Electric flaps

[kestrel]

A few people have been asking about the electric flap system in my 4 place Bearhawk. This information is in the old yahoo group, but thought it might be useful to re-post it here. I find the break-down of forums a bit odd on this site because there is no "4 place" forum and so much information is not specific to "plans build" or "quick build". Posting in both makes no sense. Posting in one could cause general 4 place information to be missed. Also, the information is probably not even 4 place specific. ...so, I'm posting in "General".

I am not a builder. I am the 4th owner of my Bearhawk. That will limit my ability to answer some questions. My flaps are very easy to operate compared with what I hear about the manual flaps. The entire system is overhead with no cables running around places. Cable/manual flaps use springs to hold them up and they can blow around when parked with a tailwind. These flaps don't have that characteristic.

Here is a link to the thread on the bearhawk yahoo group:

https://groups.yahoo.com/neo/groups/...s/topics/33172

Try this link for pictures of the installation:

https://get.google.com/albumarchive/...LfC?source=pwa

If that doesn't work, try this one:

https://picasaweb.google.com/1104562...eat=directlink

By zooming in one of the pictures I posted, I can see that it is an "Electrack 10" by Thomson:

http://www.thomsonlinear.com/website...lectrak_10.php

The system has been absolutely trouble free, though I'm suspicious of the weight of the actuator. I'd love to experiment with an overhead manual handle. I believe that Pat Fagan has tried it and didn't like the ergonomics/pull force. I suspect it can be done.

I also suspect that a lighter actuator could be used for the flaps. I'm
quite certain that the one I have is over-kill.

This page shows the one used by the RV-10:

http://buildingrv10.blogspot.com/201...-finished.html

This one gives 330 lbs with 0.5 ft of travel for 165 ft-lbs of work available.

http://www.aircraftspruce.com/catalo...clickkey=15503

If a Bearhawk flap handle is 2 ft long and it takes 40 lbs of force
over 90 degrees of travel, it would require 125 ft-lbs of work to
operate. ...if I did my calculations correctly. ...and those numbers
should be well on the high side?

I'm happy to answer more detailed questions. ...and hope that Mark doesn't mind me posting a mod. ;-)

[Mark Goldberg]

These are homebuilts, and we can build them as we want. However, sticking to Bob's plans is a good idea from my point of view. I won't get into why I think the flaps as designed are better. But in a general way, sticking with the tried and proven is good. But no problem posting what the original builder did here if guys are asking you about it. Mark

[Zzz]

Thanks for sharing, Kestrel. Though I don't particularly like electric flaps, especially for shortfield work, it is good to have this reference included in the forum. This is becoming a better resource every day.

[Bdflies]

I agree completely with your assessment.

Bill

[jaredyates]

Also, there is a great utility available for searching the old Yahoo groups called "PG Offline". I have a copy and had intentions of one day using it to republish the old archive, but unfortunately that project is so far down the to-do list it might not ever get done. I purchased a couple of extra licenses with the intent of providing them to volunteers who wanted to help clean out the old archive, but never got much past that stage.

[Battson]

Thanks for sharing this info, great to see how it was done!

I have been mulling over electric flaps because my wife can't use the manual handle (too much force required). Apart from the occasional very difficult (reckless?) landing in a tight spot or on a gusty day, I have never found myself wanting manual flaps. I think the manual flaps are nice to have and probably save some weight, but they have disadvantages too.

I believe the flap system truly warrants a redesign by Bob himself, to maximise usefulness of the aircraft.
I think there are many improvements (albeit massive diversions from the current plans) waiting to be realised.
I would love to see a redesign by Bob himself, including either slotted or fowler flaps which extend inward to the fuselage, plus a longer flap handle for the pilot's comfort.

[Battson]

I need to retract my comment about manual flaps, now that my flying has progressed to a more advanced level. I have realised the importance of the manual flaps in so many backcountry and STOL applications. They are a necessity.

Edit: Of particular note specific to the Bearhawk - you can brake a LOT harder once the flaps are retracted. More weight on the tailwheel with flaps up, so the tail doesn't lift under heavy braking. Also it allows you to "dump the lift" from the wing, which drops the plan firmly onto the ground when the flaps are retracted quickly.

[svyolo]

I am starting to level the fuselage and get ready to drill the wings and have been looking at the flap geometry. I prefer manual flaps for simplicity, but would sort of like the ability to reflex the flaps 5-8 degrees so i would need positive actuation instead of cables and springs. It looks like there is plenty of room in the ceiling for a torque tube connecting the two actuating tubes.
Then I found this thread.
Anybody else use an overhead bar or an electric actuator. Plenty of room up in the ceiling area.

[Chris In Milwaukee]

I am starting to level the fuselage and get ready to drill the wings and have been looking at the flap geometry. I prefer manual flaps for simplicity, but would sort of like the ability to reflex the flaps 5-8 degrees so i would need positive actuation instead of cables and springs. It looks like there is plenty of room in the ceiling for a torque tube connecting the two actuating tubes.
Then I found this thread.
Anybody else use an overhead bar or an electric actuator. Plenty of room up in the ceiling area.

Post #5 here shows how Maule reflexes flaps with a flap handle. It would be a lot easier with an electric actuator, I think.

https://bearhawkforums.com/forum/tools-technics-and-best-practices/25793-flap-arms?p=35630#post35630

[svyolo]

It looks like an overhead actuator would be super easy. Easier than the stock system. But it also looks like it would be easy to do later, after the plane is built and flying. The only issue would be deciding where to attach the actuator, as you probably have 100-200 lbs of linear force on the actuator.

My handle and cable is already installed, so it will probably fly that way first.

[AZBearhawk272]

If you were really inclined to do electric flaps
consider an actuator mounted vertical behind the rear baggage bulkhead. Lower end terminated at the V cluster and the top at the
Bottom of the Y bridle fitting.
Pull through the existing cable setup.
Just keep the unit light!

[tailwind]

I have not explored this idea at all but I think you could extend the flap tubes across the cabin connecting both sides together and use a light linear drive to a bell crank to activate the flaps. The advantage to this system would be that the flaps would not deflect down while parked or taxing down wind. The weight probably will be a wash when you remove all of the old system design. The penalty will be slower operation.

[svyolo]

The overhead system looks like the way to go for the reason I wanted it. If you use cables to pull down, and springs/air too pull up, you can't get the flaps to reflex. Electric or manual.

I found a couple of linear actuators that should be suitable at just under 4 lbs. 3 seconds to go full throw at 4 inches. I think I would put the actuator aft, and carry the load to the overhead tube cluster that holds the elevator trim cable fairlead. I would needs Bobs blessing for this but I think it would be fine. It sure looks easy. It shouldn't be much of a weight penalty. The flap return springs alone weigh just over a pound.

[rodsmith]

I believe others have tried reflexing the flaps and have not seen any benefit. You have the B model, Harry Ribblett said his airfoils don't benefit from reflexing the flaps.

[svyolo]

Good info. Thanks.

[kestrel]

The original builder of my 4 place built it to reflex. I never had a chance to talk with him about it, but he re-adjusted the flaps to not reflex.

[svyolo]

More good info. Thanks. I still think electric flaps are simpler, and weight neutral. I have read of several complaining about the effort to get full flaps. Not a problem for me yet.

All that being said I have zero experience bush flying. Maybe I will find value in the stock system. Most of it is installed, so that is how it will fly first.