How to get the C of G right with heavy Foam Board

As do many builders in Europe I find the foam board I can easily get is somewhat heavier than the DTFB seems to be. One result of this is I find it very hard to achieve the required Centre of gravity without adding  more weight, Often as much as 20 - 30 gms!.

To combat this I have come up with a simple idea.

I have built several of the FT designs and have had this balance problem with all of them. I see from the Forums this isn't uncommon. Perhaps I am heavy handed with the hot melt glue or it's the foam board I use but whatever the reason I always end up tail heavy, not, as Josh says, a good position to be in.

After some thought I have devised a simple way to combat this which should work with all of the swappable designs which use the standard power pod and should be adaptable for other designs.

My choices were to add weight to the nose to make it heavier, shorten the tail section or make it lighter but all these are less than desirable because of the added weight, change in the control action and because foam board is hard to lighten without the loss of a lot of the inherent strength.

The alternative then is to allow the motor and battery to balance the aircraft by lengthening the nose, but by how much?

With this idea in mind I built a sliding nose which contained the motor, the electronics and the battery. This slides inside the normal full sized power pod and allows me to extend the nose until I get a satisfactory balance point.

I hot glue the power pod to the wings or the fuselage to fix it in place and insert the sliding fit extra pod with all the electronics and battery fitted inside the now fixed power pod and adjust until the C of G is correct. I mark the sliding pod with a pencil so I can easily reset the position if required.

I then fix the position of the sliding pod with a couple of skewers through the entire fuselage. I find I sometimes have to extend the power pod by up to 2 inches (50 mm) to get a good C of G as per the plans.