Fuse length and new gear

[rlmankins 1]

I just purchased a Mk4 with heavy hauler wings. It had been landed hard and ground looped. Damage to fuse has been repaired in a worksman like manner and I need to replace 2 end ribs and the wing tip, included in purchase. This is a very nice plane and I would like to keep it that way. I have been going through th NTSB and air Canada accident reports for these planes and there seems to be 2 common causes of accidents, engine failure and landing gear collapse. I am haveing firewall forward (582 c box 3-1) zero timed at Oregon Aircraft Designs.

Tha strength of the crossmember under the seats looks questionable. I plan on plating both sides with light sheet metal to increase shear load, maybe 2 lb weight penalty. I have a set of super cub landing gear that happen to be very close to the same size as my float attachment points. These would raise my fuse about 4 inches and widen my track about 18". I am not sure that I want the drag of the carbane and oleo struts but do need advice on it. Does this seem a reasonable upgrade?

While all my cover is off it would be a perfect time for a fuse stretch. I am a low time tail wheel pilot and want my daughter and my grandson to learn to fly in this plane. I have a Cherokee 180 but there is no way that either one of them can afford to fly it, besides the gear is on backwards. Does this increase the directional stability enough to justify the work. Weight penalty look very negligble. Advice for and against would be appreciated.

Plane is very well built but was completed in 1994, has 186 hours on it. Empty weight currently with BRS is 537 lbs without floats, no idea with floats, gross with BRS and floats is 1200. There must be some collective wisdom on failure points, upgrades, best tweaks for the plane. Not looking to redesign the plane or add a bunch of weight, but it will be carrying precious cargo and should be as safe as possible. I have purchased a BRS for it and am interested in the collective wisdom for mounting it.

Last but not least, where do I put my fly rod?

thanks

[1avidflyer 1983]

Beefing up the seat truss is a good idea. That is definatly a weak point. A suggestion from the Avid factory was to fill in the triangles in the seat truss with plywood and it was a requirement if you went with the wide gear. A number of different controls and such run through the truss so you have to plan for them. The fusaloge stretch is also a good idea especially if you intend to put a heavier engine on the plane at some point in the future. As long as you have the fus. uncovered, now would be the time to do it. If you go to www.airdale.com you can see a fus. being stretched. Click on the Avid box on the top of the page. If you have never flown behind a 2 stroke, before, be sure to learn about how to operate it before flight. They are VERY sensitive to high EGTs and will burn up if EGTs are run hot (especially at full power). Also, cold seizure can be a problem from running hard before the engine is warmed up. You really need to run a thermostat in cold weather. Hope I didn't scare you to much on the engine part, and one other thing, welcome to the group! Take care, Jim Chuk (another MK IV flyer)

I just purchased a Mk4 with heavy hauler wings. It had been landed hard and ground looped. Damage to fuse has been repaired in a worksman like manner and I need to replace 2 end ribs and the wing tip, included in purchase. This is a very nice plane and I would like to keep it that way. I have been going through th NTSB and air Canada accident reports for these planes and there seems to be 2 common causes of accidents, engine failure and landing gear collapse. I am haveing firewall forward (582 c box 3-1) zero timed at Oregon Aircraft Designs.

Tha strength of the crossmember under the seats looks questionable. I plan on plating both sides with light sheet metal to increase shear load, maybe 2 lb weight penalty. I have a set of super cub landing gear that happen to be very close to the same size as my float attachment points. These would raise my fuse about 4 inches and widen my track about 18". I am not sure that I want the drag of the carbane and oleo struts but do need advice on it. Does this seem a reasonable upgrade?

While all my cover is off it would be a perfect time for a fuse stretch. I am a low time tail wheel pilot and want my daughter and my grandson to learn to fly in this plane. I have a Cherokee 180 but there is no way that either one of them can afford to fly it, besides the gear is on backwards. Does this increase the directional stability enough to justify the work. Weight penalty look very negligble. Advice for and against would be appreciated.

Plane is very well built but was completed in 1994, has 186 hours on it. Empty weight currently with BRS is 537 lbs without floats, no idea with floats, gross with BRS and floats is 1200. There must be some collective wisdom on failure points, upgrades, best tweaks for the plane. Not looking to redesign the plane or add a bunch of weight, but it will be carrying precious cargo and should be as safe as possible. I have purchased a BRS for it and am interested in the collective wisdom for mounting it.

Last but not least, where do I put my fly rod?

thanks

[dholly 718]

rlmankins

I would only add the following: During my Avid Mk-IV build, I fabbed up extra mounting brackets for the main tubing cluster in the tail behind the main strut attach point for floats, plus brackets for under the front door posts in case I swapped out the oem gear legs for a 3-point gear attach setup like the Highlander has. If you think there is even a remote possibility of adding wider gear, in addition to strengthening the seat truss, I would definitely plate the side longerons below the door as well. Having bent my KF3 in that exact location, I now think it is imperative to spread the force over three mounts rather than two AND plate the sides. These little birds were not designed to endure that kind of repeated stress. IMHO, that side plating may well have saved my plane. Not a pancake landing, but dropped a wheel into a drainage ditch and the horizontal force rearward twisted the Grove spring gear mounting block and lower longeron tube (plus a bunch more after that ) all to hell. A lot easier to head trouble off at the pass than fix and recover that kind mess I say! Another idea: Kitfox 3 and 4-1050 required an add on fuselage brace when on floats. (see pic) Wouldn't be terribly hard to make something similar and it might be weight well spent if you're pounding your plane into short or unimproved strips on a regular basis. As for the stretch, I have never seen a negative comment from anyone who has done it aside from the cost. I got mine the easy way when I sold my Mk-IV for an Avid+ kit, but starting a build all over should tell you how strongly I feel about longer and wider. In any event, whatever gear you use, make sure you check for proper wheel alignment before high speed taxi tests or takeoff/landing. If you've done any reading, you know the Avid TDs with bungee gear can be a real handful if not set up correctly. Post your progress please, we always like to read about other folks builds!

-Doug

[SuberAvid 617]

Ditto on the Welcome. I will throw in my two cents to your questions as well. I have an Avid MkIV that I flew for quite a while before I completed my Avid+ which is about an 18" stretch and 6" wider Avid. The Avid Mk IV is a pretty easy tail dragger WITH the wide gear on it and reasonable brakes. The wide Airdale bungee gear that I had on mine is 14" wider than the stock Avid gear. I don't know of anyone who has used actual Cub ger adapted to one and as you say, there will be a drag penalty, but the other thing you will need to do is fabricate the cubane bungees to match the weight of the Avid. As far as the added width, this will certainly help the ground handling. Reinforcing the seat truss may not be necessary with the cabane type gear, as it is with the bungee gear, since it does not apply a bending load to the seat truss like the bungee gear does. I did the plywood reinforcement to my seat truss with microlam plywood epoxied into the web openings between the tubing and it worked just great.

As far as the fusalage strech, As Jim said, it is primarily to allow heavier engines without having to add weight to the tail but it does add some improvement to ground handing, but not enough that I would do it just for that reason. The longer fusalage also tracks straighter in flight, which is nice on a longer trip, but he best part about it is the added bagage area if you convert it to the push/pull cable controls as the Avid+ has; or you could modify your bagage area to fit around the push/pull tubes and control mixer; possibly deepening and lengthening the bagage box and disconnecting the PP tubes when you fold the wings.

You have to run your fishing poles down througn the fusalage which is hard to do if you ave the standard bagage box in the MK IV. I just used takedown rods and bungeed them on my wing strut; same with rifles, snowshoes, etc.

[akflyer 1427]

I echo every thing Doug said (big surprise there! )

When I got my airplane it was balled up from TWO landing gear failures. The seat truss area was bent up and the lower longerons under the door sill. The first thing I did after I got the tubes straight was to plate the sides.

http://www.avidfoxfl...ic/14-my-mod-c/

Click that and take a look at the pictures and you can see where I plated the sides. The seat truss was beefed up using triangles welded in instead of the plywood gussets that the factory said to put in. I had the fuse torn down and the welded plates seemed the way to go. If the plane is covered then the glued in gussets would probably be the way to go unless you are good with a TIG rig.

If you go with the wide gear, make sure the wheels are aligned. The tree sets I have installed were all off a pretty good bit making for exciting ground handling on pavement (grass and gravel or sand are a non issue)

To stop most ground loops DO THE BRAKE UPGRADE to the pedals and cylinders that Mikesk (member here) sells. The brakes are night and day difference due to the better pedal geometry. You can easily lock up a brake now to hold her from spinning instead of mashing the stock pedal through the firewall and still not being able to hold it. It is an overall small expense to be able to maintain control of the plane when things start going bad.

Cub gear... I have thought 1000 times about moding a set of cub gear to put on my plane. I have a set of 1 1/4" and 1 1/2" sitting in storage but if I swap to those, I will have to change out brakes, get new skis etc to use them. I don't see any reason why you couldn't use them, you will just have to use smaller bungees on them as the cub bungees are for a plane that weighs twice what yous will weigh so you wont have crap for travel on the gear.

Fly pole holder.... You can see in my pictures the tube for the rod holder behind the passengers seat. It was used once. The cabin is too short to really get a good rod in there so 99% of the time I do the same as Randy and bungee the rod holder to the wing strut where the jury struts are. Same with Rifle and Shotguns. If I was to re-design anything, it would be to put a bigger baggage door in it more like a cub extended baggage so you can get more stuff in there easier. My baggage goes from behind the seat to the front of the vertical stab. With the 582 the plane generally comes out nose heavy anyway, so I stuff my survival gear in the back of the plane and forget about it. No need to carry lead on the tail spring that way If I have to move weight around I want it to be useful not just dead weight.

As Doug said, welcome aboard here and post up build pictures!

[EDMO 1078]

"you will just have to use smaller bungees on them as the cub bungees are for a plane that weighs twice what yous will weigh so you wont have crap for travel on the gear."

Not so sure about that statement - Guessing that the bungees may end up somewhere between the Avid size and the Cub size, although they go on differently, and considering the extra width of mount may put extra strain on them.

- The J3 Cub comes in under 800 EW, and gross is only 1200 and certainly not "twice as heavy".

SuperCubs are a whole different story!

ED in MO

P.S. Add my Welcome Aboard - You can get lots of help from members here - We may not always agree, but we try not to be "Disagreeable".

Edited 3 Feb 2013 by Ed In Missouri

[rlmankins 1]

Thanks for the advice, I spent the day doing an inventory and taking a hard look. Looks good.

[Av8r3400 1179]

Not wanting to piss is too many bowls of cornflakes here, but in light of recent events, added to some engineering consideration, I am more and more happy with my choice to go with a Grove spring gear conversion on my plane rather than any one of the number of "bush gear" options.

Just saying...

Edited 3 Feb 2013 by Av8r3400

[rlmankins 1]

Not wanting to piss is too many bowls of cornflakes here, but in light of recent events, added to some engineering consideration, I am more and more happy with my choice to go with a Grove spring gear conversion on my plane rather than any one of the number of "bush gear" options.

Just saying...

I am not sure how I would attach my floats with the grove gear. I really like the gear, what I wanted to do first but do not want to have to remove them.

Roy

[1avidflyer 1983]

Not sure if it would work the same way, but about 10 years ago I got a fiberglass gear from a guy out in Pennsilvania for my Himax. It was conciderably lighter than an aluminum gear, and it sure made the plane better. Course the Himaxs were usually built with no suspension at all so anything that didn't break and wasn't rock solid was an improvement. I tried to talk him into looking into building a gear for an Avid or Kitfox, he would have probably done it if he had a plane to work with, but didn't so... He does have a nice website where he explains and shows how to build a fiberglass gear as well as other things. Also writes a good story on how run a two stroke to make it keep it running. His web site where he shows that is http://curedcomposites.com/gear.html Maybe the guy that might build the leading edges might want to take a look at it as well. Here's a pic of my Himax with the fiberglass gear that I used to have. Take care, Jim Chuk

Not wanting to piss is too many bowls of cornflakes here, but in light of recent events, added to some engineering consideration, I am more and more happy with my choice to go with a Grove spring gear conversion on my plane rather than any one of the number of "bush gear" options.

Just saying...

[akflyer 1427]

I was just talking to an engineer geek buddy of mine and he is going to run a stress analysis on the gear and fuse components for me to see if we can come up with solution. If anyone is close to their airplanes and can get some measurements for me today that would be awesome!

I need the lengths on the gear legs and on all of the components. So the width of the fuse at the gear attach points, the gear leg length, the length of the cabane struts for the vee and the strut coming off the gear leg.

It would be helpful to know the length of the slot in the strut for total travel allowed to so we can run the numbers on the spring compression and the loads put on it.

I think I have a VERY easy solution for the fuselage buckling depending on where the fuse is buckling at...

Any details you guys can give on the failures would be very helpful for me to give this guy so we can come up with a real solution to the gear issues, and not just use a TLAR shade tree solution.... No disrespect to the guys that have built their own on the TLAR principle, that is what he experimental world is all about! I am just trying to get a solution to a problem so we dont bend any more birds from a faulty design

[dholly 718]

I am not sure how I would attach my floats with the grove gear. I really like the gear, what I wanted to do first but do not want to have to remove them.

Roy

Why? It's only 4 bolts, same as oem gear. Not hard at all, particularly since you don't need to dicker with bungees.

Edited 3 Feb 2013 by dholly

[EDMO 1078]

Not sure if it would work the same way, but about 10 years ago I got a fiberglass gear from a guy out in Pennsilvania for my Himax. It was conciderably lighter than an aluminum gear, and it sure made the plane better. Course the Himaxs were usually built with no suspension at all so anything that didn't break and wasn't rock solid was an improvement. I tried to talk him into looking into building a gear for an Avid or Kitfox, he would have probably done it if he had a plane to work with, but didn't so... He does have a nice website where he explains and shows how to build a fiberglass gear as well as other things. Also writes a good story on how run a two stroke to make it keep it running. His web site where he shows that is http://curedcomposites.com/gear.html Maybe the guy that might build the leading edges might want to take a look at it as well. Here's a pic of my Himax with the fiberglass gear that I used to have. Take care, Jim Chuk

Now, you've got me thinking - Pazmany in his book on "Landing Gears" showed the making of a fiberglas gear -

A carbon-fibre gear would be still lighter, and maybe better?

ED in MO

[EDMO 1078]

I was just talking to an engineer geek buddy of mine and he is going to run a stress analysis on the gear and fuse components for me to see if we can come up with solution. If anyone is close to their airplanes and can get some measurements for me today that would be awesome!

I need the lengths on the gear legs and on all of the components. So the width of the fuse at the gear attach points, the gear leg length, the length of the cabane struts for the vee and the strut coming off the gear leg.

It would be helpful to know the length of the slot in the strut for total travel allowed to so we can run the numbers on the spring compression and the loads put on it.

I think I have a VERY easy solution for the fuselage buckling depending on where the fuse is buckling at...

Any details you guys can give on the failures would be very helpful for me to give this guy so we can come up with a real solution to the gear issues, and not just use a TLAR shade tree solution.... No disrespect to the guys that have built their own on the TLAR principle, that is what he experimental world is all about! I am just trying to get a solution to a problem so we dont bend any more birds from a faulty design

:BC:/>

Leni, I will look at my old photos, and if I can find the ones of my KF2 that bent the longeron and other parts, I will post them. This was a side-thrust, going down on one leg.

ED in MO

[EDMO 1078]

I am not sure how I would attach my floats with the grove gear. I really like the gear, what I wanted to do first but do not want to have to remove them.

Roy

I agree with Doug - The Grove gear is easier to remove than the standard with bungees, or the Cub type gear.

I have a Grove for sale - cheap.

ED in MO

Edited 3 Feb 2013 by Ed In Missouri

[akflyer 1427]

Leni, I will look at my old photos, and if I can find the ones of my KF2 that bent the longeron and other parts, I will post them. This was a side-thrust, going down on one leg.

ED in MO

Ed,

I was thinking more about the guys that bent the fuse using the new cub style spring gear. I was not sure if it was pulling the sides of the fuse in due to the loads being put on the lower longerons from the cabane vee or if the longerons were getting pushed up. Either way, I think we may have a workable solution that would be pretty easy to fix the problem.

#1 I dont want to just beef the fuse up to take the load. If we can design some of it out in the gear geometry that is the real answer. If we cant, then changes to the vee could do the trick. I wont know for sure till I get the measurements and go from there.

[EDMO 1078]

Ed,

I was thinking more about the guys that bent the fuse using the new cub style spring gear. I was not sure if it was pulling the sides of the fuse in do to the loads being put on the lower longerons from the cabane vee or if the longerons were getting pushed up. Either way, I think we may have a workable solution that would be pretty easy to fix the problem.

#1 I dont want to just beef the fuse up to take the load. If we can design some of it out in the gear geometry that is the real answer. If we cant, then changes to the vee could do the trick. I wont know for sure till I get the measurements and go from there.

:BC:/>/>

OK - I see now what you intend - All of the several planes I have looked at with the bungee system ended up with a bent longeron - That is sure the weakest spot in the fuselage - The Airdale system strengthened this a lot, but that was a totaly different kind of gear than most of us use. My attach design for my Grove gear takes all the stress off of the longerons.

Good luck with your research.

ED in MO

Edited 3 Feb 2013 by Ed In Missouri

[rlmankins 1]

Any updates on the engineering. Getting ready to start bracing and if I need to change anything it's time

[RDavidson 183]

Any updates on the engineering. Getting ready to start bracing and if I need to change anything it's time

Here is an idea for your fly rod...wish I could call it my own idea, but it was the previous owners.

This is on a magnum with the heavier engine up front.

It is an 8" construction tube that stretches from the cargo bay to the tail.

Only down side I see is the weight, and if you drop something in there you might have to wait for the next cover job to get it back!

[EDMO 1078]

Here is an idea for your fly rod...wish I could call it my own idea, but it was the previous owners.

This is on a magnum with the heavier engine up front.

It is an 8" construction tube that stretches from the cargo bay to the tail.

Only down side I see is the weight, and if you drop something in there you might have to wait for the next cover job to get it back!

I would think that a fiberglass or carbon fiber tube would be lighter and longer-lasting --- Guess you could use an aluminum stovepipe too.

Dropped parts in tube - no problem - just stand plane on its nose and shake well, :lol:/>

ED in MO

Edited 23 Feb 2013 by Ed In Missouri

[wypaul 448]

I was just talking to an engineer geek buddy of mine and he is going to run a stress analysis on the gear and fuse components for me to see if we can come up with solution. If anyone is close to their airplanes and can get some measurements for me today that would be awesome!

I need the lengths on the gear legs and on all of the components. So the width of the fuse at the gear attach points, the gear leg length, the length of the cabane struts for the vee and the strut coming off the gear leg.

It would be helpful to know the length of the slot in the strut for total travel allowed to so we can run the numbers on the spring compression and the loads put on it.

I think I have a VERY easy solution for the fuselage buckling depending on where the fuse is buckling at...

Any details you guys can give on the failures would be very helpful for me to give this guy so we can come up with a real solution to the gear issues, and not just use a TLAR shade tree solution.... No disrespect to the guys that have built their own on the TLAR principle, that is what he experimental world is all about! I am just trying to get a solution to a problem so we dont bend any more birds from a faulty design

Leni, I have the new spring gear and the bent fuselage.  I was wondering if you have any progress on your idea for a fix.  I have the fabric pulled away and can get a good picture of the damages tomorrow.  I had hoped that the cabine vee would help carry the load but the side to side bar, top of the vee buckled allowing the side of the lower fuselage tube to buckle inward.

Paul

[1avidflyer 1983]

Hi Paul, sorry about your plane. Are you saying that the bottom tube on the seat truss buckled? I'm also interested in this cause I have all the tubing bought to build the bush gear myself.

[wypaul 448]

Jim, that is correct.  In addition the bottom longeron was bent ahead of the gear attachment fitting.  Also as I mentioned the top member of the cabane cross member buckled.  I am not sure if this happen in the ground loop or if it happened in a slight bounced land.  The good news is that it stayed on its gear due to the wider stance and did not get the wing.  I am 2 for 2 on the ground loops/ fuselage damage and now thinking about the tri gear.  I will do some fuselage beefing this time to take care of the weak points in the gear and the fuselage.  I have a picture of the damage to the gear now and is attached.  The other pictures will follow. 

 

I think that the spring on the gear is to strong for the weight of the plane.  This is the gear sold by Highwing LLC but I think that the Airdale gear uses the same spring.

 

As you can see the cross member could benefit IMHO from a brace going from the top center to the center of the vee and also a heavier top tube making this a much stronger truss.

[Av8r3400 1179]

Not wanting to open an old wound, but can you give us the details of what happened?

Airdale has been shipping with a softer spring lately. This may or may not help.

My buddy with that gear has also had some issues - bent legs and bent hardware...

Edited 31 Mar 2013 by Av8r3400

[1avidflyer 1983]

I've been thinking of making my own gear, have the tubing now for it.  I'm not sure it's the right thing to do, but I'm wondering about using bungees instead of the springs.  Multiple wraps of 3/8" bungee would make it easier to adjust the tension, If you wanted, the slots could be longer which would give more travel as well.  Bungees would be less weight than the springs.  Can any one give me the actual advantages of the springs besides not having to replace them? Thanks,  Jim Chuk

 

PS I mentioned longer travel, and thought about how often when a seat truss bends with the standard gear, it happens when you reach the limiter cable.  Ofcourse you can only have so much travel before the prop would hit, but maybe sometimes a bit more would help.