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Trampoline material?


tonyquoll
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"Proper" trampolines are made of Polyvinyl-chloride (PVC or vinyl) coated polypropelene (Coke bottle plastic), loaded up with carbon to provide UV light resistance.

This material only seems to be available retail as pre-frabicated trampolines, and only comes in black.

"Soltis 86" awning material can be used for a cat trampoline. This is a PVC coated polyester mesh. See: http://www.innovaint.com.au/soltis8692.html

Polyester generally is stronger but less elastic than polypropelene. For a cat tramp, the polyester is probably better

"Outlook" awning material also recommended, which is also PVC coated polyester. It weighs 490 gsm (grams per square metre). The gsm provides an idea of strength. Regular shade cloth is around 250gsm.

I've found a 'local' supplier (only 200km away from here in Mallacoota) who stocks "Vistaweave", which is 465 gsm. Will update on how this turns out.

Tony

_________________________________

With thanks to Dave Stumbles, Ian Marcovitch and Meg at "Window Decor".

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I compared my current (30year old) trampoline material with "Outlook" and "Vistaweave". They both seem to have slightly lighter threads, thinner coatings with larger air holes. Not much different though & probably just as strong.

There is a great range of colours and stripy patterns available, but when I asked if I could order 1.5m of the 2.2m wide roll, they looked at me and said "it's $90 a metre," offering me instead a 2.5m x 1m offcut in shade-cloth green for $25.

Perhaps the price per m was exaggerated, as it's not worth their while retailing small pieces of cloth.

They also said they use a waxed thread for stiching it, which of course is not avilable locally, so I'm either going for fine fishing line or dental floss.

After buying the fabric, and $100 for a handful of other boat fittings, a friend and I sailed our boats in a friendly club race, which blew out with 30+ knot winds. Replacing a broken mast, sealing hull cracks and fixing up other fittings now takes priority over the new tramp. That's sailing, ay?

tonyquoll@yahoo.com

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As long as you are enjoying yourself Tony!

Some of the fondest memories seem like a disaster at the time i guess.

I imagine you already know but when you make a trampoline be sure to have the weave oriented at 45degrees to the centre line of the boat, that way the trampoline will stretch as you tension it front to rear.

Cheers. Tom.

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Thanks Tom. Yep, am enjoying designing and constructing various boat bits. I'm a artist/designer/ecologist, having studied Industrial Design, Mechanical Engineering, Interactive Multimedia, Natural Resource Management & Conservation Ecology. I have experience making prototypes & moulds, etc. All good fun.

Recent/in-progress jobs are:

- build & test centreboards of various section shapes & profiles. So far a blade with parallel edges; 8% NACA leading edge & straight trailing edges seems best. Worst performer was spitfire wing profile & NACA 6% section

- tramp as discussed in this thread. New design anchors mostly to the beams & less to the hulls.

- rudder pull-up / down control system.

- swap sails for 1464 "Why Worry?" (old heavy PT), with re-shaped battens to improve position of curve in sail. Requires re-numbering 2128's old sail.

- adjustable cam-cleat outhaul fitted to "Why Worry"

- swivelling, adjustable vang fitted to "Pelikinetic"

- swivelling adjustable cam-cleat downhaul to be constructed (can you believe how much those parts cost?!)

- leaks & cracks fixed in both boats

- rudders that have ailerons; able to curve the blade rather than just angle it to the water. It wouldn't make the boat faster in a straight line, but might reduce drag in tacks. This might allow more tactics & wind-shift chasing.

- battened hiking shorts, again can you believe $200 new?! How about $2 2nd hand board-shorts, $2 2nd hand wetsuit cut up for material, old useless sail battens & some glue & stitches?

Not many of these will improve the boat’s speed; really needs a new mast. I like making the boats the best they can be anyhow. Or I might get a job and start making money instead of spending it. Help anyone? See more at: http://www.green.net.au/quoll

All going well, both boats will appear in top form at Twofold Bay Regatta (Feb 14-15), Wallagoot Lake Regatta (7-8 March) & Batemans Bay Anzac Regatta (25-26 April). Hope to see you there!

Also planning to chase those stiff, light PT's with wing mast profiles & new sails around at the Paper Tiger Internationals (Easter).

Great to have a sport/hobby that so fully distracts from life's worries, and includes exhilarating blasts around the lake!

Tony Hastings

tonyquoll@yahoo.com

Mobile: 0427 534 548

PO Box 543 Mallacoota VIC 3892

[This message has been edited by tonyquoll (edited 29 January 2009).]

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  • 4 weeks later...

Tony, you seem to be re-inventing the centreboard; "- build & test centreboards of various section shapes & profiles. So far a blade with parallel edges; 8% NACA leading edge & straight trailing edges seems best. Worst performer was spitfire wing profile & NACA 6% section".

Is it going to make the boat feel faster?

I wish I had that much spare time.

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Careful what you wish for, ay? I'm looking for any art, design or ecologically related work, see http://www.green.net.au/quoll/

The old centreboards I'm still using have twisted from being left in the sun, and they do slow the boat down, especially in light winds. So long as there's enough wind to fly a hull & lift one up, it's OK.

The top 2 boats at the PT nationals had very different boards, which suggests either they need to be tailored to the skipper, or it doesn't make much difference. One had spoon-shaped boards with NACA profile, the other long, straight boards with concave trailng edges, based on A-class cat designs.

Shaping a board from hardwood takes under 3 hours, mostly using an angle-grinder with coarse sanding disk & profile template, then finishing with block sanding. Hardwood is strong enough for testing, but probably needs fibreglass coating for ongoing use. That's the expensive bit, and it makes hardwood too heavy. Cedar & pine laminate is much lighter & strong enough once 'glass coated, but these aren't strong enough for testing in raw form.

In testing different shapes, the difference is not so much the speed as the pointing angle; some hold the boat to a line while others allow it to drift sideways.

Minor differences like this are not noticable when sailing around on your own, but I'm trying to improve from being one of the slowest to be competetive against 50 boats at the Internationals.

Of the improvements I'm attempting, This is how i'd rate the importance:

10/ polish underside of hull

9/ fix leaks

8/ re-shape sail battens

7/ new centreboards of improved shape

6/ improve adjustment systems, so downhual, vang etc can be adjusted while racing

5/ align rudder blades so they are parallel in the straight ahead position

4/ bend rudder handles & shorten cross-bar to toe-in blades when turning, maintaining speed through tacks

3/ new straight mast, of improved sectional shape

2/ Fill gaps around the centreboard cases from big open rectangular slots to reduce drag.

1/ Replace 30 year old Lidguard sial with 26 year old (but little used) Williams / Ottoman sail

Speed to windward (with traveller centered) in 15 knots so far raised from average 13km/h to 16km/h. Cant wait to test it with a new mast! The new trampoline is still a pile of material and ideas in a corner. No matter how much time you have, it's never enough.

[This message has been edited by tonyquoll (edited 01 March 2009).]

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  • 2 weeks later...

Tramopline dramas continue:

The old tramp split down the middle during the last regatta, which adds to the 4 small splits and eyelets giving way down the port edge. Seriously need to fix it now!

I've threaded up the old sewing machine with dental floss (single filament nylon) but of course am having trouble getting it to stitch properly. It looks OK from the top, but underneath the bobbin thread is a mess. Probably thread tension issues.

I stripped some annex track off an old caravan at the tip, looking to replace the eyelets and zig-zag string with the neat looking flush-fit system. However, it seems a bit heavy....

.... Several days later... the sewing machine broke; bobbin getting out of sinch with the needle. "New" machine brought home from the tip, works well. Tested different threads and found dental floss wont sew in any domestic machine, so am now using polyester thread. Have broken 2 needles when trying to stitch through more than 3 ply; hand sew the thick bits. Reduced the amount of sewing by patching up the old tramp instead of sewing whole new one.

Sailmakers sure earn their keep!

On above list, move "new mast" into top spot - the increase in speed was HUGE. Seems that the air flows smoothly onto the sail now, where the old oval shape lead onto the sail with a small turbulent pocket. The new mast effectively becomes part of the sail, and makes full use of the luff, so it's about (mast width 80mm + luff edge 70mm x mast height 7m =) 1 meter square extra sail area.

Cheers, back to the sewing.

[This message has been edited by tonyquoll (edited 16 March 2009).]

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