Preventing a plane from being a tail sitter.

Thanks for the great tips.  I recently had to open up the deck under the windscreen of my f84 for this.  I have also used clear sprue for tail stand when I totally screwed up.  

The AMT F7F tigercat kit came with a barrel and a crate for the tail stand.  Creative

JohnnyK

Adding weights to the engine nacells does not work very well because the weights are too close to the landing gear.

Sometime, though, you need that extra little bit.

An old buddy of mine would make impressions of the insides of engines, nose areas, and the like and use those to make molds and casting lead to use as form-fitting wieghts.

Knew of a fellow who would set up the main portions of the engines and make moulds and then cast the bodies in Lab Metal or Brittainia (very low and low temperature).

Where there is a will, ther eis a way.

keavdog

Thanks for the great tips.  I recently had to open up the deck under the windscreen of my f84 for this.  I have also used clear sprue for tail stand when I totally screwed up.  

The AMT F7F tigercat kit came with a barrel and a crate for the tail stand.  Creative

 

If you put the model on a base, you can pin the nose wheel to the base.

JohnnyK

 

I am currently working on a Monogram 1/48, B-25. This has a tricycle landing gear setup, and the instructions indicate that a crew ladder is to be used to hold up the tail of the model. I do not like that solution, so I'll be adding weights to the nose to prevent a tail sitter. Unfortunetly, most model manufacturers do not include weights, nor do they indicate how much weight is required to keep the nose down. Tamiya does include weights on some of its models. 

 

Now, the big problem is determining just how much weight is required to prevent a tail sitter. I could just guess, but what happens if I underestimate? I would like to share a pretty much fool-proof way of determining the required amount of nose weight.

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I always use a Sharpie to write the word "weights" on the inside of the nose of my models. That way I won't forget to add weights before I button up the fuselage. I did that once, never again.

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Next I find places to install solid weights, such as Pinewood Derby weights that can be purchased at Home Depot. In this case, the weights were installed under the deck of the flight crew. I taped the weights in place using aluminum duct tape. I find the tape to be more secure than exopy.

 

To test if the weight that I added is enough weigh to prevent a tail sitter, I assemble the entire model using tape. I place a support (red arrow) under the aircraft in the location of the landing gear and watch if the nose goes up or down. In this case, the nose went up, so additional weight is required.

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I determined that I could locate additioinal weight in front of the cockpit, so I added lead fishing sinkers into a small plastic bag in front of the cockpit until the nose drops down. Then I add additioinal sinkers just for luck. The weight bag will be shoved into the plane's nose cone. The location of the weight bag varies with the type of aircraft. This aircraft is a B-25 straffer, so it has a solid nose. If it was an earlier B-25 with a glazed nose I would have to locate the weights in a different location. For example:

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I located the solid weights under the flight deck and the weight bag behind the pilot/copilot's bulkhead of my B-29. Once assembled, the weight bag was not visible.

 

On my B-24J (nose turret version), the solid weights were located in front of the wheel well and the weight bag was located behing the wheel well.

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On my F-104, the weights were located behind the flight deck.

One final thought, try to locate the weights as far forward from the main landing gear as possible. The closer the weights are located to the landing gear the more weights will be required. Adding weights to the engine nacells does not work very well because the weights are too close to the landing gear.

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SO, what happens if you goof and don't add enough weight? That happened to me with my P-38. After I assembled the entire model and installed the landing gear the plane sat on it's tail. My only option was to drill a hole in the front of the nacell and pour white gue into the hole. Next I poured small fishing sinkers into the hole until the nose of the model dropped down.

 

 

 

That is pretty much how I determine the weight also, although I do not actually stick the main gear on.  I mark on the fuselage where the main gear go, and balance it on a large dowel at that point.

Sure do like it when the kit mfgr does indicate how much weight!

One advantage of modeling tail-sitters. I have never had a tail sitter sit on nose, even without adding tail-weights :-)

I also do not install the landing gear when calculating the required amount of weight. I put a rectangular sanding block under the fuselage at the location of the main gear (red arrow in my photos). I used to  use a dowel, but the airplane would roll around too much. I really liked building my B-17. I  didn't use an ounce of tail weight.

Thanks Johnny. This is great info. I had that happen on my Accurate Miniatures B-25 and they even supplied the weights.  I infor had to used the pin in the nose wheel trick. 

I was starting a Minicraft Cessna 172.  It had a very nice engine.  But the instructions said if you installed the engine there was not enough room for weight in nose, so they included a strut to hold up tail.  You had the choice, nice engine or strut

A nice engine cast in pot metal would be a great third party add-on, but doubt if there is enough demand.  Maybe I should build another, make an RTV mold, and cast in that low temp metal that Micro-Mark sells.

I raided my reloading supplies for the monogram p 38 I built and used 380 caliber 100 grain bullets for my weights, sorry I can't remember how many. I never have made any calculations though. I just added them until it sat properly.

what I do---

All planes should balance close to the leading edge of the wing. Dry fit major parts with sticky tape----tape enough weight to the nose to get plane to balance with your fingers under the wings-- then add a tad more.

For weights go to gun store and buy Speer muzzle loader round bullets---32 or 36 caliber.

Take a few and smash flat with hammer--they are soft. Cut up into small pieces aand glue until the plane balances in the right place

Andy

I've used 2-part epoxy putty to hold BBs in place, too.

GMorrison

If you put the model on a base, you can pin the nose wheel to the base.

Hi;

 What I usually do on tri gear planes is this. I put a finishing nail in the gear holes and add weight till the plane balances. Then I add a few more to guarantee a sure thing nose sitter. Then I take the weight material( Lead weight sheets.) and fold and hammer to shape and drop in the spaces it will fit.

Don;

     I found that if you add weight to the plane under the instrument panel and under the engine in the lower cowl area this works most of the time. Sometimes, as in the case of the old Monogram kits you can even fit some weight,( A very finite amount ) under the molded instrument panel top.

    I also take sheet weight material and shape it to the inside leaving it hollow. That way if it needs more then here come the B.Bs and Elmers carpenters glue. Not the regular Elmers!

Wirraway

Having trouble with the Revell B25 at the moment. I filled the bombardiers access and underneath the cockpit floor with steel BB. Maybe I should have used lead weights instead. she is still sitting on her nose.

 

the Baron

 

 

GMorrison

If you put the model on a base, you can pin the nose wheel to the base.

 

 

 

 

Or use a fine bolt, too.  If the nose wheel is injection-molded in left and right halves, you can catch the bolt head between them, and then insert it through a hole in the base.

 

I used a small pin...clipped off a paper clip. This is CAed into the base, at a forward angle. I drilled a corrosponding angle into the nose wheel. The angle will keep the model in place, without having to glue the model to the pin. Model is easily removable for transport or cleaning.

Wirraway

Having trouble with the Revell B25 at the moment. I filled the bombardiers access and underneath the cockpit floor with steel BB. Maybe I should have used lead weights instead. she is still sitting on her nose.

 

Weights can be added under the flight crew floor and behind the flight crew bulkhead.

As a last resort, weight can be added inside the engine nacelles. Add the weight as far forward as possible.

JohnnyK

 

As a last resort, weight can be added inside the engine nacelles. Add the weight as far forward as possible. 

Pennies fit nicely...and they're cheap!!!

If the plane is really tailheavy, there may be a problem packing it with pieces- something called the packing factor.  Spheres are the best example.  If you pack spheres, like BBs, in an arbitrary volume, the density will be a certain value less than the solid density of the material.  The strange fact is that that density will not increase by using smaller spheres.

I have learned an easy way to pack available volume with solid metal (lead or any of the low melting temp metals).  I carve a little block of wood to fit as well as practical in some volume in the nose.  Then I use the carved block to make an RTV or plaster mold.  I bought some of that low-temp casting material that Micro Mark sells, and have cast several nose weights that way. Many years ago I bought a toy soldier making kit that came with a little electric pot to melt lead and other low-temp metals.

Not nearly as easy as when the mfgr supplies a cast metal weight, but handy when nothing else works. I am thinking about using that on second attempts on some of the Minicraft 1:48 lightplanes, using the kit-supplied plastic engine to cast a metal one, and eliminate the tail rod.