Canopy cutting

Hi all,

I've reached the point where I can start strimming the canopy.
Like many people, after drilling the canopy latch 5/8 hole I felt the first time the increase in blood pressure and freaked out about cracking the bubble. 5/8 is one **** of a hole in your expensive and fragile canopy.

Now the plans call for trimming the molding flanges off.
Unfortunatly I live in a cold climate and it's winter time in Belgium. Even in summer we don't get high temps.
I've tried getting my workshop over 80degrees but without succes.

Alternatively, when I cut the hole, I heated up the canopy from underneath the bubble with an electric heating element and got the inside the bubble temp up to 93degrees.
The bubble loved it as the material heated up nicely even though the surrounding temp was only about 70 degrees. So I drilled the holes while it was heating from underneath.

What I'm wondering is how safe it is to turn the canopy around in it's warm state and start cutting the flanges off without the additional heating underneath. Basically my question is, is there any danger in the variations of temperature over short period of time each time exposing it to additional heat and then cutting for 10 minutes and turning it back around to reheat it again in incremental steps.

Secondly, I read in a couple posts here that enlarging and existing pilot hole using a drill bit is a no no..
Does this also apply if you use these special pointy acrylic drill bits ? (so a #40 pilot in acrylic and then enlarging it to 5/32 using an acrylic drill bit) I found the canopy to be too thick for needle unibit. I have the impression you always countersink the hole with the next step size.

gr

Jurgen

Canopy

I'm no Engineer but do live in the mountains at 7,500'. Winter is cold. Running the heater constantly, the shop got up to 68. No problems.
My opinion is the canopy should be a uniform stable temp and any tooling marks should be sanded smooth before moving it. I also feel the canopy should be attached in a natural shape and not pinched with clamps. Each clamped area is a stress point.
However, I'm no expert. Maybe an Engineer will commment.

I feared drilling all the rivet holes so went with the Sika Flex bonding method. No issues after nearly 4 years and 350 hours Hobbs time.

I think warming the Plexiglas is a wise thing to do prior to cutting. I used a very course file to remove rough edges, then a finer file to smooth further. Clamped in place with weak hand clamps while bonding but one spot squeezed down a little more than desired - though not a problem so far.

I ended up bringing it inside in the living room. My wife looks at me in a different way now but at least the canopy felt great.

Started cutting with the supplied disc from Vans and I have to say that it is easier as I thought it would be.

However a word of advice the someone gave me is that you have to be real carefull when heating the bubble from underneath not to go to high in the temperatures.
I seems you can get a milky shine in the plexi if it gets too hot.

Here's what I received :
" if you have a direct hot source on Lexan it will change the lexan properties and will show a thin milk layer at some points! You don't want that! You can warm the ambiance room but not a hot point on the Lexan, Try to not touch the bubble unless it is room temp achieve on all surfaces."

I guess I don't recall for sure, but I don't think the canopy is Lexan (polycarbonate - very flexible and forgiving in cutting and drilling). Instead, I thought it was Plexi (acrylic - very brittle and not so forgiving - needs to be warm - the Van's advice is "...[c]utting or drilling the acrylic transparencies in temperatures under 60º F is asking for trouble. Heat ... to 75-80º...").

I can recall using duct tape across the bottom to keep the sides from moving around and to provide stability. I used a die-grinder for the cuts (multi passes to avoid heat/melting) and a plexi drill bit for setting up the attachment).

So far so good (12 years).

Dan

JurgenRoeland said:

...is there any danger in the variations of temperature over short period of time each time exposing it to additional heat and then cutting for 10 minutes and turning it back around to reheat it again in incremental steps.

Click to expand...

I wouldn't do it. Plexiglass has a huge coefficient of thermal expansion (0.062 inches per foot per 100F, about 4x aluminum), so uneven heating seems like it could really stress the end of a cut. For example, it would be too easy to create a warm bubble and a cold flange.

Enlarging holes, deburring, etc...don't discount the value of little bitty grindstones in a die grinder or Dremel tool. Often better than cutting tools.

Heating the canopy

DanH said:

I wouldn't do it. Plexiglass has a huge coefficient of thermal expansion (0.062 inches per foot per 100F, about 4x aluminum), so uneven heating seems like it could really stress the end of a cut. For example, it would be too easy to create a warm bubble and a cold flange.

Enlarging holes, deburring, etc...don't discount the value of little bitty grindstones in a die grinder or Dremel tool. Often better than cutting tools.

Click to expand...

I agree. Uniform temp. Warm the room it's in, not the canopy. Make a cut. Sand the tooling marks. Go have an adult beverage. Try and explain the white plexi dust everywhere to the significant other. Lather, rinse, repeat.