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FB weight: what to choose when you have choice?

#1
Hi!
I'm actually cutting 2 kinds of foam boards: a white made for digital printing, very smooth, strong, and a black more for artistic or model purpose.
Just because I'm curious, I have thrown them on a balance. And then whoa... Not the same:

IMG_20190702_130028.jpg
IMG_20190702_130010.jpg

The black is almost 2x lighter!
So now I know that, I would like to know your opinion about an optimized usage of them.

My thoughts are that the white one can be preferred for impactable parts, or those in need of rigidity, or maybe even for helping to balance or lower CG.
About the black FB, when searching for light weight, for inside construction (frame without too much constraints).

Do you have any preference for specific usage with your own FB?
 

FDS

Well-known member
#2
Lightest is always best. FT foamboard is a lot lighter than hobby stuff and the lighter your plane is the better it will fly.
If I want it a different colour I paint it, it doesn’t add much weight.
All hobby foam board in the UK is the heavy white type, we can’t get lighter core board here at all.
 
#3
Thanks FDS, and by the way now I've started to build a wing with the black FB, I already can tell that life is easier... Which is a good thing as it's a MM Corsair :D
But I've heard that it could be a little bit tail heavy, so maybe using white foam board could help to get CG more comfortable.

My first build is a TT using white FB, another in black FB is ready to assemble, and I know it will be better (more square, light weight, plus some mods).
Only 1 flight, duration about 5 or 7 seconds... Needs some fixes :ROFLMAO:

I guess my Mighty Mini Corsair will be more safe if tested by a real rc pilot :unsure:
Well, at least that's my plan.
 
Last edited:

Hondo76251

Well-known member
#4
For FliteTest stuff it's best to go with something of similar weight to their foam for best results. I do use the heavier board in custom builds a lot though because it is substantially stronger...
 

Hai-Lee

Old and Bold RC PILOT
#5
@Pougnagna With the white FB you will find that once you know how to remove the paper the extra strength of the foam can be a bonus when trying to build light and strong. I have built a few tail booms and full fuselages without paper and a known number of wings with a single layer of the paper removed.
Generally when you learn how it can be simple to build a plane very close to the FT weight but just as strong if not stronger. Sadly it is a lot of extra work but the results can be worth it!

You will also learn over time what changes to a FT design work for you and those that do not!

Have fun!
 

FDS

Well-known member
#6
To make the CG better you can lengthen the nose a little, also move the rudder and aileron servos forward and use absolutely minimal glue on the tail, white Gorilla glue is good for saving weight vs hot glue. As noted above taking the paper off one side (underside) can help a lot with weight too. There’s several posts on how to do that. @CarolineTyler has a great method.
You can also use a slightly heavier battery to balance the CG. Don’t add any weight that isn’t giving more power, you are always best off losing weight in the heavy parts and using fuel (battery) to balance vs adding ballast.
 
#7
@Hai-Lee : The white FB is designed for digital printing. I've already tried to remove the "paper", but it's more comparable to very thin, rigid and glossy carton. I've made a quick test and the best result was by cutting instead of peeling. Fortunately, the white layer is strong enough to be "shaved" from foam.

@FDS : Thanks for pointing that, because it was absolutely not obvious to me. Adding weight was my tought. So let's add more power when in needs of weight.

@CarolineTyler : Thanks for the IPA mix tips!

I now have more options (and more brainstorming :LOL:) in order to continue my builds.
 
#9
@FDS : Thanks for pointing that, because it was absolutely not obvious to me. Adding weight was my tought. So let's add more power when in needs of weight.
Ok, wrong statement.

Remove as much weight as possible first, then see where you are!
Ok that's very logical but it didn't hit me before you said. I'm a noob :giggle:

So today's lesson is: instead of adding weight in order to balance CG, make everything as light as possible and especially on tail side. Then move useful weight, or add some if in a dead end.
 

Hai-Lee

Old and Bold RC PILOT
#10
@Pougnagna The FB I use is also for printing, painting, and the like and is the bleached, Acid-free variety. The paper makes up about 60% of the total FB weight and the foam itself is quite rigid in itself.

Removing the paper is something that you need to perform to build many of the FB designs found on this forum/website. On small pieces the paper to foam bond has a definite direction that makes it easier to peel off the foam whereas on larger pieces you may need to destroy the bond to remove the paper successfully.

Here is a link to the method I use for quickly stripping the paper from the FB that I use. https://forum.flitetest.com/index.php?threads/quick-tip-involving-the-new-foam.32740/#post-329044

You may also find it interesting at see a plane built from the heavier Fb with paper removed and the reinforcing of the structure added later, (I used 1mm Balsa as reinforcing). https://forum.flitetest.com/index.php?threads/balsa-foamboard-test-build-ft-spitfire.32734/

I encourage you to experiment with any FB scraps you have to hand to find your own method to remove the paper from the FB as it really makes the planes lighter and better handling.

Have fun!