Hi!
My name is Nikita. I've been more of a spectator than an active FPV pilot and watched a lot of videos by Flite Test, Rotor Riot, Joshua Bardwell, etc. I'm now finishing my first build that uses the Lumenier QAV-R 2 frame and, while everything has gone smooth, I've encountered a problem when doing the final assembly. When I was tightening the screws on the bottom plate I accidentally tightened the screws on the top plate too and noticed that the top clear layer of the carbon frame started to separate from the frame. The same happened on the other side of top plate where it meets with the standoffs and for some motor and arm screws.
To avoid doing the same mistake in future I'd like to ask whether you think this is caused by tightening the screws to much and applying high pressure to the frame or there is an issue with my particular frame. I'm a little bit disappointed since I've thought that the frame is the most durable part of the build and haven't expected this to happen.

Welcome to intoFPV.

Carbon fibre can be brittle and chips/breaks if the screws are over tightened.

I am not sure how you were torquing the screws but using a hex bit in a wrench is a no no since you have too much leverage.

Simply use a standard size hex key to snug the screws. You can add loctite (blue not red as red requires heat to break the bond) to all the screws on the frame after completing the build (except for the top plate since you may need to take it off for repairs).

Hi Grassydragon,

First, Welcome 

Since that is a brand new frame, I would contact the vendor and see if I could get
them to replace the "faulty" top plate. After all, it is new and it did "splinter" so 
maybe you can get a new top plate. If they will not replace that top plate, use it
anyway. I will be fine. Any minor damage to the plate in that area will likely not
adversely effect anything and will like NOT break further. I would not consider that 
plate to really be damaged. Although, it may be a quality issue, you run that risk when
tightening bolts directly against a material that is multi-layered as is carbon fiber.

Yes, you could just not tighten the bolts vey tight, however, it is not  purely about the 
"tightness", but rather the rotary action of the bolt head against the material once 
the bolt head makes contact, even before it is "tight. This phenomenon is not limited 
to carbon fiber quad plates; it has the same effect on any material that is soft, 
"non-durable", or multi-layered. Consequently, I almost always use a flat metal washer 
on the bolt between the plate and the bolt head. Now, you can tighten away or at least 
until you can't, something bends, or something breaks (ha, ha...but true none the less).  
Just by using a metal washer, you will resolve this issue.

NOTE: Nylon washers can also be damaged by the turning bolt head.

I generally do not use Locktite unless a bolt loosens during test flights. I will check
them before each flight. If I notice one or more becoming loose, then I might use
some of the blue Locktite. I probably should use it on motor bolts, but I don't. 
Interestingly, I have never had a bolt come out and only a few times where one or 
two became loose. Yeah, I probably should use the Locktite, but I generally tighten 
my bolts enough that they just don't come loose. I tighten them pretty tight and
don't use any type of torque wrench or such. I just tighten the bolts pretty tight and 
the carbon fiber does NOT get damaged regardless of how much I tighten them.
I do use metal washers.

For FC stacks and such and on some bolts that hold the bottom frame plates
together, I will use nyloc nuts. Now, these are NOT generally feasible for the
standoff columns. Also, I have been know to use nylon standoff columns to
save weight and I do NOT use Locktite on these.  

Sometimes, I will use an "O" ring and a flat metal washer instead of a locking
nyloc nut. The "O" ring provides some tension {like a spring} which prevents the 
nut from backing off. Now, I don't normally do this for the frame plates, however, 
I have used this method on FC stacks. 

Interestingly, I don't think that I have seen any builds {except mine} where
metal washers are used; washers are generally not included in frame kits.
For some reason {maybe cost?}, the FPV world doesn't seem to use washers.
On the other hand, I DO. 

My knowledge of the use of washers was acquired from a long history of
construction and repair of a wide variety of things {from car motors to 
houses}. When I started building quads, M2 and M3 flat stainless steel
washers were some of the first things that I purchased. I use them all 
the time and my builds always stay together and I have not damaged 
any of the carbon fiber plates. 

Hi kafie1980 and iFly4rotors!
Thanks for your wisdom!

Quote:I am not sure how you were torquing the screws but using a hex bit in a wrench is a no no since you have too much leverage.

I wasn't using a wrench but rather a screwdriver with a hex bit. It had a big handle though so in the end I switched to an L-shaped hex key. I forgot how simple it was to select an appropriate leverage by adjusting the position of my fingers. These keys comes from my RC car there stripping threads in plastic parts is a common issue.

Quote:Since that is a brand new frame, I would contact the vendor and see if I could get them to replace the "faulty" top plate.

Unfortunately, I purchased the frame two years ago so there is no chance I can replace the top plate. However, I hope that only the top clear layer was damaged and it only provides a smooth finish and not a structural strength.

Hi Grassydragon,

From the looks of it, I would agree that what actually splintered was a clear coat
and not the actual carbon fiber. So, it likely will not effect the structural integrity.
In that front location on the top plate, I don't think that you will have any issues
with stength. Personally, I would not worry about it especailly at this point.

I have repaired broken carbon fiber frames and arms with very good success.
What you have is not actually broken. In fact, I bet  you could scrape that off
and discover that the actual carbon fiber has not been broken or even splintered.

Since the cam brace is also wedged between the top and bottom plated that will
also serve to hold things in place and add a bit of strength to the structure. I 
believe that everything will be fine. There is a higher probability that you will
break an arm. 

Let's get this bird completed and in the air. 


By the way, I would suggest {please do} that you start a BUILD thread in the
Mini Quad section so that we might all follow along. That would also be a better
place for questions and comments since it would get better exposure and keep
everything about that build in one thread. 

Hi!
I've created a build thread here: https://intofpv.com/t-lumenier-qav-r-2-6
By the way, Alex Vanover now offers a frame that comes with washers (for some reason I can't see them on the website, however, they were presented in his video): https://vannystyle.com/products/vannystyle-frame

i never had that on quality carbon, as tight as "possible" by hand, the frame is something we like to be as stiff as possible. i would suggest to skip that frame, maybe for later experiments, not for a beginner build.

Quote:i would suggest to skip that frame, maybe for later experiments, not for a beginner build.

Since the quad has already been built and flies well, I'll continue flying it and see whether anything breaks

I like Chris Rosser's rule of thumb: use the same number of fingers to torque screws as the metric size ... so use 2 fingers for M2, 3 for M3. For me, it's not so much crushing the CF but stripping the screws.

Welcome to the forum!

Quote:I like Chris Rosser's rule of thumb: use the same number of fingers to torque screws as the metric size ... so use 2 fingers for M2, 3 for M3.

Sounds interesting! I sometimes hold a screwdriver more loosely so that it starts to slip in my hand when tension increases.

(20-Sep-2022, 01:15 AM)the.ronin Wrote: I like Chris Rosser's rule of thumb: use the same number of fingers to torque screws as the metric size ... so use 2 fingers for M2, 3 for M3. For me, it's not so much crushing the CF but stripping the screws.

Welcome to the forum!

xD funny rule from chris xD but any hand has different abilities. my two finger torq will be completly different to others... that rule cant be adapted to others. for true precision a "torq meter" is needed, for a particular torqlevel you could use the tool to check your added nm, if you are able to adjust by feel.

i guess the general rule is; on quality screws, nuts, standoffs and carbon - its pretty difficult to do something worng.

to get good tight fit on a new build, retighten them after maiden flights does help.

Hi Bat,

What torque wrench do you use?  Got a Link?

I tighten my frame and motor bolts just until they will not turn and the bolt "Feels" 
REAL tight. When the bolt will no longer turn, I sort of "test the torque" by trying 
to turn it just a "wee" bit with moderate, but not too much pressure. 
I do NOT Force it.

I use nyloc nuts or "O" ring washers on FC bolts. 
An "O" ring acts like a spring and applies pressure when compressed 
preventing the nut from turning. It might sound crazy, but it does work.

I have both black steel and stainless steel bolts, nuts, and nyloc nuts. Oddly, there are 
different sizes of each, however, both types seem to be quality...at least quality enough 
to NOT easily strip or break. I also use aluminum stand offs most of the time. I will use 
a bolt that goes down into the column about 5mm so that they have plenty of "grip". 
If the bolt only goes into the column a mm or 2 then get a longer bolt because a couple 
of threads will not tighten enough, will strip easily, and generally Do NOT not hold well.
{yeah, I generally chuck those short top plate bolts and use longer ones}.

So far, I have never stripped a bolt, nut, nor column. 

A word to the wise: When starting a bolt into the column, motor, or nut; turn slowly,
gently, and sort of "vibrate" it a little until the correct alignment is found where the bolt
turns easily into the threads. Do NOT force it {it is likely Not lined up straight}.  If the 
bolt does not turn easily then STOP, remove the bolt, and try it again. 

NEVER force a bolt to start into the threads as you might cross thread it and damage 
the threads on the nut, the column, or the bolt. 

Side Note:  

The only bolts that I have ever used a torque wrench on were Head Bolts on car motors.

https://nz.element14.com/duratool/d03003...dp/2581865

this is what i found so far. personal i feel comfortable without any tool.

(20-Sep-2022, 01:55 PM)hugnosed_bat Wrote: https://nz.element14.com/duratool/d03003...dp/2581865

this is what i found so far. personal i feel comfortable without any tool.

Hi Bat,

Thanks for the link. I have never seen one of those.

I couldn't find it on the US website, but will look other places.

The other thing is the price at over $ 150.00 USD. WOW. 

i didnt watch the price xD a proud price for tightening screws xD