I was reading some kayak manufacturer's literature recently (trying to prepare for buying my next boat) and would like to get some more information concerning the methods used to join the hull and deck of FIBERGLASS kayaks. Necky talks about an "outside seam". Current Designs describes using a vinyl "H" channel with hull and deck glued to the channel rather than to each other (at least I think that is what they meant). Current Designs also says that "outside seams" are available. 1. What is an "outside" seam exactly? 2. Current Designs info says the "H" channel method produces a "seam that has a hollow center which accommodates the rudder cables inside". How are the deck and hull glued to the "H" to leave a hollow center? Is the hollow center going to be a weak point particulaly up forward where there is no need for rudder cables.? 3. What are the pro's and con's of each construction (or does it even matter to the paddler)? 4. Are there other options for joining the hull and deck together besides the two I have mentioned? 5. Can you tell by looking at the boat how the deck and hull are joined? This may be asking for more than can be described here on paddlewise, but I would appreciate any information you may be able to give. Mark J. Arnold MJAkayaker_at_aol.com *************************************************************************** PaddleWise Paddling Mailing List - All postings copyright the author and not to be reproduced outside PaddleWise without author's permission Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
I'm no expert on this, I just pick bits and pieces up along the way - I'm sure there are designers/builders on the list who know more then me. I'd like to hear from them myself on these issues. but from what I gather the 'h' join is out of favour here - relatively weak, prone to leaks if not done well etc. (???) outside seam is a strip of tape (of what ?) glassed along the hull on the outside - inside is usually standard. Extra strength is the reason, although one boat designer here disagrees. If I was buying a glass boat I'd probably get this. Extra weight I suppose. on other methods- One builder here uses a method similar to what sailing dinghy builders use. the deck overlaps the hull and is glassed in under the lip. Very strong apparently but leaves a 'lip' edge. they are thinking of changing this to eliminate the lip by using a channel in the underside of the deck into which the hull will fit and be glassed. having rudder cables running through a join sounds potentially complicated to me, but maybe it's well designed? nick Nicholas Gill School of Geography and Oceanography University of NSW Australian Defence Force Academy Canberra ACT 2600 Ph. 02 6268 8317 Mob. 041 7659440 Fax 02 6268 8313 Email: nicholas.gill_at_adfa.edu.au ---------- > From: MJAkayaker_at_aol.com > To: paddlewise_at_lists.intelenet.net > Subject: [Paddlewise] Hull/Deck Seam Construction > Date: Thursday, 16 December 1999 3:52 > > I was reading some kayak manufacturer's literature recently (trying to > prepare for buying my next boat) and would like to get some more information > concerning the methods used to join the hull and deck of FIBERGLASS kayaks. > Necky talks about an "outside seam". Current Designs describes using a vinyl > "H" channel with hull and deck glued to the channel rather than to each other > (at least I think that is what they meant). Current Designs also says that > "outside seams" are available. > > 1. What is an "outside" seam exactly? > > 2. Current Designs info says the "H" channel method produces a "seam that has > a hollow center which accommodates the rudder cables inside". How are the > deck and hull glued to the "H" to leave a hollow center? Is the hollow > center going to be a weak point particulaly up forward where there is no need > for rudder cables.? > > 3. What are the pro's and con's of each construction (or does it even matter > to the paddler)? > > 4. Are there other options for joining the hull and deck together besides the > two I have mentioned? > > 5. Can you tell by looking at the boat how the deck and hull are joined? > > This may be asking for more than can be described here on paddlewise, but I > would appreciate any information you may be able to give. > > Mark J. Arnold > MJAkayaker_at_aol.com > > *************************************************************************** > PaddleWise Paddling Mailing List - All postings copyright the author and not > to be reproduced outside PaddleWise without author's permission > Submissions: paddlewise_at_lists.intelenet.net > Subscriptions: paddlewise-request_at_lists.intelenet.net > Website: http://www.paddlewise.net/ > *************************************************************************** *************************************************************************** PaddleWise Paddling Mailing List - All postings copyright the author and not to be reproduced outside PaddleWise without author's permission Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
MJAkayaker_at_aol.com wrote: > > 1. What is an "outside" seam exactly? > A fiberglass strip covering the outside of the seam. The CD kayaks have a fiberglass strip covering the inside of the H channel. > 2. Current Designs info says the "H" channel method produces a "seam that has > a hollow center which accommodates the rudder cables inside". How are the > deck and hull glued to the "H" to leave a hollow center? Is the hollow > center going to be a weak point particulaly up forward where there is no need > for rudder cables.? My understanding is that the cross bar in the H is hollow, so it provides a separate passage for the cable. Since the H section is backed by a fiberglass seam cover, its strength shouldn't be an issue. The H section allows them to make a waterproof seal with a passage for the cable. The glass provides the strength. > > 3. What are the pro's and con's of each construction (or does it even matter > to the paddler)? _Properly_done_, it shouldn't matter. I haven't heard of CD kayaks having a higher failure rate than those boats that are fiberglassed inside and out. Maybe they do. There may be weight differences, but leave that for the fanatics. > > 5. Can you tell by looking at the boat how the deck and hull are joined? > Maybe,... usually? Sometimes I can't figure out how the plastic strip is made by examining the outside. Is it like the CD or is it all fiberglass with a thin bumper strip covering? T shaped? You should be able to tell if it's glassed over on the inside , since there's no gel coat or anything to hide it. Anyone know what the techy details are on the beautiful strip that Boreal Designs puts on their kayaks? Mike *************************************************************************** PaddleWise Paddling Mailing List - All postings copyright the author and not to be reproduced outside PaddleWise without author's permission Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
Mark Arnold wrote: > > 1. What is an "outside" seam exactly? > Fiberglass kayak hulls and decks are made separately, and then the two halves are joined in some fashion. If a woven fiberglass cloth tape (looks like a ribbon woven of fiberglass cloth and available in many widths) impregnated with some sort of resin is used to glue the top and bottom halves of the boat together, these gluing strips can be put either on the inside or the outside (or both) of the boat. Appearance is not as much of an issue on the inside of the boat, so the inside seams can be wider and stronger (more layers) than outside seams. In order to make the outside of the boat look the best, the seam (if there is one) must be very narrow, and more carefully applied. It stands to reason that if all other things are equal, a boat built with both inside and outside seams will be stronger than a boat built with only an inside seam of the same thickness/construction. It is possible, however, to not use an outside seam, and still have comparable structural strength. > 2. Current Designs info says the "H" channel method produces a "seam that has > a hollow center which accommodates the rudder cables inside". How are the > deck and hull glued to the "H" to leave a hollow center? Is the hollow > center going to be a weak point particulaly up forward where there is no need > for rudder cables.? > I've not seen (paid any attention to) this type of construction, but from the description I'd guess that the weakest part of such a joint would be in how the deck and the hull are glued to the H-channel. Any time you have to bond dissimilar materials together - especially in a long-lasting, tough, and waterproof joint - the trick is to find an adhesive that sticks equally well to both parts. And though such adhesive joints may be good when 'young', the bond may change with time and exposure. The molded H channel should be pretty tough, and shouldn't split in the middle. - although years of UV exposure could change the toughness of the channel as well. > 3. What are the pro's and con's of each construction (or does it even matter > to the paddler)? > If the major consideration is ultimate boat strength, it would make sense to opt for a heavy-duty layups joined by heavy-duty seams both inside and out. One can also argue for having a seam weaker than either the hull and the deck construction (which _can_ be the case with both construction methods). In such a system, a catastrophic impact would break the seam first, and leave the hull and deck pretty much structurally intact, thereby making it easier to repair the boat. With a real heavy-duty seam job, and assuming the hull and deck don't break independantly of the seam, the boat will be able to take a much bigger impact before breaking. But if and when it finally *does* break, it probably won't break along the seam, and will be much harder to repair. It's ultimately up to the paddler to decide where and in what kind of conditions they're going to paddle, and then specify the appropriate boat layup and construction methods. A Tsunami Ranger will need a much tougher boat than a twice-a-year paddler. Nobody wants to have a boat spring a leak in the middle of a long tour or in real nasty conditions when a long ways from shore. Very light layups can also be serviceable for many, many years, IF one is aware of the relative fragility of a boat so constructed and 'babies' it accordingly. All boats will eventually need some repair or maintenance work. > 4. Are there other options for joining the hull and deck together besides the > two I have mentioned? > Plastic boats truly are of 'unibody' construction, and there is no seam. Plastic is arguably the most maintenance-free boat material, but it suffers in areas of weight, and (usually) relative hull speed. In wood boats, the hull and deck are held together with a combination of glue, nails or screws, and sometimes a fiberglass skin coat. Wood boats are labor-intensive to build, but can of the lightest weights - and pretty tough. > 5. Can you tell by looking at the boat how the deck and hull are joined? > It's usually easiest to see how the hull and deck are joined on the inside of the boat, as the gel coat and decorative strips/moldings on the outside make it harder to see exactly how the hull and deck are joined. The manufacturer should tell you how the boat is built, but remember that each manufacturer will point out the 'good' aspects of their own means of boatbuilding, so take their comments with a grain of salt. Caveat: I'm not a boat-builder, though I have played quite a bit with fiberglass repairs over the years (and am currently repairing and reinforcing the aged and cracked fiberglass vent cover for my attic fan). I too hope that the builders will jump in to add to the commentary. Erik Sprenne (at the southern end of Lake Michigan) *************************************************************************** PaddleWise Paddling Mailing List - All postings copyright the author and not to be reproduced outside PaddleWise without author's permission Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
>>Date: Wed, 15 Dec 1999 11:52:03 EST From: MJAkayaker_at_aol.com Subject: [Paddlewise] Hull/Deck Seam Construction I was reading some kayak manufacturer's literature recently (trying to prepare for buying my next boat) and would like to get some more information concerning the methods used to join the hull and deck of FIBERGLASS kayaks. Necky talks about an "outside seam". Current Designs describes using a vinyl "H" channel with hull and deck glued to the channel rather than to each other (at least I think that is what they meant). Current Designs also says that "outside seams" are available. 1. What is an "outside" seam exactly?<< A bonded seam on the outside of the hull and deck. Most likely fiberglass tape bonded across the seam line with fiberglass resin or gelcoat (sometimes even a layer of resin in the tape and a layer of gelcoat over that). Aside: Somebody asked about Boreal Designs outside seams--it looks to me to be a tape (probably nylon or polyester cloth rather than fiberglass) that has an existing pattern in it and clear resin to let the pattern show through. The process to mating the deck to hull using an outside seam is: Tape the deck and hull together every 4 or 5 inches and run a strip of masking tape over the joint on the outside. Seam the halves together on the inside with fiberglass tapes (sanding or another way to roughen the surface to get a good bond is necessary on vacuum-bagged boats but not on hand-laid boats). Next peel off all the tape on the outside and place another strip of masking tape along the seam line where you want the tape, place two more rows of masking tape one on each side of the one that bridges the seam. Peel up the middle one and carefully sand the gelcoat between the other two tape strips to get a good rough bonding surface without tearing up the strips of masking tape on each side (or retape if you do). Fill in and smooth any major gaps or holes between the hull and deck with a fiberglass putty or paste. Wet out (with resin--or if this is going to be the last step, with pigmented resin or gelcoat) and lay in the fiberglass tape between the masking tape strips and peel up the masking tape before the resin kicks off. Let that side cure and turn the kayak over and do the other side. Often two more strips of masking tape are taped on each side again and gelcoat (which includes a smoothing and/or surface sealing agent) is put over the first layer to leave a smooth hard shiny finish. Some are even sanded and buffed at this point (or sanded between layers). >2. Current Designs info says the "H" channel method produces a "seam that has a hollow center which accommodates the rudder cables inside". How are the deck and hull glued to the "H" to leave a hollow center? Is the hollow center going to be a weak point particularly up forward where there is no need for rudder cables.?< The H extrusion (usually of vinyl) most often has the outside leg longer than the inside leg and often has a hole in the crossbar large enough for a rudder cable to easily run through. The H is placed around the hull and the deck is fitted into the top of the H. Some manufactures place a glue or sealant into the H at this time to prevent the water leaks that are common with many kayaks built with extrusion if this is not done. The glue (if used) is not intended to be structural but is used as a sealant. (One exception to this I know of is Eddyline's polycarbonite kayaks--such as the Merlin--where this glue is what holds the hull and deck together and into the extrusion.) Once the parts are mated together in the extrusion several masking tape strips bridge the seam and hold it together. Next the inside is seamed with fiberglass tapes much as was done above with outside seams. Once the resin cures the masking tape is removed and the seam is completed. The strength in this H molding (extrusion) system comes from the fiberglass tape rather than the vinyl. As with any system the better the materials and the more material thickness used the stronger and more ridged the seam (but the more materials used the more it will weigh too). >3. What are the pro's and con's of each construction (or does it even matter to the paddler)?< Caveat: I'm a manufacturer and we use outside seams (although early on we made a few boats with vinyl extrusion seams). Outside seams are much more labor intensive and therefore more expensive (how much more depends on the amount of extra labor used and the cost of labor where they are built). Current Designs $150 (US $ I believe) extra reflects the extra labor costs. $200 is probably more typical for a US manufacturers retail price difference. As some have already mentioned vinyl seams have a reputation for being leaky. This usually occurs near the ends of the boat where the inside seam has been applied at some distance from the applier. The applier is using (most likely) a brush on the end of a stick and can't really see how good a job he is doing. If enough resin doesn't get where it saturates the cloth and the gap where the cloth bridges to go over the inside leg of the H (therefore doesn't leave any pin holes or bubble holes this can cause a leak. In use the water that falls on the deck that flows down to and is held in the channel formed by the upper outside arm of the H can get inside (if not well sealed) This can happen either from gravity or from suction due to air pressure changes inside the compartments (noted in the bulging in or out hatch lid discussion). As someone mentioned the best test for this is to stand the kayak on end and fill the end that is down with about 4 feet of water (or up to the hatch opening). If water comes out the seams you found your leak (but unfortunately these seam leaks can be very difficult to fix). If this is not the source of the leak close the hatch and let the water inside sit over the hatch area (sometimes it is the hatch seal sometimes it is how it is mounted to the deck that leaks). Other common leak points are where holes such as for rudder cables have been put through the deck and sometimes it is the rudder pin hole or end toggle holes. Note: Seams are usually leaking above where you first see water coming out. Other differences are minor, pound for pound a well done outside seam is probably stronger than a well done extrusion seam but this is not a big deal because kayaks rarely break in this area. They are usually stronger at the seams because the seams most likely are the thicker and stiffer areas of the kayak because there is the extra material in the seams adding thickness to this area. Serious damage to both systems is rare but would usually be easier to fix (and a professional repair would most likely be less expensive and look nicer) in the outside seam kayak. This is kind of splitting hairs because few of us (we will make Doug Lloyd and Tsunami Rangers and surf and rock garden kayakers an exception here) are going to have to deal with this kind of damage. (Note: someone suggested that it would be better to have a kayak break in the seams because it would be easier to fix. This is wrong, it is much harder to fix a break across or along a seam than breaks in other areas of the hull or deck because of the greater complexity in the seam area. Also a weakened seam as suggested is more likely to produce a catastrophic failure with the hull and the deck coming partly or even completely apart. Not the kind of thing you want to have happen out to sea or after hard contact with a rock along a cliffy shoreline. It will be a lot harder to duct tape up over a seam for an emergency repair as well) >4. Are there other options for joining the hull and deck together besides the two I have mentioned?< Yes but they are not much used in modern fiberglass kayaks except sit-on-tops. >5. Can you tell by looking at the boat how the deck and hull are joined?< Yes if you know what to look for or feel for. For example, you can usually get a fingernail under a vinyl extrusion to confirm it is an extrusion.You will often see a wider dark (or seam color) line inside under the fiberglass tapes (which is the short legs of the H) if clear resin and no cover coating is used inside. Unsheathed rudder cables emerging from the seam in back and the seam area inside the cockpit area point to an extrusion seam as well. Fiberglass outside seams will not likely have as crisp an edge if you look closely. Matt Broze http://www.marinerkayaks.com >This may be asking for more than can be described here on paddlewise, but I would appreciate any information you may be able to give. Mark J. Arnold MJAkayaker_at_aol.com< *************************************************************************** PaddleWise Paddling Mailing List - All postings copyright the author and not to be reproduced outside PaddleWise without author's permission Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
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