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carbon fibre and antenna

Old 04-06-2005, 09:29 PM
  #26  
rdresch
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Default RE: carbon fibre and antenna

Interesting, I also tested with a dual conversion pcm futaba reciever. Yet, as I understand it, this just covers up intermittant hits. If the interference is strong enough the reciever will go into failsafe. I read some where of a case where carbon fibre was being rubbed by some metal and that drove the reciever nuts. This makes sense since metal to metal,especialy dissimialar metals,is a prime generator of unwhanted rf. Can a small piece of delaminated carbon rubbing create some of these carbon issues?
Old 04-06-2005, 10:42 PM
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Default RE: carbon fibre and antenna

rdresch,

what futaba told you?

danj31, as far as I know, kevelar Is as well a good option as there is not cearting interferences...(if I am not mistaken...)
Old 04-07-2005, 12:16 AM
  #28  
tommyboy1229
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Default RE: carbon fibre and antenna

" Can a small piece of delaminated carbon rubbing create some of these carbon issues? "

Yes it can, and it will.

We went through a lot of different tests with the carbon and antenna problems. We are starting to produce the 44 sized F7- Cutlass that is pictured in the Jets forum.
This airframe was originally all carbon. What we found was that the carbon in our case almost never caused a problem, in fact when range checking we would have to rub the antenna on the carbon to cause a problem. We did fly several prototypes in all carbon exept for the hatches, and we mounted a Deans antenna to one of the fiberglass hatches. No problems there. However the production airframe now has a Kevlar front. The wings and rear half of the fuse are still all carbon. We had to continue to use a base loaded antenna on the outside of the fuse because the front of the fuse is to full of radio gear. Kevlar is lighter and stronger than cabon fiber but it is not as stiff, however it is a little difficult to work with compared to carbon, as far as cutting and sanding. The main thing about using a whip type antenna is that it is perpindicular to all your wiring etc.,this is what really helps. The thing about it is, even with all those tests it's that one time you get into a position when the carbon will cause a problem and then what. Play it safe with that type of investment.

Good luck with your project,
Old 04-07-2005, 01:24 AM
  #29  
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Default RE: carbon fibre and antenna

after all those discussions on the matter, here is part of my plan for the construction:
- kevlar noze up to wing root (70cm)
- kevlar body with carbon reinforcement on all the wing root lenght (an other (70 cm)
- full carbon wings and other control surfaces
- then, kevlar up to the end, with some carbon reinforcement at some locations...
- I am thinking to have the formers made from carbon laminated balsa.
- the "sanding/cutting" junctions will be made of carbon, this means that body will not be full carbon but still have carbon from noze to tip...

regarding the antena, I have two solutions:
- receiver down the canopy ,then antena routed strait to the noze.
- antena routed in a pvc tube perpendicular to the body just in the back of the canopy.

With the solutions above,I have still one problem (which is maybe not): carbon formers and carbone junctions will give a "cage" structure which might not be good for Interferences...

.....hum....I have to say that I an confused with this carbon issue...on one side carbone is very good because of the rigidity it can provide compare to weight...on the other side interferences issues are not so predictable....
Old 04-07-2005, 06:59 PM
  #30  
rdresch
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Default RE: carbon fibre and antenna

Just got off phone with futaba. They are unaware of any issue with carbon and reception. That being said, they havent done any tests either that the tech was aware of. Back to square one. My own projects includes a hatch under the belly for turbine access Ill make that from glass sandwich. Ill also avoid laying up multi layers of carbon on top of each other. I'll use thin layer of glass or Kevlar between them to avoid rubbing.
Old 04-15-2005, 08:13 AM
  #31  
Bruce Thompson
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Default RE: carbon fibre and antenna

RDR, I haven't been back to this post in a while and it appears I helped stir up a nest. First I am amazed that people are successfully enclosing antenna in carbon booms. Someone posted earlier about playing it safe with such a big investment. I want to comment on that. Earlier I posted about other solutions for construction. What is the exact lay-up for this model, ie. sandwich core, vacuum bagging, solid skins, not bagging? If you went to vacuum bagging with a core, you could use glass and have a structure you could sit on and still be light with no reception worries.
Old 04-16-2005, 04:22 PM
  #32  
rdresch
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Default RE: carbon fibre and antenna

I'm playing it safe. Since I was going to install kevlar fuel tanks on both sides of fuselage anyway I'll incoporate them into the structure and make them load bearing. Also since I'm new to composites I'll build a glass prototype to learn on and it should tell me where I really need extra strength. Finally I'll use the turbine itself as a structural member. This model V22 osprey is mainly center section loads. It supports the turbine gearox and pulleys to wing.
Old 05-04-2005, 05:48 PM
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Default RE: carbon fibre and antenna

Do not glass in your antenna.
During ;testing let it hang free, or band it to non carbon strucure underneath, loosely, then range check with motor running, with restraints, etc.

If glassed in, you will not have options, obviously, it is not prudent.
M
Old 05-07-2005, 09:47 AM
  #34  
rdresch
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Default RE: carbon fibre and antenna

I would not glass in the antenna. I was going to glass in a tube for the antenna to slide in. That way if it doesnt work out I just pull and relocate the antenna. I read a interesting post on a Large scale Harrier with a Turbofan jet engine. He was having fits with RF issues. He ended up reworking the carbon shroud for the fan in fiberglass. That seems to have solved the RF issue. Again it seems that not so much a issue of carbon blocking the signal as one of it conducting RF. In this case where you have large amounts of air flowing past the carbon shroud I would assume it picks up a static charge then becomes an antenna to send this as rf to fritz the receiver. Is this possible? if so could grounding the carbon to the battery eliminate the issue? There is more to this carbon and rf than just carbon blocking the signal. You electronic wizards could jump in here and set me straight!!!

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