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[Motorman]

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[Brett Buck]

I did a search and found the balance point should be 2-3/4" and mine 3-3/4". I must have gotten the heaviest ARF to come out of China. I made a big acorn prop nut out of brass (2.5 oz.) and that brought me to 3-1/4". I hate adding a ton of weight the the shaft and it's not enough anyway.

After some weight and balance work, I find I have to add about 5 oz. of lead right behind the engine. Is that allot?

I'm thinking of doing something radical like demate the wing and move it back. If I took out the engine and put in an electric system would that be heavier?

Thoughts and suggestions always welcome.

    Unfortunately there's no real good option to adding the necessary weight. There's no trim trick that will correct the CG being misplaced. Moving the wing back will shorten the tail moment in addition to moving the CG. But that's such a serious change that you would be better off making a new fuselage, at which point you could correct the CG and some of the weight issue a the same time.

    A some point you have to consider just "punting" as well. It pains me to say it but by the time this is sorted out you may end up with something that is nearly unusable, OR, take more time fixing it than it would take to build a replacement.

    Brett

[Balsa Butcher]

Both have comparable power IMHO although the B-40 is more user friendly.  Nonetheless the LA-40 would help your CG situation, especiallyl with a stock muffler. My late-great kit built Vector had an FP-40 and had plenty of power. Have you examined the elevators? If they are made out of surplus Sterling balsahogony you may want to consider replacing them. A lighter set could be made with a minimum of effort and as they are about as far back as you can get on the fuselage weight saved there would make a diffence in nose weight needed to balance.

[Joe Yau]

I built an ARF Vector with a Brodak 40. I followed the plans very carefully since I've never done flaps before but it came out very touchy on the controls. The speed of the controls seems normal to me. I adjusted the handle several times and got down to 3" spacing and now it's sluggish and stiff when you first go into a loop then it all of a sudden over rotates. It's a handful to fly.

I did a search and found the balance point should be 2-3/4" and mine 3-3/4". I must have gotten the heaviest ARF to come out of China. I made a big acorn prop nut out of brass (2.5 oz.) and that brought me to 3-1/4". I hate adding a ton of weight the the shaft and it's not enough anyway.

After some weight and balance work, I find I have to add about 5 oz. of lead right behind the engine. Is that allot?

I'm thinking of doing something radical like demate the wing and move it back. If I took out the engine and put in an electric system would that be heavier?

Thoughts and suggestions always welcome.

MM

Are you running the stock muffler? or a tongue muffler.  The stock .46LA muffler weights about 2.8oz.

[RandySmith]

I built an ARF Vector with a Brodak 40. I followed the plans very carefully since I've never done flaps before but it came out very touchy on the controls. The speed of the controls seems normal to me. I adjusted the handle several times and got down to 3" spacing and now it's sluggish and stiff when you first go into a loop then it all of a sudden over rotates. It's a handful to fly.

I did a search and found the balance point should be 2-3/4" and mine 3-3/4". I must have gotten the heaviest ARF to come out of China. I made a big acorn prop nut out of brass (2.5 oz.) and that brought me to 3-1/4". I hate adding a ton of weight the the shaft and it's not enough anyway.

After some weight and balance work, I find I have to add about 5 oz. of lead right behind the engine. Is that allot?

I'm thinking of doing something radical like demate the wing and move it back. If I took out the engine and put in an electric system would that be heavier?

Thoughts and suggestions always welcome.

MM

Hi MM
Do not run it at 2 3/4 inch, it will fly much better at 3 to 3/1/4 inch, measured back from LE at the center of the wing, this will be close to the high point of the airfoil at the root rib.
Your controls should be 4 inch bellcrank, drilled with an output arm of 3/4 inch, the pushrod should then go to 1.25 inches on the flap horn, then 1 to 1 back to the elevators.
If you need help you can call. 678 407 9376,  the LA 40 or 46 may be better to run with the additional weight and larger props.

Randy

[EddyR]

Motorman, you did not mention the total weight. It it weighs 40 ounces and needs 5 ounces of weight that is still a light plane. It it weighs 50 ounces and needs 5 ounces then it will be to heavy. So adding 5 ounces means nothing unless you tell us the total weight with and without the added weight. Mine flys very well at 52 ounces with a ST/46 and .018 62 ft lines
Ed

[Steve Helmick]

The OS .40LA doesn't run all that badly if you get the setup right. Add a head gasket, a good hot glowplug, 10-22 and a TT Cyclone 11 x 4.5 prop, with the stock venturi (about .265/.272). This engine is fussy about being loaded with too much prop.  Whatever muffler helps get the CG right will work fine.  Steve

[Brett Buck]

I wish I had a scale to measure it with.

I saw in another thread you recommended 2-7/8" but 3-1/4" is good news, I can get that with my heavy hub. Maybe there's a range for personal preference?

MM

   Don't worry too much about it at this point, just put the nose weight in there, no matter how much it takes, and then see how it works.

   Brett

[Randy Cuberly]

Uuuhhhhh...
I would be very inclined to listen to Randy Smith about this situation.  He is after all the designer of this airplane and has probably seen and flown more of them than anyone else, and at a diversity of weights etc..
Do what he says...The LA 46 is definitely the best choice for a powerplant for this airplane.
With the stock muffler it weighs about 10.5 ounces and runs very well, and is very easy to use!
Put the CG and control functions where Randy Smith said!!!

I've flown two of these (that belonged to other people) and they both balanced on about the high point of the wing and after minimal trimming flew very well.  Both had LA46's with 11.5 X 4 APC props.

Try it you'll like it!!

Randy Cuberly

[RandySmith]

Yes we know. I've seen him recommend different balance points that's why I'm a little confused.

Hi Motorman

The CG can be a little forward or back depending on who is flying the plane, how it is setup, what size handle they are using etc.. the optimal point is shown on my plans and is right in the 2 7/8 to 3 1/8 range. ( I USE 3 Inches when I setup these for my use) You can go back a little further if you have to, but you do not need to try to put the CG at 2 3/4 inches or further forward, that is what I was trying to tell you. This is measured at the center rib from the LE.
If you want to measure from the TE it will be right at 6 3/4 inches

Randy

[Doug Moon]

Just a note here, heavy hubs are not the same as added nose weight.  That spinning weight can cause some VERY unwanted effects.  Some of which you describe.  Input input input then all of a sudden it comes around way to fast.  

It is better to just hammer out some lead weight nice and flat and put it in under the engine in the top of the nose.  I use silicone for the initial tests to make sure its the right amount then epoxy in place.  The actual amounts mean nothing at this point.  Just use enough to get it where it needs to be to fly correctly.  Heavier with the CG in the proper range will fly better than lighter with it in the incorrect range. 5oz is bunch of weight!  If it were me and the B40 was the only option I would first add 2.5 oz under the motor and remove the heavy hub and start there.  Heavier prop nuts or washers can help even out the fine trimming but too much and its very counterproductive.

LA 40 is a good choice if you have that option. APC 11x4 in a wet 2cycle on the ground and you are good to go.  LA 46 is also a good choice and swings a bit bigger prop, stay with the flatter pitches in a wet 2cycle and its flip and fly. Its not a 2-4 breaking motor so dont try to run it that way.  All you need is a couple of beeps in level flight and it will stay cool enough to make plenty of power all the way through.  This is actually a very preditcable way to run it and the flatter pitches and higher rpm are much less prone to whipping up in the winds. 

The nose weight needed will be minimal with the motor change.

You also want to put the handle spacing back to a normal range, I would start with 4".

I would not persue moving the wing back.  As BB said this changes everything. And I think it would most likely not be for the better.

[Joseph Lijoi]

Just a note here, heavy hubs are not the same as added nose weight.  That spinning weight can cause some VERY unwanted effects.  Some of which you describe.  Input input input then all of a sudden it comes around way to fast.  

It is better to just hammer out some lead weight nice and flat and put it in under the engine in the top of the nose.  I use silicone for the initial tests to make sure its the right amount then epoxy in place.  The actual amounts mean nothing at this point.  Just use enough to get it where it needs to be to fly correctly.  Heavier with the CG in the proper range will fly better than lighter with it in the incorrect range. 5oz is bunch of weight!  If it were me and the B40 was the only option I would first add 2.5 oz under the motor and remove the heavy hub and start there.  Heavier prop nuts or washers can help even out the fine trimming but too much and its very counterproductive.

LA 40 is a good choice if you have that option. APC 11x4 in a wet 2cycle on the ground and you are good to go.  LA 46 is also a good choice and swings a bit bigger prop, stay with the flatter pitches in a wet 2cycle and its flip and fly. Its not a 2-4 breaking motor so dont try to run it that way.  All you need is a couple of beeps in level flight and it will stay cool enough to make plenty of power all the way through.  This is actually a very preditcable way to run it and the flatter pitches and higher rpm are much less prone to whipping up in the winds. 

The nose weight needed will be minimal with the motor change.

You also want to put the handle spacing back to a normal range, I would start with 4".

I would not persue moving the wing back.  As BB said this changes everything. And I think it would most likely not be for the better.

I don't neceesarily think that since the weight is so close to the center of rotation that it has as much effect as a heavy prop, but those heavy hubs are a bad ided for a lot of reasons and potential reasons.

Here is an idea.  Get additional backplate for your LA40.  If these are plastic mix up some lead shot and jb weld and make a lead tapioca pudding and pour this into your backplate.  If your backplate is aluminum you can melt lead right in it it to make a lead slug and jb weld that in.  You can make a tin cover or safety wire using the backplate screws if you feel the need.  For example a backplate for an Evo 36 is like three bucks.  I have two Evo 36's and four backplates.  One of them probably weighs five ounces and looks ridiculous.  Set up the airplane to the designers specs and don't worry about the weight.  Don't alter the design.  It is well proven and although I don't have any experience with it there are probably some guys flying this design well even if they are heavy.  Randy Smith would know.

[Prentice D. Hill]

Randy just wanted to say your design of the Vector 40 is a great plane. Built mine with OS LA .46 cover in monokote and trimmed in the same. No weight added to nose or tail balance is dead on the plans 3 1/8 center rib or 2 7/8 at the wing tips. Just wish there was a Vector 60.

Thanks again 

[RandySmith]

Randy just wanted to say your design of the Vector 40 is a great plane. Built mine with OS LA .46 cover in monokote and trimmed in the same. No weight added to nose or tail balance is dead on the plans 3 1/8 center rib or 2 7/8 at the wing tips. Just wish there was a Vector 60.

Thanks again 

Thanks
There is a Vector 51, the original Vector works great with a ST 51 sized motor. as far as a Vector 60, a  SHRIKE is  very very close

Randy

[Tim Wescott]

MM:

No one's given you the symptoms of a tail- or nose-heavy plane.

So do a search!  In the mean time, here's my attempt, subject to correction by experts:

Tail heavy planes will:

• Not track well in level flight
• Really slow down when the engine cuts out, and be difficult or impossible to whip effectively
• Be very sensitive on the controls

The tendency to tighten up in maneuvers that you report is, I think, a tail-heavy symptom, too, but I'm not standing behind that one until I'm smarter.

Nose heavy planes will:

• Be "heavy" in maneuvers
• Track really well in level flight (assuming everything else is right)
• Whip very easily, particularly if they're heavy overall

So to some extent you should probably mess around with the CG, within the limits that Randy's mentioned, and see what you like, keeping in mind what the CG will do to you.  I think it's been said already, but get the CG where it belongs first, then decide if the plane is too heavy.

[RandySmith]

The best way to go about this is to put the CG where it shows on the plan, I posted the center part of the plan that shows the CG location. Then trim to suit, set your spacing on the handle. and if you change anything to make the plane more forward or rearward, you started at the correct place. This will make it much easier to trim.
Look above in the thread and you can see where the CG is supposed to be , shown at the root rib.
If you go this way, you do not have to figure out if it is too nose or tail heavy.

Randy