Is the extra light through 4 porthole pigeon box, worth the extra £700?

[dmr]

We have three pigeon boxes, each with four little ports, they let a lot of light in, so much that we hang a little curtain inside the engine room box so that the sun does not wake us up too early (we sleep in the back cabin).

The boxes don't leak but the tops do not shut totally (an extra bit of ventilation) and very hard rain can bounce of the roof and a tiny bit then gets in.

Opening the boxes is a very good way to help cool the boat when it gets too hot, and one provides good ventilation in the galley.

As they are steel they can be a source of condensation in the winter so some sort of lining is a good idea.

 

............Dave

[Cheshire cat]

In summer you do get more light than you need at four o'clock in the morning

[Phil Ambrose]

One more vote for a double glazed dog box, don't even think about Houdini hatches. There are photos of a six port pigeon box and a double glazed dog box in my gallery. If you go for the brass or stainless bars on top of your box, do consider the hinging system shown, it makes cleaning the glass and bars much easier.

I don't ever think about my Houdini hatches, they just sit there quietly letting in the light and not leaking, can't ask more of them.

Phil

[LEO]

Hi,

 

Pigeon box in the engine room with 4 ports, the units do leak a bit (hinged joints at the top) and can be can be made wind and watertight - I had a canvas hood made with clear plastic sections over the ports - very effective.

 

Other than that I have a prism and a bull's eye - both effective.

 

L

[Mike Jordan]

My opposition to the use of Houdini hatches is based on the number of times I have seen them cause problems with condensation dripping from the alloy frames. One of my local live aboard friends became desperate enough to have a thick slab of polystyrene and a purpose made cover mounted on top of the hatch for the winter months in a largely futile attempt to cure the problem. If you are happy with yours then I am pleased to hear it. During the summer months they allow a nice big hole in the roof for ventilation but in winter some form of secondary glazing is needed for live aboard users.

Mike.

[nicknorman]

On a slightly different subject, consider some internal glazed doors for your side hatch. It is a bit grim to have to have the side hatch closed just because it's cold. We have glazed Internal doors which means the steel side hatch doors can be open without letting the cold and wind in. Our only slight problem is the inner doors are not really weather proof so we have to have the outer closed when it's raining, but not when it's cold or windy. You can achieve the same effect with a sheet of Perspex but having it integral makes it look less of a bodge.

[blackrose]

15" portholes, QS? Blimey, those must be amongst the biggest on the inland waterways

All my portholes are 15" diameter. I have 7 on each side of the boat. I think 15" is a fairly standard size. I've even seen a few boats with 18" portholes, but they do look a bit big.

 

15" porthole

Edited January 31, 2016 by blackrose

[Athy]

All my portholes are 15" diameter. I have 7 on each side of the boat. I think 15" is a fairly standard size. I've even seen a few boats with 18" portholes, but they do look a bit big.

 

15" porthole

Is that the glazed or overall diameter?

[blackrose]

Is that the glazed or overall diameter?

 

Overall diameter.

 

I'm pretty sure that's how the dimensions of portholes are generally specified, but it's probably worth checking with any supplier.

[bottle]

On a slightly different subject, consider some internal glazed doors for your side hatch. It is a bit grim to have to have the side hatch closed just because it's cold. We have glazed Internal doors which means the steel side hatch doors can be open without letting the cold and wind in. Our only slight problem is the inner doors are not really weather proof so we have to have the outer closed when it's raining, but not when it's cold or windy. You can achieve the same effect with a sheet of Perspex but having it integral makes it look less of a bodge.

 

Our solution a cover that fits over the two outer doors made with the same material as a cratch cover.

 

difficult to describe but possibly like two open envelopes, fitted over the doors, with a window in between, obviously some extra pieces required to stop rain entering from the top.

Edited January 31, 2016 by bottle

[blackrose]

What about any condensation issues? Do pigeon and dog boxes suffer from this problem? I know some people have had this problem with single-glazed houdini hatches. Unlike cabin windows, the condensation on a horizontal glass surface can't easily be drained into a gutter so it ends up dripping into the boat. Is condensation an issue with prisms?

Edited January 31, 2016 by blackrose

[Athy]

 

Overall diameter.

 

I'm pretty sure that's how the dimensions of portholes are generally specified, but it's probably worth checking with any supplier.

Not sure about that, but it does make the glazed diameter sound more in proportion. Our portholes are about 10" to 11" across, but their frames will add another 4" to that measurement, making - yep - about 15"!

[nicknorman]

What about any condensation issues? Do pigeon and dog boxes suffer from this problem? I know some people have had this problem with single-glazed houdini hatches. Unlike cabin windows, the condensation on a horizontal glass surface can't easily be drained into a gutter so it ends up dripping into the boat. Is condensation an issue with prisms?

 

We have a prism in the bedroom. We were careful not to have it over the bed! Yes it does drip a bit but this is from the narrow strip of exposed brass frame rather than the prism itself (although it then runs down the prism to its inverted apex). On my list of job is to put a narrow strip of foam over the brass frame to stop this, it will be done once I have got that vital item, a round tuit.

[Theo]

 

 

Yes you wouldn't think it beyond the wit of man to design a rain-proof pigeon box would you?

No you wouldn't. But since it is get a woman on it.

 

N

[blackrose]

Not sure about that, but it does make the glazed diameter sound more in proportion. Our portholes are about 10" to 11" across, but their frames will add another 4" to that measurement, making - yep - about 15"!

 

So what is it you're not sure about? Your own example would also suggest that porthole dimensions are specified in terms of overall diameter - as I said.

 

Of course you should always be able to find the glazed diameter of a porthole in the specs, but when a porthole is listed as being of a certain diameter by a manufacturer or supplier, they're generally referring to overall diameter.

Edited January 31, 2016 by blackrose

[Mike Jordan]

Ref Blackrose & Condensation

Ive made a good number of double glazed dog boxes for narrow boats and the larger versions as deck lights for dutch barges. The glazing is made up as - 4mm toughened X 6mm spacer bar X 6.4mm laminated clear, the glazing is set flush with the top surface of the opening lights.

I have not to date recieved any reports of condensation on the undersides. In fairness the glazing of the Houdinis seems to be no problem, its the alloy surround that drips.

It's possible to cut vent slots in the top lower edges of a dog box to give high level ventilation but I can only recall having done this on one customers boat. (photo is in the gallery).

Mike.

[Athy]

 

So what is it you're not sure about?

About your assertion in the post which I was answering, of course.

 

Your own example would also suggest that porthole dimensions are specified in terms of overall diameter - as I said.

 

.

Not to me, it wouldn't.

[waterworks]

Cut a hole, weld in angle frame, and silicone in a double glazed unit. Job done. No leaks, no heat loss, low profile.

[DHutch]

Having started with two pigeon boxes and a glazed hatch, the pigeon box over the engine was changed around 15 years ago ten years into the boats life, and as of September last year we cut out and replaced the one over the galley as well, leaving us with just glazed hatches, much better.

 

- They let a huge amount more light in.

- They open fully any without issue when wanted.

- They shut tightly and seal when not wanted.

 

Sold!

[DHutch]

Out with the old, in with the new....

 

 

 

[mark99]

Bulls eyes definitely concentrate sun rays - if the focal point lands on flammable material then it could lead to a fire. The focal point varies of course with sun position and boat position.

 

How do I know? I set up a digital themometer, found the focal point with my finger (moved it about to find the 3d position in space in line with sun rays to where my finger got hot ) and replaced my finger with temp probe. It got to 700c before the probe charred.

 

I now have a lid for the bulls eye which covers it up when I leave the boat - just in case although the focal point does always seem to fall into a space where there is no flammable stuff.

Edited February 2, 2016 by mark99

[Phil Ambrose]

To add, the focal point of a lens, any lens is a fixed point this determined by the power of the lens, of course the focal point can be varied by using another lens ( or 2 or 3) think how a telescope works.

Phil

[LEO]

Bulls eyes definitely concentrate sun rays - if the focal point lands on flammable material then it could lead to a fire. The focal point varies of course with sun position and boat position.

 

How do I know? I set up a digital themometer, found the focal point with my finger (moved it about to find the 3d position in space in line with sun rays to where my finger got hot ) and replaced my finger with temp probe. It got to 700c before the probe charred.

 

I now have a lid for the bulls eye which covers it up when I leave the boat - just in case although the focal point does always seem to fall into a space where there is no flammable stuff.

 

I found a self adhesive semi - transparent sticker on the underside of the lens helped overcome this problem...

 

Interesting set of measurements though.

 

M.

[mark99]

 

I found a self adhesive semi - transparent sticker on the underside of the lens helped overcome this problem...

 

Interesting set of measurements though.

 

M.

 

 

I went and checked notes - sorry it was 180c before the temp probe outer sheath started smoking. That was in about 90 seconds.

 

Dunno where 700 came from............ old fart memory syndrome.

[ditchcrawler]

Take a look here for dog boxes http://nbsiskin.co.uk/?p=3478