Go Back  RCU Forums > RC Airplanes > Kit Building
Reload this Page >

how do you fasten lead weights to model

Kit Building If you're building a kit and have questions or want to discuss kit building post it here.

how do you fasten lead weights to model

Reply

Old 08-23-2017, 04:21 PM
  #1  
YellowBlueBird
Thread Starter
 
Join Date: Oct 2007
Location: raleigh, NC
Posts: 265
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default how do you fasten lead weights to model

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
YellowBlueBird is offline  
Reply With Quote
Old 08-24-2017, 03:29 AM
  #2  
TomCrump
 
TomCrump's Avatar
 
Join Date: Apr 2003
Location: Traverse City, MI
Posts: 7,609
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

I use Goop to adhere lead weights. https://www.amazon.com/Amazing-GOOP-...SIN=B008AF1NHQ
TomCrump is offline  
Reply With Quote
Old 08-24-2017, 03:43 AM
  #3  
RCFlyerDan
My Feedback: (51)
 
RCFlyerDan's Avatar
 
Join Date: Apr 2002
Location: Cape Coral
Posts: 1,459
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

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.
RCFlyerDan is offline  
Reply With Quote
Old 08-24-2017, 06:23 AM
  #4  
Hydro Junkie
 
Join Date: Nov 2004
Location: Marysville, WA
Posts: 7,584
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

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
Hydro Junkie is offline  
Reply With Quote
Old 08-24-2017, 07:35 AM
  #5  
Rafael23cc
My Feedback: (6)
 
Rafael23cc's Avatar
 
Join Date: May 2002
Location: Junction City, KS
Posts: 2,955
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

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
Rafael23cc is offline  
Reply With Quote
Old 08-24-2017, 07:41 AM
  #6  
Hydro Junkie
 
Join Date: Nov 2004
Location: Marysville, WA
Posts: 7,584
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Originally Posted by Rafael23cc View Post
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
Are you thinking off balanced prop or spinner?
Hydro Junkie is offline  
Reply With Quote
Old 08-24-2017, 11:50 AM
  #7  
RCFlyerDan
My Feedback: (51)
 
RCFlyerDan's Avatar
 
Join Date: Apr 2002
Location: Cape Coral
Posts: 1,459
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

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.

Last edited by RCFlyerDan; 08-24-2017 at 12:09 PM.
RCFlyerDan is offline  
Reply With Quote
Old 08-24-2017, 12:15 PM
  #8  
daveopam
My Feedback: (9)
 
daveopam's Avatar
 
Join Date: Oct 2002
Location: ELK CITY, OK
Posts: 7,440
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

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
daveopam is offline  
Reply With Quote
Old 08-24-2017, 12:20 PM
  #9  
RCFlyerDan
My Feedback: (51)
 
RCFlyerDan's Avatar
 
Join Date: Apr 2002
Location: Cape Coral
Posts: 1,459
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Originally Posted by daveopam View Post
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
David! Thanks for hitting the basics that the rest of us missed. As David said, always move everything you can to balance, then weight.
RCFlyerDan is offline  
Reply With Quote
Old 08-24-2017, 12:35 PM
  #10  
Rafael23cc
My Feedback: (6)
 
Rafael23cc's Avatar
 
Join Date: May 2002
Location: Junction City, KS
Posts: 2,955
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

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
Rafael23cc is offline  
Reply With Quote
Old 08-24-2017, 02:10 PM
  #11  
YellowBlueBird
Thread Starter
 
Join Date: Oct 2007
Location: raleigh, NC
Posts: 265
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

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
YellowBlueBird is offline  
Reply With Quote
Old 08-24-2017, 02:36 PM
  #12  
Rafael23cc
My Feedback: (6)
 
Rafael23cc's Avatar
 
Join Date: May 2002
Location: Junction City, KS
Posts: 2,955
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

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
Rafael23cc is offline  
Reply With Quote
Old 08-24-2017, 02:55 PM
  #13  
RBACONS
My Feedback: (3)
 
Join Date: May 2005
Location: Vero Beach, FL
Posts: 587
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

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.
RBACONS is offline  
Reply With Quote
Old 08-24-2017, 07:06 PM
  #14  
YellowBlueBird
Thread Starter
 
Join Date: Oct 2007
Location: raleigh, NC
Posts: 265
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

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
YellowBlueBird is offline  
Reply With Quote
Old 08-25-2017, 04:25 AM
  #15  
RCFlyerDan
My Feedback: (51)
 
RCFlyerDan's Avatar
 
Join Date: Apr 2002
Location: Cape Coral
Posts: 1,459
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Originally Posted by YellowBlueBird View Post
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
​Hello Jerry;To balance an aluminum spinner, you will want to permanently mark the spinner either on the inside or on the outside, so that you will always assemble it back the same way when changing out props. Put the spinner on your balancer and mark the low spot on the back of the spinner plate. Take the marked back plate and if you have a drill press, drill small dimples on the back of the spinner plate until balanced. It usually doesn't take more than a dimple or two, sometime three to balance the spinner. Of course a regular drill works too, just not as refined. This is the way I was taught, and like everything, there is probably more then one way to balance a spinner. ​​Just a suggestion on the prop, this same technique works for it too. Especially the carbon fiber props. Drilling the back of the hub area. I never add to a prop. I am now sure we are going to get into a discussion on prop balancing too. I personally sand the back of the prop for a wood prop, so as to not change the airfoil and drill dimples in a carbon fiber prop, . Never sand the tip, leading or trailing edges. Again, everyone does it different, and not everyone uses a correct procedure.
RCFlyerDan is offline  
Reply With Quote
Old 09-11-2017, 11:14 PM
  #16  
YellowBlueBird
Thread Starter
 
Join Date: Oct 2007
Location: raleigh, NC
Posts: 265
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

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.
YellowBlueBird is offline  
Reply With Quote
Old 09-12-2017, 09:16 AM
  #17  
Rafael23cc
My Feedback: (6)
 
Rafael23cc's Avatar
 
Join Date: May 2002
Location: Junction City, KS
Posts: 2,955
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Originally Posted by YellowBlueBird View Post
....... 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.....
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
Rafael23cc is offline  
Reply With Quote
Old 09-12-2017, 01:28 PM
  #18  
YellowBlueBird
Thread Starter
 
Join Date: Oct 2007
Location: raleigh, NC
Posts: 265
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

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.
YellowBlueBird is offline  
Reply With Quote
Old 09-12-2017, 03:34 PM
  #19  
Doog-meister
 
Join Date: Jan 2006
Location: Colorado Springs, CO
Posts: 76
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default Weight?

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.
Doog-meister is offline  
Reply With Quote

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service