US\UK foamboard comparison (now with added maths!)

[Big_James]

Hi All,

There seems to be some debate on here over the Hobbycraft foam board available in the UK and how much heavier it seems to be than the stuff the yanks get.

I brought a few sheets from Hobbycraft on Friday after watching a few scratch build based videos at work but before I signed up and looked at the forum. I have just done the maths on how much they weigh in comparison to the quoted size on the Flite test site (http://flitetest.com/support under the general questions section). The board I Purchased from HC is I believe this stuff http://www.hobbycraft.co.uk/hobbycraft-a1-white-foamboard/539724-1000 it was on offer as well

Being from England I am going with the metric system (because the rest of the world uses it America ) and shall convert to metric accordingly.

A sheet of the FT dollar tree foam is 20" x 30" x 0.17" and weighs 4.4oz according to their site. In real money this is 50.8cm x 76.2cm x 4.318mm and weighs 124.738 grams.

This is very close to the size of a sheet of A1 59.4cm x 84.1cm (http://en.wikipedia.org/wiki/Paper_..._size_illustration2_with_letter_and_legal.svg)
which is the size of the board that Hobby craft sell.

Working out the area of each we get an area of:
50.8cm * 76.2cm = 3870.96 cm² for the DTFB
59.4cm * 84.1cm = 4995.54 cm² for the HC A1 foam board

The difference in size is about 29%
(4995.54cm² - 3870.96cm²) / 3870.96cm² * 100 = 29.0517081%

So we would need the weight of an A1 HC sheet to be 160.9765197 grams to match the DT foamboard for the given area
(124.738g / 100) = 1.24738g * 29.0517081% = 36.23851965g + 124.738g = 160.9765197g

Having weighed the HC sheet is is about 225 grams five or take 1 or 2 percent. I don't own drug dealer accurate scales just kitchen scales that have a resolution of 25g.

This means the the HC board is 40.6% heavier than the DT board for any comparable size of area you wish to choose.
(225g - 160g) / 160g * 100 = 40.625%

While I may not be able to tell you how to modify your designs to account for the added weight I hope this helps all the UK scratch builders out there and if any one spots any errors in my maths please say and I will correct my maths

Also if anyone does have any advice on modifying designs to compensate for the extra weight please feel free to share too!

 

[KenJ]

Impressive maths exercise, but you really don't need to be comparing based on the dimensions of the board. Most of that gets thrown away anyway and the parts that are kept would be the same size unless the plan was scaled. The parameters of interest are the thickness of the board and the weight for a given area of foam board.

For thickness of the board, we have a direct comparison: The Dollar Tree (Adams) is 4.318mm and the Hobby Craft (UK) board is 5 mm. This is going to affect both the weight of the material, but will also affect any fold cuts.

From a weight perspective, if the density of the foam was the same and assuming similar paper coating, we'd assume a roughly 20% increase in thickness would cause less than a 20% increase in weight since paper weighs more than foam and the paper dimensions haven't changed.

With your numbers, Dollar Tree (Adams) board weighs 124.738 grams and has an area of 3870.96 cm². That gives us 0.032 grams per cm². HK is 225 grams and an area of 4995.54 cm², or 0.045 grams per cm².

About a 40% increase in weight for any given area. Since the foam itself looks to be similar in both products, my guess is that the HK foamboard uses thicker (i.e. heavier) paper, hence the increase in overall board thickness and disproportionate increase in weight. That probably results in a stronger part, but at a cost in weight.

Interesting exercise - thanks for posting!

 

[MarkWoody]

Interesting , maiden flight yesterday of my FT 22 was a bit of a disappointment , it takes full throttle just to keep it in the air , will not loop at all
Prop is 8x3.8 (on the correct way)
motor is 24g 1500kv Blue Wonder brush less
ESC is 12a LBEC (all 3 bought as kit)
Battery is 3 cell ( tried a 2 cell but couldnt get the CoG ),
i also came to the conclusion that the foamboard in the uk is heavier (but without the maths )
My FT Flyer is just finished and is AUW of 12oz , do you think it will fly ?
i thought i could remove the paper but soaking in methylated spirits for half an hour does not work ,still shreds the sheet trying to get it off
Depron ? but where the hell would you find that in the UK ?

 

[KenJ]

I was using the numbers posted below, but just went and used a micrometer to measure some from Dollartree (Adams) and some from FT speed build kit. Both were 5mm thick, so I'm not sure why there's such a difference in weight, unless the UK HK board uses heavier paper and less foam.

Amazon UK has a selection of foam board from several different vendors. Might be worth trying a few sample orders.

http://www.amazon.co.uk/Centafoam-D...97xD5xH420mm/dp/B000J69FGA/ref=pd_cp_office_3
http://www.amazon.co.uk/West-Design...TF8&qid=1409606123&sr=8-3&keywords=foam+board
http://www.amazon.co.uk/Foam-Board-...TF8&qid=1409606123&sr=8-1&keywords=foam+board

 

[Balu]

I really need to make an article on foamboards

Can you find out what material the HC foamboard is? Is it Polyurethan (like used in Kapa foamboards) or (extruded) Polystyrene like the DTFB?

 

[KenJ]

Depron ? but where the hell would you find that in the UK ?

As it turns out, from Depron: http://www.depron.co.uk/

 

[MarkWoody]

Cool , ta for that , i was thinking more local shop with just a couple of sheets , that is way handier
Maidened my FT Flyer today , flew fine but not as slow and floaty as in other peoples videos ,had to add a weight up front to get the CoG .