Overhang tolerances on laser cutting foam board

[HappyRCFlyer]

I'm trying out cutting some black Rediboard on my laser cutter. After many different settings and pass adjustments and tests, the best I'm coming up with so far still has the foam shrink just slightly smaller then the paper backing. The amount of shrinking is just under the thickness of the paper. Is this normal and is this the same as what the Flight Test kits stock comes out to as well?

 

[Merv]

... Is this normal and is this the same as what the Flight Test kits stock comes out to as well?

I'm not a laser guy, but as far as I know, this is normal. Every FT I have seen has a similar foam under cut. Some say this allows the joint to hold more glue.

 

[HappyRCFlyer]

That's the going word on the Facebook Flight test fans group too. I also took a look with new eyes on the FT planes, sharing one, that if you zoom in, you see the overhang on the nose.

I'm using a lightweight diod laser and it's not able to cut through white foam, I was pretty elated that it's able to cut through this, it opens up a great big world of new kits I can design and produce along with have fun with.

 

[Dan-O]

Yep. Totally normal. The laser opens up all kinds of cool possibilities.

 

[HappyRCFlyer]

I'm going to be doing this one up into a kit form, was originally thinking of a balsa style conversion with it, foam board one will be vastly easier to do. I call it the Ring Wing flying thing. Possibilities with such a range and there are even plans pre-done to cut up for fun that I don't have to design up on my own too galore.

 

[Mr Man]

I have a 20w laser, but am converting it to a needle cutter since I like white foam better. (but will still have the ability to swap back to the laser head)

 

[LitterBug]

Yes, there is always "shrinkage" between the paper on laser cuts. The 10W laser diode I have will cut through white FB with a perfect setup of focus, speed, air assist, and power. It is super finicky and not worth my time since foamboard varies widely. I just use the laser to transfer the plan to the foamboard and cut with a knife. The settings I use creates a small groove which guides the knife for cutting. That gives my perfect edges, although that isn't really required. A little give can be helpful as others have said for glue bonding.

 

[HappyRCFlyer]

Yes, there is always "shrinkage" between the paper on laser cuts. The 10W laser diode I have will cut through white FB with a perfect setup of focus, speed, air assist, and power. It is super finicky and not worth my time since foamboard varies widely. I just use the laser to transfer the plan to the foamboard and cut with a knife. The settings I use creates a small groove which guides the knife for cutting. That gives my perfect edges, although that isn't really required. A little give can be helpful as others have said for glue bonding.

I'm used to balsa and thin ply based construction where everything needs to be severely dialed on, not this slack and gaps to be filled in so was wondering if I was expecting too much laser cutting foam board. Understanding now, it's been just getting the right foam board with my gear perfectly capable of has made a world of difference along what I can design up and kit out now.

Thanks for the input along with the rest that have chimed in.

 

[Merv]

I'm used to balsa and thin ply based construction where everything needs to be severely dialed on...

Yes, FB has far more forgiveness than balsa. FB planes are also not nearly as fragile, they will take a crash that would have destroyed a balsa plane.

 

[HappyRCFlyer]

Yes, FB has far more forgiveness than balsa. FB planes are also not nearly as fragile, they will take a crash that would have destroyed a balsa plane.

Unfortunately too many peoples balsa experience is entirely some terrible Guillows free flight plane model. Those are fragile, terrible wood, meant more for display and strictly free flight and flying them will destroy them quickly. The range on quality balsa based planes produces some absolute tanks along the fuel based ones, my electric versions can also take a serious beating with little to no damage that the foam board versions would not remotely handle. Still, changing directions, I did try out recently covering some EPS with tissue, using watered down wood glue to get it to adhere to the surface. This produced some serious strength with very little weight penalty and will be using it for my EPS based planes from now on. I'll be testing it with de-papered foam board next.

 

[LitterBug]

Yes, FB has far more forgiveness than balsa. FB planes are also not nearly as fragile, they will take a crash that would have destroyed a balsa plane.

I have done cartwheels down the field with foamboard planes. Picked them up and threw them back in the air with no problem.

 

[HappyRCFlyer]

I have done cartwheels down the field with foamboard planes. Picked them up and threw them back in the air with no problem.

I've done the same with the balsa based ones, it's really up to how you design them, they range all over the place and your design intention along with. Intertia is also a huge factor where the smaller planes are not going to face as much stress on impact compared to the larger ones. I'm sharing the fuse/stick area that's used on my Slow Stick lines, it's using a three dowel system with light ply spacers and mounting areas. I've only recently retired the original one I did up years ago, only retired because I've both advanced and refined the system, I needed the servo tray further aft to accommodate my other wings. It handled some serious crashing and took next to nothing to put back together.