Ok, lot's covered in the posts above and I'll probably repeat some of it but here goes.
The form:
You need stout dowels of at least 3/8" or 7/16". Use real hardwood dowells. Many of them are made of soft wood that easily breaks. You can put side stops on the form using a single wood screw that allows you to loosen them or tighten them as needed.
There is no formula for how far apart they should be or how far from the form surface, but leave about 1 3/4" working space between the dowells and place them about two inches from the form surface. Mine extend out two inches on each side.
My forms have end stops and the lams are cut to fit exactly to the stops. If not exact, definetly not too long. trial fit to be sure that there is no tension on the lams between the stops when they are fitted.
I use five full bike tubes for each layup. They are cut as already described above by cutting across on each side of the valve stem and then cutting around the tube for full length bands. I cut four per tube.
This is what it looks like after it's banded down.
I put a lot of pressure on the bands when applying them but also try to bring the band over the top and then and stretch down the other side without pulling across the stack.
My form in the picture does not have provision for applying a clamp to the riser, but all of them will be modified to do so before they are used again. I found centering the riser and clamping it down with just bands to be pretty simple with an ASL, but NOT so with this RD.
My fit of the riser to the lams in layup was very good. I think it helped that I did not fit the riser to the form, but rather tied all the lams that go under the riser tightly into the form using the dowels and then placed the riser block up against the side of the form and drew a pencil line of the actual fit. So this was just a blank riser block about a half inch over length on each end. Then I sawed outside the line and carefully sanded on a belt sander to a perfect fit. All before cutting out the ramps and tapering the fades in. If you try to sand this to fit on a drum, you are headed for disaster unless you are an absolute artist with a sanding drum.
Guys with better tools and bigger brains have simpler solutions to this but until I get better tools and a bigger brain I'll stick with my primitive ways.
Regarding the post above by Bvas, I concur with everything he says.
You simply must get your ramps and fades as perfect as possible. I take mine to a bout 1/32 to 1/16 of the line with a drum and then do the rest with a flexible sanding stick. I do the final shape and feathering on a piece of thick mirror (any piece of thick glass will do) like in the photo below. it;s time to make your surfaces as perfect as possible to get any dips out of the ramps and to get your fades as thin as possijble.
Your sanding slab needs to be flexible enough that you can follow the curve you already made but not flexible enough to flow into the dips left by the drum sander.
Lastly and very importantly, the pressure strips. If your strips are too thick and stiff, they become part of the problem in getting the top lams pulled down tight to the riser. If they are not a bit thicker in the centerline and thinning toward the edges the center of the stack will not be forced down tight. If the edges are too thin they will put a slight curl in the layup edges.
Here's what the pressure strips look like for this layup. They are about 1/8" at the centerline and about 3/64" at the edges. If you steam them and prebend the pressure strips in the ramp area they will tighten down easier.
I've also done similar to Bvas does with the electrical cord glued down the centerline and that works good. Only difference is I used a piece of 1/4" poly rope.
At this point, the thing that can kibosh your lay up on the ramps are pressure strips that are too thick and inflexible and lams on the ramps that are too thick and difficult to bend (that can be a problem with a hose form also if the top half doesn't fit well). If, for example, you are going to use three core lams, Put the taper(s) under the riser and plan the stack so the third lam on top is a parallel as thin as possible. In the bow I'm using for illustration here, there are no core lams on the top. There is one taper and one paralel under the riser and just stabilcore and glass on the top.
Just for clarification, in the future I'll be using at least three core lams and probably one of them will be very thin and go on the ramps.
The suggestion already made to have your fades taper at a rate of 1/16" for the first inch can't be overemphasized Thats a "no more than 1/16" recommendation. If you have the skill and patience to taper even slower, do it. Also, keep those glue joints out of the fade area as already mentioned.
Ok, that's it for now. Hopefully others will chime in with more suggestions. I'm no expert and I'd like to learn a few new things here too.
Topic: Inner tube clamping method (Read 2953 times)
