Balancing the Beast

Bob,

This should get you in the ball park. I think you are a little aft of where you should be.



You could very well be correct about the engine. CL planes require more oomph to drag lines around. If you just plan on flying level laps it may be fine though.

Ron

Way too far back.  Without the dimensions and wing areas, I couldn't give you more specifics, but just looking at the pics, I'd guestimate the balance point should be just ahead of the lower wing leading edge.  I like to balance my control line planes at 20% chord to start, then adjust from there.  Just going by the pics, I'd say to start at about the 25% chord of the upper wing.  But that's just a guestimate from the pictures.  It also looks like there's a lot of positive incidence in the upper wing compared to the lower wing?

The Out of His Hat Mark

edit: Man! there are a lot of guys looking at this forum early on a Sunday morning. Two replies between the time I started writing my reply and posting it. Ron, that drawing is good, but the lower wing is so much smaller than the top that I'd think the balance point would be farther forward than just faring a line between the two c.g. points.

Yes, it seems like the angle of incidence (aka angle of attack) is out of whack on this model when compared with my Nieuport 28's and pictures of German planes of the era.  It looks greater than it should be.  But, I have not wanted to tinker with those struts or wing saddles until I was sure, Ron's picture should help.

The plans type is difficult to read and is out of focus but it looks like the balance point should be right above the front strut.



Looking at the AOA on the plan, against the AOA on the plane, it looks like the planes angle is a bit more severe. But I have reason to believe that the original builder flew it as it is, so it may be ok.

I have some stick on lead weights, I will have to remove the engine and make space for them ahead of the engine then tack them in incase I want to install the .15 later.  

Bob

It may no be suitable for all model aeroplanes but I find this stuff very versatile.

Eric mentioned you having a muffler for the .09.. Will it fit? It may not be the best way to add weight to the nose though. If it's under-powered for control-line.. that will make matters worse. How about a "Harry's Heavy-Hub" prop-nut? The wood prop looks nice.. but they're are heavier props you can try.

Do the .09 and .15 share the same mount-pattern?

Does the top wing still have dihedral? Not sure how/if that affects control-line flight.

Thanks roddie,  There is no dihedral in the top wing, I didn't build any into it because the plans don't show it and the wing saddles were built flat.  But I think it was designed for dihedral or should have been.  Flying C/L it should make no difference.

The .09 has a tighter mounting hole pattern than the .15 but I can get by that.  The problem is - even with the larger engine, prop nut, and all the stick on lead weight that I have it still balances tail heavy, a mystery to me as there has to be less tail weight than before.  But there is no battery sitting up front either.  





Perhaps if I stick to the .09, add all that nose weight, add some engine down thrust and a full tank of fuel, that will help?
Come to think of it, there was considerable down-thrust built into that .09 when I got it.



The muffler/exhaust on the .15 is on the "wrong" side.  I would have to remove some balsa from the right side or it would restrict the exhaust while the .09 is fine in that regard.  

Bob

Sorry Bob, I forgot that you built a replacement wing. The weight-distribution thing is often an issue with conversions. Like you said; there's no battery/servos (wherever they were located..) but fuel weight goes away.. so make sure you're well-balanced dry. I don't recall what you used for wheels.. (they look great.. btw) but if they're for an electric model, they're probably much lighter than what was on there.. or designed to be on there. You could pick-up some functional weight forward by going to a heavier set. The old set looks like they might have been Trexler inflatables? If you still have them, you could weigh the hubs for comparison.

Bob,

You don't want or need any down thrust, it won't counteract a tail heavy issue. It will make things much worse. It may be best to just go with the .15.

With high lift wing platforms when the engine is at speed the excessive lift will have it climbing hence engine down thrust.
Once the engine stops your in cherry mode for a sweet landing or if in idle.

Cribbs is spot on..
For tail heavy planes its lead time, or more engine, or extend the engine mount, or heavy brass spinner nut.
Wouldn't it be nice to put a .10 size 4 stroke on the nose, the added weight would be perfect and the sound..

Well, calling up the plans from Outerzone and expanding them on the screen, I took a ruler and measured the c.g. at the upper wing. I expanded the upper wing chord to 21cm (I was aiming for 20, but oh well.), and measured the c.g. as 5.5cm from the L.E., for a position of 26% of chord. Call it 25%. But, control line planes fly with a farther forward c.g. than RC planes do. So I'd still say start at 20% chord and move it according to flight experience.

The Thumb Ruler Mark

Thanks guys, but my ignorance is showing.  Hasn't down thrust always been used to counter lift as lift is related to AOA?  

1/2 A - It seems like your first paragraph counters the second.  This flat bottomed high cambered wing should generate a lot of lift.  My thought on this is to have a model that hangs on the lines and generates just enough lift to keep it in the air because I tend to get dizzy.  

But I yield to your greater experience and common sense and will add enough nose weight to offset the heavy tail and forget about off-set.  I'm thinking about using those wheel weights which are marked in 1/8th" increments and if enough imagination is used could resemble exhaust manifolds if placed on the fuselage under the engine on each side as far forward as I can put them.  I can inlet the fuselage sides and epoxy them in.  There is just not enough space under the engine for all of them and I need to place them as far forward as I can.  If someone has a better idea please chime in.  I'm not eager to trash up this project.  



Boy, I would love to find a .10 sized four stroke, but the smallest I have found is 26 sized.  That would be fun.  I have a 46 Enya four stroke, but it swamps the Aircrate.  But it does look great.  



I may look into Ian’s “Liquid Gravity” solution as well.  I watched the video and loved the narrators accent.  Also it would work well as depicted on my model railroad rolling stock.

I appreciate all the comments and extra miles that everyone here has contributed.  Thanks Mark for going to the trouble of looking up the outerzone plan and figuring the proper CG.

I really want this model to be successful.  I will probably tag my son with it’s first flight on some soft field with tall grass.  But it will also have to ROG.  If I can figure out how to use his smart phone I should have video.

Oh yes,  Those wheels are new Williams bros. 3 1/8 inchers from Tower.  I had been using the 35 year old wheels off my N-28 but the tires are hard and worn from many landings on tarmac.  
Bob

Those strip-weights.. can you easily access the tank compartment? I see hatch-screws. Could you possibly tuck a pair on each side of the tank forward; just behind the firewall.. wrapped in foam-rubber padding? (no cutting/gluing into the nose needed) That plus a heavy-hub might put you in the ballpark.

According to the Harry Higley site, the Enyas .09-.11 have a 5 x .8mm prop-shaft.. for which they make a heavy-hub.. (HVY005)

Harry Higley

Any chance you can REMOVE weight from the tail section. I know this is a tall order, but carving out some wood might offset a lot of weight.

Phil

pkrankow wrote:Any chance you can REMOVE weight from the tail section.  I know this is a tall order, but carving out some wood might offset a lot of weight.

Phil

I have thought of that.  I did it once before when I removed the lightweight fillets on either side of the tail and replaced with standard spackling.  Not a big job.  Just a round router bit on a dremel and a couple of minutes then a couple of coats of sanding sealer and finish with lustrkote spray which blends in really well.  I used filler because the balsa around the tail was so rough.  I will just remove the filler and live with it.



The problem is time, the weather looks really good the next few days, then turns rotten again.  I never have been a patient person and I want to try this thing airtime.  But, I don't want to kit it again either, so here we go.

Yes roddie, I made the hatch removable, but the tank fills most of the forward area.  There is enough balsa in the nose under the engine that I can mill out, fill with those weights then spackle over and refinish, more time expended.  



I have ebays Bobby Brooks on the lookout for a small four stroke.  I love the idea, it just fits for this old timer.  He has an OS 26, but I'm afraid it's to large.  I think OS made a 20 too.  Is there a 10?  

Bob

Edit add:  Oh my, look at that.  I made Diamond member dispite my many boring posts.  A few thousand more before I catch up with most of you.  The charity of the administrators and the participants here knows no bounds.  

To late Eric...





Hogged it out and didn't even hit an artery.  





I also drilled two 2 inch holes on either side and filled with fishing line weights and cemented in place.



Not to worry.  I can't get this model to nose heavy.  I had the .15 on it along with all those wheel weights plus the fish line weights and it was still tail heavy.

roddie thanks for that link.  If I use the .09 I will order one of his brass heavy prop nuts.  But Bob Brooks says he may have a OS 20 four stroke, that may help solve my problem.

Bob