Fuselage measurements and dimensions drawing?

[gregpro50 64]

I damaged the gear mount trusses on my plane.  Is there such a thing as a fuselage or frame dimension chart to cross check measurements?  I've rebuild several salvage cars and there are dimension charts available that you use to cross check frame components at specific measurement locations.  The construction of the fuselage in these is even simpler because either a tube is bent or it's straight and it's pretty easy to locate the bent tubes by either placing a straight edge on them or using a laser.  I can make a jig to weld in new tubes to get everything aligned.  I'd just like to have some measurements to go by to verify everything.  Does such a thing exist?

[LSaupe 123]

It might.  Imagine the Kitfox factory may have them available (as the Model IV is still in production).  Probably worth a call if you haven't already.

[Av8r3400 1178]

It doesn't, Sorry.  Kitfox will not share dimensioned drawings or dimensions at all.  They view it as proprietary.

Your best bet to to let us know what you are looking for and we can measure our planes for you.  One of the reasons these owner forums exist.

[EDMO 1078]

Greg,  You may be able to straighten the bent tubes to get a measurement if they have to be replaced.  Be sure and check all the old welds, as that is usually where MIG -welded tubes break if no one annealed them after welding, which Kitfox didn't do on my planes.  I would like to see dimensions of the Kitfox 4 from lower strut to WS post and to firewall posted and compare them with my earlier models.  I have a Kitfox 3 FOR SALE that needs rebuilt in that area.

On the Grove gear - If yours don't look like it is really bent bad, set it upside down with some solid floor, and squared center section with a wall that you can measure from, and measure from floor up to center of axles, and from the wall to axles.  When I mounted mine, I set the fuselage upside down and measured from bottom of fuselage tail to each side of the center part, and to each axle before drilling mounting holes in my modified fuselage mounts - my axles are within 1/16" of being centered with tail and squared with fuselage, although on my nose-dragger it should not matter as much as a taildragger.   I know a J3 with 3/4" difference in gear axles front-to-back and it still handles OK.

Grove will straighten gear if made of 7075 aluminum and stamped that way.  I have the Kitfox 5-7 gear - 1500 gw and It is 8" wider.

EDMO

Edited 26 Apr 2016 by EDMO

[gregpro50 64]

That makes sense.  If they had dimensions published it would make it all too easy to copy the design.

My plan is to weld together a couple rails to mount the fuselage on similar to the way a car is mounted to a frame machine.  That way you have something square and plumb to get measurements from and check for twist anywhere.  It can also be used as a jig to reassemble the tubing.

After that is done I'll put together a drawing from the strut mount forward to obtain a measurement chart.  

I took the seat out over the weekend to get a good look at what needs to be done.  It sure seems like a pretty straightforward repair.  Cars are much more complicated than this.  I was surprised that some of the factory welds were a little ugly.  I also think it would be a good idea to box in the trusses at the gear mounts to add rigidity to the design.  It shouldn't add much for weight.

The gear definitely has a bit of a twist to it.  I did talk to Grove and got information on straightening and pricing when I'm ready for that.

I think my biggest obstacle in this whole adventure will be learning to do the fabric work.  I've never done that before but I've been reading the build manual and I'm sure I can do it.

[gregpro50 64]

This wide body mod looks really neat.  Now would be the time to add it.

http://www.murlewilliamsaviation.com/

Edited 26 Apr 2016 by gregpro50

[EDMO 1078]

Greg,   If you are considering altering the fuselage, I could send you a copy from the Kitfox 5 manual which shows a better way to mount the radius blocks to the fuselage instead of using the adapters that they used on the earlier models to replace the stock gear with Grove.     EDMO

Edited 26 Apr 2016 by EDMO

[Av8r3400 1178]

Here's my favorite mod for those that wear Grove Gear...

Link

[gregpro50 64]

Here's my favorite mod for those that wear Grove Gear...

Link

Yes!  Thats exactly what I was thinking.  Good idea with the holes to lighten it.  I haven't thought that far ahead yet.

[Av8r3400 1178]

Greg,   If you are considering altering the fuselage, I could send you a copy from the Kitfox 5 manual which shows a better way to mount the radius blocks to the fuselage instead of using the adapters that they used on the earlier models to replace the stock gear with Grove.     EDMO

The model IV doesn't use or need radius blocks.  Mine work just fine without them.

[gregpro50 64]

Greg,   If you are considering altering the fuselage, I could send you a copy from the Kitfox 5 manual which shows a better way to mount the radius blocks to the fuselage instead of using the adapters that they used on the earlier models to replace the stock gear with Grove.     EDMO

I'm having a tough time picturing that in my head.  I'm certainly open to anything which might improve design.  So yes, I will consider modifications.

[EDMO 1078]

Greg,   If the 4 is like the earlier 1-3 models, it used an adapter and aluminum clamps to modify the original gear mounts to take the Grove gear.   The Kitfox 5 came out standard with the Grove gear, and the mounts for it were tubes welded into the fuselage, with a radius block on top of the spring gear and another under it.  It seems to me to be a lot stronger than the original mounts on the longerons.   I will look at my KF 5 manual and see what I can scan for you in another post.   The only thing you might change is the spacing, since your gear is smaller than the one for the KF5.    EDMO

Edited 26 Apr 2016 by EDMO

[Av8r3400 1178]

With the gussets in my design, the Grove mounts are just as strong or more so than the model V mounts without needing to completely redesign the mounting system.  The model V gear is larger and wider, 4.6 x 1" on the V versus 4 x 7/8" on the IV in order to make up for the 1550 gross weight.  The thicker wider gear require the radius mounts to flex.  The smaller spring does not.

 

Why redesign and make more complicate what doesn't need to be?  If it ain't broke, don't fix it…  

 

[1avidflyer 1983]

Don't worry about the fabric work, it's really very easy if you follow the manual.  I widened the fuselage on my Avid MK IV using 7' of 1/2" tubing on each side.  Here is a picture of it.  I have a baggage compartment door on the left side of the plane, therefore, I transitioned the bulge in the fuselage only back that far.  If I was doing a Kitfox or Avid without the baggage compartment door, I would go back at least another foot.  I don't think I will ever recover another Kitfox or Avid without doing this mod first.  Jim Chuk

[EDMO 1078]

Grove catalog shows pictures of radius blocks, and recommends them.  Zenith uses them too.  I don't remember if I still have a set for the 4 gear or if I sold them.

NOW I HAVE TO MAKE A BIG CORRECTION:  I had forgotten that originally Grove used CONCAVE radius blocks with Nylon inserts for the 5 - It was a Mickey-Mouse rig!  I have a set like the ones shown in the drawing I will post.  This was changed to only Two CONVEX radius blocks on each side without all the other parts later - that is what I am using, and what is now used on KF5-7 models.

Also note in the photos that they used rectangular tubing near the gear mount which strengthens it sort of like Larry made his.  I think any kind of strengthening in that area would be beneficial.

Here is another scan of the Grove catalog about the radius blocks.  The $249 price for the KF5 is for the old Mickey Mouse setup.   I think that 4 of these new blocks would be a lot cheaper and better than buying the old type adapters and clamps.  I don't know why they show the radius PLATES - You don't need them.    EDMO

Edited 26 Apr 2016 by EDMO

[EDMO 1078]

Jim,   I widened mine 3" each side at the rear of the doors, but I didn't extend the bottom of the door like you did - I just have to bow my doors out more at the rear.  Simple to do.  I could post a photo if wanted.   EDMO

Edited 26 Apr 2016 by EDMO

[TJay 1041]

Fabric is fairly easy but time consuming, I just sprayed the last coat of paint on my tail feathers about 30 minutes ago. Got close to 300 hrs in fabric and finish alone but I am a rookie,

[LSaupe 123]

Here's my favorite mod for those that wear Grove Gear...

Link

When doing these just be cognizant that you will change the yield point when something happens, which may or may not have an impact on the passengers.  Anyone have a crash response to this type of mod?  Unfortunately it looks like we have a number of failure mechanisms when the original style lets go.

[gregpro50 64]

I was thinking about that when looking at my damage.  Really the existing tube construction did a pretty good job of absorbing the damage and keeping it localized in that area.

[EDMO 1078]

I can see where the largest soft tires you can get would be a good safety factor.   EDMO

[gregpro50 64]

[1avidflyer 1983]

Greg,  I see on the Team Kitfox site that John Mcbean said that they could supply just a Kitfox 4 fuselage, I wonder if they would make up a partial?  Like all the tubing under the doors like your's needs.  If they would, that would simplify the rebuild conciderably.  They have the jig, and all the stuff they would need, it should be fairly easy for them to do if they wanted to do it.  It might be worth a shot to give them a call.  Jim Chuk

[gregpro50 64]

I gave him a call to talk about the replacement fuselage and the cost was just more than I could justify spending.  He was very helpful though.  I never did ask him about a partial but really the more I look at it this will be easy for me to fabricate on my own and I even see opportunities to make some structural improvements.  Right now I'm in the process of fabricating a jig to mount the fuselage on so I can get everything square.  I cobbed together a rolling dolly out of an old pallet in the meantime just to get it mobile in the hangar.  Once that happens it's just basically filling in tubing.  I had the local metal supplier cut some pieces of angle iron for me which I am welding together to get a rolling jig.  I have to buy a tubing notcher that does tubing this small.  The one that I have is for large tubing in race cars.

There are a couple different alloy options for the welding wire used for 4130 which I am researching but ER80S-D2 looks like the best one.  I see how the factory welds the fuselage and they controlled the heat with the welds by trigger pulsing.  I'm surprised that MIG seems to be a dirty word when welding 4130 but yet there are all kinds of manufacturers that do it.

I'll post more pictures as I make headway with this.

[akflyer 1427]

er 60 or 70 is fine, 80 is overkill.    Nothing wrong with MIG on the tubing, I repaired mine that way and as you said, they are building them with MIG anyways.

 

 

[EDMO 1078]

I mig'd my fuselage, and the repairs were all O/A - One thing I have seen on the factory welds of 3 of them, is that the tubing will crack or break at or just shy of the welds when wrecked - simple fix for that is to heat/reheat the weld area and let it cool slowly.  EDMO

Edited 10 May 2016 by EDMO