----- Original Message -----

From: TM Graefe

To: kbsailing@mac.com

Cc: uncle-al@cogeco.ca ; Richard C. Harrington ; tmgraefe@comcast.net

Sent: Wednesday, September 14, 2005 10:04 PM

Subject: Boom tent

Hey Barry,

I see the boom tent discussion continues so I thought I'd put some pictures together from the tent I designed and had made. I have had it up in a severe downpour and I have spent two nights under it so far, and am looking forward to many more!

pattern

 

Here is a summary of the design:

 

1. Materials: Sunbrella with Top Gun reinforcement along boom, and sandwiched between two layers of sunbrella around rubrail , transom and splashboard and layered on all other points of friction (and snap locations).  Top Gun is a slightly heavier synthetic material that wears extremely well and has a finished/slick surface.  I used standard snaps (dome).  I looked at other options but the standard snaps are very unobtrusive (unlike common sense snaps, etc).  I used a light colored tan sunbrella to provide a light atmosphere.

front view


side view

2. Attachment to hull: I shaped small blocks of oak molding that comes with a rounded top and is about 1.25 inches wide by 3/4 inch thick by 1" long, primed,  painted all surfaces that would not be glued and then glued them under the gunnel with 3M5200.  These hold the male parts of the snaps.  There are 6 per side (two at shroud on either side, two at  side zipper on either side and one between shroud and zipper and one betwen zipper and stern).  Of course there are snaps on the transom and the splash board as well but these are just screwed into pilot holes and caulked with marine silicone.  By the way, I had my tent made with the little 'pockets' at the snap points that Dick mentioned (all but at shrouds and on bow) so that it is easier to fasten to underside or transom from inside--it is just a matter of leaving a small gap in sticthing between reinforcing layers above the snap).

 

3.  Boom tent shape and support: As you will see in the pictures, the boom tent is a variation from the standard A-frame.  I made a gooseneck, like Dick did, but with other piece parts.  So I position the boom about 10 inches  above the normal sailing position.  And I use a boom crutch designed to hold the boom level.

The biggest difference is that I borrowed from my backpacking experience and added a single collapsible aluminum frame pole at the thwart, to bow the boom tent out and provide some additional elbow and head room.  The ends of the aluminum pole sit in the oarlock holes (the last inch of the aluminum pole is inserted  in a piece of rubber automobile hose to make it the right diameter to be snug in the oarlock. ) The pole itself goes over and just rests on the top of the boom.  You can sit on a thwart with little or no constriction at shoulders or head.  This works quite well at very little extra setup pain.  You can see from the pics that it required two darts be put into the boom tent to give it shape (and of course a thin strip of Top Gun on the Sunbrella where the pole touches the tent.  There are 4 small ties on the tent hemisphere that get tied around the pole to keep it centered forward and aft.

 

4.  Because the Mark III has no bilge I was especially concerned about water getting in around the mast - a common weakpoint in all these designs.  Jim Fraser, who has cruised extensively in a Mark III, emphasized this as a problem area when I exchanged email with him.  So the wrap around the mast is foam between Sunbrella with a small additional gasket added on the inside (see picture below).  There some healthy lines that can be tied around the outside to really snug up the collar against the mast.  If need be, I could add an additional gasket to the inside of the collar, but in the rain storm I weathered, very little water came down the mast (phew!).

collar

 

5. You will note in the pictures that each side not only has a zipper opening approx. midway between thwart and rear compartment, but in fact the zipper goes all the way from side to boom.  In fact, you can take the entire rear section off if you want, or unzip it all the way to boom or as little as you want.  There is not a lot of advantage to taking the whole aft section off compared to just folding the aft section forward until ready to button it up for the night (as I am sure Dick described)  but  it was not more complicated to make and it allows a lot of access if you want to unzip to boom.  The other benefit for a Mark III design is that this gives you a bit more flexibility in that you can stow two smaller parts.  So my only real comment here is: think about stowage, because the Mark III does not have the depth in the bow behind the mast that the Woodies do.

 

6. Another area of concern for water getting in is the forward windows.  Mine are made so they can be easily rolled up or fixed at half open or closed all the way.  I hope I never have to close them all the way because the air flow from bow to stern is important for all inmates.  I have some ideas for how to fashion a vent to replace the top 1/3 of the closure, but it may not be worth the trouble.  If you get interested in such refinements I can send my ideas along. They are derived from a feature on a backpacking tent I own.

 

7. Another difference compared to Dick's boat is, what to do with the oars at night?  I decided to just tie them to the boom (see interior pictures below).  The down side is they are slightly less accessible, but with only two reef knots, I think that is a minimal issue.  Also, you will find that the hiking strap is in the way at night.  Since it runs through a stainless ring on the Mark III, I added a shackle and tightened it up.  At night, I just unhook it and now the rear floor is clear.  It is a given in my mind, that the rear seats are out if you are cruising.  I am veering off pure boom tent and into other issues related to the Mark III now;  hope you don't mind.

 

 

8. People have questioned how you can get the floor of the Mark III dry at night since it has no bilge.  I think this is a bit of a red herring.  The floor itself will be no more wet or dry than any other Wayfarer, given you get all the water out of it at the end of the day, and you have solved the problem of additional water getting in at night (see above item on Mast gasket). 

 

So that's most of the details.  I looked at many other options before working with this adaptation of the tried and true design.  I exchanged emails with some thru-hikers that design their own tarp tents and now market them.  One guy uses a 3-D aeronautical design program to work out his catenary cut angles.   I called up Eureka to talk about fabrics for single wall tents (got zero help from them), spoke with fabric retailers like Sailrite in Florida (extremely helpful!!) among many others, as well as several manufacturers.  I was very interested in lighter breathable fabrics, but at the end of the day came back to Sunbrella and a modified A-frame design.  Oh, and I worked through three different canvas makers in the area before I found someone that was interested in something besides making replacement bimini tops and was nice enough to work on the design with me.  I also considered making it myself, but decided I would have to make at least two tents--the first to learn how and the second to maybe get it right.  Given it would have required also buying a sewing machine that can handle 4 layers of Sunbrella, it seemed a no-brainer when I found a good guy to make it.  

 

Let me know any questions or if you want to chat--in high tech it's called 'end user innovation'! 

 

The pictures should be mostly self-explanatory.   There are a couple of the finished tent on the boat in my driveway, one of the plastic pattern that allows you to see the framing such as it is, a front view, a side view of the rolled tent on the boat--taken on Lake Champlain in July, and a couple of interior shots that give you a feel for the interior space - cozy.  That's my striped feet and my brother asleep on the floor.  I am lying on a collapsible cot I designed and built (about the size of the collapsible chairs that slide into the nylon sacks, but that's a whole other story!

 

Tom Graefe (W9668)