Luke's MK IV Project

[Luked 71]

Well, here is a quick run down on my new to me Avid project. I bought it in January, but have not done anything on it yet. I actually have an ultralight project that I am planning to finish before diving into this one.

Fuselage:
The previous builder added some extra things that I'm planning to remove. Because of my engine plans, I will need to keep things as light as possible. Mostly it's just a lot of extra sheet metal in the baggage areas. An extra baggage area was also created farther back in the lower part of the tail. This kit also came with dual brakes. The previous builder did the tail stretch mod. I was told it was extended by 16". I was wondering if the plates welded into the tubing under the front of the seat are stock. You can see the stretched tail in the second picture.
 

Wings:
Not sure if I will use these wings or not. The previous builder had planned to have "convertible" wings so that they could be converted from speed wings to long wings and back again with a spar socket system. Each wing has 3 parts (wing, extension, and tip). After looking at the way this was done, I think the only way that I would use the existing wings is as speed wings. I would just attach the tips permenently to the short wings. It looks like the system adds quite a bit of extra weight, and there are a lot of extra pieces to connect together. I'd rather keep things simple, and go with a proven setup. Also, they have a very noticeable amount of washout. I measured it from one spar to the other, and it's 2" over the span of the 12' wing panel. Below are the wing panels, the tips, and the extensions.

 

Misc parts:
It looks like I've got most of the parts in various boxes. There is also a cowling that I don't have a picture of. I think I'll make my own. I've always wanted to design my own cowling from scratch.

 

 

The tail surfaces are all stock. I didn't get any pictures of them. That's pretty much what I'm starting with. I also bought an engine (sort of) last week. I'll do another post to get all the details on that.

[Luked 71]

Here are some details about the engine I'm planning to use. It's a Continental A-65. I know this isn't the engine most people would choose for this plane, but I think it will be a good fit for what I'm planning to use the plane for. I will probably build it as an A-75, but even still, I expect performnce to be modest for an Avid. About like a J-3 with an A-65. Maybe my next Avid will be a STOL fire breather!

 

The engine I bought was kind of a gamble. It was cheap, and local, and it has the flanged crank shaft, but no logs. It was also missing all accessories, and the accessory case. The main thing I wanted was the crank. I'm planning to tear it down this week, and send the crank for inspection and have them do whatever needs to be done to it (assuming it's usable). I asked the seller if I could pay him half of what he was asking to start with, and pay him the the other half if the crank checks out. Fingers crossed. Here are the pictures.

 

Engine the way I brought it home.

 

Setting it on the stand

 

Parts to save

 

Parts to trash

 

Engine after I stripped off the cooling tins, and induction system

 

That's about it for now. Any comments of advice are welcome.

 

Thanks,

Luke D.

[1avidflyer 1983]

The extra metal welded into the seat truss is a good thing,(in the third and fourth pics.)  as this is a weak area in these planes.  Jim Chuk

Edited 8 Mar 2014 by Jim Chuk

[EDMO 1078]

Luke,

     Keep this site in mind if you end up with extra parts to sell.  And let us know how the crank turns out.

Very interesting innovations on the plug and play extensions!

EDMO

[Av8r3400 1179]

The continentals are an interesting motor in an Avid. You may be surprised at the performance you get from a 75-80 hp C.

With the stretch, it will balance just fine, too.

[EDMO 1078]

Even an O-200 is lighter than a Soob - should fly good - a friend of mine put  an 0-290 in Kitfox 5 - I just had a Soob that cost a lot less, so I am using it - Oh, BTW, Soob repairs are a LOT cheaper - cheap plugs are good for 100,000 miles, and overhauls should be maybe once in a lifetime of flying!

EDMO

Edited 8 Mar 2014 by Ed In Missouri

[Luked 71]

Thanks for the comments and suggestions guys. Good to know about the extra webbing plates under the seat. I'm hopping that the lack of electrical system on this engine will give me a little edge on the weight situation. I'm going to try to eliminate every bit of extra airframe weight that is not absolutely needed. We'll see.

 

I pulled two cylinders on the engine this morning before the rest of the family got up. The last two look like they are going to be harder. I ate some breakfast, and headed into the shop to get some work done. I'll see if I can get the other two off tonight. The cylinders are no good, but hopefully the crank was protected enough to survive. I'll post some pictures tonight. I'm hoping I might even get the case split tonight if I have time.

 

Oh, I forgot to mention Ed that I considered the Subaru. Our family van is an 87 Wolfsburg Vanagon that I put a EJ22 in. It's a great engine. I don't know much about the EA81, but I'm sure it would be good too. The main reason I was put off by the Subaru was because I felt like it would take me longer to get the plane in the air. After installing the Subaru in the van, I know there is always a bit of tinkering to get things just right. The continental will probably take longer than the more standard Avid engines, but it is pretty simple mechanically and electrically.

Edited 8 Mar 2014 by Luked

[akflyer 1427]

I would not be so hasty getting rid of the baggage area.. it is worth it!.. Maybe replace it with Kydex or something like that, but I would keep that area!  I would rather have it and not need it every flight, than need it once and not have it.  you only talking a couple pounds tops so you would do better by hitting the head before you go fly instead of taking out the baggage area in terms of weight loss

 

[EDMO 1078]

I have not kept up with the market or availability of C-65 and C-75 parts - I know at one time there was an O-200 crank conversion for the C-85 because 85 cranks were no longer available - $pendy, tho!

EDMO

[Luked 71]

Good point Leni. I think I'll keep the normal baggage area but try to make it lighter. I'm thinking of something like the "baggage sack" I saw in the Kitfox catalog.

[Luked 71]

I have not kept up with the market or availability of C-65 and C-75 parts - I know at one time there was an O-200 crank conversion for the C-85 because 85 cranks were no longer available - $pendy, tho!

EDMO

 

That's exactly right. I've been doing a lot of searching for info on small Continentals. I actually got a lot of my info from this page:

 

http://www.bowersflybaby.com/tech/fenton.htm

 

I had actually given up on the A-65/75 for this very reason (hard to find crank shafts). The tapered crank engines need a serviceable hub, and they are getting more scarce. Once the hub gets a crack in it you have to find a replacement. I decided that I didn't want an A-65 if I couldn't find a flanged crank. If this one turns out to be a boat anchor, then I'll be back to square one. I was strongly considering an O-200 because all parts are readily available. I'd prefer the A-65 though because of weight and simplicity.

 

In any case, my plan is to nail down my engine for sure at the very beginning because this will have the biggest affect on W&B. Once I have the engine I can mockup the weight of all components on the airframe and do a W&B. This should tell me how long to make the mount. Then I can hang the engine off a 4x4 stuck into the fuselage at the calculated distance, and do one final W&B check before making the mount. I don't want any lead in the plane if I can avoid it. That's the theory anyway.

[EDMO 1078]

Luke,

     I know you can go up to a C-90 without hardly any weight penalty - don't know weight of O-200, but it cant be much more - and betting less than Soob 81 with redrive - and parts are plentiful, but still costly, like all "real" engines - Hard for me to say that because the Soob and VW are both boxer engines, just like the "real" ones, but with modern engineering!  Ha!

EDMO

Edited 9 Mar 2014 by Ed In Missouri

[Av8r_Sed 82]

Hi Luke,

You'll want to look at the brake pedal / master cylinder geometry.  I believe the setup you have provides poor mechanical advantage and the brakes will be ineffective.  Have a look at the Matco Manufacturing website.  They should have some engineering data on how to set up your master cylinders.  http://www.matcomfg.com/

[Luked 71]

Yeah Ed, the O-200 will probably be what I'll end up with if this one doesn't pan out. The trade of is that the A-65 saves the weight of the electrical system. If I go to a bigger Continental, I could just leave off the electrical I guess, but then I'm hand propping a bigger engine. I know it's probably not that big of a deal, but the A-65 should be easy to prop (A-75 would be the same).

 

Thanks for the heads up on the brakes Sed. I'll have to check it out. Might need to do a little cutting and re-welding.

 

I got the engine apart tonight with the help of my youngest son. He likes to hang out in the garage with me. Here are some pictures:

 

Cylinders off

 

Case off

 

Case halves

 

My 4 year old removing the rods. He took off 3 (I loosened them)

 

Here's the prize (I hope)...

 

I'll probably send it out for inspection this week.

 

 

[Luked 71]

Just a little update to my project. I got my crankshaft back from Oklahoma yesterday. Everything checked out, and it's now got a yellow tag. Based on this, I think I will be building up a C-85 for the Avid. Hope to have some other updates in the near future!

 

 

 

 

[ChrisBolkan 130]

Nice that the crank worked out. After further reading of your threads I think going super light with no electrical and the stretch that this plane may just work out and fly like a dream.

 

So many people go in with eyes closed when choosing to put big engines in these planes and then stack more on. You are not doing that. You are thinking about everything and have the right perspective for your project to be a success.

 

I think you have a winner. With 80+hp these planes perform really well if kept relatively light.

 

Forgive my don't use the big engine rant. I can't wait to see how this turns out.

[Luked 71]

No problem Chris. I know where you were coming from. I think It's human nature to want to add stuff to things we build. Hopefully I can resist that.

[Luked 71]

Small update for today. I got some stuff from Kitfox...

 

John and Debra McBean were great to deal with, and got my order of parts to me pretty quickly. Parts quality and packaging was excellent. From what I can tell so far, I would recommend using Kitfox parts.

 

This is my first wave of wing parts. I will be ordering most of the remaining items from Aircraft Spruce. Probably some more from Kitfox too though. We'll see how things go. Here's what came today:

 

3 big boxes

 

Gas tanks

 

Various gas tank parts

 

Various wing parts

 

I also got PVC leading edge pieces, some ribs, and trailing edges that are not in the pictures.

[Av8r3400 1179]

Happy wing-ing!  

[Luked 71]

Ha!, Thanks Larry.

[akflyer 1427]

I like the updated drag tube holders versus just bending the tubes and riveting them.  Now the work starts for ya!

 

[Luked 71]

Yeah, I like those too. It seems like Kitfox has continued to refine it's design over the years the way Avid probably would have if they had continued on as a full fledged kit manufacturer. I guess that's the nice thing about having another design out there that is almost identical.

 

I still have some parts to get though before I can put too many things together. Then I can get off my butt and actually get some work done on this 

[Luked 71]

Well, after lots of planning and talking about my project, I finally got started actually doing something on it.

 

The first thing I did was to make a down and dirty rotisserie.

 

 

 

 

Since I decided to modify a significant amount of the forward fuselage, I needed to brace it up before cutting it apart. I used some clamp on shaft collars to attach the brace tubes.

 

 

Not sure if you can tell what's going on from the pictures, but I basically made some triangulated structures to replace the support that's currently coming from the overhead tubing structure.

 

 

 

Next step is to start cutting

[akflyer 1427]

good to see the wheels of progress turning!  Keep the pics coming, it will help you stay working on it to post the progress. 

 

[Luked 71]

Thanks Leni. I'll post pictures and updates as I go. Got a little more done yesterday, but realized I need some more 7/8 shaft collars to move forward jigging up the new structure. Hope to get a goo rhythm and get something done on it each weekend.