In a previous post on “What splines are best” I was hoping to get a response from the modeling fraternity to see what the material of choice was but with dismal results. Not one opinion, I can only assume that the majority of modelers no longer care or use the spline as a means of ensuring a quality surface, maybe the digital world has taken over and it’s just the case of scraping out the mill marks and calling it a day. Even so I’m sure that many modelers do use splines for controlling the surface and with that I will share my findings with using carbon fiber.
Since that posting our studio has made numerous carbon fiber splines with great success, gone are the twists in the spline that you associate with wood, now we have the option of using the straight carbon fibers. This success did not come overnight though, it took several attempts to get the right amount of resin to carbon fiber, the thickness was also a factor. With carbon fiber it tends to be more rigid than the regular wooden spline so a thickness of 6.0mm in wood is more flexible than a carbon fiber at 6.0mm. To get the same sort of feeling we found that the thickness would have to be reduced by 1.0-1.5mm for the same length and width on the carbon fiber spline.
The cloth that we were using had a thickness of approximately 0.012″ therefore twelve layers would give you a 4.0mm spline including resin, fifteen layers a 6.0mm spline and so on. These sizes are not exact but it will give you the general idea.
To ensure uniformity and flatness, the surface plate was used as a base for the resin lay-up, with spacers to control thickness. The first operation is to paste wax the plate and buff out to reduce the amount of grab the resin will have to the surface plate. On top of the lay-up a 6.0mm Plexiglas® sheet was placed together with a large Norton angle plate to flatten the the layers of the fiber glass to the desired thickness. The whole process required team participation to ensure minimal mess, laying down the carbon fiber with two people reduces twist in the weave and minimizes loose strands. The wet resin is worked into the cloth to eliminate any air bubbles or air pockets that will spoil the aesthetic look of the finished sheet, care has to be taken to place the Plexiglas® onto the spacers without introducing any air while the Norton angle plate is placed on top to squeeze out any excess resin until the Plexiglas® actually beds down onto the spacers.
The curing process is overnight and only the next day will tell if the surface is free from any air intrusions. The additional precaution at the setup stage will eliminate a lot of unwanted surface blemish giving a glass like finished surface. Luckily for us the outcome was successful, giving us a sheet 1650.0 mm x 300.0 mm x 4.0 mm in size, enough for four 800.0 mm x 75.0 mm, two 600.00 mm x 50.0 mm, one 1600.00 mm x 90.0 mm and one 400.0 mm x 50.0 mm carbon fiber splines.
You may well ask, “How do you cut up the sheet.” The answer is simply on a bandsaw but remember to use safety precautions such as dust masks, extraction system and safety glasses. These items are a must to keep the fine particles to a minimum. The bandsaw blade should only be used for this one task as the saw set will quickly be removed with this type of material, cut slowly and let the saw do the work and do not power push it through. Time taken cutting the material will reduce the amount of finish work later. Once the splines have been cut to width and length the edges can be flattened by using long board self adhesive sheets stuck to the surface plate. If the bandsaw cuts are such that there is minimal work to attain a completely flat edge then 120 grit is sufficient to finish the spline, if there is more than a little work, use a more aggressive grit such as 80 and then finish off with the 120. Sand the edge of the spline on the longboards using a bracket to keep the edge at ninety degrees to get the best results.
In a nutshell that is the easiest way to make your carbon fiber splines with minimal equipment. I found that they were very uniform in thickness and cut the hard clay easily. The only thing I found a little disconcerting was the weave, it’s very strange on the eyes when checking the surface for hollows compared to a wooden spline. The checked effect of the weave and the high gloss of the resin is a total reversal compared to the wood, it’s something you have to get use to I guess.
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