better landing gear surface enforcement?

[MaxSpeed]

hello guys,
i want to pick your brain and see if you have any tricks on making a strong surface to mount landing gear on. this is the only plane out my planes that is not forgiving on landing!! and by that i mean if i get just a little bouncy on landing, it will rip the bolts and crack the wood right out of my fuselage!!. i know that this is not supposed to happen, so let me know how would you solve this issue.

thanks.

[mclarkson]

Give us some more info. What plane is it? What's your current gear?

Often, the best solution is to make the gear itself more flexible, if you can, so that it absorbs the shock of landing and transfers less energy to the fuselage.

[Glacier Girl]

Ditto what Mark said, little hard to give advice without knowing the plane.

Is it stationary gear or retracts too?

And a follow up to Mark's advice, at least if it's a bounce problem, and not one say coming in too hot and slamming the gear into the pavement.

Look at the Piper Cub. It's gear is hinged to allow it to flex. The amount of flex is controlled by the bungees strung across the gear. This takes a lot of the direct shock out of the mounts and moves it to the bungees.

[solentlife]

If bolted - do away with steel bolts - replace with nylon.

If not scale or you don't mind the look - mount alloy plate legs by rubber bands to dowels instead of bolting.

Beware of strengthening / beefing up structure - it usually results in worse damage in event of U/C failure etc.

My thoughts without knowing what plane you are talking about.

Nigel

[MaxSpeed]

the plane is a discontinued item from hobby people they called it "Mad Dog" and thats what it looked like:

http://www.google.com/search?hl=en&s...tm%3B448%3B336

as far as the landing gear goes its a 2 piece fixed landing gear that mounts next to each other on the fuselage, made out of hard metal i am guessing, because it is stiff.

Thanks guys

[kyleservicetech]

Originally Posted by MaxSpeed

hello guys,
i want to pick your brain and see if you have any tricks on making a strong surface to mount landing gear on. this is the only plane out my planes that is not forgiving on landing!! and by that i mean if i get just a little bouncy on landing, it will rip the bolts and crack the wood right out of my fuselage!!. i know that this is not supposed to happen, so let me know how would you solve this issue.

thanks.

I've had a few ARF's that did that. If you have access to inside the model at the landing gear location, one option is to lay some 2 ounce or so fiberglass cloth on top of the LG plate inside the model. Run the cloth up the sides of the fuse. Then carefully "wet" the glass with epoxy. If the model has blind nuts, be prepaired to run a tap through the blind nuts to clean out the epoxy.

This does not add a lot of weight, but is stronger than heck.

If this is a very small model, try 3/4 ounce fiberglass cloth.

[hayofstacks]

X2.

I've found a lot of arf aren't as touch and go freindly as I like. Use nylon wing bolts and drill out the holes and add larger wing nuts to accept it. This will give you pretty sturdy bolts, but they will still break off in a bad crash/hard landing. Cover where the top of the nylon bolts poke into the fuse with vaseline, then lay down some epoxy.

[Dereck]

Assuming it's a wooden structure - that photo is a little fuzzy, but it looks wooden-ish

Go to local hardware store, buy a length of 1/2" or 3/4" alloy L section. Not too pricey, three feet long. Most big box stores stock it.

remove fuselage bottom from landing gear mount to firewall former. Cut two short lengths of L section - around 2" to 3" long - to fit with one face against fuselage insides, the other to line with with the fuselage sides' bottom edges.

If the fuselage sides are heavily perforated cheap plywood, consider a thin ply doubler around 1/2" wider all round than the L section and of decent birth ply, not liteply, to give a solid attachment surface.

Epoxy the L section pieces in place as per the attached photos.

Make a new fuselage bottom from 1/16" or 1/8" ply, glue into place - at least epoxy for the alloy to wood, then wood glue for the ply to ply joints. Epoxy all round will do though.

Drill through new fus bottom and alloy L section for UC - make new holes in UC mount region if needed. Shouldn't hurt. Epoxy T nuts to inside of L section alloy - turn T nuts over so blank face sits on L section.

Use 30 minute epoxy throughout, let sit to cure overnight.

I use 6-32 steel bolts, unless it's a lighter model when 4-40 will do. Some folk may advocate nylon bolts, both work but you'll want to use thicker nylon bolts.

At risk of being shouted at, this method cures that many ready-made models are not very well made in reality and failures such as you've experienced occur in high loading areas like UC fixings.

I work on the principle of the model will finish a landing with model and UC in tight formation. If that doesn't happen, it is re-defined as a crash Hence the steel bolts. This UC fix method was developed a long while ago, when I flew with 20 cell nicad batteries that weighed around 42oz and it was not unusual for a heavy landing to be followed by the model and the UC ending up in different places on the runway.

This alloy L section business fixed that. I now use it on pretty much all of my designs.

Hope that helps.

Dereck

[solentlife]

WOW Dereck !! You build Tanks ?

Personally - I am dead against really beefing up any structure - having done it myself previously and then paid the price of much greater damage to model as a result.

The model in question is a wood job ... and the most I would consider to add to structure is possibly a touch of Glass-fibre as Kyleservice suggested or ply pieces .... but then it would only be sparing so as not overdo it.

Nigel

[road king 97]

EPOXY ,joe

[kyleservicetech]

Originally Posted by solentlife

WOW Dereck !! You build Tanks ?

Personally - I am dead against really beefing up any structure - having done it myself previously and then paid the price of much greater damage to model as a result.

The model in question is a wood job ... and the most I would consider to add to structure is possibly a touch of Glass-fibre as Kyleservice suggested or ply pieces .... but then it would only be sparing so as not overdo it.

Nigel

One of my models used a similar small ply plate for the LG came loose. The wheel pants poked holes through the bottom and top of the wing.

That one was beefed up with a triangle shaped piece of 1/4 inch lite ply. The ply was epoxied to the top of the LG plate, and the "tail end" of the triangle piece of ply was epoxied to the next bulkhead about 4 inches to the rear of the LG plate. That added perhaps an ounce of weight, and along with that, supplied a LOT of torsion support that prevents the LG from twisting out its ply plate.

After four years, still flying that model.

[hayofstacks]

I did something similar to my mini ultra stick before I finally went to nylon bolts. I actually ended up breaking the fuse in half without any damage to the landing gear block on a hard landing.

[fhhuber]

Provide pictures of the actual model's belly to show the mounting... with and without the gear on plus interior of the fuselage if you can show the gear mount plate.

If its surface bolted to the fuselage (2 to 3 bolts each strut)
And if you are breaking the gear mounting plate.
Then adding a thin aluminum plate that catches all the bolts and goes on sandwiching the gear struts between the metal and bottom of the fuselage can help.

There are many common ways for ARF LG mountings to fail... and for each common failure there is a different fix.

[solentlife]

I would refer people back to old world model building and the general engineering aspects of spreading out loads / not creating abrupt stops to stiffening.
Check out traditional model fuselage doublers. The shape is such to spread load .. and method of glueing was contact glue - which allowed the final product to flex, absorb stress.
The worst thing a person could do was to beef that up and use a hard set glue ... you then often ended up with snapped fuselages, firewalls tearing out etc.

Landing gear plates usually married into formers and doublers to spread the load, to even out stress. Glueing was such that it aided - not prevented such. With GRP fuselages and many large models - it was common to glass up the area once ply plate was in ... but spreading out the glassing to surrounding structure .... again to spread that stress. The ply plate was purely a bolt down plate - NOT the load bearer.

Careful thinking about how to strengthen ... spread the load is worth the time and effort. Just whacking in alloy plates is a fools errand IMHO.

Modern materials are marvellous - but there are also many more suitable older materials that looked after big models in the past ...

Every flight line needs an old world builder ... just for all those tricks and tips of bygone era ...

Nigel

[kyleservicetech]

Originally Posted by solentlife

I would refer people back to old world model building and the general engineering aspects of spreading out loads / not creating abrupt stops to stiffening.
Check out traditional model fuselage doublers. The shape is such to spread load .. and method of glueing was contact glue - which allowed the final product to flex, absorb stress.
The worst thing a person could do was to beef that up and use a hard set glue ... you then often ended up with snapped fuselages, firewalls tearing out etc.

Landing gear plates usually married into formers and doublers to spread the load, to even out stress. Glueing was such that it aided - not prevented such. With GRP fuselages and many large models - it was common to glass up the area once ply plate was in ... but spreading out the glassing to surrounding structure .... again to spread that stress. The ply plate was purely a bolt down plate - NOT the load bearer.


Nigel

Hi Nigel
That's assuming the LG was properly designed in the first place!

The LG that came loose on one of my models was simply bolted to an 1/8 inch piece of lite ply about 1 1/4 by 3 inches. No locking tabs or anything similar was found. That lite ply was simply butt glued to the stringers on both sides of the fuse. And, they used thin CA for the job.

As you've indicated, doing this created a LOT of stress risers. That CA simply let loose, allowing the LG to rotate backwards. Looking at the CA joints, only about 20% of it was glued to anything. Gaps and thin CA is not a good combination.

FYI, that LG let loose on a very smooth landing on a pretty smooth grass field.

Right now I'm stripping out a ARF model from NE Sailplanes purchased some 10 years ago. This model had absolutely the worst design LG I've ever seen. It used torsion bar construction for the landing gear. The "Torsion" bar was only 3/8 inch long, and was sandwiched between two pieces of 1/8 inch lite ply with zero other support. That landing gear folded up just taxiing around on my concrete driveway.

Something else on this model, the fuse sheeting in the tail was all made in the wrong direction. The grain was vertical on the sides, and crosswise top and bottom. Only thing that gave it any strength was the shrink covering. Even that had to be beefed up. It was designed for an Astro 05 motor. The nose structure was so weak, a speed 400 motor would have ripped it out.

This model really was a POS, and after getting it into the air, it flew like a POS.

[road king 97]

Lets get to the flying part of this mess ,i cant tell you how many times i see guys diving at the field not like they are landing but like they are making a scraffing run. You have to bleed off airspeed and come in slower with a little power on and flair right before you touch down . This will help keeping your gear on plus the right mounting and glue (epoxy). Just my two cents . joe

[kyleservicetech]

Originally Posted by road king 97

Lets get to the flying part of this mess ,i cant tell you how many times i see guys diving at the field not like they are landing but like they are making a scraffing run. You have to bleed off airspeed and come in slower with a little power on and flair right before you touch down . This will help keeping your gear on plus the right mounting and glue (epoxy). Just my two cents . joe

Back in the mid 1980's one of my club members was known for doing touch and go landings at full power. He was good, and never busted anything.

So good, that later on, he put a second set of wheels on the TOP of the model, and did touch and go landings upside down, again at full power. Yup, that WAS a very strange looking model. Wish I'd taken photos of it.

[road king 97]

When i was alot younger with much better eyes and my fingers were a little more nimble i could do one wheel touch and go's ,alternating wheels each time around. I tried it not to long ago and now i know iam feeling my age after seeing my attempt .lol It did teach me how to use ail and rudder on cross wind landings . This summer i plan and getting more practice time in to get my fingers working alot better by trying to do things i use to with a plane. joe

[mclarkson]

The first ARF I ever built (my 3rd plane ever) was the GWS Tiger Moth 400. Everyone agreed that the landing gear was a weak point and I modded mine based on another guy's mod, anchoring the gear on the firewall and also under the fuse where they normally mount.

When I had a botched landing and caught the wheels on a sort of curb, the landing gear held up perfectly ... but they tore the fuselage in two.

[MaxSpeed]

Thank you all for your replies,
here's what i have done with my plane by taking different ideas from your replie:

1. i cut a 3/4 of in inch piece of wood.
2. cleaned the surface on the bottom of the fuselage where the LG will mount.
3. i then applied 30 Min epoxy on the surface and on the 3/4 piece of wood as well.
4. let it heal over night.

next morning i mounted the landing gear then, i head out to the flying filed to test it out. i did roughly 15- 20 touch and go and the plane held up just fine, i had a few bouncy landings, but it was completely ok.

Surprisingly, the plane wasn't nose heavy it seems like it was flying just as fast as before and i got more landing out of it then i ever did.

i know thats not the "right" way of doing it, but this plane is my beater, so i figured what the heck, lets try something thats "less time consuming"

thank you all for replying

[solentlife]

Originally Posted by kyleservicetech

Back in the mid 1980's one of my club members was known for doing touch and go landings at full power. He was good, and never busted anything.

So good, that later on, he put a second set of wheels on the TOP of the model, and did touch and go landings upside down, again at full power. Yup, that WAS a very strange looking model. Wish I'd taken photos of it.

Knew a few guys who did the inverted T&G's in UK ... one guy used to do it with the WEDGE biplane ... another with a WOT4 ..... others various sport machines. They did it for Displays .... all part of their routine.

Nigel

[mclarkson]

Glad you got it sorted out MaxSpeed. Indeed, sometimes I have to remind myself, "It's just a chunk of foam, etc." Try stuff out.

[kyleservicetech]

Originally Posted by MaxSpeed

i know thats not the "right" way of doing it, but this plane is my beater, so i figured what the heck, lets try something thats "less time consuming"

Naw
The "right way" of doing something is doing what ever works

[CHELLIE]

Epoxy all the wood around the Landing gear and use some rubber sheet, like about 1/8" to1/4" thick between the landing gear and the wood mount, use nylon bolts, the rubber will absorb a lot of Abuse, Ask me how i know

[road king 97]

They make a great set of cub landing gear even a new one for my funcub but iam to cheap to spend 50 bucks and will build my own. joe http://www.cublandinggear.com/