|
Note that the weigth of fibreglass and resin together is 96 lb per cubic foot (Skeen's Elelments of Yacht Design, 30% fibregalss, 70% resin), and a 1/4" thick layer is 2 lb per square foot. That makes 1/8" layer 1 lb per square foot, and 1/16" layer half a pound per square foot. I don't know how thick the various weights of cloth are, Perhaps you could find out. The cloth has to be more than filled out to it's thickness with resin to cover the thread and have a smooth hull. There's also the matter of getting enough glass and resin on the fir plywood to keep it from developing little surface cracks (checking) which it does from chages in temp and humidity. I don't know how much is needed, Storing the boat in the shade is said to help. I don't know if you've started to build but meranti (luan) plywood is cheap, rot resistant, and does not check. I assume because you are using lumberyard plywood, as I do, that you are interested in a cheap boat. I've built in lauan and virola (not rot resistant) and just painted. I've also fished from cheap painted (fir and spruce?) plywood punts. You can't get spruce plywood any more as far as I know. Dave Allyn ) writes: I am building a S&G canoe. I am going to use fiberglass cloth on the entire outside for extra strength, and to prevent any checking in the plywood. I'm useing 1/4" BCx plywood. What weight of cloth would I want to use for this aplication? And the next question, how would I decide that on future projects? Is there a general rule of thumb for weight? One last question, I know I need to tape the inside and outside with fiberglass tape on the seams, but If I cover the whole outside with cloth, do I still need the tape on the outside of the seams? Thanks, dave email: dallyn_spam at yahoo dot com please respond in this NG so others can share your wisdom as well! -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-FreeNet email must have "notspam" in subject or it's returned |
William R. Watt ) writes: I don't know if you've started to build but meranti (luan) plywood is cheap, rot resistant, and does not check. I assume because you are using lumberyard plywood, as I do, that you are interested in a cheap boat. I've built in lauan and virola (not rot resistant) and just painted. I've also fished from cheap painted (fir and spruce?) plywood punts. You can't get spruce plywood any more as far as I know. I should also note that when I weighed sheets of 1/4" plywood, fir was 22 lb, lauan (meranti) 17, and virola 8.5 lb. Lauan and virola are metric and actually 1/5". I don't recommend virola becase I don't think the boat will last long. I have used it for the light weight and because it bends to a tigher curve than the others. -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-FreeNet email must have "notspam" in subject or it's returned |
William R. Watt wrote:
Note that the weigth of fibreglass and resin together is 96 lb per cubic foot (Skeen's Elelments of Yacht Design, 30% fibregalss, 70% resin), and a 1/4" thick layer is 2 lb per square foot. That makes 1/8" layer 1 lb per square foot, and 1/16" layer half a pound per square foot. snip The above applies ONLY to polyester, mat and roving. It definitely does not apply to knitted glass and epoxy where the glass/resin ration is about 50/50. Also, epoxy/knitted glass laminates are much thinner and lighter weight than polyester/mat/roving for equal strength. HTH Lew |
Lew Hodgett ) writes: The above applies ONLY to polyester, mat and roving. It definitely does not apply to knitted glass and epoxy where the glass/resin ration is about 50/50. The above applies ONLY to vacuum bagging. 70% resin is optimistic for a home builder filling weave by hand. Also, epoxy/knitted glass laminates are much thinner and lighter weight than polyester/mat/roving for equal strength. This is NOT a structural application. It's canoe hull sheathing, abraision resistance and fir ply check checking. -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-FreeNet email must have "notspam" in subject or it's returned |
William R. Watt wrote:
The above applies ONLY to vacuum bagging. 70% resin is optimistic for a home builder filling weave by hand. Rubbish. According to the total material invoices for the 55ft hull I built, was able to achieve about a 50/50 wet out using hand layup techniques. BTW, "hand layup techniques" is just another way of saying a lot of hard workG. This is NOT a structural application. It's canoe hull sheathing, abraision resistance and fir ply check checking. All the more reason to have a high strength, low weight, high strength laminate that cloth and epoxy provide. Lew |
On Fri, 18 Feb 2005 14:25:05 GMT, Brian Nystrom
wrote: Dave Allyn wrote: For information like this, there are better places for you to ask than here. I suggest posting on the kayak building forum at kayakforum.com. I'll check it out. Thanks! I am building a S&G canoe. I am going to use fiberglass cloth on the entire outside for extra strength, and to prevent any checking in the plywood. I'm useing 1/4" BCx plywood. What weight of cloth would I want to use for this aplication? And the next question, how would I decide that on future projects? Is there a general rule of thumb for weight? Most canoe and kayak builders use 6 oz. cloth, typically one layer over the entire outside of the hull and often a second layer over just the high wear "football" area on the bottom. Another common and lighter alternative is 4 oz. cloth. Is there a disadvantage for the 4oz? not over the chines or the bottom, but over the rest of the sides? One last question, I know I need to tape the inside and outside with fiberglass tape on the seams, but If I cover the whole outside with cloth, do I still need the tape on the outside of the seams? No it's not necessary, but extra wear protection on the chines is a good idea. The outside should be completely glassed for durability. How much glass/tape you use on the outside depends on how rugged you want the boat to be. Ah.. okay. email: dallyn_spam at yahoo dot com please respond in this NG so others can share your wisdom as well! |
|
On Fri, 18 Feb 2005 02:17:01 +0000, boatbuilder.org
wrote: It is a good idea to double up the glass on all joints. If you are not after a clear finish then Dynel is a good choice on the exterior over the glass tape on the joints. The Dynel will give you better abrasion resistance and will work better to stop the checking in the plywood. After reading here, I will definatly double up the joints and the bottom. Is there much of a cost differance for the Dynel vs. the fiberglass? Also, can I mix and match? Maybe Dynel on the bottom with glass on the sides? or do they not wet out the same? dave email: dallyn_spam at yahoo dot com please respond in this NG so others can share your wisdom as well! |
On Fri, 18 Feb 2005 08:11:18 +0800, OldNick
wrote: A _rough_ rule of thumb is that if you use full thickness of ply as designed, and only want this to stop checking and help keep the wood dry, then use a really light cloth, but reinforce all corners, as that's where most abrasion is. Also two layers on the bottom. If you use thinner ply, then build up with cloth until the boat weighs the same as it would have in ply (reasonably well-laid glass cloth will take up its own weight in resin, roughly), and you will probably have a stronger boat. So, probably tape chines, inside and out, cover entire boat again with like a 4 ounce glass and then throw a second layer of 6oz, or a synthetic, on the bottom, and maybe wrap it a couple of inches up the sides. Otherwise, talk to the canoe's designer. Always a good idea. Will do. One last question, I know I need to tape the inside and outside with fiberglass tape on the seams, but If I cover the whole outside with cloth, do I still need the tape on the outside of the seams? Unless you can cover the whole boat with cloth before you move it from the building jig, then yes. It's literally what holds the whole boat together. I don't have a building jig on this design. It is a simple canoe with only two "corners"--One chine in the middle of the side, and then a chine where it hits the bottom. Not sure if that would be considered one chine or two, but either way it is a simple design. dave email: dallyn_spam at yahoo dot com please respond in this NG so others can share your wisdom as well! |
On Sat, 19 Feb 2005 13:06:47 -0600, Dave Allyn
vaguely proposed a theory .......and in reply I say!: remove ns from my header address to reply via email So, probably tape chines, inside and out, cover entire boat again with like a 4 ounce glass and then throw a second layer of 6oz, or a synthetic, on the bottom, and maybe wrap it a couple of inches up the sides. The second layer at 6 0z may be only 4? Watch the weight. You have to carry this thing. Looking at the canoe as a 2' 6" half tube 5 yards long, 10 oz of glass + resin = 28 lbs! A lot depends on your usage. If you are goping to simply work open water with the occasional beach landing, then leave it at 1 layer. If you are going to be really bashing it about, go for 2 layers. The one that interested me was Syntex, where they showed 2.8 oz cloth holding up better than 6oz of glass. But I bet it's $$$$. And they said it was a bitch to cut. I don't have a building jig on this design. It is a simple canoe with only two "corners"--One chine in the middle of the side, and then a chine where it hits the bottom. Not sure if that would be considered one chine or two, but either way it is a simple design. Ok. Make sure the boat is very straight and true before you tape the outside seams particularly. That is probably my point. |
| All times are GMT +1. The time now is 07:31 PM. |
Powered by vBulletin® Copyright ©2000 - 2025, Jelsoft Enterprises Ltd.
Copyright ©2004 - 2014 BoatBanter.com