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Sunday, February 15, 2009

'A' Frame Tent Covers...

... at a great price!

----- Original Message -----
Sent: Friday, February 13, 2009 9:00 PM
Subject: Wedge Tent Blow-Out Sale #3

I have acquired another 70, yes 70 wedge tents that are ready for re-sale.
For those who remember, I formed a partnership with an artist from Toronto
who is using wedge tents as part of his art expositions. We have done shows
in Toronto, New York City and our latest show in Ottawa this past fall. The
tents were only used for 3 days in Ottawa and are brand new. This lot of
tents are taller and longer then the 2 previous lots that I had acquired. I
am selling the tents for $190.00 each including poles
and spikes. The tent specifications are as follows:

9 Feet Long
7 Feet High
8 Feet Wide (At Bottom)
9 Webbing Loops
Sun Forger Treated Canvas
10.38oz Canvas
1 Pine Ridge Pole
2 Pine Uprights
9 Modern Spikes
Straight Back (No Bell)
The tents have solid backs with one door.

If you have any questions let me know ... Payment guarantees a tent. If you would
like to be put on the tent list let me know and you can forward your payment
to the address below. I also take paypal and other forms of e-payments.
Shipping and handling is extra if needed.
I will be attending the Living History Conference in Hamilton on February
27th & 28th and will bring tents for those who are attending or have made
arrangements with friends to pick them up.

David J. Brunelle
23 Byrnes Crescent
Penetanguishene, ON, Canada
L9M 1W4
Cell - 705-716-7124

Anyone in the Viking Age re-enactment circle who is needing a tent might look at this:

I have known David casually for a number of years. He has been behind the War of 1812 events up at Penetanguishine. This will be the real deal, you can't beat the price!
These tents are a bit small, but can easily be re poled for a classic A frame. Looking at the images, a bit of modification would be required, with a hole cut in front and back at the peak for an externally mounted frame.
This is an excellent deal for anyone looking for a primary (or even second storage) tent. The poles that come with it are perfect for any Settlement Era encampment as well. For that price you could not even buy the fabric!


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Tuesday, May 13, 2008

Tents - Ribe Viking Centre

Sam wrote:

I need to make new A-frame for a tent ... What size boards have some of you used for an A-frame?

(Readers should refer to the section on the DARC web site depicting past camp presentations for images of various A frame tents the group uses.)

I take it you have a COVER for a standard 'wedge' tent?
First decision is if you want the beams inside the canvas (like I set mine up) or outside (Like Neil and most others do ). Advantage to inside is that it holds the tent sides open better. Disadvantage is that you need a larger hole at the peak for the boards to fit through. Its also more difficult to set the tent up. Outside planks with an X of ropes from corner to corner is the way most people solve the sagging sides but keep the tent fast to set up.

See the set of plans on the Encampment part of the Wareham Forge web site

So you are making measurements for the side rails and the ridge pole from the length of the canvas. Again along the ridge line and each of the sides (likely the same measurement). Then you add on the extra for the joints and pins, maybe an extra 6 inches on either end.

The bottom of the three end boards should be the length of the base line of the door end and back end of the tent. Plus the extra for the insert of the side rail beam. If you check the plan drawing you can see what I mean.

On the two uprights, the measurement is taken from the corner of the base line up to the peak. Then you add on the joint amounts for top and bottom (as with the bottom beam). On top of the planks goes the allowance for any kind of carved head you want to add to the finished support structure. Typically this amounts to 8 - 12 inches extra on each of the four pieces.

The actual Oseburg tent is something like 16 x 16. Neil's tent is patterned on that version (bloody huge). My own is about 2/3 scale, with the side rails at about 10 foot and the carved boards at roughly 11 feet. Fits very comfortably on top the Astro.

Consider your materials in terms of cost and strength At a rural building supply, you can usually get 'barn pine' - used for exterior planking on barns. The cost for this rough one side in 1 x 12 inch is roughly $1 per foot (Ontario Canada). With a large table saw that you can use to rip these in half to 1 x 6 planks. I have standard 2 x 4's and ripped them as well, down to 3 inches wide, for the two side rails. Taken together this modifies the look of the boards away from 'non standard' lumber.
I strongly suggest using a complete sapling as by far the best material to use for the ridge pole - in terms of strength vs size. A little hunting and you should be able to find a spruce or pine sapling the right size for the ridge pole. You will need a piece long enough when cut to span the ridge, typically this will work out to be roughly 4 inches at the base, tapering to about 1 1/2 where cut at the top for length.

Just for comparison, here are a couple of images of tents from the Ribe Viking Centre. For background, this is an 'open air museum' as they are called in Denmark (living history site for us NA's). It is loosely broken into three sections. The first is a recreation of a large section of the original market place layout of Ribe itself, as it existed in the Viking Age. A timber plank street is flanked by regular plots. These are bounded by ditches held in place with low withy sections.
The original Ribe Market would NOT have had any permanent buildings. There are several in the re-creation, each some variant on the 'pit house'. These are small, shallow dug outs that have roofs of either thatch or turf, used as various workshops (more on these in a latter posting).
A couple of details on the tents which may prove interesting. First, there were at least five on site that were part of the permanent fixtures. (I was visiting in late April. The site was closed at that point, with normal season opening at least two weeks off.) These are all fairly large, built around a roughly 12 x 16 foot print (maybe more in some cases). Large enough that Trene's bead making furnace is operated without problem from inside the tent for example. This is the tent workshop in the image above.
The covers are set up with pockets along the edges, both sides of the door and on the lower bottom seam. Into these slotted pockets are run thin natural poles. (Denmark has no shortage of willow to provide the thin straight saplings.) These poles are then lashed to the wooden frames. This method is considerably more durable than the rope or leather ties commonly used on our reconstructed tents. The covers themselves are all a modern heavy commercial tent canvas. Some were dyed most were the standard (unnatural!) bright white, with brass grommets showing. (Remember that these are in constant public use, so squint a bit as you look at them - and be forgiving.)
Several of the tents were also set up with the method of opening the sides up as awnings seen in the image above. (This tent was the storage and working area for the archery field.) The addition of the extra side board and linking rail is certainly more durable than the 'single pole' method that I have used in the past for the same effect. Significantly more material required, and thus unlikely inside a strictly historic context.

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Tuesday, April 1, 2008

Wooden Beams for Tents

Note: This is adapted from a post to NORSEFOLK.

When planning the materials for a period tent, either A frame or Geteld type, consider something about the structural nature of wood as it applies to the loads imposed by tents. Then work backwards against availability and cost (rather than the other way round).

Now several of my old friends will be rolling their eyes. Repeating my own mantra back to me : " Metal good - wood EVIL " !

The thing to consider is grain in the wood - and how grain effects strength.
You are applying two load types to the wood used in a tent. One is compression - the weight of the tent itself applied straight down the long axis of the beam. This aspect effects the uprights, especially the vertical pieces on a Geteld style. The second load is a sideways thrust, contributed by both tent and the force of wind against the horizontal cross beam.

Against these forces, consider the direction of the grain in the timber. Also the relative density of the wood, and how fine the grain is. Individual species will also differ in their basic flexibility (I suspect largely determined by the relationship of density and grain structure - but ask a wood guy.) Fast growing soft woods ( southern pine) are going to have the weakest grain structure. Slow growing hard woods (northern oak) are going to have the strongest. Certain species (as noted by others) will combine strength and flexibility - ash for example.

Modern timber is almost without exception cut to maximize production. This most often results in individual pieces having diagonal lines of the grain that run against the line of the beam: ///////// : Imagine applying force to either the end or the side of a stack of these diagonal lines...
On the compression members, there will be less effect (leading to failure). Practical experiences (related by many here) show that even smaller sizes of cheaper, lighter materials are less likely to fail. You can likely get away with 2 x 2 pine for the uprights.
The greatest effect will be seen on the horizontal beam. The sideways stress from wind can easily shear sawn lumber. We all have seen the warping effect that even the weight of a tent cover can exert on sawn planks.

If you could fix a plank used for the horizontal beam so that it rested with the largest dimension at 90 degrees to the ground : l : this would put the greatest mass of wood against the line of greatest stress. (It would not help with the sideways stress of wind load however). In practice, this would require the use of some kind of quite strong mortise and tendon arrangement where the upright joined to the horizontal. The tenancy is for the tall thin cross section to try to 'roll over', so there is a great sideways force applied to the pin used to join the two members.

Historically, timber was not sawn - but split. This results in the grain running in straight lines along the length of the timber, so this diagonal weakness in the grain is not present. Think of the thin split timbers used for ship construction.

The other way to avoid the whole problem is to use whole saplings. This gives the gain an uninterupted set of circluar 'tubes' that provide the maximum strength for the size and weight of the material. This is by far the superior solution to the problem of stress loads.

Getting the required saplings, for the longer horizontal beam especially, may prove a bit of a problem for urban dwellers. I'd suggest contacting your rural living friends. My own A frame uses a spruce sapling cut from about a 16 foot tree down to the required 12 foot length. It runs about 4 inches to about 2 inches. This tent is over 15 years old, and has weathered repeated violent storms (including one legendary one at L'Anse aux Meadows in 96). The main overhead beam still remains solid and straight.
In practical terms, you want to look for a small grove of trees growing too close together, This tends to force them upwards - rather than spreading outwards. The trees towards the centre are likely to have few sideways branches as well. (Imagine a single pine cone hitting fertile soil.)

One other important effect of the use of natural saplings is that you are also duplicating the type of wood used by the Norse. No cut 2 x 2 in the Viking Age. We have replaced all our commercial uprights with saplings for just that reason.

There are a set of simple plans for a classic Norse A frame tent available on the Norse Encampment series:

oh - one piece of advice:
Strip off all the bark. With the increasing contamination from alien insects, many regions do not allow transport of any timber with the bark on. You can NOT transport bark on timber across the US / Canada boarder for example. Easy to do with the wood green.


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