Thread Tools
Mar 09, 2018, 11:16 AM
Registered User
Thread OP
Discussion

5mm x 36” bamboo spar vs carbon fiber for foam wings with wingspan 30” to 70”


Hey
I’ve read on a few threads that some folks used bamboo skewers for wing reinforcements and spars.

I was just wonder if anyone has any ideas on the weight to strength differences?
Sign up now
to remove ads between posts
Mar 09, 2018, 08:47 PM
Registered User
bamboo skweres?? really? im using a wooden dowl on a 40" wing, on heavier 3d foamies a wooden spar can snap so cf is used instead...

I dont see how bbw skweres can offer any reinforcmentto such large wings.
Mar 09, 2018, 10:23 PM
treefinder
springer's Avatar
Bamboo actually has a great stiffness to weight ratio, so is often a good material to use. If you can find larger diameter skewers that are straight enough, they can be used as spars. C.F. is straighter and stronger, but more expensive , so it depends on how you fly and how much you want to spend. I generally use wood spars for planes in the 36 and larger sizes, but as a woodworker, I have lots of wood in all sizes. But I do use skewers for the smaller sizes and they fly well and are generally durable.
Mar 09, 2018, 11:40 PM
Registered User
ninjasword71's Avatar
Wood spars don't need to be the length of the wing. Not much force at the tips unless you fly 100mph. I use wood spars or better yet, 30" arrow shafts up to 50".
Mar 10, 2018, 06:27 AM
gpw
gpw
“There’s no place like Foam”
gpw's Avatar
We’ve used bamboo skewers and slats for everything for many years ( even long before Foamies) … they work great and almost never break , glue easily , and you CAN bend them to shape with heat … something you CAN’T do with CF … Although easily affordable and found in most any grocery store , there seems to be some bias and snobbery , by those who use CF … and although CF is the “latest thing” we never did like it … or need it … JMHO …

Being around here for a while the original intent of Foamies was to build airplanes that were INEXPENSIVE and Fun … and not have to resort to the High priced materials offered by the large Hobby corporations … Anyone who has built many Balsa planes knows what I mean…
Last edited by gpw; Mar 11, 2018 at 07:23 AM.
Mar 10, 2018, 06:33 AM
Registered User
Extreme Sports's Avatar
5mm? I doubt it. Larger diameter? Almost certainly. If you can find some.

Two 5mm bamboo skewers firmly glued in slots, one on the top of the wing and the other on the bottom to form a rough I beam might work. Here the question mark is on the foam that forms the shear web...probably not strong enough relative to the bamboo.

Third alternative is to build up a proper I-beam spar with the bamboo for the flanges and some better material than foam for the shear web. But if going to this amount of effort, balsa and spruce or a GRP moulding would make a better I-beam spar.
Mar 10, 2018, 08:01 AM
Registered User
Thread OP

5mm x 36” bamboo spar vs carbon fiber for foam wings with wingspan 30” to 70”


This is what I was think of using...
and when I’m done using it in my plane I can use it as a stake in my garden or even use them as long bbq skewers

Beyonder Bamboo Marshmallow Roasting Sticks with 30 Inch 5mm Thick Extra Long Heavy Duty Wooden Skewers, Roaster Barbecue Smores Skewers & Hot Dog Forks for Camping ,Party,Kebab Sausage (40 Pcs) https://www.amazon.com/dp/B01MTRABFA..._iC9OAbTM7PTMC
Mar 10, 2018, 08:26 AM
Build, crash...repeat
AleRRon's Avatar
40 bamboo skewers? Wow, that’s a lot of planes! Also when they are “done”, lots of marshmallows to roast!

But seriously, they are strong but not that rigid so it depends on your plane. Should be fine for 36” and under unless it’s supposed to be a high performance racer in which case CF might be better. Also, the bamboo spar glued to the foam wing will be more rigid than the spar alone. If you want CF, you can get arrows at Walmart for about 3 bucks.
Mar 11, 2018, 07:26 AM
gpw
gpw
“There’s no place like Foam”
gpw's Avatar
Thing about bamboo skewers , if you need more strength , you use TWO … ( or more) … Many of the first airplane models were built with Bamboo , and powered by rubber bands … I know that’s unbelieveable , but it’s true !
Latest blog entry: Lost plans
Mar 11, 2018, 01:48 PM
Registered User
RJD1234's Avatar
For 36" or more wingspan, go with CF rods. Yeah a little pricey, but stronger than bamboo. However I use skewers for repairs. Very small weight gain but good reinforcement.
Mar 11, 2018, 02:33 PM
Kimbers Keeper.
BHOFM's Avatar
My experience with the longer skewers is that they are not straight, not even close. Not worth
the time to straighten.
Mar 11, 2018, 09:46 PM
Registered User
Depending on what I am using them on, straight, twisty is not a problem. I just finished a Canard Stick for my brother. I use 3/16" wood dowels top and bottom. They were not really straight but the wing is almost 2 inches thick so not really going to warp the wing. I used one top and bottom. I was really surprised at how strong it was. Twice as strong as I would have guessed.

Plane flew great. Super stable fast, had a 3 blade prop that gave it this sound like it was ripping up the air. The expiration date on the plane came up rather fast though. On the fifth flight went in full throttle. So glad it was a pusher as the plane just about exploded. Foam, packing tape went every where. I could use the wing again. It survived pretty well.

Now if I am using a single layer of DTFB, I too would use carbon, but thick heavy foam, squiggly dowels are OK.


Buzz.
Mar 17, 2018, 04:09 AM
Registered User
Head down to WalMart, those long BBQ skewers are 88 cents a dozen.

I did actually break one last weekend on a 40" wing. I had an oversized lipo in it and I was jerking the sticks around really testing out a new build. Shoulda doubled up.
Mar 18, 2018, 12:21 PM
Round is Fun
I ordered some of the skewers mentioned back farther in this thread. They are pretty flexible and not terribly straight. I will likely use bits of them in some places, but in a 36" length, they seem rather flexible. They will gain stiffness when glued to something, I suppose. Additionally, they are probably easier to glue than carbon fiber. I wonder if they have the flexibility to go around a NutBall and form a leading edge? I'll have to take a look at that should I build a plane for combat. Anyhow, they will likely have their uses over time.

Mike
Mar 18, 2018, 06:42 PM
gpw
gpw
“There’s no place like Foam”
gpw's Avatar
To bend skewers around a radius , soak in water overnight then bend it around something hot like the barrel of a soldering iron or candle flame … Keep it wet , don’t scorch it … That’s how rounded wingtips used to be formed …. some time ago …
Latest blog entry: Lost plans


Quick Reply
Message:

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
New Product Thor 210V2 205mm - 5mm 75g Carbon Fiber X-Frame D Gains Mini Multirotor Drones 0 Jul 17, 2017 05:12 AM
Question Tubes for Carbon Fiber Spars (in removable wings) FPV_Habu_Flyer Scale Kit/Scratch Built 7 Aug 07, 2016 12:44 AM
Cool 100 5mm x 36" bamboo skewers for $28 balsa or carbon Foamies (Scratchbuilt) 2 Feb 09, 2015 06:29 PM
Discussion 1mm carbon fiber plate vs 1.5mm g10 danielpetrescu Scratchbuilt Multirotor Drones 5 Sep 24, 2014 06:56 AM
Carbon Fiber Spar or Carbon fiber skin? soholingo Composites Fabrication 0 Mar 22, 2005 10:35 PM