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    I’m looking for simple, positive and light weight ideas for transfering flap motion thru a dihedral joint and sealing it. Pictures of some of the F1A or F1C systems or sketches of them would be welcome.


    Lee Hines

    Yes Paul, as are many amongst us.
    OK, how about: Oragami folded tissue and bubble gum?
    Nooo, not too good…hmmm.

    Sorry. I couldn’t help it.:wink: 🙄 😆



    Paul– not much action on your question. Here’s my thoughts and what I have seen.

    I looked at Ed Carroll’s Eugene V’s flapper and M&K’s. They did nothing special other than the flaps in the down / glide were very close, .020 inch gap maybe.

    Years ago, I saw a Bill Giesking flaper had thin sheet metal joined to the inb’d flap top and bottom. These metal strips where bent at the dihedral angle. I remember they worked well.

    I would think a simple mylar strip on one side with enough slack to allow the flap movement but prevent the bottom to top air flow.

    At San Val cotest, Alex A was asked if if he was working on a flapper– he answered not now.

    What are you thinking Paul?


    In the UK there is a strong rumour that someone is working on a folding glider. We have an open event where anything goes off 50m towline, so no wing area or weight limits and therefore its legal. The story goes that this flyer has an ‘old’ Babenko wing that he’s using. Madness I say !


    >no wing area or weight limits and therefore its legal.

    Actually, CHE, there probably is an upper limit on total area – and on maximum weight (not that it applies in this instance) – for gliders, etc. still existant in the SMAE/BMFA ‘general rules’ … back in the days when gliders had distinction such as the Thermalist and Thunderking were built to near those area limits.

    Would be enlightening to see one such today with modern airfoils, aerodynamics and structures – the one problem with the big gliders was that it’s almost impossible to d/t the things without damage as they rarely come down in a stable manner



    Yes you are correct. The upper weight limit for an Open Glider in the UK is set by the model airplane definitions; I think is down the the CAA and is a number so large as to make anyone contemplating exceeding it for a FF model certifiably insane. Not sure there is a maximum area limit of any kind.

    The new rules now being used in the UK allow a 75m line for models with no facility for circle towing. Thus some large, modern structure and airfoil models are being/have been constructed. This is like the old days of open models in the UK where things like 3x Caprices were flown. As yet I don’t know how they perform against the oppostion.


    I’ve now seen the Findhal flapper in action and it makes an interesting comparison with the M&K model seen at Lost Hills. I believe details have been published in a few organs so the geometries are clear. Per does not move the flaps between straight and circle tow whilst M&K do. This doesn’t seen to affect how the model performs on tow however and it is obviously manoeuvrerable. His launch technique is also unchanged from his normal style of getting the model low and straight before commencing his launch whilst M starts the launch before the model has even turned the bottom corner. I would say that M gets higher than F simply due to the method of launch but then he may have been toying with the audience. !

    Internals are M&K with Futaba digital servos for tail, flaps and rudder. There is no obvious wiggler.

    The system doesn’t look difficult and I’m seriously tempted to make one.


    >Not sure there is a maximum area limit of any kind.

    I had a vague idea that there was .. or maybe used to be .. long time ago, but on the other hand I do remember that Graham Gates and other members of Southern Cross once produced a real monster … 17′? 20′? ..which they towed up on the beach. Never heard any more about it so maybe not too successful. 10′ was my largest.


    I seem to recal that Gil Morris’ version has nothing at the gaps. I agree that using thin mylar would work or possibly some thin rigid mylar that slides next to each other.

    Or, just use Vee dihedral like Dick Swenson and I did and not worry about it- We built these flappers back in the ’70’s with minimal success. Wings were foam and balsa and just were not rigid enough. But they were cool…


    M&K do use a mechanical release to provide differential “flap” for glide, ie washin. I saw the unit in the model but did not figure out how it worked and did not ask. It is integral to the cable-roller mechanism that drives the flaps. I do know they must remember to reset it before each flight.

    I’m hoping M&K article, photo and drawings of the Flapper they are sending to me to edit will make the the NFFS Sympo dead line. JIM


    In discussion with a few luminaries of the FF scene, it would appear the need to flap or not on tow is not yet clear. The position as I (think) I know it is :-

    Van Wallene – Tows flaps down
    M – Tows flaps down for circle, up for straight tow
    Findahl – Flaps up for tow
    Aringer – Tried up and down flaps, likes then down for tow

    There seems to be comments that towing with flaps up for tow is difficult and the results can be inconsistant with poor line tension etc. However, obviously it can be made to work.

    I plan to follow a long line of British FF tradition and attempt to make a flapper just using bent wire and baleing twine.


    In reading the issue #27 of the Free Flight Quarterly, Per Findahl sugests that maybe flaps should be outlawed in interest of the sport.

    In looking at the airfoil shown in supposedly the launch position, it appears that the flaps up position is a VERY high drag airfoil shape, and they are wasting their time with all of the complexity to attain mediocrity!

    Waiting to see someone show that they work!

    I am sure that the FLAPPING in the F1C power models does not show the HIGH drag airfoils in the flap up position.



    I suspect the drawing of the Findahl flapper in FFQ is just a sketch and not showing the accurate shape. Per told me at the weekend that he flies on slight camber and can reach 90 metres. Is that mediocrity ? I think not. Having seen the model in action and noting that he won the flyoff with the model (Stonehenge Cup – prehistoric open international) its potential is clear.

    Also its not too complex as the FFQ article shows.


    A height gain of almost 80% is one hell of a height gain. I have not been around grown-up FAI models for a long time, so my question is simple; is that really true (or almost true)?

    Certainly it would imply that the flaps-up airfoil is no great drag source.


    it’s very possible, John. Peter Allnutt demonstrates at least 50% height gain off 50 metres with an unflapped glider equipped with a ‘new’ Eggleston airfoil

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