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Pumpkin drop event

FT Explorer Wing Loading

#1
Hi,

I've just completer an FT Explorer which I plan to use as a test bed for a Matek 411 Flight Controller that I'm experimenting with. Having conducted some initial test flights (in manual mode - this thread is not about the flight controller it's about the basic design of the aircraft) I have concluded that I only marginally have enought power.

I looked at the basic FT spec for the aircraft and particularly at the span, chord, weight and derived wing loading. Here are the comparison figured for my aircraft as built to the plan

 

FT spec

My aircraft built to plans

Span

57 inch

53 inches

Chord

8 inches

7.3 inches

Weight (AUW)

34 oz

24 oz

Wing Loading

7.54 oz/ft2

12.6 oz/ft2



First let me say that I believe the weight difference is down to the foamboard as I've had this problem with other designs.

The key point is that my wing is smaller so the plans don't reflect the spec. (I've checked the printer scaling and the black and white reference bar is 10 cm in length on the printed paper copy.

Does anyone have any idea what the story is here? Is this a late design change, for example or just a mistake somehow?

In the end I'm probably just going to up the power as this is not an excessive wing loading for a model - better penetration etc.

Cheers
 

Piotrsko

Well-known member
#2
Your spec is ideal for slope, but 10 ounce gain? Something is odd. I'll bet the only one that light was the original and you used walmart borden style thick foamboard.

Did you have to fiddle with battery placement to get the CofG FORWARD? Then heavy material is the answer. The 10% size reduction I will leave to others, but sounds like software settings converting the plan for your printer
 
#4
Hi,

I don't live in the US. My foamboard is sourced from the UK and I know it is more dense as I explained. Using a higher density material will not change the C of G (unless the density varies behind and in front of the C of G which it will not) So no, getting the C of G right was not a problem. As for software printer settings as I said the scale of the printouts was right so far as the black and white scale was concerned so that is definitely not the problem.

I suspect you are right the foamboard the FT guys use is very light but not available to me in Europe (unfortunately). Had no effect on my Mini-Scout, Simple Scout, FT 22 and Storch which all worked very well built to the FT plans. Hence my question about the Explorer.

Good to hear from you.

Cheers.
 
#5
Hi,

Ah! OK. Tip to tip you are right here. But the profile of the wing tips reduces the wing area...I used a mean dimension for span but derived the chord as specified on the FT plans (not quoted on the plans) from the quoted area and quoted span, which is tip to tip.

Point is the plans are right and the wing I've built is to the FT plans...good news for me. Thanks. I still have the foam density problem but have to live with that.

Thanks for the input guys.

Cheers
 

BATTLEAXE

Well-known member
#6
Your wing loading is up oz/ft2 because you have less wing surface area given the dimensions you have chosen, am I correct?

Just asking for my own knowledge, to see I am on the right train of thought.

Thanks
 

Piotrsko

Well-known member
#7
Yup the wing is smaller, but not 2 oz a square smaller. Denser board accounts for the weight difference, not sure still if there is a fit to size reduction going on in the printer. The scale could be attached to a borders/header/footer/ different page which the software loading the image treats one way, where the tiling is sent in a separate image. Some here have resorted to printing at 107%.
 

BATTLEAXE

Well-known member
#8
I usually find that tiled plans from model to model are inconsistent. I download full plans and use Adobe Acrobat tile them down. More accurate that way. Have you tried that yet?
 
#10
Your wing loading is up oz/ft2 because you have less wing surface area given the dimensions you have chosen, am I correct?

Just asking for my own knowledge, to see I am on the right train of thought.

Thanks
Hi,

The loading is high because my All Up Weight is higher due to the use of heavier foam. Does anyone know the area density of the FT white foam as originally used on the Explorer as a matter of interest? It would be good to compare the figures.