View Full Version : Frame for tarp cover - tent poles in blocks & trolley base
08-17-2009, 12:04 PM
Rigged up a new system to cover my Cosine Wherry yesterday.
I've been experimenting with using the fiberglass poles from an old 12x12 nylon tent, but they can't be placed in the oarlock bases or inwales as the angle is wrong and the ends break.
Used duct tape to hold the pole sections together as the shock cord wasn't strong enough plus being too old.
Worked up a new system of pieces of 2x4 blocks drilled to take the pole ends, suspended/lashed to the inwales on the sides. The lashing allows them to take the correct angles and also keep the tarp out a bit from the sides for ventilation.
The front brace is propped against the trailer winch tower base, with a slot cut for the bow eye to keep it upright. The rear end of the fore and aft pole goes into a hole drilled into the trolley-wheel base.
Blocks can have multiple poles mounted, as the forward block shows here -
08-17-2009, 04:34 PM
5' of snow in our neck, would be the end of that rig. nice idea for your area.
08-17-2009, 04:44 PM
Very cool, I may copy that.
08-17-2009, 04:45 PM
Yeah, biggest problem here is UV, followed by leaves and the occasional raindrop.
Just ordered one of the good UV-resistant white tarps for this cover.
I'm hoping that the suspended blocks with the pole ends will move enough to shed any sudden wind loads, but you may want to put padding or tape over the blocks in case they get pressed up against the gunwale or hull.
08-17-2009, 08:51 PM
Way cool, and inspiring! "Buckminster Fuller meets traditional boat." Aluminum tent poles are much stronger and lighter than fiberglass, should you need them. Of course your existing poles are already paid for, which is a huge advantage.
08-17-2009, 10:22 PM
Great, creative thinking, Thorne! I like it! Well done.
08-17-2009, 11:57 PM
We shall see.
There are numerous potential points of failure (mostly the poles), also several places where the lashing lines, blocks or tarps might rub on the boat. So the system needs testing, but I'm hoping it maintains the critical ventilation by holding the tarp edges away from the hull and gunwales.
Lots of more traditional tarp frames are out there, including some clever ones that use bent/curved hoops of wood running from gunwale to gunwale.
I'm just trying this one because I've been playing with the tent poles and trying to get a support point (the blocks) at an angle that doesn't break the pole ends when stressed.
08-18-2009, 12:23 AM
How about them thwarts???:D:p
08-18-2009, 08:07 AM
They are on my mind, never you worry! I've got them coated with boat soup and drying, will begin varnishing starting tomorrow am == as it is WAY too windy to varnish when I get home after work, even in a garage.
Will shift the wherry into the garage for the installation, but that means the dory skiff needs a cover. Whatever shall I do about that, eh?:D
08-18-2009, 08:08 AM
Those blocks seem perfect for the job. Very clever solution, Thorne.
08-18-2009, 08:12 AM
Here's a place (http://www.fibraplex.com/Default.htm)where we've purchased custom carbon fiber poles. They have some on-line calculators and can bend as small as a 30" radius.
These guys (http://www.polesforyou.com/)do fiberglass and aluminum.
Custom is good.
08-18-2009, 08:25 AM
Interesting links, Canoez.
Back in my salad daze I worked for Early Winters, Ltd in Seattle for a few years. Not only were they the first to produce any mountaineering tents or garments from Gore-Tex (nobody else would touch the stuff), but they made the Finest Tent In The World -- aptly named "The Omnipotent".
The poles for their tents were made from fiberglass sections laid up by an outfit in San Diego (if memory serves) that made flyfishing rods. These were made from the same topnotch materials but not tapered.
I'd glue up the metal sleeves on the pole sections, then string the shockcord through with a long wire. Once assembled the poles could be bent **in a full double circle**! Lots of creaking and popping noises from the fiberglass sections but no failures -- possibly the best tent poles ever made, probably for the best mountaineering tent.
08-18-2009, 08:28 AM
I miss the old "Early Winters". :( Since they became "Sahalie", it seems to have become mostly a woman's clothing supplier.
Perhaps REI, Campmor, EMS and LL Bean have "eaten their lunch"?
Didn't Early Winters used to have naked women in their catalogs? Or was that Stephenson? I forget which, but I know one of them did. Sorry about the thread drift!
08-18-2009, 09:12 AM
Neat idea, but most of the bent-arch frames I've tried tend to collapse in heavy snow. The arches themselves tend to buckle, and slide sideways under the tarp under load. The problem seemed to be that if they were flexible enough to form an arch, they usually were too soft to hold shape under a serious load.
08-18-2009, 09:41 AM
Bejabbers! Hijacked me own thread, I have...
Yep, naked people in the '76 EW catalog.
Dan, I hear you, and the poles are certainly the weakest part of this system.
Biggest issue would be the sections coming apart under stress -- either the pole end sliding back out of the sleeve, or separating from its own sleeve section (glue failure).
Perhaps using a strong longitudinal fiber tape or something along the length of the poles would help keep them together in one piece? I'm using duct tape but suspect it would fail after awhile...
08-18-2009, 10:50 AM
Theoretically, an arch puts the whole thing in compression, so I don't think the issue is the joints. We can get some heavy, wet snow here in the winter--probably SF doesn't get any. I did find that if you tie the arches by running lines fore and aft, keeping them from wobbling from side to side, the whole thing gets pretty rigid. We used shrink-wrap line, which is a kind of waxed strapping, to run lines fore and aft. I've built maybe five different' tarp framing systems. All start out simple, then when you put in extras to solve this and than, they end up with more pieces than you really want. There is a basic principle here, I think.
08-18-2009, 11:55 AM
Seems like either bent metal emt pipe, or curved small-diameter PVC might work better than tent poles, dot's fer sure...
No snow in SF, not allowed by State law as it interferes with the whole tan beachbunny rollerblade thang...oh sorry, that's LA, isn't it? (grin)
08-18-2009, 12:08 PM
I don't know why the tent poles wouldn't work for arches. I'd tend to use a 3/4 ins. PVC pipe as a ridge pole. I like the idea of the way the tent poles would store. Arches made of PVC stay bent, and don't make neat piles.
08-18-2009, 05:11 PM
You can buy shock cord to 'recondition' your poles. I seem to recall that REI sells it.
08-18-2009, 06:07 PM
Actually the join between pole sections is what I **don't trust**, elastic or no elastic. My concern is that wind load could press down on any of the poles and cause the sections to back out of the metal sleeve ends.
Hence the use of tape to bind the sections together, and the recommendation to use PVC as the support sections. As pointed out above, solid sections of poles or pipe won't store as easily as tent poles with shockcord -- but I think they will be necessary to keep the boat cover up during really bad weather.
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