Using Splines For Roadbed. I Have Lots Of Questions.

[Jon Banquer]

I have the following questions that the video doesn't explain that I need help with:

I'm not sure I understand how he plans what the curve will be. I see he uses nails in risers to establish the curve. Does he use string to decide where to place the nail in the riser as he moves from riser to riser? How does he know where to screw in the riser? He clamps the risers in place till the string creates a radius that looks right? What decides how the strips of wood get staggered? Also, when the glue dries does he take all the screws out? How would you determine how to set elevation changes for the splines?

[John]

The advantage of the spline is the curve will be smooth .. and helps with the easements as well .. It is also strong.  The staggering needs to be enough so that there isn't a kink in the spline .. it looks like he is using a foot or so .. I'd probably go a little more like 18" ..  Using the screws as he shows is probably overkill if the glue is carpenter grade .. but they do add extra strength especially on the ends of the spline .  a spline will have a little vertical flexibility, so you can use that to your advantage to get a nice smooth vertical curve transition. The risers are put in place initially to help define the curve - so you can use the string method to plan out where you want the risers for the rough location. I would probably have a min radius template to check as well ..

Check out this page .. http://s145079212.onlinehome.us/rr/howto/splines/index.shtml

[Jon Banquer]

Super helpful, John. Thank you so much!

[Lemosteam]

If I were ever to build an open framework layout, I would use the spline method as well.  My only concern with splines is that each layer can become out of alignment on the top surface relative to themselves, i.e.:
  __
_|  |____     ______
|        |  |__|    |    |

Or:

           ___----   
___----

Leveling that can be a challenge, especially with smooth materials be used, as they tend to slip vertically.  I think a belt sander would be crucial to maintain horizontal as the sander follows the top of the spline.

I suspect that is why he uses the screws as he goes, not as a strengthener, but more as an alignment device.

This could be an OCD nightmare for me, lol.

[pdx1955]

I was in a club that built their layout using splines. A belt sander was used at the end to level everything as there would be varying spline heights. It's a good way to minimize waste and produces a strong product in the end.

[Sokramiketes]

If I were ever to build an open framework layout, I would use the spline method as well.  My only concern with splines is that each layer can become out of alignment on the top surface relative to themselves, i.e.:
  __
_|  |____     ______
|        |  |__|    |    |

Or:

           ___----   
___----

Leveling that can be a challenge, especially with smooth materials be used, as they tend to slip vertically.  I think a belt sander would be crucial to maintain horizontal as the sander follows the top of the spline.

I suspect that is why he uses the screws as he goes, not as a strengthener, but more as an alignment device.

This could be an OCD nightmare for me, lol.

Yes, on the misalignment.  We cap our spline for this reason.  That way we can also use less material, with spline only on the outsides or every other layer.