MTK

After completing my Aesthesis last Fall, I needed a new project. I am calling this one Derivative.

I acquired a XIGRIS fuse complete with chin cowl and canopy....extremely light weight. Wing, stab and rudder will be my tried and true surfaces from Temptress. Before building this plane, I intend to make a set of molds for it for future experimentation

I also acquired a BME 58 gasoline engine, intended to power Derivative. Weightwise, it's gonna be close. The 58 weighs just 43 1/2 ozs., only 1 1/2 ozs more than the ZDZ 40 F3A, but at 6 HP, puts out about 1 1/2 times the power of the ZDZ. This is gonna be fun

cmoulder

Matt, will this one be ready for the upcoming season?

I like the name. It says it all!

Can't wait to see it - I applaud your relentless effort in the pattern gasser niche. I am guessing the BME has thin cylinder walls and big fins. From the photo I have seen, the carb location isn't exactly pattern cowl compatible. Any modifications on that... some way to make it rear induction?

I will fire up the SAP 180 when the snow clears from the fields and will continue flying the Focus II as I work on the electric Pentathlon Evo.

MTK

Bob,

I will try. With the knee well on it's way of being whole again, I am finding myself with lots of creative ideas. The BME 58 is the Xtreme version, high compression and moderate timing, that "requires" 100LL Avgas. The carb is awkwardly located but I can modify the fuse to fit everything.

The guy at BME was adamant about NOT building a rear intake version. The engine has a far rear bearing in addition to the regular rear bearing. The crank is supported from both sides. I can see his point; the engine is reported to put out considerably more power than others in this size, but we shall see. It will be interesting

Talking SAP 180, I hadn't looked at Aesthesis since last November, early, last time we had flying weather here. Then of course, the leg operation sidelined me for the past 2 months. Anyway, this past Friday I looked at her and saw that I left gas in the tank. I had not winterized the plane...damn. Well, I emptied the tank, rocked the prop a few times, and powered the ignition. Son of a gun started on 1 flip. How 'bout that!!

rcpattern

My Feedback: (45)

Very cool. I'm anxious to see this baby come to life. Hope everything is going well after your surgery. Send some pics, I can always use them in a K-factor article.

Arch

MTK

Archie,

I'm taking snaps of the mold making process. Since I did an article around 9 years ago for the KF on mold making, I don't recall if anyone has done a new version in that time frame. The original photos were of very poor quality. This one will be much better.

Are you the new KF editor?

rcpattern

My Feedback: (45)

Nope, I'm the new D1 VP. Shoot me a pm with your email address. I had a couple of questions for you since you are the judging guy...

Arch

MTK

I am still in the process of molding the parts. The canopy and chin cowl are completed; the fuse remains. If anyone crunches a canopy or chin cowl for Xigris, I've got you covered. PM me

I have not started to build the plane as yet but will discuss some of the finer points adapting the large gasoline engine to this airframe. Pipe and header will be here next week so I can get the pipe tunnel built.

J Lachowski

My Feedback: (46)

Matt,

My stock finished canopy weighs 5.2 ozs(148 g). Based on the way it is constructed (nice and stiff though), I bet you you could knock out one that might be a bit lighter?

In contrast, my Integral canopy which is very close to the same size and shape is 3.7 ozs.

can773

My Feedback: (1)

Hi Matt,

While I certainly appreciate your efforts, I don't think it is very respectful to the owner of the Xigris design (ZN Line) to publicly announce that you are copying it, and offering up replacement parts to individuals.

I have worked with Jean-Pierre and ZN line for many years, and know they put a lot of time and effort into their designs. It would be unfortunate if activity such as this would ever cause them to move away from F3A. We all know there are few options available today, and having even less would be unfortunate.

To say that he was extremely unhappy to read your post is a grand understatement.

MTK

No disrespect intended. Thanks for your input

Why would they "move away from F3A"? First, I am not going into the business of building model kits for the world stage....I am not their competitor. Second, mine is strictly academic curiosity to see if I could do something. Have no interest in building whole airframes for others, just myself. Third, longer term, my intent is to experiment on this fuse design. As I said before, the power plant is a 58 cc gasoline engine. The front of the fuse will be highly modified to accept the large engine.

Jean-Pierre should be glad that I chose this model to play with. There were others I considered. He is free to use the ideas I will present here-in. The only thing I will ask is that he give credit.

If any one is interested in using similar equipment in theirs, then follow along. This will not be another mondane build thread of the model; that's been covered by others. But I do have a couple new things I am interested in teaching others, and I will showcase them in this thread

MTK

Joe,

I've molded nearly identical canopies before (Temptress, Impact) and these weighed around 4 ozs, painted in the mold. 5.2 ozs is a little heavy. The original part I used to make the mold weighed around 4 ozs. so yours may just be a heavier part. Hand lay-up tends to be a little variable.

When I pull the first parts from my mold, we'll see where we are weight-wise, and if we can take weight out, we will.

MTK

Just weighed the canopy of my model and it was very light, 3.9 ozs.

MTK

The fuse has holes cut in it for wing and stab. These looked very low on the fuse.

I put the fuse on my reference table and started to measure locations of cut outs.

Nose is square to the table top when the bottom of the fuse in flush to the bench and the tail is raised 3/4" off the bench. The center of the shaft (nose ring center) is 7.225" above the bench top

As I thought, wing is about 3" lower than the thrust reference line inscribed by the crankshaft. A wing this low will require a bunch of dihedral and I just don't want that much dihedral; also don't like a wing that low, a very 70's retro look.

The stab is about 2" below the reference line which is also much too low for my liking. The 1" separation will require about 5 degrees of dihedral in the wing for zero roll couple. The wing I will use has 3 degrees of dihedral...so the 1" separation will be reduced to 5/8"

Looks like I'll be filling and sanding tonight

Here're a couple snaps showing what I'm talking about

MTK

On a friend's input, I made a few more checks on the fuse. With nose ring vertical (zero downthrust), the canopy floor line is NOT parallel to the bench top. If the wing CL and canopy floor line are made parallel, the nose ring will have about 4 degees upthrust. Provision will need to be made to get thrust to zero (or 1/2 degree down)

J-P

My Feedback: (1)

I think you should double check again....

J-P

My Feedback: (1)

[quote]ORIGINAL: MTK

Build it as the designer intended and you won't go wrong


_____________________________

Regards,
MattK



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That's a very good advice ...

DagTheElder

MTK,
Do establish the datum line propshaft and stab tube center. This should result in cockpit floor at app. -3,7 degrees.

Regards
Take a look at this thread
http://www.rcuniverse.com/forum/m_10206028/tm.htm

MTK

Dag,

Doing that requires a few degrees downthrust

MTK

I measured again as J-P requested.

Nose ring perpendicular to my reference table. Canopy deck was visibly tilted forward. Measuring with a height gauge I got a height at the front of the deck of 9.112" and at the back of the deck, 9.680". The canopy deck has a length of 13.25"

Doing the trig, the deck is tilted fore 2.496 degrees; in other words the deck flange is at -2.5 degrees.

Anyway, I prefer stab and wing closer to thrust line so that's where I am going in my set-up. I raised the stab CL 20 mm. Wing CL is set at 15 mm below the stab CL (meaning the wing was raised), or an average of about 95 mm below the center of the canopy's deck. Downthrust is zero

DagTheElder

So you are going to re-position the wings on your rebuild, interesting!
How much dihedral are you going to put into the wings measured at tip from root cord or center line??

Regards

mjfrederick

Matt,

Is there a reason you decided to remove the built-in down thrust by moving the wing rather than making a wedge shim for the nose ring and adjusting the angle of the firewall when you glue it in? Just seems to me like that would have been easier than filling, sanding, and recutting the wing tube holes on the fuse.

Matt

MTK

Dag,

Both wing and stab are moved. I like them both closer to the true thrust line of the model.

A separation of wing (lower) to stab of 14-15 mm requires 1.5 degrees of dihedral per panel (3 degrees inclusive) for zero roll couple. For my wing design this works out conveniently: I build in the sockets with the wing upside down, flat on my refernce table.

I've used these parameters for years with really outstanding success. I expect similar with this fuse. The main variable is fuse depth.....much much deeper than anything I've built earlier. We'll see if I need to build a second wing with different dihedral

MTK

I don't want 2 1/2 degrees downtrust. The plane will need about 2 1/2 degrees right thrust for the powerplant I am planning, and that's bad enough. Putting a shim in the front to compensate is fine but it didn't solve the main issue to suit my taste

I needed to move the wing and stab to my liking regardless. That requires filling, sanding and refinishing so that I can build the mold

A side note on the existing cutouts for wing and stab. With the nose ring square, wing holes are cut to produce approximately 1/2 positive incidence; stab holes are cut to produce zero incidence.

Bulding the thing stock, the only reference you need is to make sure the nose ring is square to the reference table. If you use a different reference, you're on your own.

mjfrederick

OK, so you wanted to move the wing anyway, and this just made it one mod instead of two, just checking, thanks.

DagTheElder

MTK,

I have also been using this method for years to install sockets into wings. Why Iam asking is for a kind of check and balance.
The separation of wing from thrust line Iam using is 5-10mm down to the max thicknes of wing.
Well, all the figures remain to be verified as soon as the temperature rises some, currently it is well below zero and forcast is bad temp. vice.

Good luck with your re-build.

Best regards