KA wrote:Hi Jim,
I like the fenders that you are using. I think they look better on the Benroy than the kind often seen on the Kenskills. Where did you get yours?
asianflava wrote:When people ask me how much money I have wrapped up in my tear, I mention that the fenders are most expensive single item on the whole project.
Andrew posted some profiles of a fender similar to mine. They are "slices" of my fender that you cut out of wood. After cutting out the slices you stack them and glue them together. When they are dry, You sand them smooth to take the steps put of them.
Cheaper yes, but definitely labor intensive. When I get a few projects out of the way, I may makeup a pair for S&Gs.
angib wrote:Here is the next chapter of the wood fender novel!
Firstly, the 'bread and butter' method. Here is a cross-section though the highest point of the fender. It doesn't make sense to use bread and butter for the inner 2/3rds of the fender as that is single curvature, except for the flare-out at the back, and so that can be made from a single piece of ply. It's too tight for 1/4" ply so it's made of two layers of (red) 1/8" ply.
The outer 4" of the fender is made by bread and butter. I've shown it in (green) 1/2" ply 'slices' which means more pieces have to be cut than if using 3/4", but there's less fairing to do. The outer slice is replaced with two 1/4" slices, as the outermost slice hangs down quite a way in places.
Each of those slices is sized so that there's 1" overlap with the next slice - it's tempting to reduce this to make the fender lighter and increase the (marginal) tyre clearance, but then the slice becomes quite floppy until it's bonded to the next slice.
To overcome this problem, each slice has four bosses incorporated in it and a hole through each boss connects all the slices together. Here are the shapes of some of the slices, to try to make this clear:
Note that slices 1 and 15 are mostly inset to receive the curved ply skin, but that recess stops before the flare-out at the back, when the fender goes back to bread and butter construction. Slices 2 to 14 are identical and just extend over the flare-out.
After the whole fender has been assembled, those bosses all have to be cut off - not easy inside the curve of the fender but, at worst, they can be sanded off with an angle-grinder-with-sanding-pad ('electric spokeshave').
On that subject, let's not forget the safety warning like Norm gives: Sanding plywood must only be done wearing a industrial-quality facemask - wood dust is not just a nuisance, it is a direct health risk and the dust from some hardwoods is a carcinogen.
Juneaudave asked for the geometry of the Slumbercoach fender and I've sent you and John/micro a PDF, as it's not very legible like this:
Anyone else who wants this material as a PDF, pm or email me - and don't forget to tell me (a) that it's the Slumbercoach fender PDF you want and (b) your email address!
Please note that the fender size is closely related to the tyre size - what I've shown is using a 26.1" diameter 205/75-14 tyre - but if another tyre is used, the fender size may need to be altered.
Switching back to bread and butter to make the flare-out on the back of the fender is a bit of hard work. Here is an alternative fender that just has a straight taper on the back, which I think would look very nice and be simpler:
This fender also does not have the fault that the flared one has - as drawn, it is 49.5" long, so it doesn't quite fit in the width of a sheet of ply. Darn.
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