Apex in a Avid C Model Thoughts

[Jumpingjack 2]

I been following the Yamaha Conversions on Facebook for a while. Im wondering if the Apex is way too much or doable with derating on my Avid Model C HH?

[1avidflyer 1983]

My first thoughts are that a 582 set up is probably about 130 lbs or so all up.  The Apex is what? 175 maybe?  And it's  out on the nose of a type of plane that tends to be on the nose heavy side with the 582.   Balance it out with weight in the tail of course, but that takes away useable load.  Maybe you are making a super performing nearly one place plane??? Course if that doesn't matter, then maybe it's the way to go.  Just some random thoughts, others have used heavier engines and flew their planes a lot and were happy with them.  Mostly I'm just babbling, don't have any first hand experience with this setup.   JImChuk

PS  welcome to the group if I haven't said that already!  

 

Edited 2 Jan 2020 by 1avidflyer

[nlappos 413]

Jim Chuck has a good memory, this was posted by one of the yamaha guys.

[Jumpingjack 2]

 

Thanks for the info guys!  

The Yamaha group is slowly working on a 2 cylinder Phazor project, 80 hp which from what I read would be a great choice if they get it going. Same weight as the 582.

Guess I'm just looking for other options besides a two stroke. I thought I read some put rotax 912 $$$ engines in the kitfox 3's?  Isn't the kitfox 3 close to the same as the Avid C model?  

Thanks for welcoming me to the group!!

Jack

[lostman 198]

Jack, welcome to the group. I don’t have any first hand knowledge of guys putting the 912 in C or 3 models but it seems I have heard that too. I just purchased a IV to install the Apex on myself. I have been following it since the Facebook group started up and had my engine for almost two years now. Personally if I was going to anything earlier than the IV model I would want an uncovered aircraft to stretch and make the weight and balance work out. Just my thoughts. 

[1avidflyer 1983]

Lots of people have put 912s in Kitfox 3s.  Some no doubt in Avid C models as well.  As lostman says, a stretched fuselage would help the CG issues.  Kitfoxes after the model 1 or 2 have longer fuselages then the Avid, and that helps the forward CG situation as well.  JImChuk

[Jumpingjack 2]

Guys

Is the fuselage tubing the same size on the C model as the IV?  If so a stretch would be the right choice IMHO.  If not I have to question the stretch option. 

Also, I gotten lost on this site finding a detailed drawing/steps to stretch a C model as I have been pondering this also for awhile. The PO did cover the fuselage but that's as far as he got before he passed, so taking of the fabric is not an issue.

Thanks so much in advance!

Jack

[1avidflyer 1983]

There are some differences between the model C and the MK IV.  Seat truss uses heavier tubing, additions gussets around the rear spar carrythrough, and I think other things as well.  There is a post on this site from years ago, where Steve Winder from the Avid factory listed some of the differences.   Maybe someone can put up a link to that post. Within the last week or so, one of the members here posted a bunch of pictures showing how he stretched his fuselage I believe as well.  I see you found that info when I went looking for it to put a link in this message.  Other things that would make sense if you are going to have a bare fuselage is strengthen the seat truss, beef up the fuselage above the landing gear, and widen the fuselage while you are at it.  Here are some pics of how I did that on a Kitfox 4 and a MK IV.  The MK IV is the first 2 pictures, the Kitfox the other 2.  JImChuk

[Jumpingjack 2]

JimChuk,

You're awesome!

I like your recommendations. Since my ultimate goal is more power to operate out of my farm strip ( sloped and 1300ft tree to tree) the fuselage mods make sense safety wise with any engine choice Rotax or Yamaha. 

I've been on this site a while seeing most the mods your talking about, just have to put a project list together combining them all. 

While Im jawing here,  after doing all these above mods, heavier engine ( Rotax Yamaha) what's your recomendation on landing gear? Or is the stock bungee good enough?  I do want big 27 tires.

Jack

 

[1avidflyer 1983]

I've had the cabane gear made by Lowell Fitt on my Avid for the last year or so, and I do like it.  Seems to make the plane way more stable on the ground.  If money isn't much of an issue, the monster shocks would make it even better.  I have the grove gear on my Kitfox, but have yet to finish and fly it, so can't speak from experience on it.  The cabane gear is probably lighter and less expensive then the grove gear as well.  JImChuk 

[Jumpingjack 2]

I was looking at the monster shock option it looks great. Your statement about "money isn't an issue" is funny,  Just a working guy with bills. Lol.

I will look into the cabana gear.  I'm not sure about Grove but looks simple and buy as a complete unit with wheels and brakes as opposedto the matco's I now have. Obviously attach points on the fuselage all need reinforcing and/or moves fore or aft. So I have to make the decision early on while cutting and welding.

Speaking of welding, tig, mig or gas? I'm thinking mig would be hard to do on the thin 4130 tube.

Jack

[1avidflyer 1983]

I believe the fuselages were welded with mig in the factory.  If you have the required skill, any one would work.  You can use your Matco wheels and such with either gear.  If you go with the cabane style and use your own wheels, verses grove gear and new wheels, you may have most of what you need $ wise for the monster shocks.  JImChuk

[lostman 198]

I cannot speak for tubing sizes either but Pursang, which was the only Avid MK V started as a C model, was stretched 16” then had a Subaru engine on it. It did well that way. Still had C model tail feathers although also had electric trim. It is what became the Airdale. Huge cabin space and different mixer/controls, etc. 

[allonsye 85]

Great thread you started Jack - and welcome to the group.

I'm all in and wanting to get my mods going this spring. I've been all over the place what with researching the most viable 4-stroke application on the Model C having considered HKS Turbo, Jab 2200A and 912.  So far, I've only committed to going 4 stroke but haven't come up with an engine.

Ahhhhh............and fuselage stretching.  I love Jim's work above..........

As far as landing gear, Whizzers (Bob McCaa) has built some very nice Super Cub style gear using springs instead of bungees which I've seen. There was someone else building this style but the long outside tubing were bending even with uneventful landings.  Bob came up w/the solution by adding a joint at the inside end of the axle where it connects to the cabane essentially allowing the loading to the spring.  There's some engineering data for cabane style gear in FAA AC.43.13 Acceptable Techniques and Practices and referred to on this board.

Paul

Edited 4 Jan 2020 by allonsye

[Jumpingjack 2]

Great thread you started Jack - and welcome to the group.

I'm all in and wanting to get my mods going this spring. I've been all over the place what with researching the most viable 4-stroke application on the Model C having considered HKS Turbo, Jab 2200A and 912.  So far, I've only committed to going 4 stroke but haven't come up with an engine.

Ahhhhh............and fuselage stretching.  I love Jim's work above..........

As far as landing gear, Whizzers (Bob McCaa) has built some very nice Super Cub style gear using springs instead of bungees which I've seen. There was someone else building this style but the long outside tubing were bending even with uneventful landings.  Bob came up w/the solution by adding a joint at the inside end of the axle where it connects to the cabane essentially allowing the loading to the spring.  There's some engineering data for cabane style gear in FAA AC.43.13 Acceptable Techniques and Practices and referred to on this board.

Paul

Paul, 

Thanks for the wwelcome!

I'm like you on the engine decision gotta be 4 stroke.  For that to happen the stretch and all the other mods need to be done so I can fly out of the short strip at my farm. 

Thanks for your added input on the cabane gear.

Jack

[Jumpingjack 2]

I believe the fuselages were welded with mig in the factory.  If you have the required skill, any one would work.  You can use your Matco wheels and such with either gear.  If you go with the cabane style and use your own wheels, verses grove gear and new wheels, you may have most of what you need $ wise for the monster shocks.  JImChuk

I need to get some scrap tubing and brush up my mig skills. I printed all your fuselage pics to compare to the C model when I get the fabric off.  

Did you move gear mount tabs for your cabane gear mod?  Monster Shock looks like the way to go. 

Jack

 

[1avidflyer 1983]

Only real changes I did to the fuselage, were the extra infilled areas below the doors, and seat truss, and widened the fuselage at the doors.  Didn't change the landing gear attachments.   If you look at the rear strut carry through on the Avid fuselage, you see some of the extra gussets the factory added for the MK IV, also at the top back, and middle back of the door area.  JImChuk

[allonsye 85]

Only real changes I did to the fuselage, were the extra infilled areas below the doors, and seat truss, and widened the fuselage at the doors.  Didn't change the landing gear attachments.   If you look at the rear strut carry through on the Avid fuselage, you see some of the extra gussets the factory added for the MK IV, also at the top back, and middle back of the door area.  JImChuk

Jim,

What's your power plant set up on your MkIV?

Does it have standard MKIV gear?

cheers:)
paul

[1avidflyer 1983]

I have a 2200 CC 4 cylinder Jabiru engine in my Avid MK IV.  For the last year, I've had the Lowell Fitt cabane gear on the plane, and I like it.  JImChuk

[Jumpingjack 2]

Only real changes I did to the fuselage, were the extra infilled areas below the doors, and seat truss, and widened the fuselage at the doors.  Didn't change the landing gear attachments.   If you look at the rear strut carry through on the Avid fuselage, you see some of the extra gussets the factory added for the MK IV, also at the top back, and middle back of the door area.  JImChuk

Jim, 

i see the strengthing you did and you say that's the only real changes to the fuselage. Trying to understand, is it lenghtend 16 inches? 

Jack

[1avidflyer 1983]

No, I never lengthened my fuselage.  It's standard length.  JImChuk

[Pascal 29]

There are some differences between the model C and the MK IV.  Seat truss uses heavier tubing, additions gussets around the rear spar carrythrough, and I think other things as well.  There is a post on this site from years ago, where Steve Winder from the Avid factory listed some of the differences.   Maybe someone can put up a link to that post. i

I think the link you are looking for is this one:

and then there is the wikia page here:

http://avidflyer.wikia.com/wiki/Models

i am planning to install a 100hp Rotax 912is into my Model C that i've purchased covered but unfinished about a year ago. as far as i could find out, the engine mount of the mark iv should fit also the model c and it is supposedly produced again by the new owners of avid. however, mine is on order since last summer and i still haven't received it or an invoice for it yet. so in case you need one, order early he is after all doing this as a hobby and has got family too, so i can understand that it takes some time to get it all figured out and organized. I hear Leny also produce(d) some 912 mounts which might be another option. for me a "original" mount is best due to the regulations here in Switzerland concerning experimental aircraft.

 

does anybody know how much horse power the Model C fuselage can handle before it needs to be reinforced? from what i read so far, the reinforcements on the MK IV where probably all to increase the VNE and Maximum Take-Off weight of the aircraft plus the reinforcements on the seat truss to help with the bending issue and the stock gear. Would be really helpful to hear if there where really some changes to the MK IV that actually are necessary to go from 65 to 100 or even more HP on the Model C.

in the wikia page they mention this: "In order to accomodate different engine choices, the vertical stabilizer was straightened and different engine mounts were built for left or right turning engines or gearboxes."

i am not sure what they mean by straightening the vertical stabilizer, hope that's not an issue here..

 

as for the apex, there are insanely performant Apex conversions available from Edge performance, but i doubt that a model C frame can handle 300hp without any modification .. also keep an eye on your VNE .. even if you build everything for STOL, your cruise might improve as well.. the Model C Heavy Hauler (which is what i have) has a VNE of 85kts if i remember correctly.. i've figured this might be a number to keep an eye on even with the 100hp Rotax, not to mention more powerful Apex variants. However, it allows me to add drag with skis, big tires and all that fun stuff without sacrificing actual cruise speed always look at the bright side i guess

cheers

Pascal

[Jumpingjack 2]

Pascal,

I think we're on the same thoughts. My C model is also partially covered fuselage only and I purchased it little over a year ago.  Originally wanting the 100hp roatax but the price, wow!  Still might have to go that route since there are some out there flying that engine.  Like you, I want the big tires and maybe amphibious floats! 

The Apex from what I've read, I think does not have to be the 300hp but detuned around 140hp stock, correct me if I'm wrong anyone.  I wouldn't want to exceed Vne but would like that reserve power on takeoff if needed.

Do you or anyone know if the fuselage mods will increase the gross wt.  on a C model?  It would be nice if it did.

Jack

[Pascal 29]

Hi Jack. i think money should not be the motivation to go for an Apex engine. People tend to compare a brand new airplane engine to a converted car, bike or snowmobile engine where the conversion starts off with a used engine with mostly unknown past. if you look at used 100hp rotax ULS or even overhauled ones, they are a lot more affordable than factory new ones. Stick around for long enough and you might find a good bargain that includes already some accessories like engine monitor, exhaust etc.

if you don't like to buy a used rotax, then don't start with a used Apex or whatever engine, because that engine could have been over-revved, crashed, run out of oil etc. just like any other engine out there.. only that people tend to care more for the engine when their life depends on it (as in an airplane at some situations) and less if it's just a fun toy..

after you factor in the cost for all the custom made parts you are going to need, the psru, engine mounts etc. you might end up with a higher price tag than a comparable rotax.

mind you, i say all this without knowing too much about the Apex conversions available, i've just spent a lot of time looking at conversions of all sorts of engines for all sorts of aircraft that i was considering to build or at least dreamed about building in the past.

the benefits you can get from a conversion are: better power-to-weight ratio (sometimes) or simply more power, use of a different fuel (i.e. diesel, Jet-A1, E85), sound (i.e. V8 conversions ;))

since you have trees at each end of your runway i suppose there aren't too many spots to land in case of an engine failure during take-off.. so you might want to consider reliability of an engine as an important factor in choosing your engine . If you go with an engine like a rotax, you not only get an engine that has proven its airworthyness in thousands of airplanes with millions of flight hours accumulated, but you get also an engine for which an information channel is in place to inform users of the same engine of defects found on others that might affect you as well. there is no such thing as AD's and all that for a converted engine from some other vehicle.

if you are on a tight budget but want to install a 4-stroke anyway, take a look at the 4-cylinder jabiru 2200. I've read on this forum that the whole insatllation weighs about the same as the rotax 582 but you get a few HP more out of it. There is even an engine mount available for the avid by jabiru which you can buy together with the engine in case you go for a new one. there are also plenty of avid model C's flying with the jabiru and every now and then one of them becomes available (or at least the engine and mounts do)..

i'm not a rotax sales rep or anything.. these where just my thoughts as i was weighing my options for the engine i wanted to mount into my avid ..

i may have to add, that here in switzerland we don't seem to be as free as you guys are, when ti comes to for example welding an engine mount.. here we need to have the work done by a professional welder (which i'm not), we also need to have every modification from a previously approved design checked by a certified engineer (which again, i am not) to verify the stability and what not. so for example stretching the fuselage would be a huge deal here. so in the end, for me it is also a benefit to being able to buy an engine mount that is already flying on an avid in switzerland and that's the case for both the jabiru and rotax.

cheers

pascal

 

[Jumpingjack 2]

Pascal,

Thank you for your very common sense approach to engine options. A bolt in safe proven option would be my first choice so the rotax 912 would be it.  This is the engine the manufacturers of ready to fly light Sport aircraft are using hands down. I witnessed this at Sun n Fun last year.  

With the 912 I shouldn't have to do all the fuselage mods and keep it as designed. 

As you say and one of my biggest concerns is my airstrip with trees at each end.  Proven reliability of the 912 would ease my concerns considerably.

Again thanks fo your advice!

Jack