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vacume form canoe
- Thread starter gib2j
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MikeHalloran
Mechanical
Filling the bow and stern is a problem.
Here's a "Canadian Style" canoe molded in two parts in FRP:
The gunwale seam would be a problem in HDPE, because adhesives and sealants don't stick to it. You'd need a gasket and a lot of mechanical fasteners.
How about a nice double ended dory?
Mike Halloran
Pembroke Pines, FL, USA
Here's a "Canadian Style" canoe molded in two parts in FRP:
The gunwale seam would be a problem in HDPE, because adhesives and sealants don't stick to it. You'd need a gasket and a lot of mechanical fasteners.
How about a nice double ended dory?
Mike Halloran
Pembroke Pines, FL, USA
Hi,
I assume the Royalex(tm) canoes are thermoformed - cannot see how the stem and stern are done though....
Cheers
Harry
I assume the Royalex(tm) canoes are thermoformed - cannot see how the stem and stern are done though....
Cheers
Harry
MikeHalloran
Mechanical
Royalex is bondable. Photos on eBay suggest there may be a bonded seam down the center of the canoe.
In which case it would be possible to inflate the hulls in the un-obvious way. I have no evidence that Old Town actually does it that way; it just seems a possibility.
It doesn't seem possible to vacuum form such a hull in the obvious way, given the recurve at each end, and the relatively fine radius at the stem.
The vinyl/ABS/ABS foam/ABS/vinyl laminate would surely produce a much lighter hull than 10mm of HDPE.
Mike Halloran
Pembroke Pines, FL, USA
In which case it would be possible to inflate the hulls in the un-obvious way. I have no evidence that Old Town actually does it that way; it just seems a possibility.
It doesn't seem possible to vacuum form such a hull in the obvious way, given the recurve at each end, and the relatively fine radius at the stem.
The vinyl/ABS/ABS foam/ABS/vinyl laminate would surely produce a much lighter hull than 10mm of HDPE.
Mike Halloran
Pembroke Pines, FL, USA
patprimmer
New member
HDPE is very tough and abrasion resistant when used to scrape over and bounce of rocks and sandbars etc.
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eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
MikeHalloran
Mechanical
Well, it sure would get scraped and bounced a lot.
If you start with 10mm HDPE, I'm estimating > 100lbs for the hull. No way would anyone portage the damn thing.
Mike Halloran
Pembroke Pines, FL, USA
If you start with 10mm HDPE, I'm estimating > 100lbs for the hull. No way would anyone portage the damn thing.
Mike Halloran
Pembroke Pines, FL, USA
- Thread starter
- #7
The canoes are going to be made and used by a scout group, if it is a sucess other groups will be invited to use the mould.
so yes they have to be very rhobust and im not too concerned about the weight, (i worked it out to be about 29kg, 64lb in ye olde weight)
my main concerns are that the bow and stern are going to be stretched the most, therfor thinner wall thickness and weakest area that is going to take the most damage...
the gunwhale, im looking to bond and fasten strips of spare sheet, after the canoe is formed. What is the best method for bonding HDPE to HDPE?
Thankyou all for your valuable input
so yes they have to be very rhobust and im not too concerned about the weight, (i worked it out to be about 29kg, 64lb in ye olde weight)
my main concerns are that the bow and stern are going to be stretched the most, therfor thinner wall thickness and weakest area that is going to take the most damage...
the gunwhale, im looking to bond and fasten strips of spare sheet, after the canoe is formed. What is the best method for bonding HDPE to HDPE?
Thankyou all for your valuable input
patprimmer
New member
Nuts and bolts or welding are the only methods to give a strong bond.
3M make some adhesives that work OK if applied under ideal conditions.
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
3M make some adhesives that work OK if applied under ideal conditions.
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
- Thread starter
- #9
MikeHalloran
Mechanical
ABS stacks up well against all your requirements except the last.
Under nonideal conditions, e.g. with scouts, you can't bond PE to PE, period.
If you can do without the recurved ends, i.e. everywhere concave up, and use a generous radius at the stems, you could use HDPE. It would look more like a skinny dory than a canoe. You could probably use sheet as thin as 3..4 mm if you flange the gunwales.
Or you could use HDPE, blanked to the shape of a birchbark canoe, with recurved ends, but each end would have a vertical stem seam that must be caulked or gasketed and have a mechanical retention means. Use a row of bolts and nuts, or lace it with wire or fishline.
Instead of making the canoes durable, you might consider making them disposable, or at least constructed from cast-off materials. They are using more stretched fabric these days, but billboards and signs used to be constructed of masonite or galvanized sheet steel. Maybe you can locate a source of used sheet ... something ... that could be adapted.
Mike Halloran
Pembroke Pines, FL, USA
Under nonideal conditions, e.g. with scouts, you can't bond PE to PE, period.
If you can do without the recurved ends, i.e. everywhere concave up, and use a generous radius at the stems, you could use HDPE. It would look more like a skinny dory than a canoe. You could probably use sheet as thin as 3..4 mm if you flange the gunwales.
Or you could use HDPE, blanked to the shape of a birchbark canoe, with recurved ends, but each end would have a vertical stem seam that must be caulked or gasketed and have a mechanical retention means. Use a row of bolts and nuts, or lace it with wire or fishline.
Instead of making the canoes durable, you might consider making them disposable, or at least constructed from cast-off materials. They are using more stretched fabric these days, but billboards and signs used to be constructed of masonite or galvanized sheet steel. Maybe you can locate a source of used sheet ... something ... that could be adapted.
Mike Halloran
Pembroke Pines, FL, USA
btrueblood
Mechanical
I have a poly canoe at home, I'm pretty sure the literature for these stated the (outer, poly) hull was roto-molded. The gunwales are mechanically fastened to the both inner and outer hull and seats.
patprimmer
New member
Rotomoulding PE is a popular method of making canoes, but not necessarily "Canadian" style.
For abrasion resistance, PE strakes or external stringers could be bolted on.
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
For abrasion resistance, PE strakes or external stringers could be bolted on.
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
btrueblood
Mechanical
Pat, not sure why you think a "Canadian" style canoe hull couldn't be rotomolded? Or are you saying you think the Canadian hull could be thermoformed? Like Mike has said, I can't see the prow of any canoe being thermo-formed and having (much) strength, due to the stretching/thinning of the material. Maybe the concept would work if the keel rib had provisions for adding strengthening material to the inside.
On the "other materials" topic, HDPE canoes are pretty nice, but heavy if they are to be durable. If I had the time, $$$, and wanted to build a class III capable canoe, I would find a good "fiberglass" mold for the style of canoe I wanted, and then read up on using either an epoxy/kevlar or a urethane/kevlar system instead of glass fiber. You can form some pretty complex shapes in an "open" hand-laid mold.
There are several local river boat races around where I'm from, which are usually won by people with home-built boats of the above materials. These races typically take place on class II and III rapids. Some of the winning hulls appear to be ~1/8 in. thick, extremely light, very supple (the hull can buckle over rocks/tree stumps without creasing/cracking) and strong. At least, that's what I could see from my old fiberglass tub, as the winners streaked past...
I really do like Pat's suggestion too, of a keel strake (or multiple strakes) of poly that are bolted or...dovetailed? on in some manner removably mounted onto the hull for abrasion resistance. Once they've started to get really scuffed up, you could strip it off and attach fresh grind rails...
On the "other materials" topic, HDPE canoes are pretty nice, but heavy if they are to be durable. If I had the time, $$$, and wanted to build a class III capable canoe, I would find a good "fiberglass" mold for the style of canoe I wanted, and then read up on using either an epoxy/kevlar or a urethane/kevlar system instead of glass fiber. You can form some pretty complex shapes in an "open" hand-laid mold.
There are several local river boat races around where I'm from, which are usually won by people with home-built boats of the above materials. These races typically take place on class II and III rapids. Some of the winning hulls appear to be ~1/8 in. thick, extremely light, very supple (the hull can buckle over rocks/tree stumps without creasing/cracking) and strong. At least, that's what I could see from my old fiberglass tub, as the winners streaked past...
I really do like Pat's suggestion too, of a keel strake (or multiple strakes) of poly that are bolted or...dovetailed? on in some manner removably mounted onto the hull for abrasion resistance. Once they've started to get really scuffed up, you could strip it off and attach fresh grind rails...
patprimmer
New member
I did not mean to imply Canadian style could not be rotomoulded, but to state that I never saw one.
All rotomoulded canoes I saw were simple basic designs with relatively level gunnel's and stems and sterns.
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
All rotomoulded canoes I saw were simple basic designs with relatively level gunnel's and stems and sterns.
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
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