Avid D Model?

[HoosierSMW 7]

Hoping to get some input from C5Engineer as I read this on his "History of the Avid" post. My Flyer was ordered in May of 1990 and delivered in August of 1990. In the article is says by 1990 they were producing the model D which, with modifications, became the MkIV. Of course, there is no model designation in the original paperwork with my kit. My questions are:

What are the differences between a model C and D?

Based on the ordered / delivered dates, what do I have? It does not have the additional gussets that a MkIV looks to have.

What would the suggested gross weight be with stol wings?

Is the black finish on the frame typical of what would come from the factory?

Attached are some pictures of the fuselage frame as I received it. The gear is not original to the kit (came as a tri-gear). Any information would be appreciated.

Thanks!

[saskavid 47]

So if you have the serial number of the kit listed somewhere it will be a place to start.Numbers in the 800's are C's. You do have the taller landing gear that was standard with the mark 4. Looks like an unpainted air frame and engine mount so that is just how they came unless it does have a flat black paint that doesn't show up in the pics. there is a tab on the passenger side of the air frame which is used for the side mount radiator, which is typical of a C model. You have the nose gear weldment which is a plus in some peoples books. As a kit my plane was delivered early in 1991 and is a "C".

So what kind of flying machine is that aluminum wing in the back going to become?

Edited 6 January by saskavid

[HoosierSMW 7]

Hello Sir,

Thank you for the quick reply. There is no serial number on any of the paperwork I have. The finish is matt black paint or primer. It did come with a side mount radiator (heavy!!) and was ordered as a tri-gear. Do you have any knowledge of the Model D talked about in the article? Wonder what would be different than the C or MkIV.

RV-8 wings

[saskavid 47]

I just glanced at the article and the D model was called a mark 4 simply as a marketing condition. earlier mark 4's will have the same engine mount as you will have for the 582 rotax. Later on they developed a mount they called dyna smooth. They also change the air frame at some point as well in the lower floorboard firewall area to accomadate heavier engines. Avid sold the change as a welded add on for existing airframes as well. the december 1995 issue of the avid news letter shows the install of this add on. the news letters are in the same files section as the article you are referencing.

[1avidflyer 1983]

According to Steve Winder the MK IV serial numbers start at about 1000.  If you don't have the added gussets, added tubing behind the sear for door hold opening shocks, and the door latches that are about 1/3 of the way back on the bottom of the door, It's not a MK IV  model.  I think also, the earlier models have the front of the vertical stabilizer off set to the side, and the MK IV model is centered.    There was a lot of competition between Kitfox and Avid back then, and being as how the Kitfox 4 had come out about that time, maybe that's why the last Avid got the MK IV designation.  Interesting to note, the serial numbers I've seen for MK IVs usually end in a D.  For instance,   1111D   You don't see the letter added in earlier model serial numbers that I'm aware of.  JImChuk

'

[HoosierSMW 7]

My rudder is offset and the frame seems to have all the characteristics of a C. I wish I had a serial number to confirm but it is lost to time and ownership changes. I was curious about a model D because John Larsen, the author of the article, said he had a model D that he made changes to. He said Avid incorporated those changes and made it the MkIV. It seems like that would indicate a version between the C and MkIV. This is a section of the article that had me thinking about this.

("By 1990, many changes had been made and the Model D was in production, but still had the overheating problems. My model D was no different, and since I had years of experience with 2-stroke engines and racing modifications, I began to make changes to cool the planes engine more effectively. I designed the cowling and cooling system that got rid of the cooling problems by placing two radiators in the nose of the cowl.. Changes were also made to the rudder getting rid of the parallelogram rudder for the rounded one. A trim tab was built into the elevator. Dean Wilson was next door building the Explorer so I would run over and get his sanction for many of the new design changes.

There was fierce competition between Kitfox and Avid at that time, and KF had just produced their Series 3 plane. Avid GM Jim Metzger chose to produce my design modifications of the Model D and call it the Avid MKIV just to get one PR step ahead of the KF series 3. As a result, there were few Model 3 KF planes produced as Dan Denny at KF began development of their Series 4. The Kitfox was outselling the Avid at the time as the KF had been a better looking plane to many of the buyers.

The MKIV was a real after market money maker for Avid, as most of the pilots owning Models A-D ordered up-grade kits to their earlier Models were fitted with MKIV kits to solve the cooling problem and to give them a appearance upgrade so they looked more like a real airplane.")

 

What should the max gross be on this airframe with stol wings?

 

Thanks,

Dean

[HoosierSMW 7]

Another question - does the MkIV have larger or thicker spar carry-thru tubes than the C?

[1avidflyer 1983]

I don't think so.  Measure yours, and I'll then measure the MK IV fuselage I have.  And while you are at it, measure the top and bottom tubes in the seat truss.  I know the MK IV used thicker tubes than earlier models, but not sure if the C did as well.

[HoosierSMW 7]

The spar carry-thru tubes are both 7/8" OD x .035 (I measured .040 but don't see that as a stock wall thickness). They are definitely not .049" wall. The seat truss top tube is 5/8" od and the bottom is 1/2" od. This kit was ordered as an aerobatic speedwing but the lift struts are only 3/4" od. I appreciate your help with my questions.

[marksires 484]

There was a transition period between C and MKIV that was initially called a 'D'.  I had serial number 941, and it had some, but not all of the MKIV changes, and all the build manuals called it a 'D'.

 

[HoosierSMW 7]

Thank you for that information Mark. That was what I took from the article. Do you know what was different on your plane vs the C model? When Was your kit ordered?

[1avidflyer 1983]

Finally got around to measuring my MK  IV wing carry throughs.  They are 7/8" diameter.  Some one was asking me about changing out the smaller ones on a B model.  I wondered if it would be easier to put a smaller tube inside the existing one.  May have to ream out some weld bubbles where the other tubes weld into the carry through, but wouldn't think that would be that hard with a long drill bit.  I would drill out the wing pin tubes with drill bits one size bigger than the last till there was nearly nothing left of it.  Get the last of it with a dremmel maybe.  Worse case, if you wreck it, you can then add a larger tube instead.  Any thoughts or comments why this is not an option?  JImChuk

[Avidventurous 22]

There was a transition period between C and MKIV that was initially called a 'D'.  I had serial number 941, and it had some, but not all of the MKIV changes, and all the build manuals called it a 'D'.

 

Interesting my model C has a serial number of 997. Not sure how that fits in here?

[1avidflyer 1983]

 

 

Interesting my model C has a serial number of 997. Not sure how that fits in here?

Does your C model have the MK IV upgrades I  mentioned earlier              the added gussets, added tubing behind the sear for door hold opening shocks, and the door latches that are about 1/3 of the way back on the bottom of the door,              Could also add baggage compartment, newer style cowl and rounded rudder.  

[saskavid 47]

The earliest record of mention I have reference to for the mk4 is the july 1991 avid comm news letter. All they show at that point is a covered and painted airframe on saw horses. The august news letter shows a finished plane. John Larsen did a series of articles for kitplanes magazine in which he cronicled the building of an avid flyer. First article was in may 1991.The plane he built at the avid factory for these articles was a "C". The first issue of kitplanes to have an avid flyer advertisement featuring the mark 4 was December 1991. 

[HoosierSMW 7]

Finally got around to measuring my MK  IV wing carry throughs.  They are 7/8" diameter.  Some one was asking me about changing out the smaller ones on a B model.  I wondered if it would be easier to put a smaller tube inside the existing one.  May have to ream out some weld bubbles where the other tubes weld into the carry through, but wouldn't think that would be that hard with a long drill bit.  I would drill out the wing pin tubes with drill bits one size bigger than the last till there was nearly nothing left of it.  Get the last of it with a dremmel maybe.  Worse case, if you wreck it, you can then add a larger tube instead.  Any thoughts or comments why this is not an option?  JImChuk

Did the A model have smaller carry through tubes? I wonder if that is an area of concern. In all the searching and reading I have done on the subject, I have never seen a mention of failure in that area for any of the models. Of course, that doesn't mean is hasn't happened. 

[HoosierSMW 7]

The earliest record of mention I have reference to for the mk4 is the july 1991 avid comm news letter. All they show at that point is a covered and painted airframe on saw horses. The august news letter shows a finished plane. John Larsen did a series of articles for kitplanes magazine in which he cronicled the building of an avid flyer. First article was in may 1991.The plane he built at the avid factory for these articles was a "C". The first issue of kitplanes to have an avid flyer advertisement featuring the mark 4 was December 1991. 

The article I referenced above by Mr. Larsen says by 1990 they were into production of the D model. Did the company ever reference the different models "A, B, or C) in any of their literature or kit paperwork? I see those letters all around the web but not in official company statements. The brochures available don't seem to mention a letter designation. It seems they were all called the Avid Flyer until the MkIV was introduced. I could be wrong (not out of the realm of possibility:)

Thanks for all the input.

[saskavid 47]

The "kit" that went on to become the plane I now have was invoiced and delivered in late january to mid febuary of 1991 with a serial number a bit over 800 and is referenced in all documentation as a "c" model. 

[HoosierSMW 7]

I stand corrected. I had not seen the model letter on anything else. Thanks for the information. Mine was delivered in August of 1990 so obviously would be a C based on that.

[saskavid 47]

Next thing to check is the thickness of the aluminum wing spars. This will point you in the direction of what your gross weight will be with the stol rib configuration. 

[wypaul 448]

My Avid MKIV serial #1250 was delivered in November of 1992. 11/23/92 to be exact.

[HoosierSMW 7]

My kit originally was an aerobatic speedwing with .083" spar tubes. I am (very slowly) building new wings with .063 tubes and Just Aircraft spar stiffener inserts. I believe they are the same inserts as Kitfox currently uses. The new wings should be plenty strong for a higher gross but my guess is the plane would then be limited by the fuselage construction and struts. would be nice to know the structural differences with the MkIV. Specifically tube diameters and wall thickness in critical areas. I've seen the extra gussets in a few places but can't imagine they are the only changes.

[saskavid 47]

Well if your kit is mostly complete, if you have .083 spars then you should have lift struts that are 7/8 inch in diameter, and this is what is on my heavy hauler plane. The heavy hauler wing and aerobatic speed had more ribs in them then the "lighter" models.

[HoosierSMW 7]

Unfortunately, this kit came with 3/4" lift struts which I understand lowered the gross weight. If I could find some 7/8" struts (or get better at tig welding), I would substitute them. The ribs are spaced closer than the stol wing. 

[1avidflyer 1983]

The heavy hauler wing has two ribs between the ribs with the long tailed ribs that the flaperon hinges on.  The STOL wing has only one rib between the long tailed ribs.