Teardrops n Tiny Travel Trailers

I'd like to build a woody, using a profile close to the "new cub", and would like to cut walls and trim with a router. I plan to make a template of mdf and I'd like to cut "concentric" versions or inner and outer walls, hatch, and especially hardwood trim. I thought I'd make template based on stock router base and smallest piece - inside or bottom of hardwood trim - and for larger cuts, make larger round router bases. I never for a second thought this was a new idea so went googling and can't find anything on doing this. Lots of different sub bases - but none that would follow a template on this scale as precisely as a round sub base on the router. Certainly someone here must have done this. And I strongly prefer the precision I can achieve with a router over a jig saw (which along with a sander is what I would have to use to cut template - unless I can use someone's shopbot.

QueticoBill wrote:I'd like to build a woody, using a profile close to the "new cub", and would like to cut walls and trim with a router. I plan to make a template of mdf and I'd like to cut "concentric" versions or inner and outer walls, hatch, and especially hardwood trim. I thought I'd make template based on stock router base and smallest piece - inside or bottom of hardwood trim - and for larger cuts, make larger round router bases. I never for a second thought this was a new idea so went googling and can't find anything on doing this. Lots of different sub bases - but none that would follow a template on this scale as precisely as a round sub base on the router. Certainly someone here must have done this. And I strongly prefer the precision I can achieve with a router over a jig saw (which along with a sander is what I would have to use to cut template - unless I can use someone's shopbot.

I've built three teardrops, all using a pattern. I can't imagine building another without using one. I use 1/4" plywood sub flooring for my patterns. No voids. I would think that using a 8' or 10' long MDF pattern may fail. Here's my wife working on her son's 'drop:



I cut my parts to within 3/16" with a saber saw and then use the pattern and flush trim bit to flush cut the parts.

Tony

I think I understand the question. Essentially you want to make one template matching the inner wall skin and then step off of this equally using what amounts to custom made collars of different diameters mounted to your router shoe/base plate. The shoes would be the correct diameter to place the cutter edge at profiles matching your outer skin and inside step of your profile trim.

That sounds very doable, but if you are looking for a high degree of accuracy for the stepped parts (...not sure why you would it...) you might want to make the collars on a lathe with concentric steps that fit into the opening in the router base. If the collars aren't round and aren't mounted concentrically with the cutter, as you rotate the router in the course of following the template you can get some variation. Yes, if your collars aren't perfect, keeping the router oriented the same relative to the template would help, and just how accurate you need to be is up for debate, just saying.

Sounds like it would work fine, but I wonder if it is less work than just cutting your template down incrementally for each stage of the process (what most people do).

KC - yes - but was thinking 3/4" mdf and able to do it all on trailer floor as work table. I imagined going back and forth from "sizes", in particular for wood trim applied after wall (think rail and stile paneling) and the hatch. I didn't think it would be too hard to make the bases and center them on the collet with a centering pin or cone. Basically big guide bushings.

Thanks.

In tooling, we used bits with interchangeable pilot bearings. A 1/2" flush-cut bit (bearing on the bottom of the shaft) can have a 3/8" or 3/4" bearing swap, so you end up with a perfectly stepped cut every time. A router is the way to go for this setup. Also, I recommend a "plunge" type base, not a screw base, for doing any tooling. The plunge base can be used with a "feeler gauge" by simply zeroing the cutter at the bottom, then using the thickness of material for the pass as the depth gauge. Much quicker for setups & consistency.

You still have to make a pattern, but once it's finished, repetitive cuts & precision are guaranteed & cutting time is greatly reduced. MDF works pretty well for a pattern, but watch your thickness & web width, so there isn't too much lateral movement when screwing it in place. It can flex a bit when leaned on with lateral loads. Keep some bondo handy as well, you might nip a corner or something on the pattern & bondo works pretty well for fixing small dings or chips in the wrong place. Just sayin'.....

I am trying to get a 3 or 3 1/2" difference from same template/pattern. That's why the guide bearings don't work.

I do wonder if a couple of "pins" in the base to follow the template would work, at least for "outside" cuts.

The pins will get you close, but might lose a little accuracy on tighter radii. Tangent to tangent round collars will be more exact... if that matters to you.

Although my teardrop is not a woody, I did something similar to what I think you are wanting to do to create a 1/4" MDF template to layout cuts and as a router template to cut the plywood "framing" for my sidewalls. 1/4" MDF works well as a template because it is typically 1" longer and wider than standard sheet goods. This is a picture of the template on top of 3/4" MDO plywood:



To answer your question about maintaining a parallel cut around the curved perimeter and other radius cuts, this is how I made my template. First, I drew a 3" grid. Then I started to draw the perimeter. For the straights, I marked all of the exterior straight lines on the perimeter and their starting and ending points. Then I marked the interior straight lines at the offset that I wanted. I did not mark the starting and ending points of interior straight lines. Next I started laying out the exterior curves and radii. For the radii, I used a home-made compass/trammel to mark the exterior radii and interior radii (at the desired offset). I drew the radii beyond their intersection with other curves/radii.

This is how I drew the exterior perimeter curves for the "non-radius" other curves, I eye-balled the curve and used a batten and hard points held with double-sided tape. I moved the hard points around until the curve was looked right and the starting and ending points were tangent - blended smoothly - with the previously drawn straight lines and radii.



To draw the interior curves, I made a home-made version of this scribe tool: https://www.amazon.com/M-Power-Perfect-Butt/dp/B001BLX1GM. I don't remember my offset distance, but I think it ended up being about 3" - 3-1/4". To make the tool I used a 3-1/2" hole saw and cut a "round" in 3/4" plywood. I believe the hole saw has a 1/4" pilot hole. Whatever diameter it was, I wrapped tape around a pencil until it was just snug. Then, using the tool against the batten, drew the offset interior curves. (Intermittently I removed a hard point and/or blended in the line to make a continuous line).

To cut the template, I rough cut near to the lines using a jig saw. I then used a sander and/or hand-sanded to the lines for the finish cut.

Straights? I have no straights. All ellipse.

QueticoBill wrote:I am trying to get a 3 or 3 1/2" difference from same template/pattern. That's why the guide bearings don't work.

I do wonder if a couple of "pins" in the base to follow the template would work, at least for "outside" cuts.

Hi QueticoBill,
I have been catching up on my reading and caught your question and the ideas posted... I realize this is an older thread, but in case you are still working on ideas or someone else is interested... Here is my 2 cents...

To adapt the same baseplate to the various profile differences you mention:

1-- I would probably first make a Plexiglass/Lexan baseplate (I like to see what's going on) and then...

2-- Cut a set of "donuts" (Oversized guide bushings) to match the different profiles needed, probably cut out of the same material used for the baseplate, using different size holesaws (I suggest use of a drillpress or lathe, but if careful, a hand-drill should get you close enough)...

3-- Once the outside diameters are all cut, using a bolt as the center axle, chuck each in a drillpress/lathe/hand-drill chucked in a vise and fine tune the outer diameters...

4 -- Establish a common-diameter bolt circle that can be used on all "donuts" (BEFORE the center hole is expanded using a holesaw, to be done later) and drill three equally spaced holes in each "donut" OUTSIDE the holesaw diameter to be used in 6-- below, and countersink for matching screws...

5-- Drill three holes and thread in the baseplate to match the locations in the "donuts"...

6-- NOW, using a holesaw, cut the center hole to allow room for the router bit...

7-- Using three screws of the correct size and length, attach the appropriate "donut"/Guide Bushing needed...

Anyway, I would probably do something like this if I wanted to use a common template to cut progressively larger profiles... See the very rough quick sketch of one of the "donuts".... Remember the Profile to Pattern distance is from the router bit to outer diameter of your "donut"/Guide Bushing...

Good luck and this is just and idea for thought...

As another possible option, take a look at the Milescraft Base plate/bushing set. The clear base screws into the bottom of your router and you use interchangeable bushings. You may not even have to remove the router bit to change bushing sizes if your bit is small enough:

https://www.milescraft.com/product/baseplatebushingset/

Good concept but I'm looking for up to 3 1/2" offset, and this is not 1/2".

Hi Bill,
I don't know of anyone that makes the size bushings you want and the suggestion I previously made would be an easy way to go; the bushing diameter is only limited by your imagination and practicality...

I am not sure where you would need to follow a large or small radius, as the case may be, with progressively larger set of bushings (3-1/2" rad., we're talking a 7" plus the radius of the cutter bit)...

Just another thought... a glue-up bent frame foamy... I prefer the aesthetics of curves and am considering building a TD or short Standee (Following the late forties or early fifties design shapes) next year for a charity project and still in the planning stages. All depends on permits, zoning for a garage and getting the garage built to house the project, and time. But more to the point, I have decided it would be to build a glue-up bent frame foamy with framing (studs and cross-members) as required for the roof, doors, windows, vent, accesses, penetrations, etc. and spray-foam all voids. Anyway, that's just another idea for you to mull over...


Good luck on your build, I like the plans you have drawn and can't wait to see the build progress...

aggie79 wrote:Although my teardrop is not a woody, I did something similar to what I think you are wanting to do to create a 1/4" MDF template to layout cuts and as a router template to cut the plywood "framing" for my sidewalls. 1/4" MDF works well as a template because it is typically 1" longer and wider than standard sheet goods. This is a picture of the template on top of 3/4" MDO plywood: ...

You did a nice job on the template Aggie...
And of course, the trailer turned out equally as nice... great job...

Sorry to jump in on your thread Bill, but I had to comment on Aggie's template...

Not a problem AZ. I studied the pictures quite a bit.