John Kimball

I’ve always wanted to have real composite curing oven in my work shop. I only work in small objects, so an economical small curing oven has been out of the question. I decided to buy a the smallest toaster oven I could find on the Brazilian rain forest site and settled on a cheap ($54) oven with a dial thermostat. I was pretty pleased with it, but it had some issues that kept me from trusting it. 1) it had 4 burner units. This can cause extreme heat on the surface of the part which can flash cure prepreg and even melt the vacuum bag. 2) The heat was wither On or Off, no ramp rate or easing to the temperature that prepreg really needs. 3) It required you to use a 60 minute timer to operate it. This is annoying because most cures are over 2 hours. 4) I also want to use it for a warming oven to cure paint and speed cure adhesive. This oven could only go as low as 130ºF, so it was still a bit high for my liking. 5) It got pretty hot on the outer shell when heating and caused the room to heat up and was kind of dangerous in my opinion. With all that in mind and after some research, I decided to “modify” this cheap oven into something a little more usable for my needs. I started by replacing the dial thermostat with a simple PID temperature controller with solid state relay (SSR) and a toggle power switch to bypass the silly timer. There was plenty of room inside for some simple electronics. I also added ceramic insulation to the areas that would allow. I also eliminated the 2 top burners to slow down the heating process. The remaining 2 burners are more than enough to heat the tiny space. It was at this point that things started spiraling out of control. I realized that I wanted to control the power to the heaters even if the controller was powered on, so I added another switch. The SSR was mounted to a heat sink, so I figured it probably got pretty hot, so I mounted a small cooling fan to the back of the oven to provide some circulation while it’s running. It was running great, but it still got pretty hot on the outside, especially on the bottom. I found some heat deflection material that insulates with a very thin layer and put that on the bottom and the back of the unit. The PID allowed me to set a temperature and it would climb to that temp and then hold there. I thought I would be satisfied with that, but alas, I wasn’t. I found another PID controller that was programmable for ramp and soak for up to 20 different programs. A gold mine. and it was affordable. I also needed a way to monitor the temps of the part, so I added some internal thermocouple receptacles to the interior with connections on the front panel for easy readings. This is where almost done turned into start over and, oh yeah, I’ll need vacuum in there. More research. I found a small vacuum pump about 4” x 3” x 1.5”. Perfect. It only pulls 20 in/Hg, but that will do for my projects just fine. so I bought a small vacuum gauge, some high temp vacuum hose and a few fittings and got back to building the oven properly. I added another switch to control the vacuum pump and mounted the vacuum gauge. I also added some more heat deflection material to the interior to keep it more efficient. I covered the glass with the insulation, so I also covered the glass with a carbon fiber plate to make it look a bit more finished. Next I needed some small vacuum ports for my tiny hoses and parts, so I fabbed a couple of them from some brass fittings and washers. The controller is fantastic. It can be tuned to the oven or even a mold or part in the oven for optimal heat control. It also has Bluetooth, so I can use my phone or iPad to program, control, and monitor cure cycles. All said, I spent about $250 to build the final version. Considering that a small lab oven could cost much more than that, I’m pleased.

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Here’s my first attempt at a skateboard. Resin infused 6k woven fabric Divinycell foam core. I topped it off with a spray on grip surface that allowed you to see the carbon pattern underneath. All other skateboard hardware and grip surface was purchased on the Brazilian rain forest site.

You may need to increase the percentage of 0º fibers to get what you need. If you can’t increase the outer diameter, can you decrease the Inner diameter? Also you may want to consider a post cure to increase the properties of the resin. The post cure may take 8-12 hours to perform. Also be sure to apply proper pressure when roll wrapping. Proper consolidation is key to maintain proper mechanical properties. I’m assuming that you are referring to prestressing like a span bridge beam. The only way to properly do that with composites is to create a mold with that prestressed shape in it. That would make everything more difficult to do.

Welcome to the forum! That’s not too odd a question, but there is much to be considered when laminating. The quick answer is yes. You can laminate it as it is a basic woven fabric. If you want to. You can laminate with cotton fabricHowever, the insulation aspect of the material is lost due the relatively low temperature of resin. Polyester can withstand about 125ºF with out damage, vinylester about 225ºF. Epoxies have a range based on the chemistry of the particular resin, but it ranges between 200º-400ºF. The 400º version is pretty special though. On average, most resins are in the 220º-300º range. Room temp cure resins are in the 220º range unless you buy a high-temp resin, but it will require a second “post cure” at higher temps to achieve the higher temperature properties. Rock West has a good selection of room and high-temp resins here: https://www.rockwestcomposites.com/shop/materials-tools/resins-adhesives/resin-systems/pro-set-resins One other thing to consider is that insulation is achieved with spacing between the fibers. Once you close the gaps with resin, insulation is greatly reduced. Consider the fiberglass insulation used in homes. It’s quite lofty, and the thicker the insulation, the higher the R value. If you pack that insulation and reduce the loft, you lose R value. The same would be true of using fiberglass tape (header wrap, even if made from other materials) and laminating it. Hope this helps.

Hi Brian. Welcome to the forum. This is a great question. For tubes that have fabric on them, we use different pattern fabrics to visually discern which tubes are standard, intermediate , or high modulus fabricated tubes. The entirety of the tubes are fabricated from unidirectional fibers, but the outer fabric layer (which is always standard modulus) will dictate which modulus fiber the tube is constructed from. If you look through our catalog, you’ll see a pattern emerge that you may not have noticed before. once a material is cured, it is very difficult to determine which fiber it was made from. This is away for us to visually keep them organized.

Roll wrapped is a good option as it is a bit more precise on the OD. For fabric prepreg or unidirectional prepreg on a roll wrapped tube, and to get better deflection properties, your best bet is intermediate modulus fiber with at least a 250°F cure resin. With roll wrapped, your best bet is 3K fabric and 150gsm unidirectional.

Welcome to the forum! Your situation may require some redesign if possible. The first thing you can do is to eliminate the 14 degree winds and replace as many plies as possible with 0 degree fibers. You don't want to use 100% 0 degree, as this will increase kinking potential. This can be difficult with filament winding, but not impossible. If that doesn't work, then you will need to increase wall thickness as much as possible, as stiffness in a tube is increases as the tube diameter increases and wall thickness increases.

That’s great. It’s kind of our passion too. Hopefully, we can all learn from each other.

Welcome Cody! There a few topics here for you to look at. Start there first, then come back with some questions. Also, Rock West’s YouTube channel has some pretty good processes to look at. https://youtube.com/@RockWestComposites

Yes you can. You just want to keep the materials from coming in intimate contact with each other. But I would highly suggest just using a very thin layer of fiberglass instead. a 120 style or 105 style is most commonly used for galvanic corrosion prevention. Fiberglass is much more consistent in thickness and as it's glass, is the best insulator for galvanic corrosion. You can also use glass beads to provide a nice bond line that will prevent intimate contact of the metallic piece and the carbon fiber. Just a few grams mixed in with the adhesive and you're good to go. https://www.rockwestcomposites.com/shop/materials-tools/resins-adhesives/bond-line-controller/bond-line-controller-group

Welcome Sean! We’ll be interested to hear your questions.

I think the only way to get away with that is if you have multiple latch points. At that thin, it’s just going to very twisty and not rigid in the sense of a typical door. A piano hinge be highly recommended with something thin, as this would stiffen at least one edge.

For something that large, you would probably be looking at something starting at 1/2" and going thicker from there. It all depends on what the actual purpose of the door is. If it's just a cover and would be closed most of the time, then thinner is ok. However, if you want it to swing like a door on your house, then thicker is better.

Those thicknesses would be far too thin to be rigid or stiff enough for a door application of that size. If you used a cored panel, you can have light weight, but not thin. Cored panels are stiffer by nature, and lighter. Unfortunately, for your application, you’d need a panel that is about 1/2” thick to maintain stiffness.

I've wanted to make this hobby lamp for quite a while. One of the problems with scale modeling is getting enough light on the small parts to see what you are doing. Your hands or head will cast shadows on your work and make it very difficult to work on them. Regular desk lamps just don't provide enough light and headlamps don't always place the light where you need it. The arch desk lamp casts light from dozens of angles to help eliminate shadows. I started by bonding 2 carbon fiber pultruded rectangular strips together with 3M DP420 adhesive in an arch shape. I used the 3M DP420 adhesive because of its superior shear strength. This allowed me to form the carbon fiber strips in a natural arc very similar to bent wood processes. the arch you see in the photos is the natural shape of the bonded arch and is free standing. The rivets seen in the photos were used to aid in locating while bonding, but I liked the look, so I left them in. Next I used some 5" roll wrapped tubes to create the base for each end of the arch. I used simple hand tools like rotary tools and sand paper to create the cutouts and recesses for the electrical and USB outlets, and light controls. The ends caps were created from resin infused plate made from chopped strand, 3k 2x2 twill fabric, and Pro-Set Infusion Resin for a forged carbon look (check our youtube channel in the coming weeks to see how I made this plate). The supports are made from 3 sections of telescoping tube from Rock West. I used sizes 03, 04, and 05. I could have been more creative with the design, but its design is mostly for added strength in the bond between the base and the arch. The smalIest tube passes through the base. I also wanted to use as many off-the-shelf items as possible in order to minimize fabricating special parts. After attaching the LED light strips and routing the wiring, I bonded the arch into the support tubes and then bonded the support tubes into the base units all with 3M DP420 adhesive. After it cured, I cast the support tubes full of epoxy casting resin. some rubber edge strips to close out the edges for some table friction and the lamp was compete. All of the non-composite hardware was purchased from another unnamed online reseller, so the options are plentiful. The final product is extremely stable and sturdy, and provides incredible light. I like the low profile aspect of it. There's a lot going on on my work bench, so It may seem large, but it stays out of the way of my screens and camera, and gives me plenty of room to work without getting in the way. Not to mention it gives me great lighting for shooting images and video while I'm building. The entire project was probably around 10-15 hours of design, part selection, planning, and assembly.

As we don't have specific data for compression on our tubes, and our tubes are all manufactured differently for different performance requirements, we can't give you a perfect answer for you. However, we can tell you that Intermediate modulus tubes will give you the best performance for tensile strength and stiffness, which can come in handy in compression situations as it will deflect less and be less prone to failure. The image attachment below will give you an idea of the different properties that can be obtained from different materials. AS you can see, intermediate modulus carbon fiber has the best overall performance when it comes to stiffness AND tensile strength. If I read your inputs correctly, you have a 25.4mm tube (ID or OD?) and a 1.57mm wall thickness. Is that correct? As a word of advice, the thicker the carbon fiber tube, the better the compression. Even if you double the wall thickness, you will still be much lighter than mild steel. Here's a couple tubes to consider. All are IM carbon fiber, but nothing over 1.6mm https://www.rockwestcomposites.com/tubing/round-tubing/round-carbon-fiber-tubing/roll-wrapped-carbon-fiber-tubing/intermediate_modulus_carbon?inside_dimension=0.75-1.25%2C0.750-1.250&pattern=1057 As an option, here are some standard modulus tubes with a few more options for thickness. https://www.rockwestcomposites.com/tubing/round-tubing/round-carbon-fiber-tubing/roll-wrapped-carbon-fiber-tubing/standard_modulus_carbon?inside_dimension=0.750-1.250

To be more clear, if cured properly, commercial epoxy resin is generally food-safe (at least in most cases). It is therefore not dangerous if a foodstuff comes into contact with an epoxy resin surface for a short time and without heat. However, most epoxy resins use Bisphenol-A (BPA) as an ingredient in epoxy resins because of it's superior curing properties. There are concerns that when plastics that contain BPA are heated (like a water bottle in a hot car), the BPA can leach into the contents. A lot of casting resins are considered food grade and most likely use Bisphenol-F as a curing agent ingredient. But it is always wise to check with a manufacturer if the resin is considered food grade and heat resistant. I would also add that epoxies formulated for laminating structural composites may contain other ingredients that can leach into foods, so I would advise against using those structural epoxies for anything food related. This site has some good information regarding food grade epoxy and what to look for if you need a food grade resin. https://resin-expert.com/en/guide/food-safe-epoxy

In this video, you can watch Mike layup his first part using the Rock West Starter kit.

Correct. Definitely NOT food grade. There are special resins that are food grade, but epoxy isn't. Dry goods might be okay, but probably best to avoid any consumed items due to leaching.

There are many reasons why you wouldn't want to use polyester with carbon fiber, and odor and fumes are some very good reasons. Strength, compatibility, and durability are some others. Most fabrics have a sizing or starch material on them that helps in the weaving process. They use specific sizing for different resins. It is expected that carbon fiber will use epoxy, so in some cases the polyester resin will not breakdown the sizing on the fabric. However, recent advances has made it possible to have universal sizing, but these seem to be mainly used in fiberglass materials. You'll always be better of using a cheap laminating epoxy over polyester. We do have a good selection at Rock West. Different viscosities and cure times. https://www.rockwestcomposites.com/shop/materials-tools/resins-adhesives/resin-systems/pro-set-resins/laminating-epoxies All are room temp cure, and some can benefit from elevated post cure for better mechanical properties.

Welcome to the forum. After a bit of research on Paraloid B72, It is a toughened thermoplastic acrylic used in inks. This implies that it is flexible and may not be great for structure if you need it. It's not clear how it work in thicknesses used in laminating and how flexible/brittle it becomes. The UV cure acrylics are great to work with as they can be cured in minutes with great cosmetic results, and seem to be pretty tough, but they are not as structural as epoxy. So if structure isn't necessary, it may be ok to use. The UV cure resins are cheap to experiment with. You should give it a try.

Unfortunately we don't know of any places that repair this type of issue. With everything bonded together the way it is, it would be extremely difficult to repair the surface without affecting the space between the inner liner and outer sleeve. If I remember correctly, the space between is critical for air pressure to allow the ball to pop off the bat. I did find this service company that may be able to help: https://www.bigdawgbatrolling.com/bat-repair.htm We wish you good luck and hope we have been able to help you understand the nuances of composites.

Thermoset and thermoplastic can not be co-manufactured, but they can be bonded together after curing with the right adhesive. It appears that some of the cracks are just paint blemishes, but some do appear to be fractures in the fiber. You can tell by tapping the surface with a quarter and listening for changes in the tone. The good surfaces will have a higher pitched "ping" sound, while delaminated fractures will have a more distinctive "thunk" sound. These bats are usually thin walled, so repair is more difficult. From the appearance, it looks like the outer wall is filament wound, so is probably the thermoset resin. Oil and gas pipelines are specifically designed for the heat and pressure of product flowing through. They have very specific materials and safety factors designed into the pipe. Repair is probably one of the things that is taken into consideration in the design process.

Welcome to the forum. As the bats are very proprietary, it's almost impossible to know which part of the barrel is thermoplastic and which is thermoset. And a repair, even if successful, would certainly change the characteristics of the bat. Any crack that has developed would most certainly include a fracture in the carbon fiber, so a repair would include adding more material repair the crack. Simply adding resin would only be cosmetic. And reheating thermoplastic to a melt temp (whatever that is) could ruin the surrounding area, more than it would provide a fix. Thermoplastics come in many different forms, so knowing the reforming temperature is critical. Any repair made to it would most likely turn it into a practice bat at best. Louisville Slugger does have a warranty period of 1 year for the composite bats. That may be an option for you.