Over Boom Tent

I am going to construct an over boom tent for my mirror, I have an old canvas tent which I plan to modify but I have a small problem. Owing to storage difficulties my dinghy is here at home but my mast and boom are stored in a friends house about 100km away, so I cannot rig the dinghy to take measurements. Can anyone tell me how high the boom is from the deck? I assume the boom is roughly parallel to the side decks?

sail_and_oar's picture

I wish I could add a bit more detail but at the moment I would like to make a suggestion;

That you build the tent so you can sit on the aft buoyancy tank with the tent up, otherwise you will have to do everything lying down horizontal. This means kicking the boom and gaff up in the air a bit.

I really think the only practical way to measure the tent for fit is to drape it over the boom and see where it touches.

I'm currently on my third Mirror tent and built a couple for a Wayfarer. If you need any help with details I will help all I can.

Camping on a Mirror works well. If you've not done this kind of thing before it will revolutionise the way you think about sailing


PuffinInTegel's picture

@Joeb : Chapter 5 of the class rules
(http://www.sailing.org/tools/documents/MIR2012CR300812-%5B13372%5D.pdf ) state :
>>>> 5.1.6 The distance between the bottom end of the mast and the top edge of the boom shall be
669mm ± 10mm. <<<<
That means that if your boom/gooseneck is about 60 mm high, you have 609 mm left under the boom.
I'm average height and need ~ 940 mm to sit upright, so I would not be able to sit on the deck under a boom-height tent.

I have been toying with the idea of sleeping aboard too.
Nowadays there are relatively low-cost tents igloo and barrel-shaped tents available. I was wondering whether anyone has already tried adapting these for dinghies. A near semicular cross-section would definitely provide a bit more room to move about in. An old CANVAS tent has the disadvantage that it tends to leak if it's wet and you bump against it (at least that's what happened when I was in the Scouts). Modern synthetics are much lighter and more waterproof. I assume a used tent to chop apart can be had for peanuts on e-bay.
I have a three-section air mattress that can fold into a sort of armchair configuration and could be put into the cockpit for sitting on (eating, reading) which should give me adequate headroom and intend to try slinging a net over the cockpit and putting the air mattress on that to sleep on. However that's a project that'll have to wait for warmer days.
I don't want to jump around in the boat when there's no water to counteract my weight on the bottom boards.
Let us know how you progress !
@ Cliff: have you written an equally excellent description of your tents as on the sail-area topic ?
Have you seen Heather's videos of the British Columbia inner passage cruise (*) ? I find those "Deck coverS" over the bows an ingenious invention and asked her about it - she wrote that they came with her Mirrors. I may try making something like that some day.

Gernot H.

* http://www.youtube.com/watch?v=vNDdkEIOnls

curlew's picture

I agree with Cliff 100%. You probably need a scissors device to solidly hold the boom end up so you definitely have head room. You can make a tent by draping a tarpaulin over and then trimming with scissors. There are several ways of holding down the edges, but I use anorak "bullets", on cords threaded through small holes under the gunwale. A great thing to try. Get a good anchor!


sail_and_oar's picture

I never had a scissor crutch on the Mirror or Wayfarer. On the Mirror I tie the jib halyard tail to the aft end of boom and gaff, chuck the tent over boom and gaff, hook the skirt of the tent onto the little stainless hooks and haul away on the halyard. Tent pops up ready for the night. The Wayfarer was similar except we used the main halyard and added a line from boom end to each quarter to stop the boom flopping from side to side. Never had hooks on the Wayfarer tent, instead we threaded lines right under the hull. A lot of tension goes into the aft end of the tent so make it good and strong.

As David pointed out get a good anchor. I'm using a 6lb Danforth and a 5lb plough. I think David has a 10lb fishermans and a 6lb Danforth. You will need at least 5 times the tidal range of nylon or polyester line for each anchor.


sail_and_oar's picture

I wrote this about 5 years ago for the Dinghy Cruising Association. It really needs updating but not tonight

The simple boat tent
Every so often we see new members square up to the task of shelter. Our regulars laughed at my first tent, and my second (thanks Len)
It’s been a while since Rogers article on boat tents for Dinghy Sailing Magazine and very little has appeared in recent issues of the bulletin. One new material has appeared in recent years which can be very cheap.
Sarah and I started making a boom tent for the Wayfarer using a cheap (thin) polytarp. I had misgivings about whether it would be strong enough, it seemed awful lightweight. 2 years later and it’s still OK . This stuff is really good, the main problem is condensation and to a lesser extent cold.

Tyvec is the Dupont trademark for a range of non woven textiles made from polyethelene fibre. It is waterproof (pretty much) and breathable. It is also marketed by companies other than Dupont under different names. The stuff I have made my new tent from is intended for wrapping timber frame houses up prior to the outer layer of bricks being built. It is silver on the outside and white inside and has a much warmer feel than polytarp. I am hoping it may cure condensation problems. Normally available as a roll 100m long, 9 feet wide. Offcuts occasionally appear, sometimes for free.

Gaffer tape
Cloth reinforced sticky tape 2” wide Silver or occasionally black. Buy some decent stuff from somewhere other than the 99p shop. A big roll 6”across should do one tent.

In the past I have managed to rescue the old eyelets from the polytarp and reposition them in the tent. You have to crunch them up to get them out, cut a hole in the tent in the right place and flatten them out into it. As my latest tent was from Tyvek I had no eyelets so I had to use an eyelet kit from a chandlery. I used the 3/8 size which comes with a punch and setting tool. Slow and fiddly but works well enough.

String- anything 4 mm upwards

Holding it up

All I’ve ever used is a halyard from somewhere up the mast to support the boom end to hold the tent up. The boom can slop from side to side but this can be cured with a line from each aft quarter to hold it steady. It’s been fine in a F7. I’ve not investigated moving the gooseneck up each night but it would give more headroom. It’s a trade off with windage. Enough people think a boom crutch is vital equipment to suggest it’s worth investigating.

Holding it down
Tent tied to hooks under gunwale.
This is the favourite, either with line or elastic. Fix hook to boat. Fix eyelet to tent. Attach line between them, done. Having a single line joining onto two separate eyelets can work. The line goes from one eyelet, under a hook, along to the next hook back up to the other eyelet.
Tied under boat.
People grizzle about this. It’s worked well on our Wayfarer. Obviously you have to be afloat to put the tent up and down. We have 5 lines attached to the tent of the correct length with a hook on each. The lines are passed under the transom and each hooked onto a loop on the opposite side of the tent, The main halyard is tied to the aft end of the boom. Haul on the halyard, the tent pops up tensioned evenly every time.

Getting down to it
You need a dry day, not too windy, ideally with the boat on a trailer
Polytarp (or whatever) Scissors, masking tape, gaffer tape, marker pen, extra string, tape measure
First thing is to work out the headroom. In a very small boat you may not be able to sit up straight but you should be able to sit up enough to cook. The aft buoyancy tank is the only “comfortable” seat in my Mirror. Prop or tie the boom in place at about the right height above the boat. It’s worth making sure the aft end of the boom is higher than the front so that if you need to fit a gutter under the boom the water will run the right way. If you are planning to furl the sail around the boom (recommended) when you overnight, do this before you start making the tent. It alters the headroom and the amount of material needed
Throw the polytarp over the boom so it hangs down the sides of the boat. You will probably be able to make the tent in one piece with no joins so make sure there is enough aft of the transom to form the doors. The same goes for in front of the mast. Start sticking the tarp to the topsides of the boat with masking tape, cutting the spare off the hem as you go. Cut from the very front of the tent to the mast so the material lies along the boom and from the very back to the aft end of the boom to form the doors. Tape the doors shut and cut off the surplus. Cut around any standing rigging which gets in the way.
Mark on the polytarp where the eyelets will go. Our Wayfarer uses 5 each side aft of the shrouds and one in front whilst my Mirror uses 4 aft and 2 in front for a tent which covers the whole boat. Try and make it about the same on both sides of the boat.
Take the polytarp off and lay it on the ground. All cut edges will be “hemmed” on at least one side with gaffer tape. Where eyelets and Velcro are to go it wants at least a single layer on both sides. Any inside corners such as where the tent is cut around a shroud need to be thoroughly reinforced.
Sewing the Velcro is hassle. You’ve got to be in the right frame of mind. Stick the Velcro in place with a little bit of tape every 4” to keep it flat, Get some beers in, empty the ashtray. It’s going to be a long haul. I use a sail needle and thick polyester thread (for everything, even fixing my jeans). It is mainly the ends of the Velcro which are going to fail. Plenty of stitches here, the middles are less important.

Solving problems
Drips from the boom
I suspect this has a lot to do with using a halyard to hold the boom up. Rain hits the halyard, runs down to the boom, into the sail and drips off it right in the middle of the boat. It wasn’t funny the night I spent at Ashlett in a F7 when there was 2” of rain recorded at St Catherine’s point. A piece of waterproof material the length of the boom can be tied up under it to run any water to the mast. Just don’t touch the mast. My original was a piece of polytarp. A better version with strings attached was made for our Wayfarer. It’s good but not very durable and the slightest hole makes it as good as useless. Possibly better than this is “damp proof course” A heavy polythene ribbon available by the roll in various lengths and widths from builders merchants.

Can’t knot bungee cord
“Knottable “bungee cord is a big con. Standard bungee knots just fine if you use the right knot. For a bend try the fishermans knot, for a loop the perfection (or anglers) loop. For the most part neither slip or jam.

Gaffer tape won’t stick to old, dirty or salty polytarp
White spirit and loo roll works wonders

Worried about chafe wearing through the tent, spiky fittings on the gaff
Gaffer tape, multiple layers.

Tyvec update;
Shortly after making my tyvec tent I was rather disappointed to find it had lost it's waterproof qualities. Rain was getting in where the tent pressed against the sail and gaff. I covered the ridge of the tent with a strip of polytarp about a foot wide. When a tent has quite a steep pitch as here it doesn't have to be waterproof. Any water which oozes through the tent material will run down the inside and onto the gunwale as would condensation in any tent. It is important that if any sewing is done on the sides of the tent that the loose ends of the sewing thread are on the outside of the tent or they will drip as will any edges such as sticky tape which is coming away.

Lacing hooks into thin ply
I originally thought it would not be practical to attempt to screw into the 5mm ply of the hull as any screws would pull out. I had horrible wooden hooks glued to the hull which are best forgotten. Later I went back on my thinking and used little stainless lacing hooks. The fitting process follows;

Hold hook in position and drill pilot holes for screws
Screw hook to boat
remove screws and annoint holes with epoxy resin
reattach hook while epoxy is still wet
Walk away

The hooks have got a bit bent from bashing against docks/walls/whatever but the screws have held well much to my surprise.

Thanks everyone for the huge response, I've loads of info to work my way through! do most tents encapsulate fore deck and cockpit? how do you seal around the shrouds and mast to keep rain out?


curlew's picture

Hi Joe
Cliff does it differently to me because, as with every detail of our boats, we each worked out our own ideas. In my case the tent comes as far forward as the mast. The shrouds are a slight problem, and I cut slits in the material for them. The front doors of the tent overlap in front of the mast, and ties wrap round the mast at boom level. You can make a little conical hat to wrap round the mast above the tent at this point, but I now just stuff a plastic bag into the gap! The tent has large flaps resting on the foredeck to form a seal. In my case, I have the tent permanently rolled up under the boom, on a strip of wood.
I use boards at thwart level for sleeping. It is best to somehow support them lower than the foredeck at the front, so that the bed does not slope too much if you are on a sloping beach.
The sides of the tent hang down the outside of the boat, and strings pull down through a few small holes under the gunwale. It is actually very easy to make a tent, but you need to test it a bit before your first night in it.

sail_and_oar's picture

My answer is don't bother. Water will get in and it's important to have an arrangement which means you don't end up lying in it.

If we go back to page 4 of "Setting up the Cruising Dinghy" You will see my boat "Daydream" with a stack of boards on the aft buoyancy tank. There are four of them. Two are 3 foot long and 18 inches wide and the other two are 3 foot long and 14 inches wide. They are all cut from half inch ply. The narrower boards are the correct shape to serve as replacement centreboards should I break mine (which I have 20 miles from where I launched)

These boards are the base for my bed and I use 2 polyethelene foam camping mats as a mattress.

In heavy rain, water will be trickling down the halyard and into the sail where it runs down the gutter slung under the boom and goes down the mast into the bottom of the boat. It will also run down the sides of the tent, come in through the gaps where the shrouds pass through onto the side decks and again disappear into the bottom of the boat. I stay on my little plywood island and very rarely get even damp.

If I camp in cold conditions I will stuff something up against the holes by the shrouds to slow the wind down a bit.

And bring a hot water bottle.


Link to Setting up the cruising dinghy

I have used and seen used on other boats US Army suplus shelter halves, more or less as is, as boom tents. They work quite well, and are cheap! They are also pretty much indestructible. They consist of two halves of a tent that snap together with a double overlap at the ridge. You can toss them over the boom or run a line between the two layers of overlap.... The ends close at an angle to cover the foredeck area and can either close at the same angle at the stern or be flaps to close it off vertical. They are a bit short for some boats, but might fit a mirror very well.

Here's one source--not an endorsement, but you can see them in the catalog: http://store.colemans.com/cart/us-military-pup-tent-2-half-shelter-syste...

Used they are about $20 cheaper.

Thanks for all your comments everyone, I have discovered a fly sheet from a relative modern tent at home and I am going to start experimenting with that. I think I will use ropes going under the boat as I don't want to drill any holes in my lovely Mirror, I will extend the tent as far as the Bow and make a removable platform to sleep on.


sail_and_oar's picture

Running lines under the hull demands that everything is really well prepared before you intend to use the tent. We worked this system with our Wayfarer for 3 years and rigged it in pouring rain, pitch dark and strong winds, occasionally all three at once.

After a few modifications we ended up with a row of loops down one side of the tent and a row of lines down the other each with a plastic hook which had a keeper on it to stop it dropping off the loop. They were numbered 1 to 6 starting from the bows. The length of each line is critical and needs to be set up accurately before hand. After removing the rudder and retracting the centreboard we would bunch the tent up at the transom and attach line No1 to hook No1, line No2 to hook No2 and so on until the whole lot was laced under the boat then pull the tent forwards to the bows. Haul on the Halyard and the tent pops up with nice even tension. With the Wayfarer we used the main halyard tied around the boom end. For the Mirror I suggest tying the jib halyard tail around the boom and gaff just aft of the mainsheet block.

On a first attempt this isn't going to be a quick operation. It may take an hour and if it does it will be one of the most important hours in your sailing career. Practice will speed the operation. If you get it down to 10 minutes you're doing well.

The sail will hang down inside the boat so bring a few bits of string to tie it up with or better still rig a gutter up under the boom.

Fenders are a bit awkward to rig for pontoons. I string mine from a line which is attached to the masthead so they hang down outside the tent.

Nobody said it would be easy in your first year. You are a stonesthrow from discovering a new life of sailing. Never again need you feel a prisoner to the slipway.


curlew's picture

Hi Cliff
You mention fenders, but I still have not solved how to do it when the pontoon is higher than the gunwale.

sail_and_oar's picture

Now you mention it David and I can't ever recall seeing you berthed on a pontoon. Sausage fenders are my choice. Stowage is a problem. I used to have a 24" stowed outside the hull on each side but now just have a single 18" fender which I keep on board. I often rig it to my "topping lift" line with a rolling hitch so I can adjust the height. I've never had much luck in getting a rolling hitch to hold on a stainless steel shroud. The bottom of the fender wants to be about 6 inches below the gunwale and the top of it will usually bear on the pontoon somewhere. Often pontoons are supported by concretete floats (filled with expanded polystyrene so the dont sink!) and if you can get your fender up against one of these so much the better. Use really long mooring lines, 20 feet is good so the boat isn't left hanging when it dries out. I normally use my mainsheet as a stern line and I've never had it or it's fitting come to any harm from being used in this way. I will often tie to the bottom of a dock cleat with a bowline so that anybody else wanting to use that cleat can still do so and they won't end up trapping my lines, then adjust the length of the lines from inside the boat. I used to hang a weight (sounding lead, anchor, whatever) off the aft mooring line to keep it under tension but havn't done this for years. Any bumps and scrapes can be made good with paint or varnish, in my case often about 2 years later. Amazingly I've never shredded a boat tent on a pontoon, perhaps the gods of dinghy cruising look after us.


Great information. Have any of you made any walk-around videos of your setups?

Have any of you slept TWO people aboard a Mirror?

Red Kite's picture

Re sleeping two on board, I believe it has been done! I do recall reading somewhere an account by a woman and her daughter who both managed to sleep on board, but it must be very difficult!
Red Kite 53814

curlew's picture

Here is a link to my video which includes setting up the tent:-
The issue for two people is that you really need floor space to get out of bed for dressing, cooking etc, so I don't think it is very practicable.