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RES-Eagle Glider RCME March 2018

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Ton van Munsteren13/04/2018 17:33:49
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1285 forum posts
3301 photos

Thats great and look forward to see some pics of your RES-Eagle.

Ton

_AL_29/05/2018 13:48:57
22 forum posts
12 photos

Ton,

What wing section(s)did you use on this?

Regards.

Al

Ton van Munsteren29/05/2018 21:24:53
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1285 forum posts
3301 photos

Hi Al,

Its a AG36.

Ton

_AL_30/05/2018 07:55:11
22 forum posts
12 photos
Thanks.
I may just have to build one of these.

Al
Ton van Munsteren30/05/2018 22:41:23
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1285 forum posts
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And Iam sure you will enjoy flying with the RES-Eagle.

What else can I say than go for it.

Ton

Edited By Ton van Munsteren on 30/05/2018 22:49:03

buster prop08/11/2019 10:53:27
486 forum posts
13 photos

I went for it - and ordered a kit from SMC which was delivered yesterday. It contains an enormous rolled plan and a lot of wood with C/F spars. Apparently the diameter of spars in the outer panels has been increased because of reported flutter when launching. Can’t do any harm for a tiny weight increase. Our club is proposing to hold a comp next summer for 2M F3-RES gliders using a standard bungee. Some others have ordered gliders from Hyperflight but I thought they seemed a bit light for UK conditions. The RES Eagle is a bit heavier than those but with about the same wing loading and a viable wing section, AG36. I also have the March 2018 article and plan which I’ve studied.

buster prop08/11/2019 21:21:22
486 forum posts
13 photos

I have compared the two plans and the only change seems to be the tow hook position. Originally (March 2018) it was 73mm behind F03, on the kit plan it is 63mm. CG on both plans is the same, at 90mm behind the wing leading edge above F03. What difference would that make?

Ton van Munsteren08/11/2019 22:09:23
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1285 forum posts
3301 photos

buster,

Great that you will be building the Res-Eagle and looking forward to some build pics.

For the hook position its not clear to me that its on the RCME located at 73mm, because all my cad drawings show the 63mm position.

Could be that the RCM&E made a small error using 73 instead of 63mm, but it could be better to use the 73mm to have a steeper angle on the climb and to keep the speed down.

The closer the hook to the cg the steeper the model will go up on the line, would be nice to test both if you like.

Cheers, Ton

buster prop09/11/2019 13:04:57
486 forum posts
13 photos

Thanks for replying Ton. I’ll make positions for the tow hook to be fitted at either location then. Front 63mm for windy conditions and rear at 73mm if it’s calm. I was surprised that the present plan includes details to fit a motor, if I wanted another 2M E-Glider I’d have bought the Red Eagle kit instead.

Ton van Munsteren09/11/2019 20:08:49
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1285 forum posts
3301 photos

Its getting more clear now its the modification which RBCkits has done.

The motor on the drawing is because a customer asked RBC to do the mod.

Its not me who did the mod, but I think its a good option to have both, but your right for E-flight the RedEagle would have been a good choice.

Funny when you design a model there is always someone who wants something different.

Great that you selected the Res-Eagle as a glider and Iam sure you will like it.

Cheers, Ton

Andy Botyle02/01/2020 10:19:04
1 forum posts

Hi Guys,

I got this kit as a Christmas present and can't wait to get started on building it.... It's been 20+ years since I have built a glider and hopefully, the techniques all come back to me. Lots of my questions have already been asked and answered by members on here, so that's a great start for me, but I do have some other questions that I hope you can help with.

I seem to have been given short steering cables, I believe is for the elec version when the servos are located closer to the CG and thus less distance to the elevator and rudder. Should I get longer cables in one piece or should I extend, if so how would I go about this?

For the vertical and horizontal stabilizers are these fixed to the fuselage?

Thanks in advance

buster prop02/01/2020 13:21:02
486 forum posts
13 photos

Hi Andy I'm building an RES Eagle as well, from the S M C kit. I'm hoping to get on with it now Xmas is over. Yes the wire rods are too short for the tow line version. I soldered lengths of piano wire onto them and covered the join with heat shrink tube. We shouldn't have to do this, I assume that a standard 36" wire was all that S M C stock. The fin fits into two angled balsa blocks on the upper side of the tail plane which is then glued onto the fuselage. It's a straightforward build but there are one or two things to think about. If you have any more questions please ask.

buster prop02/01/2020 21:41:40
486 forum posts
13 photos

res eagle 2.jpg This wing centre view shows that I fitted small blocks of balsa to support the covering where the wing fixing bolts go through. The spoiler will be hinged by the covering. I've planed and sanded the trailing edge to match the rib profile. The two balsa pieces attached to the W01 ribs weren't in my kit, they came from my balsa offcuts box.res eagle 1.jpgThe outer wing tip trailing edge looks too short against the plan that comes with the kit although it does match the magazine free plan from March 2018. Luckily I have a copy which I am using to build from. Everything else seems to be ok so I think it must be a drawing error.

Sussex Pete14/01/2020 11:31:49
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29 forum posts
19 photos

Seems quite a few RES-Eagles are on building boards - great news for own-built 2m competitions this year!

May I put a word in for BARCS in case anyone interested is not already a member? There's a good chance of another "postal" comp using 60m bungee+line this year and rumours of a full F3-RES comp. See the BARCS forum thread "F3-RES UK Competition Interest." I really like the own-build aspect of F3-RES in general and RES-Eagle is a great way in.

Edited By Sussex Pete on 14/01/2020 12:54:18

Sussex Pete23/01/2020 10:30:12
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29 forum posts
19 photos

Tony-- A question: just started on my wing centre section. The plans show the spoiler outline from 2mm and the spoiler from 4mm. There was no precut wood for either (and no 2mm wood at all, in the short kits we ordered. Should there be? Lovely stuff so far otherwise! Thanks.

buster prop23/01/2020 16:38:56
486 forum posts
13 photos

Hi Pete. W01 and W02 ribs are recessed by about 2mm to allow the spoiler to drop into the frame. With the 2mm frame thickness they should be flush with the upper surface of the wing when retracted. The spoiler should be sanded slightly to blend in with the aero foil. It isn’t very clear on my earlier post unless you expand the picture. I’ve covered the centre section now and am trying to get the spoiler to extend and retract fully. I’ll take a picture and explain.

Sussex Pete23/01/2020 18:05:57
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29 forum posts
19 photos

Thanks Buster. This is clearly my Doh! moment on the meaning of "Short Kit" - time to hit my balsa logpile for the other bits 8-)

I like your tip about supporting the covering around the bolt holes. Have you managed to get the spoiler servo linkage sorted?

buster prop23/01/2020 20:02:25
486 forum posts
13 photos

Ah yes, the spoiler. Getting it to work took some time. I made a pushrod from paper clip wire so that it could be bent to a length and shape that would completely open and shut the spoiler. At first I used a servo tester with the servo wedged between the W01 wing ribs at the centre, as in Ton’s picture and temporarily hinged the spoiler with Sellotape. Trying to get enough ‘up’ movement as well as closing the spoiler completely didn’t work so I used a longer horn on the servo. Better, but the pushrod was binding against the spar and lifting the front edge of the spoiler when closed. There’s very little room in there so I bent the wire to raise it away from the spar. Then it was binding at fully open, against the spoiler frame. Filing a small notch and moving the servo fixed that but it was buzzing at fully closed. After that I used the radio instead of a servo tester so that the servo’s movement can be adjusted for each direction at the Tx and finally got the spoiler opening and closing completely with no binding or servo-buzzing. I’m working it from the throttle stick on the Tx rather than a switch because it might be useful to have proportional control. A small Alturn servo from the spares box fits. Getting the spoiler right has probably been the most difficult part of building the RES-Eagle. It works now, closes completely and just about enough ‘up’. Flight tests will tell. You can see the completed fuselage. Getting there!img_5851.jpg

Sussex Pete02/02/2020 10:35:11
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29 forum posts
19 photos

Thanks again for the details Buster. My club-mate and I have decided to put the spoiler servo behind the spar to get a bit more room. Here's a sketch of my plan:

res-eagle spoiler servo and horn.jpg

With a "9g" servo glued to one centre rib I can just get a 9mm arm on it between the ribs which gives about 10-12mm of linear throw. A 14mm horn hooked round the spar a bit should give me 45 deg of spoiler angle which should be plenty to stall that part of the wing. The compromise is the servo hangs a bit further into the fuselage than the forward position but I couldn't see how to fully bury it in the wing without entirely redesigning the centre section!

I am also concerned about two risks of high-speed flight on bungee: spoiler suck-up and flutter. Following an idea from my fellow builder, I laminated the spoiler blade from 2.5mm balsa with the grain span-wise over 1.5mm with the grain fore-aft. This is nice and stiff but I still might add (also from my friend's ideas!) torsion springs to keep the ends down.

20200201_150622.jpg

20200201_150610.jpg

Several people mentioned flutter so I reached for my trusty copy of Martin Simons' "Model Aircraft Aerodynamics" which has this to say (in section 13.9 Flutter). He says the general solution is to stiffen the wing against twisting, then goes on in detail:

"If the torsional axis of the wing, i.e. the line around which the outer panels twist, lies ahead of the wing's centre of gravity, flutter is sure to occur at some speed. The stiffening should be added to the leading edge, usually in the form of sheet balsa covering and vertical spar webbing, to produce a 'D' shaped torsion tube. The extra weight added near the leading edge also helps to bring the centre of gravity nearer to the torsional 'hinge' line. This is in effect a partial mass balance. Other forms of stiffening, such as diagonal ribs, or (as in some older types of wooden full-sized aircraft) by twin spars with diagonal strutting internally between the spars, is less effective because it does not move the centre of gravity of the structural members forward. "

So flutter occurs when the effective mass of the wing is being the twist "hinge" line and the solution is to stiffen the structure and move the component's centre of mass forward. Twisting the RES-Eagle main wing section by hand puts the hinge line pretty dead on the main spar, and it's clear the wing alone balances behind the spar. Stiffening the spar itself (i.e. with the 6mm CF tube) therefore only partly helps. I will be adding some webbing between spare and the leading edge for the ply rib pairs that carry the wing-joining tubes on the main section and the tips to try to further stiffen the panel ends.

Separately, has anyone added any wash-out on the outer tip sections?

Sussex Pete02/02/2020 18:18:40
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29 forum posts
19 photos

Sorry, typos! Should read "So flutter occurs when the effective centre of mass of the wing is behind the twist "hinge" line"

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