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Help! Why is my mini mustang so heavy?

#1
I decided to build a 4-channel mighty mini mustang during the quarantine. I've almost fully built it, and I just realized how heavy it is.
The canopy and a few parts aren't even on yet and this thing weighs:

around 270g with all the electronics in apart from the battery,
205g with no electronics but the servos,
over 330g with the battery in.

I followed every step exactly on the plans and build video and made no modifications to the design, apart from using 9g servos rather than 5g (they should only make 16g difference overall). According to Flite Test themselves, the mustang should only weigh 156g without the battery, so accounting for the heavier servos, I should be at 172g, not 270.
I have no clue where the extra hundred grams come from, but I highly doubt it will fly well, if at all. I used normal foam board you'd buy in any hobby store and poster board where required.
Do Flite Test use some special kind of foam or something when doing their own measurements?
Has anyone had this problem before?
 
Last edited:

FastCrash45

Well-known member
#2
I decided to build a 4-channel mighty mini mustang during the quarantine. I've almost fully built it, and I just realized how heavy it is.
The canopy and a few parts aren't even on yet and this thing weighs:

around 270g with all the electronics in apart from the battery,
230g with no electronics but the servos,
over 330g with the battery in.

I followed every step exactly on the plans and build video and made no modifications to the design, apart from using 9g servos rather than 5g (they should only make 16g difference overall). According to Flite Test themselves, the mustang should only weigh 156g without the battery, so accounting for the heavier servos, I should be at 172g, not 270.
I have no clue where the extra hundred grams come from, but I highly doubt it will fly well, if at all. I used normal foam board you'd buy in any hobby store and poster board where required.
Do Flite Test use some special kind of foam or something when doing their own measurements?
Has anyone had this problem before?
There are many makers of foamboard but unless it's readi board it could be much heavier. I got a great deal on some from Wal-Mart but each sheet was twice the weight of the readi board. Also personally, I found I was using way too much hot glue.
 

sprzout

Knower of useless information
Mentor
#3
It's highly possible that the foamboard you used is more dense than the foamboard that FT uses. Flite Test uses the Adams Readi-Board. It's generally lighter than some of the other brands, such as Elmer's; you can generally find the Readi-Board at Dollar Tree, Dollar General, 99 Cent stores, and Family Dollar stores.

I'd agree that your Mini-Mustang might not be airworthy...While it might fly with more power, the likelihood is it'll be a brick and just wont have enough oomph to get it flying.

You can always try throwing it as a glider and see; if it just noses down or doesn't glide for beans, you'll know it's too heavy.
 

skymaster

Well-known member
#4
hello, have you checked the specs like your wing span should be 24.5 inches (622 mm). also the servos say that they are 9grams if you weight them i have found that some are heavier and some lighter. a little more weight should not matter.
 
#5
There are many makers of foamboard but unless it's readi board it could be much heavier. I got a great deal on some from Wal-Mart but each sheet was twice the weight of the readi board. Also personally, I found I was using way too much hot glue.
Thanks for the advice. Also, I'm not terribly experienced with scratch builds yet. Do you think there's any potential for it to still fly, or should I just scrap it?
 

Merv

Well-known member
#6
I agree with @FastCrash45, the foamboard & hot glue can make a huge difference in the finished weight.

Adams FB form the Dollar Tree and Ross FB from Walmart both weigh about 4 oz per 20x30 inch sheet. When you pick them up, you will be able to tell the difference. They are noticeably lighter than the other brands. A thin bead of hot glue will do the job. One stick of glue per normal size FT plane.
 
#7
Thanks guys for the replies. I live in the UK, where these foam board brands may not be available. Any recommendations of stores/brands/websites that sell lighter foamboard and are easily accessible in the UK?
 

Hai-Lee

Old and Bold RC PILOT
#8
Thanks guys for the replies. I live in the UK, where these foam board brands may not be available. Any recommendations of stores/brands/websites that sell lighter foamboard and are easily accessible in the UK?
Here in Aus we use a similar FB to that found in the UK.

Each layer of paper is 30% of the total FB weight. As the foam is denser/stronger it is possible to remove the paper from the FB on the inside of the wings and the fuselage. It is also possible ot use the 3mm FB without the internal paper and the weight is getting close to the FT original.

There are workarounds if you chose to use them.

Have fun!
 

FDS

Well-known member
#9
Uk Westboard is 40% heavier. Follow the advice above, in future make minis from 3mm UK board and if you want a good learner plane build a Simple Scout, add 30mm in front of the nose to balance the tail.
The mini mustang is not a learner flier, it’s small so you need to go fast to maintain lift and it’s a warbird so it’s twitchy, the one you have will fly but it will be hard to fly slow.
 
#10
Uk Westboard is 40% heavier. Follow the advice above, in future make minis from 3mm UK board and if you want a good learner plane build a Simple Scout, add 30mm in front of the nose to balance the tail.
The mini mustang is not a learner flier, it’s small so you need to go fast to maintain lift and it’s a warbird so it’s twitchy, the one you have will fly but it will be hard to fly slow.
I chose the mustang because, I love warbirds. I'm fairly new to scratch building, but not flying and have flown my friends' warbirds before. So I'm pretty sure I can handle it.
 
#11
Uk Westboard is 40% heavier. Follow the advice above, in future make minis from 3mm UK board and if you want a good learner plane build a Simple Scout, add 30mm in front of the nose to balance the tail.
The mini mustang is not a learner flier, it’s small so you need to go fast to maintain lift and it’s a warbird so it’s twitchy, the one you have will fly but it will be hard to fly slow.
Also, do you recommend adding winglets here and there to help increase lift?
 

quorneng

Well-known member
#12
Just remember what creates lift also creates drag and the smaller its size the less efficient it is at doing it so.
Adding winglets is more about maintaining control at the limit than generating lift directly.
The most efficient way to get more lift is to make the wing bigger or simply make better use of the lift you have by reducing weight. ;)
 

Hondo76251

Well-known member
#13
I've done a few builds with the heavy board, it can be done but generally you have to modify the build plans.

It's not the weight that's the problem, it's the balance. Generally the heavy board with make the plane tail heavy so you have to compensate for that as you build. My MM Cruiser with a wooden spar, flight controller, uhf system, FPV, and a 1500 mah battery was 400 grams! After I sorted the balance problems out it flew great..


I haven't done a MM mustang but that weight shouldn't be an issue if you can get it to balance. Sometime a little extra weight is nice because they will punch through the wind a bit better. It will, however, be faster. By what others have said, probably not going to help the characteristics of the mustang.
 
#14
Just remember what creates lift also creates drag and the smaller its size the less efficient it is at doing it so.
Adding winglets is more about maintaining control at the limit than generating lift directly.
The most efficient way to get more lift is to make the wing bigger or simply make better use of the lift you have by reducing weight. ;)
Yeah, I understand but of course extending the wing can make it structurally weaker. I can reinforce it with balsa strips and whatnot, but that will add weight and reduce the effectiveness of the extra wing.
 

FastCrash45

Well-known member
#15
Thanks for the advice. Also, I'm not terribly experienced with scratch builds yet. Do you think there's any potential for it to still fly, or should I just scrap it?
Test glide it. If it just dives immediately them it probably won't fly well, unless of course you have a lot of power. Then you'll be flying a motor but with a plane attached and it will have to fly like a rocket