Compostite Copies of Kayaks
Leif, I want to copy a boat. How do I do that? Can I do that? I'm stoked that you are thinking about this but this is a long answer so rather than typing a 10,000 word instagram message for the fourth time, let's address this in a blog article.
Short answer is yes this can be done, but let's fill the details in slowly. A good summary of everything that I am about to go over can be found in The Boatbuilder's Manual by Charlie Walbridge (yes the same Charlie Walbridge who deals with the accident reports). It's out of print but it's also extremely short so you can often find a used copy floating around the internet for cheap. Materials have progressed a lot since the book was written, and there have been some changes in what counts as popular construction methods, but his book still provides a great overview and framework which you can then innovate from. I suggest his book every two or three blog posts that I write.
The first questions are more philosophical in nature; should you do this?
Legally speaking, even if you sell a couple copies of whatever design you clone, I don't think many companies will take the time to serve you with the ol' cease and desist. Of course, if you ask for permission, any of the big companies will probably be obligated to say no, but your limited production run is probably not worth the effort for them to shut down unless you specifically did something to really make them angry. Selling kayaks comes with its own grab bag of legal details, like registering with the coast guard, putting serial numbers on the boats, and probably a bunch of other things that I don't know about. I was about to say that some minor copyright infringement is probably pretty low on the list of offenses there but then I remembered again about how I am not a lawyer, and now I actually have no idea. What I will say is that carbon copes get made, and I am not aware of anyone having legal trouble because of it. Walbridge does a better job outlining this issue and I am just shooting from the hip here. The main idea is just that this deserves to be thought about.
In either case, your plastic boat will probably be fine, although you can make decisions that will intentionally damage or destroy it, if that's what you're into. Most of the possibly destructive decisions will be things involving the cockpit rim.
For wax or liquid, you're probably going to need to prepare the plastic surface, unless you have a brand new kayak with no river rash. This preparation will probably be some kind of primer. I'm not talking about just rattlecan painting primer here, although if you're a painting expert and know of something that will work well, please feel free to let me know. The original shape that you are building your thing off of is properly called the pattern or the plug, and there is a whole industry that has developed of making composite parts off of various types of pattern, for aerospace, auto body, and marine (like serious marine like motorboats and ships) applications. Who would have guessed that you were not the first person to encounter this issue? There is no need to try to figure out some hack to prepare the surface or release the mold. There are tons of products you can use that are designed to solve these exact problems that you are about to encounter. When coating your rough plug (or pattern), you probably want something that includes a couple of the following buzzwords:
If you want to make more serious modifications or repairs to the plastic original before pulling your one-off, you can probably glue on some foam and/or coat it with bondo or other body filler or fairing filler before you apply primer. Bondo is also a polyester resin, thickened with way different stuff, so it will dissolve styrofoam too. There are epoxy-based fairing and body fillers, but we're starting to get a little lost here, so you can go do your own research if you need to. I mention this here because often you will be covering up your grab loops or grab loop attachments, and that could involve many possible levels of detail.
The other release option is that you could apply more of a membrane. Anything that prevents the resin from sticking to the plastic will work (within reason). If the resin doesn't touch the plastic it can't stick to the plastic. So you could carefully coat every inch of the plastic boat with packing tape, like I did for the Slug. This might sound horrible, and it's not fun, but it's easier and faster than I thought it would be at first. Two or three rolls will coat a boat, and resin should release off the smooth outer surface of the tape. You'll have little ridges on the inside of your one-off, but that's no big deal. You can probably also use saran wrap or fancy saran wrap (release film), although I haven't actually used either of those methods. The downside will be that you will have more wrinkles on the inside of your final boat. Depending on your specific situation, you might or might not need to return the boat to its original condition, and peeling packing tape off is easier than peeling primer off, but it's still a pain. Paint scrapers and razors can help.
Your choice of mold release will probably depend on your overall construction method. For example if you're making a one-off, you don't really care about the fine details of the surface because that will become the interior of the new boat. So let's now talk about the construction options.
Once your mold release is applied, you mark out your parting line (the divider between the upper and lower halves) and start laying up the new boat. You build one half, peel it off, then build the other half, peel it off, and then join your two halves together.
There are a lot of choices to be made here, and I will only talk about a couple things. You can definitely make a pretty nice looking outer surface if you are careful. I am not that guy. When I hand laminate, my surface does not look nice. Also, regardless of the cosmetic outer surface, your best boat will be one that is vaccuum bagged, because it will squeeze out excess resin, making it lighter and all the layers will be better stuck together, probably making it stronger. However, if you try to build a nice vaccuum bag on a plastic boat, you will probably squish it into the wrong shape. Also, the vaccuum will leave a super wrinkly outer surface. On top of all that, if you're reading this article, then I have to ask whether you own a vaccuum pump at all. Still, as I wrote in my article about the Slug, you can make things work, like if you use a shop vac and a matress bag, and after that you can apply a coat of epoxy to smooth the surface a little.
Once you have your two halves made, you stick them together with some strips of whatever fabric you built the boat from. You can buy rolls of this fabric, as straight weave or bias weave, in various widths, from a couple different sources online. There's kind of an art to doing it, and a couple tricks that can make it go faster and easier, but seaming a boat together is a big enough job that it could be its own article, and there's nothing specific to this construction method that would change, so I won't go into detail here.
So, this is at least a brief overview of the one-off process, although I have left out a ton of details about the construction, like even whether to use carbon fiber and how many layers and epoxy vs polyester resin, and really a lot. The one extra consideration that I will discuss here is foam core. Pretty much every boat needs some foam core. The core really makes a huge difference in the stiffness. The actual material isn't super important, it's the thickness, and the thicker, the stiffer. I recommend about 3/8" for most playboats, and I often use divinycell, although there are complications for some construction techniques (infusion) which I will not go into here. You can also use more flexible stuff, like Lantor Soric, which is little hexagons of foam with a flexible scrim between them. This lets the core layer bend nicely, but I don't think you can get it in crazy thicknesses. The main thing is that you will probably need some foam core in your boat. If you are building a one-off on the outside of your plastic boat, then this core will disrupt the shape of the new boat a little. People often worry about the fact that the outer surface of the old boat becomes the inner surface of the new boat, which makes the new boat larger than the original. This is true, but the change in size is only the thickness of the composite skin, which is mostly ignorable. However, if you add a nice fat 3/8" or 1/2" block of foam core, this will be more of a big deal. This will be a lump that you can see and it could change the performance of the new boat.
There could be solutions. One possibility that has occured to me but I haven't tested would be to laminate a peel ply layer first (on the inner surface of the new boat). Peel ply is a nylon fabric that is designed to not really saturate or bond to the other layers. Once your resin cures, the peel ply (ply means layer) can be peeled off the rest of the laminate, and the surface it leaves behind should be ready to bond a fresh layer onto. So you could make a minimal layup (just ontwo or three layers) as a one-off with peel ply as the innermost layer, then peel out the peel ply and laminate more layers to the interior, which could include a foam core. I haven't tried this, but my boat building reflexes are tingling, trying to warn me that this could be a pain, depending on how you go about it. I haven't tried so I don't know how it shakes down.
Some of the ideas I mention here are stolen from a video I recently saw from Easy Composites, where they go over a one-off project. As I hopefully just outlined here, you can make different choices for a lot of the steps, and not eveything they do would be optimal for a kayak, but their video is way more organized and probably more correct as well. Check it out here:
So this is at least a sketch of the one-off process. The really glaring omission is the cockpit rim and other outfitting, but that's relatively universal, and I can't say as much as I'd like to because of trade secrets, so I'll go into that later. Let's bang out a really readable bullet point list because people are going to skip all these detailed paragraphs anyway.
This is where some of the construction details start to matter. I wrote another article about resin types, but the bottom line of that whole discussion was that you probably want to use epoxy resin to build your boat, and polyester resin to build your mold. When making a mold, you are concerned with the small details of the surface, so you apply gel coat, which is like a coat of paint, let it cure, then build up a relatively strong backing with fiberglass. You'll probably use chop strand mat, which is randomly oriented fibers that turn into spooge when the resin dissolves the binder, and then they harden once it cures. This is great for elinating air bubbles but it's heavier than it needs to be. It's just fine for molds but not the best for boats.
A nice mold will have flanges where the parts of the mold meet, which allows you to attach a vaccuum bag and different hoses that you might need, or to build a boat with the two mold halves bolted together (bold move but super cool). Flanges are a pain in the butt. You have to build a temporary surface that will be the flange surface, perpendicular to the boat itself. I wrote about mold making when I built the Snail, so if you decide to go this route, give that a read.
As with the one-offs, there is an Easy Composites video that goes over this process. This video is the middle video in a series, and the other two are also informative, but the middle one is a miniature copy of something a lot like a boat mold. They go into way more detail than I have here, but they also make some slightly different choices than I usually do for my molds. Still it's a great source of information.
There are also ways to... what's a word other than "half-ass"... save time and money when building a mold. You can make a thinner mold that will be cheaper, but won't last through very many boats and could possibly deform if you vaccuum bag your boat. You can leave off flanges, which limits some of your boat construction options but saves time and effort. You can make a mold without a tooling gel coat. This tends to include a couple little air bubbles and surface imperfections, but can still make a really high quality mold. A mold doesn't take much, it's just intimidating the first time you build one. If you want a confidence boost, check out just about any video from this guy Bill from Australia who seems to just cowboy together a bunch of auto body parts one handed because his other hand is busy flipping the bird to the establishment.
On the flip side, mold making can be as complicated as you want to make it. This is the way that the professionals make good boats. So this article is not even going to try to do it justice, I'm just going to illustrate that it is a possible path. You can go absolutely nuts making really high quality molds. Hopefully this at least gives you enough that you can understand the pros and cons.
If you don't want to destroy the plastic boat, just get your boat or mold as close as you can to the original cockpit rim, knowing that you might need to trim it back a little in order to release it from the rim. Then once it's free, build a new surface that reaches inward to the right shape. I don't know exactly how best to do that. You could probably use cardboard coated with packing tape to make a little form for your extension, then build fiberglass on top of that and remove it. You might be able to kind of extend your hose form with some clay so that your rim is itself the extension piece, or maybe your hose will just be big enough that it can cover that small gap. You might even be able to do something clever like laying up multiple parts on the original boat which then get released and reassembled, but this seems prone to all kinds of problems. Basically, you're going to have to problem solve a little. You can do it. Keep things as simple as you can.
Short answer is yes this can be done, but let's fill the details in slowly. A good summary of everything that I am about to go over can be found in The Boatbuilder's Manual by Charlie Walbridge (yes the same Charlie Walbridge who deals with the accident reports). It's out of print but it's also extremely short so you can often find a used copy floating around the internet for cheap. Materials have progressed a lot since the book was written, and there have been some changes in what counts as popular construction methods, but his book still provides a great overview and framework which you can then innovate from. I suggest his book every two or three blog posts that I write.
The first questions are more philosophical in nature; should you do this?
Ethics
You are talking about copying a boat that was undoubtedly built and sold as a commercial venture. I'm no lawyer but this sounds a lot like copyright infringement. Now, if you're just building it for your own quiet enjoyment, this is probably fine, legally speaking, but you should examine your own motivations a little and try to put yourself into the shoes of the boat designer. I don't want to make any blanket statements like "the designer would be honored that you approve of the design enough to copy it". If you're copying a composite boat, there's probably an option to just buy another copy of that composite boat from the manufacturer. Trying to make your own copy because you think you can do a better or cheaper job might be a little offensive to the builder. Or they might not care. I don't have the answers here, I just want to point out that this is an area you should think about.Legally speaking, even if you sell a couple copies of whatever design you clone, I don't think many companies will take the time to serve you with the ol' cease and desist. Of course, if you ask for permission, any of the big companies will probably be obligated to say no, but your limited production run is probably not worth the effort for them to shut down unless you specifically did something to really make them angry. Selling kayaks comes with its own grab bag of legal details, like registering with the coast guard, putting serial numbers on the boats, and probably a bunch of other things that I don't know about. I was about to say that some minor copyright infringement is probably pretty low on the list of offenses there but then I remembered again about how I am not a lawyer, and now I actually have no idea. What I will say is that carbon copes get made, and I am not aware of anyone having legal trouble because of it. Walbridge does a better job outlining this issue and I am just shooting from the hip here. The main idea is just that this deserves to be thought about.
Construction Options
There are two routes available. I've actually discussed these ideas before when talking about the Slug and the Snail, a couple of my own terrible designs, so this will be more of a shallow survey that talks about the big picture and the differences between the options. If you decide to actually do this, you'll need to dig deeper on whichever method you pick. I'll talk about copying a plastic boat because then it's more clear when I'm referring to the original boat and when I'm talking about the new copy, but the same ideas obviously apply if you are copying a composite boat. You're going to apply something to the plastic boat so that resin will not bond to it. Then you're going to build a shell onto the surface of that plastic boat, and you'll peel that shell off. Route number one is that you just make a nice strong shell and that new shell is your new boat. This is called making a one-off. Route number two is that the shell you make is your new mold, and you then build a new boat from the inside surface of that mold. This is called... making a mold.In either case, your plastic boat will probably be fine, although you can make decisions that will intentionally damage or destroy it, if that's what you're into. Most of the possibly destructive decisions will be things involving the cockpit rim.
Surface Preparation
First up, whichever method you use, and regardless of how you feel about the plastic boat and its survival, you will need to apply some mold release, because you don't want the plastic boat stuck inside your new composite boat. If you wanted that, you would just still be paddling the plastic boat. Now, there are a few mold release options. You can apply wax or semipermanent liquid, both of which require a pretty smooth surface, or you can apply some kind of more durable membrane such as packing tape or release film, which can work on incredibly rough surfaces. If you apply wax or liquid, you're making the surface slippery, so the resin touches it but comes back off later. This preserves very fine detail. If you use a more physical membrane, you're blocking the resin from getting to the surface, so you lose detail.For wax or liquid, you're probably going to need to prepare the plastic surface, unless you have a brand new kayak with no river rash. This preparation will probably be some kind of primer. I'm not talking about just rattlecan painting primer here, although if you're a painting expert and know of something that will work well, please feel free to let me know. The original shape that you are building your thing off of is properly called the pattern or the plug, and there is a whole industry that has developed of making composite parts off of various types of pattern, for aerospace, auto body, and marine (like serious marine like motorboats and ships) applications. Who would have guessed that you were not the first person to encounter this issue? There is no need to try to figure out some hack to prepare the surface or release the mold. There are tons of products you can use that are designed to solve these exact problems that you are about to encounter. When coating your rough plug (or pattern), you probably want something that includes a couple of the following buzzwords:
- High build - coats the surface all thicc to hide scratches and fuzz
- Patterning - designed to be sprayed or painted onto the plug or pattern
- Sandable - code for less durable, which is ok because you only need to use it once
If you want to make more serious modifications or repairs to the plastic original before pulling your one-off, you can probably glue on some foam and/or coat it with bondo or other body filler or fairing filler before you apply primer. Bondo is also a polyester resin, thickened with way different stuff, so it will dissolve styrofoam too. There are epoxy-based fairing and body fillers, but we're starting to get a little lost here, so you can go do your own research if you need to. I mention this here because often you will be covering up your grab loops or grab loop attachments, and that could involve many possible levels of detail.
The other release option is that you could apply more of a membrane. Anything that prevents the resin from sticking to the plastic will work (within reason). If the resin doesn't touch the plastic it can't stick to the plastic. So you could carefully coat every inch of the plastic boat with packing tape, like I did for the Slug. This might sound horrible, and it's not fun, but it's easier and faster than I thought it would be at first. Two or three rolls will coat a boat, and resin should release off the smooth outer surface of the tape. You'll have little ridges on the inside of your one-off, but that's no big deal. You can probably also use saran wrap or fancy saran wrap (release film), although I haven't actually used either of those methods. The downside will be that you will have more wrinkles on the inside of your final boat. Depending on your specific situation, you might or might not need to return the boat to its original condition, and peeling packing tape off is easier than peeling primer off, but it's still a pain. Paint scrapers and razors can help.
Your choice of mold release will probably depend on your overall construction method. For example if you're making a one-off, you don't really care about the fine details of the surface because that will become the interior of the new boat. So let's now talk about the construction options.
One-Offs
A one-off is a boat that you construct around the outside of the original and then pull off. It's less repeatable and generally not the best way to build a boat, but it's quicker and simpler.Once your mold release is applied, you mark out your parting line (the divider between the upper and lower halves) and start laying up the new boat. You build one half, peel it off, then build the other half, peel it off, and then join your two halves together.
There are a lot of choices to be made here, and I will only talk about a couple things. You can definitely make a pretty nice looking outer surface if you are careful. I am not that guy. When I hand laminate, my surface does not look nice. Also, regardless of the cosmetic outer surface, your best boat will be one that is vaccuum bagged, because it will squeeze out excess resin, making it lighter and all the layers will be better stuck together, probably making it stronger. However, if you try to build a nice vaccuum bag on a plastic boat, you will probably squish it into the wrong shape. Also, the vaccuum will leave a super wrinkly outer surface. On top of all that, if you're reading this article, then I have to ask whether you own a vaccuum pump at all. Still, as I wrote in my article about the Slug, you can make things work, like if you use a shop vac and a matress bag, and after that you can apply a coat of epoxy to smooth the surface a little.
Once you have your two halves made, you stick them together with some strips of whatever fabric you built the boat from. You can buy rolls of this fabric, as straight weave or bias weave, in various widths, from a couple different sources online. There's kind of an art to doing it, and a couple tricks that can make it go faster and easier, but seaming a boat together is a big enough job that it could be its own article, and there's nothing specific to this construction method that would change, so I won't go into detail here.
So, this is at least a brief overview of the one-off process, although I have left out a ton of details about the construction, like even whether to use carbon fiber and how many layers and epoxy vs polyester resin, and really a lot. The one extra consideration that I will discuss here is foam core. Pretty much every boat needs some foam core. The core really makes a huge difference in the stiffness. The actual material isn't super important, it's the thickness, and the thicker, the stiffer. I recommend about 3/8" for most playboats, and I often use divinycell, although there are complications for some construction techniques (infusion) which I will not go into here. You can also use more flexible stuff, like Lantor Soric, which is little hexagons of foam with a flexible scrim between them. This lets the core layer bend nicely, but I don't think you can get it in crazy thicknesses. The main thing is that you will probably need some foam core in your boat. If you are building a one-off on the outside of your plastic boat, then this core will disrupt the shape of the new boat a little. People often worry about the fact that the outer surface of the old boat becomes the inner surface of the new boat, which makes the new boat larger than the original. This is true, but the change in size is only the thickness of the composite skin, which is mostly ignorable. However, if you add a nice fat 3/8" or 1/2" block of foam core, this will be more of a big deal. This will be a lump that you can see and it could change the performance of the new boat.
There could be solutions. One possibility that has occured to me but I haven't tested would be to laminate a peel ply layer first (on the inner surface of the new boat). Peel ply is a nylon fabric that is designed to not really saturate or bond to the other layers. Once your resin cures, the peel ply (ply means layer) can be peeled off the rest of the laminate, and the surface it leaves behind should be ready to bond a fresh layer onto. So you could make a minimal layup (just ontwo or three layers) as a one-off with peel ply as the innermost layer, then peel out the peel ply and laminate more layers to the interior, which could include a foam core. I haven't tried this, but my boat building reflexes are tingling, trying to warn me that this could be a pain, depending on how you go about it. I haven't tried so I don't know how it shakes down.
Some of the ideas I mention here are stolen from a video I recently saw from Easy Composites, where they go over a one-off project. As I hopefully just outlined here, you can make different choices for a lot of the steps, and not eveything they do would be optimal for a kayak, but their video is way more organized and probably more correct as well. Check it out here:
So this is at least a sketch of the one-off process. The really glaring omission is the cockpit rim and other outfitting, but that's relatively universal, and I can't say as much as I'd like to because of trade secrets, so I'll go into that later. Let's bang out a really readable bullet point list because people are going to skip all these detailed paragraphs anyway.
One-Off Pros and Cons
- Pros
- Fewer steps - the only thing you build is the boat itself, no intermediate parts
- Faster - this is a corrolary to the first point
- Cheaper - same idea as the other two
- Cons
- Poor finish - your exterior surface will probably not look great without a ton of extra work, which kind of starts to invalidate most of the pros of this path
- Foam core issues - not insurmountable, but hard to include foam core in the right way
Making a Mold
The more proper way to go about this whole thing is to make a mold. You follow a lot of the same steps that you would to make a one-off, building a shell around your original. However, this shell can be heavy and thick, because your next step will be to peel it off, apply mold release to the inner surface, and build a new boat on the inside of it. This is the way most boats are made, so there aren't many problems with the process other than that it is more time-consuming.This is where some of the construction details start to matter. I wrote another article about resin types, but the bottom line of that whole discussion was that you probably want to use epoxy resin to build your boat, and polyester resin to build your mold. When making a mold, you are concerned with the small details of the surface, so you apply gel coat, which is like a coat of paint, let it cure, then build up a relatively strong backing with fiberglass. You'll probably use chop strand mat, which is randomly oriented fibers that turn into spooge when the resin dissolves the binder, and then they harden once it cures. This is great for elinating air bubbles but it's heavier than it needs to be. It's just fine for molds but not the best for boats.
A nice mold will have flanges where the parts of the mold meet, which allows you to attach a vaccuum bag and different hoses that you might need, or to build a boat with the two mold halves bolted together (bold move but super cool). Flanges are a pain in the butt. You have to build a temporary surface that will be the flange surface, perpendicular to the boat itself. I wrote about mold making when I built the Snail, so if you decide to go this route, give that a read.
As with the one-offs, there is an Easy Composites video that goes over this process. This video is the middle video in a series, and the other two are also informative, but the middle one is a miniature copy of something a lot like a boat mold. They go into way more detail than I have here, but they also make some slightly different choices than I usually do for my molds. Still it's a great source of information.
There are also ways to... what's a word other than "half-ass"... save time and money when building a mold. You can make a thinner mold that will be cheaper, but won't last through very many boats and could possibly deform if you vaccuum bag your boat. You can leave off flanges, which limits some of your boat construction options but saves time and effort. You can make a mold without a tooling gel coat. This tends to include a couple little air bubbles and surface imperfections, but can still make a really high quality mold. A mold doesn't take much, it's just intimidating the first time you build one. If you want a confidence boost, check out just about any video from this guy Bill from Australia who seems to just cowboy together a bunch of auto body parts one handed because his other hand is busy flipping the bird to the establishment.
On the flip side, mold making can be as complicated as you want to make it. This is the way that the professionals make good boats. So this article is not even going to try to do it justice, I'm just going to illustrate that it is a possible path. You can go absolutely nuts making really high quality molds. Hopefully this at least gives you enough that you can understand the pros and cons.
Mold-making Pros and Cons
- Pros
- Perfect surface detail - you make a copy that is as exact as possible
- Foam core is easy - you can make the inner surface of the finished boat lumpy and it's ok
- Repeatable - you can produce many copies
- Stronger lighter boats are possible - this is way more compatible with vaccuum bagging
- Flexibility - once the mold is made, you still have a lot of freedom in the construction details of the boat
- Cons
- Time - you build a mold, then a boat
- Money - this will probably be more expensive, but price things out because it might not be so different as you think
- Conformity - this is how everyone does it, so if you do it too, you could be called a conformist
Some Universal Concerns
Cockpit Rims
Cockpit rims are a difficulty for every kayak. The basic problem is that they overhang, so there is no simple way to get a mold to release from the shape. It's a geometric problem. I know of about four methods that people have invented to deal with cockpit rims:Hose Rims
The simplest way to build a rim is to just leave a hole of about the right size and shape in your boat, then temporarily glue a hose to the upper surface and use that as a form to lay up a cockpit rim. This was the method that I used for the Slug, and I wrote about the process with diagrams and details deep in that article. Advantages: simplest way I know of. Disadvantages: pretty ugly, and can be kind of sharp on the spray skirt.Dreamboats Rims
You can also build your cockpit rim as part of the kayak, instead of attaching it after. Dreamboats and Murky Waters kayaks (Stephen Wright and Ed Skrzypkowski respectively) developed a pretty simple way to do this. However, this is totally a trade secret, and since Stephen showed me many of the details of that process, I don't want to say anything about it here, apart from the fact that it exists. If you go closely examine a Dreamboat, you can probably figure parts of it out, but I'm not even going to describe what you would see for yourself if you looked at the boat.Three Piece Mold
Featherweight boats also have a built-in cockpit rim, and the way they do it is written in the seam lines of those boats. They built a three piece mold with an extra parting line down the certerline of the deck, so that the two halves of the deck mold can release to the sides instead of having to lift upwards. This is an immense jump in complexity from the other methods, and it won't work on every cockpit geometry (because we started this discussion trying to copy an existing boat). It's probably not what you're looking for.Auxillary Molds
You could also design a cockpit rim that comes out of a separate mold that is not part of the boat, and then attach that rim after the boat is built. Then you can have a nice thick rim that looks super pro. Don't do this method. You don't want to build extra molds.My Advice
If you're willing to destroy your plastic boat, then cut the top part of the cockpit rim off. Leave as much of the throat of the rim as possible, so that you get a little turret kind of thing where the rim turns upward and is about to start overhanging. Keep that as tall as possible so that there's more nice smooth continuous surface for your skirt to seal against. Lay your boat or mold up to include that upturn, so that you get the exact shape of the original cockpit rim. Then use the hose method, with that ridge as a guide for the hose.If you don't want to destroy the plastic boat, just get your boat or mold as close as you can to the original cockpit rim, knowing that you might need to trim it back a little in order to release it from the rim. Then once it's free, build a new surface that reaches inward to the right shape. I don't know exactly how best to do that. You could probably use cardboard coated with packing tape to make a little form for your extension, then build fiberglass on top of that and remove it. You might be able to kind of extend your hose form with some clay so that your rim is itself the extension piece, or maybe your hose will just be big enough that it can cover that small gap. You might even be able to do something clever like laying up multiple parts on the original boat which then get released and reassembled, but this seems prone to all kinds of problems. Basically, you're going to have to problem solve a little. You can do it. Keep things as simple as you can.
Comments
Post a Comment