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Fiberglass weight
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! |
You don't need fiberglass.
The fabrics work a lot better with epoxy. The wet out is fantastic. The question a bit hard to answer since people use weights from one ounce up to six or more. A lot of builders only use tape on the inside. You can find the synthetics. Dynel, Olifin.,Xynole,Vectra at http://www.defender.com/ Once you use the fabrics you never go back to fiberglass "Dave Allyn" wrote in message ... 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! |
Twilk wrote:
You don't need fiberglass. The fabrics work a lot better with epoxy. snip Most general purpose fabrics are in fact fiber glass, and that includes ccloth and tape. Weights are expressed in ounces/square yard. Most tape is about 6 oz. HTH Lew |
Wrong
They are not fiberglass and they also do not make you itch. They are in fact' Polypropylene and polyester- "Lew Hodgett" wrote in message ink.net... Twilk wrote: You don't need fiberglass. The fabrics work a lot better with epoxy. snip Most general purpose fabrics are in fact fiber glass, and that includes ccloth and tape. Weights are expressed in ounces/square yard. Most tape is about 6 oz. HTH Lew |
On Thu, 17 Feb 2005 22:40:47 GMT, Lew Hodgett
vaguely proposed a theory .......and in reply I say!: remove ns from my header address to reply via email Lew Twilk is referring to Dynel etc. They are excellent sheathing materials. They are not as stiff as glass when dry, though IME, and so are not used solely as structural materials. They do "give" a lot more and that can be an advantage in composite wood/fibre work. IIRC again. My main gripes we - $$ - they were not as transparent as glass/resin - they get "fur" when you sand them Twilk wrote: You don't need fiberglass. The fabrics work a lot better with epoxy. snip Most general purpose fabrics are in fact fiber glass, and that includes ccloth and tape. Weights are expressed in ounces/square yard. Most tape is about 6 oz. HTH Lew |
On Thu, 17 Feb 2005 15:17:50 -0600, Dave Allyn
vaguely proposed a theory .......and in reply I say!: remove ns from my header address to reply via email 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? 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. Otherwise, talk to the canoe's designer. Always a good idea. 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. |
On Thu, 17 Feb 2005 15:17:50 -0600, Dave Allyn
vaguely proposed a theory .......and in reply I say!: remove ns from my header address to reply via email This may be of interest http://www.oneoceankayaks.com/Abrasion.htm 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 |
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.
---Joel--- |
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 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. 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. What you need to do on the inside is to fillet the seams to provide a smooth transition between the panels, then glass over the fillets. If you do decide to fully glass the interior (not a bad idea), you can skip the tape there, too. If you don't fully glass the interior, the rest of the interior plywood surface should be covered with epoxy to seal it. Once the boat is glassed, all surfaces that will be exposed to the sun must be varnished or painted to provide UV protection. Otherwise, sunlight will break down the epoxy over time. |
I believe Olifin is even tougher than Dynel.
Some builders do awesome stuff with combinations laying them at 45 degree angles and such. "boatbuilder.org" wrote in message ... 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. ---Joel--- -- boatbuilder.org |
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! |
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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. |
William R. Watt wrote:
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. I don't agree either. 30% glass might be for a weak chopper gun layup, but it's pretty easy to get up to 40-45% even with mat/roving combinations. For knitted glass figure 50/50 without vacuum bagging, maybe 54% if bagged. Evan |
On Sun, 20 Feb 2005 06:54:08 +0800, OldNick
wrote: 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! Does the strength come from layers or weight? i.e.: would one layer of 12 oz be as good, better, or worse than two layers at 6 oz? or three layers of 4 oz, 6 layers of 2oz 24 layers of 1/2 oz....etc.... I know in plywood, the more layers withina givin thickness, the stronger the plywood. is it the same in fiber/epoxy? 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. To be honest, I am building this more because I saw the idea in a magazine and it peaked my intrest. I rarely canoe, and it will probably only see water a few times a year. In the off time it will be stored in a shed, out of direct sunlight. 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've heard that about kevlar as well... 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. So noted. Thanks. dave email: dallyn_spam at yahoo dot com please respond in this NG so others can share your wisdom as well! |
Dave Allyn ) writes: To be honest, I am building this more because I saw the idea in a magazine and it peaked my intrest. I rarely canoe, and it will probably only see water a few times a year. In the off time it will be stored in a shed, out of direct sunlight. You can save yourself a lot of time and mess by just taping the seams and painting or varnishing the hull. On my small plywood boats I don't even tape the seams, just round off smooth the outside of the edges with a sanding disk on my drill and then apply 2 layers of polyester resin along the seams to seal and protect the exposed plywood edge. You have to seal all the exposed plywood edges on the boat anyway to keep moisture from getting into the edges where the end grain of the wood is open. I mix a small amount (1 teaspoon) of resin at a time and spread it along the edge with a toothpick. To each teaspoon of polyester resin you have to add 2 drops of hardener. I touch up the paint each spring and sometimes mid season as well. (Photos of the boats on my website, see below.) I keep a boating log which shows I go out about 30 times a season, usually for an afternoon or evening. Also seal the gunnel, top and bottom, if the boat is ever going to be stored outside upside down, especially over the winter. Water will drain off the bottom of an overturned boat and collect along the gunwale where it can sit and rot. It will also hang and drip of the top of the gunwale of an overturned boat. I've had to repair delmainating and rotting plywood edges along a gunwale after storing a home built boat outside inverted over the winter. The keel, skids, and bottoms have never been a proboem stored upside down because water does not collect on them. -- ------------------------------------------------------------------------------ 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 |
Dave Allyn ) writes: I almost picked up the luan, mainly for the lighter weight, but the interior glue threw me. My understanding was I needed to have exterior glue or the resin could (and probably would) delaminate the layers. Is that not true? my lumber yard does not carry exterior glued luan in 1/4" (actually, 5mm) You need exterior grade plywood. They all use moisture resistant glue except for the fancy wall panneling. If it's kept inside the store it's usually not exterior grade. If it's keep outside, even under cover, it should be exterior grade. I don't know what kind of meranti or lauan is available in the USA. Here in Ottawa we just have the underlayment, used to put on floors under carpteting and vinyl. It has one thick inner ply and two thin outer plys. You have to look for sheets whith few or no edge voids and few face flaws. I've seen some poor stuff and some excellent stuff. I have filled voids by drilling small holes through one face ply and pumping in caulk or adhesive with a caulking gun. That works well. I got one sheet with worm holes in one face ply which I filled with little drops of polyester resin before oiling (I use linseed oil on the interior). If I were covering the hull with fibreglass and resin I would not have bothered. As I understand it, the only real need to sheath the hull is to keep the fir plywood from checking and for that you need a pretty thick layer, from what I've read. -- ------------------------------------------------------------------------------ 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 |
It's easier to get good wet out with layers of lighter cloth.
It could make a big difference depending on the skill of the builder. Does the strength come from layers or weight? i.e.: would one layer of 12 oz be as good, better, or worse than two layers at 6 oz? or three layers of 4 oz, 6 layers of 2oz 24 layers of 1/2 oz....etc.... I know in plywood, the more layers withina givin thickness, the stronger the plywood. is it the same in fiber/epoxy? 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. To be honest, I am building this more because I saw the idea in a magazine and it peaked my intrest. I rarely canoe, and it will probably only see water a few times a year. In the off time it will be stored in a shed, out of direct sunlight. 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've heard that about kevlar as well... 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. So noted. 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" wrote in message ... Dave Allyn ) writes: I almost picked up the luan, mainly for the lighter weight, but the interior glue threw me. My understanding was I needed to have exterior glue or the resin could (and probably would) delaminate the layers. Is that not true? my lumber yard does not carry exterior glued luan in 1/4" (actually, 5mm) You need exterior grade plywood. They all use moisture resistant glue except for the fancy wall panneling. If it's kept inside the store it's usually not exterior grade. If it's keep outside, even under cover, it should be exterior grade. If I'm paying good $ for ply I expect it to have been kept dry and at stable moisture content. INDOORS. My supplier stores everything in the same warehouse - from marine ply through exterior through formply, chipboard .... Leave a sheet of ply flat on the concrete floor of the workshop overnight and it's no longer flat - put it out in the sun for a few hours and it's bent the other way. And if it's moisture induced curvature, it will try to go back to being flat when you make it into a boat. DF I don't know what kind of meranti or lauan is available in the USA. Here in Ottawa we just have the underlayment, used to put on floors under carpteting and vinyl. It has one thick inner ply and two thin outer plys. You have to look for sheets whith few or no edge voids and few face flaws. I've seen some poor stuff and some excellent stuff. I have filled voids by drilling small holes through one face ply and pumping in caulk or adhesive with a caulking gun. That works well. I got one sheet with worm holes in one face ply which I filled with little drops of polyester resin before oiling (I use linseed oil on the interior). If I were covering the hull with fibreglass and resin I would not have bothered. As I understand it, the only real need to sheath the hull is to keep the fir plywood from checking and for that you need a pretty thick layer, from what I've read. -- ------------------------------------------------------------------------------ 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 |
Dave,
Neither fiberglass nor fabrics like Dynel® add significant strength and the checking problem with BCX pine plywood is insignificant. Tape your joints inside and out and paint with 100% acrylic latex exterior paint of your preferred gloss. For more on this and other heresies see: http://www.angelfire.com/nc3/davecarnell/ Dave Carnell Dave Allyn wrote: 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! |
Dave Carnell ) writes: Dave, the checking problem with BCX pine plywood is insignificant. Tape your Oh, I thought he meant BC fir plywood. :) Nice to hear from you. -- ------------------------------------------------------------------------------ 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 |
Dave Allyn wrote:
On Sun, 20 Feb 2005 06:54:08 +0800, OldNick wrote: 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! Does the strength come from layers or weight? i.e.: would one layer of 12 oz be as good, better, or worse than two layers at 6 oz? or three layers of 4 oz, 6 layers of 2oz 24 layers of 1/2 oz....etc.... I know in plywood, the more layers withina givin thickness, the stronger the plywood. is it the same in fiber/epoxy? More layers of thinner cloth will be stronger and more flexible than a single layer of heavier cloth. |
Dave Carnell wrote:
Dave, Neither fiberglass nor fabrics like Dynel® add significant strength and the checking problem with BCX pine plywood is insignificant. Tape your joints inside and out and paint with 100% acrylic latex exterior paint of your preferred gloss. For more on this and other heresies see: http://www.angelfire.com/nc3/davecarnell/ Who are you kidding? Perhaps that's true of larger boats with thick wood skins, but fiberglass adds substantial strength when you're dealing with light weight, thin skinned boats like canoes and kayaks. This is especially true with sandwich construction where the core of plywood or cedar strips is fully encapsulated in fiberglass. |
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