Composite model structures
 

Hi Guys

Just thought you'd be interested to see these pics..... I was cleaning out the loft last week when I came across a pair of wings froma somewhat crashed (!) Hawk. Being the inquisitive sort, I pulled the wing apart to see how it was made and to my horror I found this! OK the model is a few years old now and the design may have changed but the internal structure looks like an accident waiting to happen. A couple of points to note....

The main spar just ends in mid air before it gets to the wing tube
There is no glue on the main spar holding it to the top or bottom surface
The main spar is just soft balsa inserted with the grain lengthways
The Main Spar is cut on the bottom to allow the insertion of the ribs - no strength at all
The ribs are made of very very soft balsa
The rear surface bearing Spar inner and outer are not joined at all

The other thing I noticed was that the same soft balsa is used on the wing skinning and peels off very easily.

It also has NO washout in the wing.....hope the newer ones are better!!;)

Cheers

Paul

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RE: Composite model structures
 

Well, if it didn't crash due to a wing failure I'd say the structure is probably ok :) A full depth spar like that in a compositie structure should be very strong, not sure exactly how strong, but I think most wings are done that way when they're composite. I can't be sure, but it looks like all the spar in my Super Bandit composite wing is all balsa too, what might be behind it I don't know, but from a quick look it looks all balsa

RE: Composite model structures
 

Composite?
That wing looks to me a built up wooden wing and then glassed. That doesn't mean it is a full composite kit. Few companies out there are advertising their models as a full composite ones. That is not completely true is the wing is a built up balsa glassed wing. So lets belive 1/2 way, just a full composite fuselage. Not saying all companies. And not mentioning any brand.

Alex

RE: Composite model structures
 

I don't understand the problem....

With that design the TUBE IS THE "SPAR", is it not?

It's the tube that carries the load and what you are thinking of as "THE SPAR" is, in fact, just a sort of span-wise rib, right?

This is not the only design I've seen like this, I wouldn't worry about it. But if I'm full of beans and completely missing something here, I'm all ears !!

RE: Composite model structures
 

the problem with the wing tube being the spar and only spar is this wing is swept. without the outer spar being tied into the wing tube, there is the potential of wing flex and or flutter. if neither occur, there still is most likey an expiration date for this wing design just from repetive stress. especially the way we fly them hard. i like the lack of landing gear beef myself. also, worth noting, hard landings will shorten the life of this wing. just my thoughts, barry

RE: Composite model structures
 

Barry I'm with you in the lack of gear beef. I had broken the gear mount twice in those not perfect landings. Just replace the broken wood rail and install a new one. Quick fix and better than buying a new wing. My thinking is that having a super strong gear mount will cause the stress to go some other place where the damage could be greater. That's why I'm using now the trailing links styles. They handle the stress better in those hard LG.

Alex