Good Morning ! 20 years and a few months ago, as I was shopping in the now, long gone Harding Mall in Nashville, I found a copy of the latest Flying Models magazine (November 1997 issue). It featured the Akro-Knat family of fliers, designed by Michael Chattin. "Wow, this looks like fun" said I, and it was off to the cashier. Being in the middle of raising a family, the magazine was lost at some point, and well..... About five years ago, I started thinking about that airplane and actually found a copy on EBAY, which I bought and then ordered the plan. This would be my first attempt, after all these years, to build an RC airplane. I actually did build much of the model, and had decided to modify the wing from straight with ailerons, to a dihedral wing and no ailerons, like a trainer. In the end, I did not have much success in joining the wing panels and scrapped the project. 2018: Now that I have one airplane finished, an old timer, and am feeling more confident and committed, I have decided to build the Akro-Knat once again, and do plan on success this time !! At first glance, there is nothing spectacular about the Knat, but I have actually always liked it's look. Michael Chattin's goal was to build a "sleeper" plane that possessed amazing flight performance, including the ability to fly slowly, really well ! As the designer states, it is the airfoil tweaking he did to achieve what he felt was the best flying airplane he had ever flown. I am surprised that there is not more on the web about this plane, but what I have found are very positive comments that this really is an airplane that flies incredibly well ! I did try to find a link to Mr. Chattin, but came up empty.... Anyone out there know him ?
My goals for this build are to convert in from .25 glow power, to electric. Build the wing as intended, but do dual aileron servos instead of one, and to build in a two dowel and two bolt setup to secure the wing, instead of the four bolt method. I am going to try and save some weight here and there, but it will still be around 3 pounds, I think... And on this build, NO PLASTIC WINDOWS !! I will also be using a heavier covering material...I did like the Microlite that I used on my first build, but this airplane will need more. I had started on a Velie Monocoupe last fall, but quickly realized that it would be a LONG build and had some difficulties that I was not ready for, so I have neatly stored the parts I built and may, or may not go back to it. The Akro-Knat is much more "straight forward" to build, not easy, but not that difficult either. I am just getting started, and will probably document most of my steps as I go. I do like Pics ! Well, that's all for now, be back soon. Have fun out there, Mike

Hey, Mike, we love seeing planes get built around here. Pictures, lotsa pictures!!!

Andy

Looks like a pretty strait forward build. Yes LOTS of photos but don't let photo taking hold up the build! The Knat looks like it will be a nice flier!

Ken

Good evening ! Andy K and Ken H, Thank you ! I hope to do a solid build, and don't mind taking plenty o' pictures ! I was really glad to get this build going this past Friday morning, and as the day wore on, I realized that I was about to get flattened by the flu... I made it through work Friday night, but barely. Today, is the first day I have felt normal-ish, if that includes keeping a box of tissue in reach at all times.... While I am working on the fuselage formers, which involves a lot of gluing/clamping/waiting, I decided to start on the tail feathers. The fin, for example, is built with 1/8" x 1/2" strips of balsa and then covered with 1/16" balsa, both sides(of course). The designer refers to the build up of the stab and fin as "stressed skin" components that are stronger and less than half the weight of solid sheet parts. Ok, cool ! As I will point out many of the design highlights of the Akro-Knat, (quoting the designer) it is clear that Mr. Chattin put a lot of thought into this aircraft's design. Back on track now, my only deviation with the fin is making the inner frame with 1/8"x7/16" balsa, And adding a tab to fit into the stab, instead of the 2 dowels on the plan. I did discover that my little balsa stripper does not like 1/8" balsa as much as 1/16", so had to try something else... I figure that using the 7/16" strips will not not save much weight, but with some other planned small changes, I hope to save an ounce or three. I am guessing that an electric powered air frame does not need quite as much as a Glow powered air frame. Glad to be started, this is going to be even more fun when the Flu has Flown ! See ya' later, Mike

I made a trade for a built Astro Gnat soon after it was published some long time back. Flew up a storm with it powered by a Norvel 15. It would do a really great flat spin along with anything else I could think of trying, it was good at touch and goes too , it would slow down real nice. You should love this model.

Thanks wingtips ! I am assuming that you had the mini Akro-Knat....(?) It seems that everyone that has flown, or seen of the these fly, have all had great impressions of it, which I am really glad to hear. So, I am going with the Hype !! Well, the Nashville Metro area got a nice coat of snow, just 3 + inches, which is a good amount for here. Still home sickly, and am about to run out of tissues, but did manage a little work today to take my mind off the last hurrahs and sniffles of the darn flu. Started on the rudder, which has a core of solid 1/8" balsa and will have 1/16" parts attached on both sides. The parts that need to be laminated, are done mostly with 30 minute epoxy. I am following the suggestions on the Airfield Models Website, of laying the epoxy down and then scraping most of it off, So it's just a very thin layer. I know that large sheet parts laminated with wood glue can possibly warp, due to the water content in it. The Airfield Models guy, whoever he is, does have some really good ideas, and I will be also using his method for mounting the servos in the wing. Here is where I am tonight, and should be done next evening or so. See ya' then, and have fun ! Mike

Good evening ! Here's a few pics of today's progress Was able to pick up some 6" wide 1/16" balsa sheets for the fin and stabilizer at the LHS. The owner commented that these had just come in--- Good Timing! Also, picked up some wide brushes for laying on the epoxy to the fin framework, for the sheeting. The rudder is done, minus the 1/64" ply "Exoskeleton" plates on the bottom. I did center all the false ribs slightly different than the plan showed. The rudder did take longer than I thought, lots o' gluing and clamping, and waiting. Anyway, let's go to the pics.... See ya' soon, Mike

Good day to all ! When mixing epoxy, I always seem to make too much, but am starting to get better at it... Did two rounds of mixing and gluing to finish the fin and I really like how it came out. It is a full 1/4" thick and seems quite solid, but it has to be a bit lighter than a one piece unit. Well, the stabilizer is next, although something happened to the plan copy(which I will explain in the next post) and I will need to draw in some minor corrections. Unfortunately, I don't have the original print, which for some stupid reason, I must have cut up when I first tried building the Knat. Suppose I could order a new one from Mr. Thayer, but I can make this work. See ya' soon, Mike

Originally Posted by ms62tn

Good day to all ! When mixing epoxy...

Please excuse the intrusion, but I'm curious as to why epoxy seems to be such a popular choice for gluing balsa. I'm an aged beginner, with little experience, and have maybe missed something somewhere. For general builds, such as the type of construction you're doing here (and very good it is too, I might add...), I use plain old wood glue (the white stuff; I think it's known as 'PVA'...). I do use epoxy, but specifically for joining dissimilar materials, such as wood to plastic, or wood to metal. What advantage does epoxy bring to the pieces you're joining here over wood glue..?
Please note: this is in no way a criticism; I'm genuinely puzzled, as I see this in quite a lot of 'builds'. What am I missing..?

Dad, actually, for me, using a lot of epoxy is something new that I am trying. The guy at Airfield Models, an old article from Don Dewey and Lee Renaud, and a few others have suggested that large gluing areas can possibly warp when using wood glue, because of the water content. My last build had mostly small joints( stick framed old timer) and I did not worry about it. With this aircraft, there are many large parts that are sub-framed, then sheeted... So, I thought that, perhaps, trying a very thin layer of 30 minute epoxy may be the ticket. My decisions are based, not scientifically, but on the suggestions of really experienced builders. With my rudder, for example, I did use wood glue for the small "false ribs" and will use it on many other parts, as well. The designer of this airplane did, in fact, state that he used mostly CA to build the prototype Akro-Knat. I am going a bit different I guess. But that's ok....Coke or Pepsi...Big Mac or Whopper.... what ever floats your boat.... I just figure that using epoxy could go wrong quickly, adding a bit more weight than necessary. I am using the method of applying the adhesive, then scraping of most of it until it is a VERY thin layer. In the end, I hope my decisions are correct, but I guess ya' gotta' try it out and see what happens. I am still pretty new at this, as well, but I do like reading build articles and gathering info, and then mixing it all up and TRY to make the best guesses, based on other peoples experiences. It is almost always Fun, which is the most important thing !! Just my two cents...... Mike

Thanks for the explanation, Mike; much appreciated. It makes sense to try things out oneself. Now back to your very interesting build...

I haven't had a problem with them warping, but I use minimal Titebond and have the wood held flat under weight while it cures. In fact, I just built a tail that way in my Neo thread (see post #7).

Andy

Dad, you're welcome. Although, Andy, you are correct, I am sure. Clamping things surely makes it flat. But again, I am just trying something new... I figure, why not. Last night I got started on the stab build, and had to add a couple of corrections to the plan. It seems that the copied image did a little shifting, and also the main rear spar(?) line had a bow. I am guessing that the shifting may have caused one side to be a bit shorter from the center line, SO, I extended the right side by 3/16". After measuring 10 times, not really, I marked the minor corrections, taped the plan down and covered it with the ol' wax paper. When I cut the main spar from the 1/8" sheet, I noticed that it had a little bow. Curious, me thinks.... I wonder why.... No biggie, It straightened up against the straight edge when I set it up. Well, heck, let's do some pics to show the first part... Having fun, Mike

This is on page 6, "Editorial". Thought I would add this, as part of the reasons for wanting to build the Akro-Knat.....

" It must have been this past February when Mike Chattin first called and told me about his KNATS. We're always open to proposals about construction articles so I listened and said sure, send some pictures and info. Then we'll talk. Mike was a little more insistent than that(nicely so), and suggested that he come up and fly the KNATS(Akro and Mini) right here at the offices. Who was I to say no to such an offer. A first hand evaluation of a proposed construction article. Well, the winds came in March and didn't stop all Spring here in northern Jersey, but Mike still wanted to trek from the far south of the state all the way up here. That's how convinced he was of his design. One fine March day( overcast, temps in the low 30's, and wind at a comfortable gust of 15-20 mph) he arrived and we flew. I will tell you I then understood his conviction. At first glance, there's really not much to distinguish the KNATS from other high wings. Get your hands on the control sticks, and this apparent mild- mannered model reveals another personality that is precision itself. Rolls are quick, points are crisp, verticals keep going, and when you slow it down it will walk along with absolute control, no tendency to break. After an hour and a half, we felt guilty about enjoying such wonderful weather, and came back to talk a little more about the design of the plane. Mike was just as enthusiastic and convincing about this as he was about the flying characteristics. It seems that this KNAT was a whole lot more than just a variation on the usual high wing theme. There was a lot of careful thought put into the plane to achieve just the results he wanted in flying ability, strong but light construction, and something you don't always consider up front: transport of the model. What was an even better part of this whole project was the fact there were two KNATS in the family, the Akro( which we flew) and the Mini. Both are presented here. It's your choice-- small and smaller. Or take both. Even if you don't build them, read Mike's article. There's a lot of intellegent design philosophy that just might stimulate you to build your own wonder ship. "

Howdy ! Cutting diagonals can be fun, for some reason. This time, I would make one for the left side, then make an exact copy for the right. The copies go really quickly, too. My only boo boo, was that I forgot to shift the right side diagonals to go along with the drawing corrections to my copy. Should not really matter, as the stab is covered with 1/16" sheet anyway. Just nit pickin'. I did do all the frame work with 7/16"x1/8" balsa, instead of the 1/2" wide strips. Actually, the 2 diagonals next to the center section are 9/16" on the plan. Overall, I hope I have saved , at least, a tiny amount of weight. I hope it adds up by the time I get to the end, by at least on ounce or three. Worth a try... The plans shows lightening holes in the rudder, elevators, and wingtips. The holes in the rudder and elevators vary in size, the wingtips holes are all the same. I could do these, or not. If I decided to do 'em, finding brass tubing this big could be expensive. Don't want to spend 50-100 bucks on a set of forstner bits. I wonder if I could use copper plumbing sweat couplings and just sharpen them ? Hmmm......Maybe more on this later. Have fun out there, Mike