Fuselage and Seat Truss Repair

27 posts in this topic

Posted

I'm new to this forum and am enjoying reading all the good technical knowledge.

This is my first post, I just thought I would introduce myself and share my MK IV project with everyone. I purchased this plane a few weeks ago and haven't started repairs yet. It was ground looped by the previous owner and sustained damage to the fuselage and seat truss at the left main gear. As far as I can tell it has the standard MK IV landing gear, the extended speed wing and is Subaru powered with Warp Drive prop.

Does anyone know the tubing sizes and wall thickness used in the seat truss and fuselage longerons at this location. It would be nice to know so that I can source material before tearing into it. Also, I'm looking for recommendations on what landing gear to consider going to. I'm not sure I want to spend the money on a grove gear, but a wider cabane style gear may fit the bill. Thoughts?

 

Thanks

 

Seth

 

 

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Posted

 Most tubing wall thickness is .035.  The damage looks like a pretty easy fix, but what's seat bridge truss look like?

where are you located?

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Posted

where are you located?

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Posted

Thanks for the heads up on the 0.35 wall thickness, that helps.

The seat truss is bent on the left side. I imagine I will try to beef up the area a bit while I'm at it. I'm hoping it won't be too difficult of a repair. The rest of the airplane is in excellent condition, it was flown very little, only 80 hours total flight time. The only other damage I will need to address is the two outboard flaperon attach ribs. They were broken off. From what I'm seeing this seems to be a chronic problem with this model.

I'm located in Central Ohio. 

 

 

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Posted

Any other Avid Flyers around Central Ohio? Would be awesome to meet some other builders / pilots.

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Posted

Don't know if you've been reading the other posts, but here are a couple of ways to address the rib tails, and one thing to do to the seat truss once it repaired.  This is with these rib tail repairs, you need to get inside the covering.  Another approach that doesn't involve getting inside is to glue and screw two scabs on, one on each side of the broken rib and sandwich the flaperon hinge between them and the original rib tail.   JImChuk

PS  if my memory is correct, the top tube in the MK IV seat truss is 5.8" od.  

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New MK IV 045 (Large).jpg

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Posted

Thanks so much for the pictures. Nice to see an example of how to reinforce the seat truss.

Yes, I figured I would have to get inside the covering to splice in the rib and then will probably sandwich the rib with aluminum to add some strength. 

Does anyone know of anyone making the wide stance landing gear for this plane. I've read about Highwing LLC?

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Posted

I think Lowell at Highwing will make more of the cabane landing gear.  He recently made me a cabane to fit my Avid Flyer cause the one for the Kitfox is to narrow.  I've talked to him recently, and it seems he is up to making more of these landing gears even though his partner is not working on them anymore.  If you need his contact info, I can get it to you.  Or if you're on the Team Kitfox site, you can PM him there.  I had picked up a Highwing gear a guy had bought for a Kitfox but never used.  JImChuk

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Posted

I'll have to check out the Team Kitfox site. I will send you a PM for Lowell's contact info. I appreciate it!

How do you like the Highwing gear? How does it compare to the stock setup? How much wider does it set the main tires?

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Posted

Only flew on it a few times so far, but is does seem to smooth out the bumps and tracks straighter.  No pavement landings yet though.  I think it's 16" wider than the stock bungee gear, but don't quote me on that.  If I remember right, it's 78" wide out side of tire to outside of tire.  I've got the Nanco 22/12/8" tires.  JImChuk

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Posted

Measured again today, and I had 69" between the insides of the brake cylinders on the wheels.  JImChuk

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Posted

Excellent, looks great! The extra width has to help the ground handling.

Were you able to reuse the original brakes with that setup, or did you have to replace them?

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Posted

I used original axels, brakes and wheels.  JImChuk

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Posted

I think Jim and I have the same gear, built by Lowell Fitt, it is the Highwing LLC gear. I agree with Jim, it makes landings look good, and tolerates much more pilot error while landing smoothly and straight. I also calculated that it is at least as strong as the gear on certified aircraft, and tolerates about 12 feet per second of drop (FAR requires 8 feet per second).

It is 72" wide to the center of the tires and about 80" wide to the outside. As Jim said it takes the Avid 3/4" axle and the wheel brake assemblies that I had on my Mk IV.

It also costs about half of what the Grove gear costs. I installed it in an afternoon.

 

 

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Posted

That's great to know. That will save quite a bit of money being able to reuse the wheels and brakes.

Does he offer a spring and bungie option? And, If so, any idea what the advantages of each may be?

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Posted

Nick, if you had put the fairings on like I did, it would have been a pretty long afternoon.   :-)  Fun getting all those holes to line up.  I actually ended up enlarging them a good bit.  As far as improving landings, you still have to add a bit of finesse or they are not so pretty.  I proved that about 45 minutes ago.  No damage, but flattened a bit of tall grass on the edge of the runway with at least one wheel.  I really have to get back on improving the brakes.  That would have brought it around a bit sooner, maybe before the swerve really got started.  (wasn't a ground loop though)  No repairs needed and went and did another just so I didn't end on a bad note.  :rolleyes:  JImChuk

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Posted

That's great to know. That will save quite a bit of money being able to reuse the wheels and brakes.

Does he offer a spring and bungie option? And, If so, any idea what the advantages of each may be?

I don't know, frankly, if there are variants - I don't think so, but if you PM me I will send you Lowell's email and you can ask. He is a great guy.

Nick

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Posted (edited)

Jim provided me his contact info the other day. Lowell is very helpful. He confirmed that the springs are the only option.

He is going to fabricate a gear for me.

I'll try to take and post pictures during the project.

Edited by Hawth200
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Posted

Hawth

One aspect that needs attention: The cabane for the kitfox is about 7/8" shorter than my Avid Mark IV. The distance between the two forward gear bracket bolts is 32 7/8 ". Lowell remade the cabane and it fit very well. I am sure he has adjusted his tooling but I thought I'd let you know.

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Posted (edited)

I had to get a new cabane made up to fit my Avid as well.  I thought about sending him the Kitfox cabane, but then I thought, maybe I'll put the gear on a Kitfox someday, and then the cabane will work on it.  New Avid cabane was $200 plus shipping.  As long  as Lowell knows what plane you have, I'm sure he will make the right one for you.  JImChuk

Edited by 1avidflyer

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Posted

How much is a set of the Lowell Fitt Highwing gear?

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Posted

Hawth

One aspect that needs attention: The cabane for the kitfox is about 7/8" shorter than my Avid Mark IV. The distance between the two forward gear bracket bolts is 32 7/8 ". Lowell remade the cabane and it fit very well. I am sure he has adjusted his tooling but I thought I'd let you know.

cabane width.jpg

Thank you for that measurement! I was just thinking about having one of you measure that for me. I can't rely on a good measurement on my plane because the fuselage longerons are bent. I may wait until I receive the new landing gear to repair the longerons and gear attach points so that I can match this up for a perfect fit.

Seth

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Posted

How much is a set of the Lowell Fitt Highwing gear?

Lowell quoted me $1550 for the gear with all installation hardware.

Seth

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Posted (edited)

Just to clarify Nick,  your post says 32 7/8" between the bolts.  If Seth is going to use that dimention when fixing his plane, were exactly is that measurement taken.  On looking at your picture again, it looks like that is a center to center dimention.   (I'm editing my post after relooking at your picture :-)   JImChuk 

Edited by 1avidflyer
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Posted

Just to clarify Nick,  your post says 32 7/8" between the bolts.  If Seth is going to use that dimention when fixing his plane, were exactly is that measurement taken.  Looks like on the bolt heads.  Maybe a center to center dimention would be less confusing and less likely to cause problems.  JImChuk 

Good question Jim. I just made the assumption this was a center to center measurement. 

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