bird of time

[southern soarer uk]

Just ordered one of these ,i used to own one several years back and wondered what anyone had come up with in the way of inprovements , on my old one i capped the spars with carbon to add some strength and fitted spoilers ,thanks Harvey

[williamson]

I inherited a very old Bird of Time which needed some rebuilding. The only modification I made was to use tapered carbon fiber as spar caps on the inner panels. These were wrapped with Kevlar tow before the sheeting went on.

I also added spoilers.

The classic Bird of Time is a great unchanging soaring machine.

[southern soarer uk]

was it a simple case of epoxing the carbon tows over the spars ? as this would make building a lot quicker as i could do this after assembling the wing

[mhodgson]

Built mine to plan, as originally designed.
Later had trouble getting the thing down and on the spot so I added flaps on the inner pannels (I hate spoilers, never could get them to fit properly).
It then up the line even better (who needs a breeze) and hit the spot every time.

In normal use it is strong enough as is (it was designed for F3b after all).

I glassed the fus/fin (doped on with tuKote fuelproofer - Poly-C would be good today) and covered the tail and rudder in litespan and the wings in Fiberfilm for some extra torsional strength.

If I built another, the only place I would consider carbon is on the T.E. of the tail and fin as they did warp after a while.

Martin

[southern soarer uk]

Thanks Martin , do you have any pictures of the flaps you built in or dimension please and it`s interesting you didn`t carbon the spars, i might not bother as i don`t plan on winch lauching and if i do it will be pulsed up the line ,Harvey

[mhodgson]

I wish I could. I no longer have the wings as it flew into a tree and they were damaged beyond repair getting it out.

The flaps were full span across the inner panel (up to where the polyhedral is). I made them 25% of the chord I think (easy to measure), bottom hinged as they only went down (90 degrees by the way, any breeze and it could go backwards). Sanded from some lovely light solid sheet I had.
I just cut away the ribs and added a 1/4" spar/T.E on the hinge line, gussets in the corners to strengthen the rib/TE joint, tacked the flaps into place, carved and sanded and then recovered (wings in Fiberfilm and flaps were glassed as per fus for a little extra toughness and rigidity).

To control them I used a servo in each wing bottom linked cause it was easier to do.
It's easy enough to do as the section is flat bottomed.

Hope that helps.

[southern soarer uk]

sorry for your loss , i`ll modify it to suit thanks

[williamson]

was it a simple case of epoxing the carbon tows over the spars ? as this would make building a lot quicker as i could do this after assembling the wing


No, it was not the simple case that you describe. Because the plane was already built, I had to remove the covering and sheeting. Then I went through the tedious process of sanding the wooden spar caps so that the carbon fiber ended up at the same level as the original wooden spar caps. After the carbon fiber was epoxied in place, I wrapped the spars with Kevlar tow and then put on the sheeting.

On my Bird of Time, I put carbon fiber on only the inner panels. Each panel is less than two feet long so I could use four-foot carbon fiber laminates (from CST) that tapered from 0.060" to 0.014". I cut the fiber in two and used the thicker piece for the tops of the spars (tapering from 0.060' to 0.37") and the thinner piece for the bottoms (tapering from 0.037" to 0.014").

It is a lot easier to epoxy the carbon fiber to the spar caps and thin them down before the spar caps are glued in place. Perhaps the attached descriptions might help.

[Barnsey]

Later had trouble getting the thing down and on the spot so I added flaps on the inner pannelsSSUK,

Along with Martin's info, at the inaugral F3J World Champs in 1998 the Greek team had a stunning BoT fitted with flaps. As I recollect, they looked to be about 20% chord, starting just outside the fuz line and finishing a little before the polyhedral break. They were setup to act as inboard ailerons and as landing flaps. The Greek lads reported that the flap mod greatly improved both directional control (more immediate response) and landing precision.

Their BoT was stunning because when I complimented them on the superb, museum-quality paint job, I was laughingly advised that it was Profilm. :o :D

John

[Davee1]

Bit of a thread ressurrection, but I wondered if anyone can tell me more about the "Fiberfilm" material that was mentioned above. A club-mate recommended it to me for use on a glider but I can't find any info on it anywhere. Thanks!

Edit: Since posting, I've come across "Fibafilm" I assume this is the same stuff?

[mhodgson]

Fibafilm is made by solarfilm company. Look on their website for details.
It has no adhesive so needs a seperate glue painting onto the airframe. Goes on well but needs careful work on tight corners. I found it best to cover the very tips in solarfilm first as that can conform to tight compoud curves better.
It is a polyester film I think and adds a good amount of torsional stiffness to the wing. It is glossy on one side (the outside) with o solid colour, no transparent colours here, and has visible fibres on the inner surface.

I like it becquse it is tought and adds that extra torsional strength for no extra weight over solarfilm.

Hope that helps

[Davee1]

Cool, thanks for the info. I think my club mate recommended it for the extra torsional stiffness on the wings. That sounds like a handy tip for wingtips.

[aeajr]

Where do you buy this Fibafilm?

[Davee1]

Don't know about the USA but in the UK you can get it here:

http://www.sussex-model-centre.co.uk/shopexd.asp?id=1980