fibreglass about 1" and turns with one finger. Your hole size, if perfect is 0.1562" and the correct hole size for steel is 0.1495", so your hole is a little (0.0067") big, which will likely be just fine. Go slow, you don't want to break the tap. A lubricant like bees or candle wax will help.

If you feel it binding, STOP and get a #21 and #20 drill bit to enlarge the hole by about 0.002" each.

Once done, as long as you don't tighten things up like it's a threaded steel connection you should not pull the threads out of the fibreglass.

 

[Comodave]

When using a self tapping screw in fiberglass you want to dill the hole minutely larger than the shank of the screw. Fiberglass isn’t like wood in that you have to carefully size the drill bit so it is the correct size. You only want the threads of the screw cutting into the fiberglass. Once you drill the hole use a countersink to cut away the gel coat a bit wider than the screw threads. This will stop the gel coat from chipping and lifting. You can also use a lubricant on the screw threads like a bar of soap. I don’t force the screw in but go in a bit and back up like you would use a tap.

 

[Bmarler]

He’s already well over the minor diameter (.122) of the #8 self tapping screw, so it’s time to cut actual threads.
When I mentioned switching to machine screws, I took it for granted that a tap would be involved.
I tap holes very often, and am probably a bit cavalier in my technique. I normally power tap with a impact tool or a drill motor. In fiberglass, I drill using the same size tap drill as I would for steel. Use lubricant on the tap, anything will work. Use a good tap. 2 or 3 flute. 4 flute don’t have enough chip clearance for my taste. I use tapmatic, or rapid tap, but have been known to use bacon grease if nothing else is available. Grease actually helps bring the tapping debris out to the surface as you back out the tap.
#29 is the drill size, or 9/64 will work if you don’t have number drills.
Don’t forget to chamfer the hole after you drill it and before you cut the threads.

 

[paulga]

He’s already well over the minor diameter (.122) of the #8 self tapping screw, so it’s time to cut actual threads.
When I mentioned switching to machine screws, I took it for granted that a tap would be involved.
I tap holes very often, and am probably a bit cavalier in my technique. I normally power tap with a impact tool or a drill motor. In fiberglass, I drill using the same size tap drill as I would for steel. Use lubricant on the tap, anything will work. Use a good tap. 2 or 3 flute. 4 flute don’t have enough chip clearance for my taste. I use tapmatic, or rapid tap, but have been known to use bacon grease if nothing else is available. Grease actually helps bring the tapping debris out to the surface as you back out the tap.
#29 is the drill size, or 9/64 will work if you don’t have number drills.
Don’t forget to chamfer the hole after you drill it and before you cut the threads.

how to determine the drill size #29 (0.136)?
i didn't find this number in the below chart

 

[luna]

He’s already well over the minor diameter (.122) of the #8 self tapping screw, so it’s time to cut actual threads.

If the existing holes are now at 5/32" (0.1563") plus a little reaming in an attempt to make the hole larger, I don't think cutting threads in the bore of the hole for any #8 sized fastener is going to be fruitful. If everything was perfect you would have about a (0.164 - 0.156) /2 = 0.004" deep thread.

I see 2 options using the existing holes.

1. Drill the holes to 11/64" (0.172") and drop in a #8-32 machine screw (d = 0.164") and tighten it up using washers and a nut. This requires access to the other side of the work.

2. Tap the existing 5/32" holes using a #10-24 tap. The hole is a bit big for the tap but likely will be fine. Only one side access is required. You need to confirm that the shank and head of a #10 fastener will fit on whatever it is that you are securing.

 

[paulga]

If the existing holes are now at 5/32" (0.1563") plus a little reaming in an attempt to make the hole larger, I don't think cutting threads in the bore of the hole for any #8 sized fastener is going to be fruitful. If everything was perfect you would have about a (0.164 - 0.156) /2 = 0.004" deep thread.

I see 2 options using the existing holes.

1. Drill the holes to 11/64" (0.172") and drop in a #8-32 machine screw (d = 0.164") and tighten it up using washers and a nut. This requires access to the other side of the work.

2. Tap the existing 5/32" holes using a #10-24 tap. The hole is a bit big for the tap but likely will be fine. Only one side access is required. You need to confirm that the shank and head of a #10 fastener will fit on whatever it is that you are securing.

in your post 19, "correct hole size for steel is 0.1495" ", is this the hole size required by a 10-24 tap / 10-24 machine screw, on steel/fiberglass?

I noticed the diameter specs of screws have a range. does this mean different manufacturers can select different diameters within the range?

this chart is from ANSI External Screw Threads Size Tolerances Chart. Basic means nominal. they also have a chart for "internal screws". I think the zinc and ss fasteners from home depot are external screws.

 

[paulga]

If the existing holes are now at 5/32" (0.1563") plus a little reaming in an attempt to make the hole larger, I don't think cutting threads in the bore of the hole for any #8 sized fastener is going to be fruitful. If everything was perfect you would have about a (0.164 - 0.156) /2 = 0.004" deep thread.

I see 2 options using the existing holes.

1. Drill the holes to 11/64" (0.172") and drop in a #8-32 machine screw (d = 0.164") and tighten it up using washers and a nut. This requires access to the other side of the work.

2. Tap the existing 5/32" holes using a #10-24 tap. The hole is a bit big for the tap but likely will be fine. Only one side access is required. You need to confirm that the shank and head of a #10 fastener will fit on whatever it is that you are securing.

the cableclam accepts up to #8 pan head screws.
The underside of the helm station is accessible. all the electrical wirings to the electronics are arranged inside the station.
I have some #8 zinc machine screws from home depot, the major dia measures 0.16", so #20 or #21 drill bit works to get it through.

 

[luna]

how to determine the drill size #29 (0.136)?
i didn't find this number in the below chart

View attachment 160835

You did not find the tap drill size on the above referenced chart as that chart is not used to select the tools to actually machine the threads. It's more of an engineering chart.

Here is a Tap-Drill Chart that lists the drill size needed to allow you to tap numerous different thread sizes.
If you can live with the usual 75% depth of thread, these will work for you.

Tap Drill Chart

 

[paulga]

You did not find the tap drill size on the above referenced chart as that chart is not used to select the tools to actually machine the threads. It's more of an engineering chart.

Here is a Tap-Drill Chart that lists the drill size needed to allow you to tap numerous different thread sizes.
If you can live with the usual 75% depth of thread, these will work for you.

Tap Drill Chart

Thanks for the education.
so the tap drill size is based on 75% depth of thread.

For this application I will get a drill bit, no need to tap.

For the screws on the an exhaust through hull fitting, which method is preferred? Drill the major diameter, or drill then tap?

The major diameter of the screw measures from 0.189" to 0.192" due to bias in measuring or manufacture

 

[luna]

The determination as to the composition of the threads that the exhaust through hull fitting's fasteners engage with is driven by a lot of things including, hull construction (cored or solid), hull skin thickness, total hull thickness, hull shape at the location, (how much clamping force is required to have the gasket seal) and what other loads are on the fitting.

Only you can make this determination on your boat.

On my boat when I installed my 70 mm diameter exhaust tube's fitting, after I had sealed the foam core that was exposed when I cut the large hole, I carefully drilled into (but not through) the outer skin, about 1/4" deep and then tapped the hole, finishing the threads with a bottoming tap.
My exhaust fitting is held in place with 3 #10-32 SS machine screws that are just the right length to work with the depth of the blind but tapped hole that I created.

So far, at 20 years on, so good.

 

[paulga]

The determination as to the composition of the threads that the exhaust through hull fitting's fasteners engage with is driven by a lot of things including, hull construction (cored or solid), hull skin thickness, total hull thickness, hull shape at the location, (how much clamping force is required to have the gasket seal) and what other loads are on the fitting.

Only you can make this determination on your boat.

On my boat when I installed my 70 mm diameter exhaust tube's fitting, after I had sealed the foam core that was exposed when I cut the large hole, I carefully drilled into (but not through) the outer skin, about 1/4" deep and then tapped the hole, finishing the threads with a bottoming tap.
My exhaust fitting is held in place with 3 #10-32 SS machine screws that are just the right length to work with the depth of the blind but tapped hole that I created.

So far, at 20 years on, so good.

This approach is interesting.
The through hull fitting only need 1/4" length of screws to secure? This is a surprise.
The topside hull on my boat is about 5/8" solid fiberglass. The outmost is a glossy layer of gelcoat with horizontal plank lines. It's visually flat between the lines. There are no additional loads other than the fitting.

 

[paulga]

You did not find the tap drill size on the above referenced chart as that chart is not used to select the tools to actually machine the threads. It's more of an engineering chart.

Here is a Tap-Drill Chart that lists the drill size needed to allow you to tap numerous different thread sizes.
If you can live with the usual 75% depth of thread, these will work for you.

Tap Drill Chart

Does this chart cover machine screws only?
For example, a screw stud on a snap fastener is a self tapping 8-15x3/8". I didn't see there is a 8-15 tap. Is a self tapping screw supposed to be used as a tap by itself, when driven into fiberglass, as described in post 20 by @Comodave?