Installing sister keelson on a flattie skiff

[Dusty88]

Building a Wyman flattie skiff which calls for a pair of sister keel-sons. I plan on fiber glassing the bottom for abrasion resistance. My question is do I install these first and fiberglass over it or, glass the bottom and then put the keel-sons on top of this. Seem like if they are a wear item, you'd want to be able to replace them.

 

[Dave G 9N]

It is a lot easier to glass a flat surface. You can still glass overt the keelson with tape after laying up the bottom if you like. Either way will work.

I find that it is easier to fair a cut edge on the tape than a selvage edge, and much less expensive to cut my own tape to any width I want. ± 90° is easy, 45° maybe not. Either buy longer or wider cloth than needed for sheathing and Roll the cloth snugly and carefully aligned on a PVC or cardboard tube. Roll a long knife or machete against the tube to cut the cloth. The glass cuts very easily with little or no sawing. A few fibers will always survive, so roll it carefully onto another small tube and cut the stragglers as you find them. Keep it on the tube because it will unravel if you don't. Yes it can get messy, but so is fairing selvage edges. With care, the cut edges can be handle without unravelling. Not for a production shop and not for everyone.

There is some information on abrasion, cloth types and thickness here.

 

[Dusty88]

Thanks... This is some useful info.

 

[sdowney717]

Thanks... This is some useful info.

I would use Nylon cloth instead of dynel or xynol, it's going to be a lot cheaper I think and Nylon cloth is also abrasion resistant.
I am talking tarp like thickness.
Glass the outer hull put on those keels and cloth over keels.

And you could use nylon instead of glass for the bottom, you know glass can crack, nylon never will. It is alround more durable.
Likely boats with glass fibers are stiffer than nylon, BUT nylon on wood is going to be great.

Nylon vs Polyester - Difference and Comparison | Diffen

I dont know why nylon is not used more on boat hulls.

What glue works best on nylon? - Glue Things
Epoxy Glue:
Prepare to be amazed by epoxy glue. This adhesive is like a ninja warrior when it comes to bonding nylon. It’s tough, water-resistant, heat-proof, and chemical-proof – basically indestructible. But beware, working with epoxy can be a bit tricky since it requires careful mixing and patience while it dries.

Exploring the Properties of Nylon:
Nylon is a type of polyamide that boasts incredible mechanical properties. It is created through polymerization, where monomers are linked together to form long chains. This process results in a material that is not only robust but also resistant to wear and tear.

Strength and Durability:
One of the key characteristics of nylon is its high tensile strength, allowing it to withstand significant force before breaking or deforming. This property makes it ideal for applications such as ropes, cables, and fabrics used in outdoor gear and sports equipment.

Resistance to Environmental Factors:
Nylon exhibits excellent resistance to abrasion, chemicals, and heat. It can maintain its integrity even in harsh environments, making it suitable for automotive parts, electrical insulators, and industrial components.

Low Coefficient of Friction:
Nylon’s smooth texture and low coefficient of friction make it perfect for reducing friction and wear in moving parts such as bearings and gears. This property ensures smooth operation and longevity.

Versatility in Processing and Modification:
Nylon’s versatility extends beyond its mechanical properties. It can be easily molded into different shapes using techniques like injection molding or extrusion. Furthermore, nylon can be blended with other materials to enhance specific properties or characteristics.

Types of Nylon:
Nylon is available in various grades and forms to suit different applications. Nylon 6/6 (PA66) offers a balance of strength, toughness, and chemical resistance. Other variations include nylon 6 (PA6) and nylon 12 (PA12), each with unique properties.

Types of Glue for Bonding Nylon
Selecting the right glue for bonding nylon is crucial to ensure a strong and long-lasting bond. Whether you’re working on a craft project or repairing a broken nylon strap, the perfect adhesive is essential. In this article, we will explore the various types of glue suitable for bonding nylon, discussing their unique advantages and considerations.

Epoxy Glue – Unmatched Strength and Durability:
Epoxy glue is a popular choice for bonding nylon due to its exceptional strength and durability. Formulated with a resin and hardener, it creates a powerful adhesive when mixed together. This type of glue is perfect for applications that require the bond to withstand heavy loads or stress. However, it’s important to note that epoxy glue can be messy to work with and requires careful mixing and application.

 

[Dave G 9N]

Cloth is woven from fibers that have been coated with a sizing to lubricate them as they pass through the machinery. The sizing is generally harmless enough, but it is coating the fibers and gets in the way of the adhesive. Adhesives stick to the first surface encountered. If there is dirt, sizing or anything else on the surface, the adhesive may stick very well to the sizing, but the overall bond strength depends on how well the sizing sticks to the fiber, which is generally not so good. Almost all cloth that you can buy is coated with something to repel water or a sizing, so it is not going to wet well and form a good bond with an adhesive.

You need to find a greige cloth, and this is where I will refer back to the link to the WBF about Xynole and Dynel. It seems that greige is not that easy to get except as noted on the WBF in 3000 yard rolls. Most polyester is supplied with a coating. "These fibers are then dyed and in the vast majority of cases, a Polyurethane Coating (PU) is applided to the backside to stabilize the fabric. This is in conjunction with a Durable Water Repellant Treatment (DWRT) which is introduced to the face of the fabric to make these fabrics highly water resistant. Additionally, other chemicals can be added to soften the hand/feel of the fabric, make it stain resistant and so forth." None of this is good for bonding.

If you are looking for a coating that will need to flex, the choice of epoxy is important. West System laminating resin has lower elongation than MAS, and from what I have read, West will crack before MAS when the cloth stretches. How much it will stretch on plywood depends on how much the plywood will bend. I am not saying anything bad about West in general, just that it is not good for a flexible joint or surface, but fine for a more rigid glass layup. System III has some flexible resins and west sells G-flex. There are plenty of other epoxies available, and you can download their tds to look for elongation.

The only good Nylon source that I have found is https://www.coreys.us/. Corey runs a big enough business to buy the bulk fabric and is small enough that I think he might work with you on a large order, but I have not tried. I would rather buy from him than deal with 2980 yards of extra cloth. As for polyester, Corey also sells it and Fiberglass Supply Depot lists 4 oz Xynol. Dynel is another fabric that should act a lot like Nylon, it is a modacrylic. I have a few yards saved from someone's trash and after 10 years have had as much need for it as they did. The fraction of a yard that I did use was as generally described. It is not easy to wet, not clear, takes a lot of resin, forms a thick coating and the resulting surface is pretty rough. Sometimes, as when looking for a somewhat non-skid deck and protecting something from abrasion, that is a good thing.

Epoxy is often the best adhesive for a wide variety of plastics. That is not to say that any particular epoxy will bond well or easily to a wide range of plastics. There are many different epoxies available and each one has to be evaluated on a case by case basis. 3m used to have some easily located guides online, as did Loctite, but today, I am not having much luck finding them. I have found data sheets with bond strengths for a wide range of substrates, and often you find excellent adhesion on everything but polyethylene, Delrin and Nylon, sometimes polycarbonate, and forget about silicone. Surface treatments and primers may be needed. Just when you think that Teflon is good for tooling because nothing, including epoxy will stick, you find that the one you are using sticks very well.

 

[messabout]

If the keelsons are for the purpose of protecting the bottom when grounding, then let them be sacrificial elements. Do not cover them with anything but some good paint. When, or if, they become ground down, or become ragged, then replace them. If you enclose them with glass or other covering, replacement will become a lot more problematic.

There may be another purpose for the keelsons. They can provide a bit of resistance to skidding. Possibly a good feature when anchored.