YellowBlueBird

My AMR stick from a kit now has about ten flights. There is a 700 gram lead weight fastened to the bottom of the fuselage behind the fire wall with two bolts. It tries to eat its way through the plywood. No other problems are occurring from the vibration so all else seems normal. A piece of foam padding between the plywood and the lead allowed enough movement that the bolt sawed an arc in the bottom of the fuselage during a four minute flight. Please give me some suggestion on how to fasten this weight to the model so that it will not cause trouble.

Jerry

TomCrump

I use Goop to adhere lead weights. https://www.amazon.com/Amazing-GOOP-...SIN=B008AF1NHQ

RCFlyerDan

My Feedback: (54)

Morning Jerry;
I think the foam between the weight and the plywood is the issue. Allows too much movement of the weight. Hard fasten with glue, double sided tape, and then the screws. Other things that I have done too is to install diver lead bb's inside the rudder. Simply drill a hole in the bottom of the rudder, fill with the bb in the amount of weight, then Monokote the hole shut. Other things that I have done is to glue the bb's in place with epoxy. First using the bb's rolled up in a small plastic bag or something, until you figure out the inflight balance point. Then, epoxy them into a place inside the fuse. You would have to drill or cut a hole, then patch it. Works great for in the nose too, especially if you have a tight area. The bb slurry can be molded to fit the area. I have used that technique in cowls too.

Hydro Junkie

I've seen, and used, a similar technique to what Dan was talking about. I've used stick on weights for initial balancing and, once the balance point was determined, I took off the stick on weights, weighed them in total, drilled out a piece of balsa and poured in lead fishing weights and epoxy until the combined weight was the same as the stick on weights. I then glued this in, giving a balance point just aft of the determined location and then rebalanced using internally installed stick on weights. A test flight or two to verify the set up and your done. I've found that, when using weight that is hard mounted in this manner, it's easier to set up the plane slightly tail heavy so that you can trim it to what you want with a minimum of additional weight

Rafael23cc

My Feedback: (6)

700 grams is 1.5 pounds! Yikes! I see two issues here, one the excessive amount of weight, and the excessive vibration that is making the weight move that much. So on top of the suggestions already given, you may want to find a way to reduce the ballast weight, and reduce the vibrations in your aircraft.

Rafael

Hydro Junkie

Are you thinking off balanced prop or spinner?

RCFlyerDan

My Feedback: (54)

If YellowBlueBird has a small engine on it, that amount of wt would be expected. Most of the sticks that I have flown have a G26 on them, which makes up for the wt. What engine are you using? Good catch on the balance of the prop, wasn't awake yet, and having first cup of coffee. The diver bb epoxy slurry I've used on scale planes/jets to help hide the wt. Great for tight spaces. Also for balancing laterally with block balsa wing tips. Drill into the balsa, put the slurry in, and patch with putty, epoxy and micro balloons, etc Put too much in or some flights down the road, you can still add or take the wt out with a Dremel.

daveopam

My Feedback: (9)

You got some great suggestions above Jerry. I have also zip tied lead strips to the motor mounts with success. I would also think about moving the battery and/or throttle servo forward to reduce overall weight. If the rudder servo is in the tail I would also think about moving it up with a pull/pull set up. I try and think of adding lead as a last resort. But sometimes you just don't have a choice.

David

RCFlyerDan

My Feedback: (54)

David! Thanks for hitting the basics that the rest of us missed. As David said, always move everything you can to balance, then weight.

Rafael23cc

My Feedback: (6)

I went to the AMR Website https://amr-rc.com/en_ca/airplanes/a...s.html?brand=8 and was greeted with no less than SEVEN stick models. From 84 inches of wingspan to 144 inches WS. While it _MAY_ be acceptable to have 1.5 pounds of ballast in the 144 inch monster, it would definitely not help in flight performance.

There is only one place where vibrations can come from in an airplane. THE ENGINE. While there may be little we can do to the engine itself, then we have to do the most we can do to the prop and spinner (depending on size) to alleviate the vibrations.

I am developing a sick feeling in my stomach. I've been around for a while and I can recognize the feeling. Someone may be over their head in their newest aircraft. A Stick is a far-far cry from a trainer. And one that needs 1.5 pounds to balance correctly is a very dangerous plane indeed.

I don't mean to insult anyone, I call them as I see them and I may very well not have all the information required. I apologize in advance and will modify this post if necessary.

Rafael

YellowBlueBird

The airplane is a low wing stick 30 with a DLE 35 RA with 19 inch prop. The prop is supposed to be factory balanced it is an xoar. The model fly's great and has tendency to be a floater when landing It all ways takes about all our 700 ft runway to get it on the ground. This is my first gas model so I did not know what to expect. It is not as agile as a Tarus but then it is not a trainer by any means. It does nice slow rolls when using low rate, with only ten flights and a problem with vibration I have not yet tried high rates. The wing area is 1470 sq inches.

I purchased two props at the same time. Last night I pulled out my prop balance and checked the second factory balanced prop. It will sit horizontal all day but if it is moved off the horizontal it will start to oscillate and settles at about 70 degrees off of horizontal. So much for factory balancing. The other one will be pulled of the plane and checked tonight.

Rafael, I am not insulted. This airplane is a different kind of bird. It is not a typical stick. It has an interesting cord to wing span ratio. The wings are very thick and really slow the plane down. Compared to some of my other models it feels like driving an old truck. It does what you tell it to do but it is not in a hurry. High rates may change that.

The rudder servo is just forward of the trailing edge of the wing, elevator servos are in the tail. If anyone else is building this plane it might be a good idea to put the elevator servos near the rudder servo.

Tom, gluing the weight in place sounds like the thing to do.

Thanks for all of the comments.

Jerry

Rafael23cc

My Feedback: (6)

Ok, here is my take based on the aircraft information. 1.5 pounds is a LOT of weight for an airplane that small. I would move much of the equipment as forward as possible to include servos even if I had to close off the "factory" holes. Moving equipment forward could include mounting the engine on "standoffs" to create the distance required. Changing to a different "heavier" engine is also an option. Bigger batteries, bigger servos, etc. I would try to exhaust all those options before adding dead weight to an aircraft.

I have built (from plans, kits and ARFs) many aircraft from the normal 40 size trainer, to my current 133-inch Citabria. I have yet to add more than a couple of ounces of dead ballast to an airframe. And as stated above, only add dead weight when I have exhausted all those options. I know that AMR is a reputable company, So I encourage you to look at the manual to make sure a step or component was not missed in the construction process. If not, that design could use some redesigning to make the nose forward of the wing a lot longer than it is now.

Rafael

RBACONS

My Feedback: (3)

I used to use epoxy to glue the lead down but now use clear silicone caulk. It grips tenaciously but can still be removed if you can slip a knife blade under the weight. Only down side is it takes a while to dry and smells vinegary while it dries.

YellowBlueBird

The propeller is slightly off balance. Just a bit of clear poly on one blade might do it for the prop. The spinner on the other hand spins toward the low side with some authority. This is most likely where the vibration is coming from. How do you balance an aluminum spinner?

Jerry

RCFlyerDan

My Feedback: (54)

YellowBlueBird

The propeller was balanced horizontally but when it was turned vertical it spun rapidly to the heavy side which put it horizontal again. I spent about two hours on four different days working on this thing. I simply did not want to believe what the balancer showed me. It took half a gram of lead inserted into a hole drilled in the hub near the edge to bring it to a near balanced condition. It now will rest in three different positions.

Rafael23cc

My Feedback: (6)

I think that you need to work on basic concepts of flight. The best flying airplanes are the LIGHTEST airframes. ADDING weight is NOT recommended if you can REMOVE it from somewhere else. I thought I was transmitting that concept, I obviously failed.

Nevertheless, i'm glad you are getting it figured out.

Rafael

YellowBlueBird

I considered taking away wood from the hub. After measuring the amount of weight needed to balance it the general consensus was that there would not be enough of the hub left to have the strength to hold the propeller together. It may not be safe as it is.

Doog-meister

Try moving the engine forward. You can put a firewall spacer or move the engine forward on a beam mount. Even 1/2" makes a HUGE difference. With a STIK, we're not talking about a close cowl fit. Good thing is, you can mock this up in the shop and see how much of that lead you can remove.