TopModel Minus Slope Plane Review - RC Groups

TopModel Minus Slope Plane Review

If you are looking for a great flying slope plane that'll fit in the tightest of spaces, even the back of a Smart Car, The TopModels Minus is the model for you!

Splash

Introduction

I first saw the Minus when I was in Japan a few years ago. Iíve always had a love for elliptical shaped wings or wing tips so the Minus immediately got my juices flowing. I knew at some point Iíd have to own this cute little model. I was pleasantly surprised to find Icare was happy to provide the review model. I highly recommend Icare: I've had nothing but excellent service from them for the past 10+ years. TopModel's motto: Reduce to the max!

Wingspan:700mm
Wing Area:6.6dm^2
Weight:75.6grams
Length:572mm
Wing Loading:12.7 oz/sq. ft.
Servos:3 TS 1002
Transmitter:Airtronics RD8000
Receiver:Castle Creations Berg 4L
Manufacturer:
Available From:

Kit Contents

Items needed to complete the TopModel Minus:

  • 3 TS 1002 sub-micro servos
  • Zap and Zap-A-Gap
  • Sub-micro Receiver (Berg 4L works perfectly for 72mHz or a Spectrum 6110 RX for those using 2.4gHz)
  • Sub-micro Battery pack (4 cell 160mah NiMh 1/3AAA works perfectly )
  • UltraCote or similar iron on film

Assembly

The first thing I noticed about the Minus is that it didnít come in a box, but in a plastic bag. The bag contains all of the wood, wire, heat shrink tubing and anything else needed to create the airframe. Youíll want to gather everything together before you start building because assembly goes very quickly. I ordered the servos from Icare when I ordered the kit. I used the Berg 4L receiver from Castle Creations and a 4 cell 160mah NiMh 1/3AAA battery pack. Donít waste your time with a switch. All of these parts fit without modification to the airframe. Don't worry about the small capacity of the battery pack: With 3 small servos, the current drain is negligible, so 160mAh will last a very long time. I used ZAP and Zap-A-Gap during assembly as they are my favorite brand of CA products.

Wing

Wing assembly starts by removing the required laser cut pieces from their resting place and installing the wing hold down connectors and trimming the sheets for the wing joiner tube. The model has very little dihedral but do your best to get as much dihedral as you can. Note that the 4 leading edge sections have different lightening hole patterns. You should use opposing cuts on each panel. If you donít itís not the end of the world, but you wonít be building the plane the way it was designed.

I shimmed the TE as directed and installed the wing and aileron ribs. The wings were basically done at this point, requiring only sanding and separation of the ailerons. Take your time sanding the airfoil into the wing. Itís more important that both wings are sanded to the same airfoil shape than it is that they meet some particular airfoil. I sanded my wing so itís not symmetrical. You can easily tell when you sand into the bottom sheet of LE wood. I just made sure both wings showed about the same amount of bottom sheeting at the LE overlap. Also, once you cut off the ailerons the wing and aileron lose some of their structural integrity. Be careful handling the wings and ailerons from this point on as it only takes a little slip before the wood chips go flying.

Tail

The tail is made up of a number of laser cut pieces and goes together very quickly using thin ZAP. I sanded the top and bottom smooth, cut the elevators free and beveled the LE to allow proper movement. Using the supplied gauge, I set the V-tail in the gauge and sanded the root of each half to get a nice tight, clean joint and then CA'd the stab halves together, again using the supplied gauge. After covering, I used a tape or covering hinge. I have a photo of a second set of tail feathers that are a little bit larger. In this reviewer's opinion the v-tail is of marginable size. I did fly the plane with the designed stab and it seemed to fly fine. Further experimention will see if a larger tail creates any benefits or not. We'll keep you posted.

Fuselage Assembly

The fuselage is expertly designed in my opinion. The 1/64Ē ply doublers are relieved in places where they donít add any strengthening value, yet there are notches and grooves to allow the rest of the parts that mate with the fuselage to fit properly. The instructions tell you to relieve the fuselage sides where the V-tail wires exit the fuselage. I found it best to have the wires exit from the top of the fuselage as shown on the model. However the top of the fuse (F5) isnít installed at this point of assembly. Go ahead and relieve F5 (the fuselage top) for the V-tail pushrods before installing it permanently.

In my opinion, there are 2 areas of the fuselage that need a second look. One is the fuselage sides right at the leading edge of the V-tail. I think the manufacturer should have us add some carbon fiber or a 1/64Ē doubler from 2Ē forward of the V-tail LE to the back of the fuselage as this is a weak area in the fuselage. The second is the underside of the servo tray as shown in the photo. There is plenty of scrap 1/64" plywood to add these doublers and they only add a gram or so to the overall weight of the plane. Other than that, you can build the fuselage exactly as described.

Radio Installation

The fuselage contains precut servo trays to fit the TS 1002 servos and they just drop in place. I used a drop of Zap-A-Gap to keep them in place. Trim the elevator servo arms as needed to align them with the pushrods. The ailerons use one servo with a long arm. Itís a good idea to have the radio turned on when installing the control linkages as they are designed without any adjustment once they are set up.

Due to the size of the Minus, standard size servo and control hook ups canít be used. You can use Z bends at the servo end which is what I did. The hook up at the control surface is where Iíd like to focus your attention. The kit comes with pushrod material, a piece of 1mm diameter carbon rod and some heat shrink tubing. After a couple of e-mails with the manufacturer, I was told to use the carbon rod as a control horn. If you have experience with indoor 3D foamies, this method will be familiar to you. This was new to me, so here is how I tackled it: I already had made the wire pushrod the length from the servo arm to the hinge line. I used a Z bend at the servo end and left the wire straight at the surface end. I cut 2 sections of the carbon rod about ĺĒ long and ďbentĒ the rod at the ľĒ point, leaving a 1/2" control horn. The carbon rod didnít break in 2 pieces but it did lose its integrity. I then put the long end of the rod into the flying surface and put a piece of 1Ē long heat shrink over the carbon rod and used Zap-A-Gap to glue the rod and heat shrink to the surface. Youíll want the pivot point to be at the hinge line so you donít get uneven throws. The heat shrink keeps the carbon rod from completly separating and allows it to be used as the control horn and part of the aileron pushrod.

I bent the control surface down and allowed the wire rod to enter the heat shrink tubing and overlap the carbon pushrod. Then I allowed it to return the surface to neutral to make sure everything was correct before shrinking the tubing. I used a covering iron to shrink the tubing so I could control it better and make sure the surfaces ended up at neutral. Making up one half of the control setup was easy. Just take your time setting up the second side to make sure the surfaces are neutral to each other before finalizing the shrinking the tubing. Looking back now I would have made the "control horn" on the ailerons longer. The aileron servo arm is so long that you need very little servo throw. By using a longer control horn, you'll get less movement at the surface.

Completion

Since the Minus has lightening holes in the fuselage, it begs you to use an iron on film. I used Ultracote Lite Purple and Apple Green to mimic the color scheme on the package. Virtually any iron on material would be fine but I would stay away from iron on fabrics as the ailerons and elevators are very light structures and are easily warped if you arenít careful. Painting anything other than maybe the canopy would be out of question.

Flying

Basics

Since all of the servo arms are fairly long, I had turned down the servo travel to 50% on ailerons and elevator to keep from having excess throw. I didnít use any exponential to start with but that changed quickly.

You may think we are nuts, and maybe we are, but the first flight of the Minus took place with winds blowing 20+ with gusts to 30! The finished weight of the Minus on the plans state it should weigh about 100 grams (just a little less than 4 ounces.) My Minus weighs in at 76.5 grams or just under 3 ounces. We added an ounce of ballast to the bottom to bring the weight up to 104 grams and threw the Minus off of the hill.

Once the Minus got away from the face of the hill and into smoother air it seemed to settle down fairly well. It was obvious we still had too much throw as I would barely move the stick and the Minus would respond RIGHT THEN! I donít like making radio adjustments myself while Iím flying so I passed the transmitter to my flying buddy Mark while I started to change the exponential setting on the ailerons. Luckily, I got the direction right and after adding 65% exponential, Mark said the ailerons were working much more smoothly. Exponential smoothed out the Minus a great deal and I recommend you start with at least 50% exponential.

The instructions call for +/-12mm on the ailerons and +/- 8mm on the elevator and rudder. You really donít need that much throw but with the exponential dialed up you can easily handle the Minus around center stick.

Taking Off and Landing

The Minus gets blown around in rough air due to its weight, or should I say lack of weight. Itís best to get the Minus away from the face of the slope where the air can get bumpy. The main thing on landing is to make sure it lands with the wings level and the nose facing into the wind. There isnít much mass, but a cartwheel landing will pretty much re-kit the Minus. On our first outing the plane got into the dirty air on the face of the hill and just pancaked in flat and the tail section of the fuselage broke off. The V-tail stayed hooked up but the fuselage at the LE of the V-tail just hung there by the covering. This is the reason for recommending a doubler during fuselage assembly.

Aerobatics/Special Flight Performance

The Minus is a very aerobatic slope plane. It carries momentum much better than youíd expect a 3 ounce airplane flying in 20mph winds would, but it really goes. Mark and I were both surprised that the plane could do all sorts of things in the winds we were flying in and the Minus had no trouble penetrating the wind.

The ailerons and elevators are large and the Minus can be set up as wild as you dare. We are only using about 20 degrees of servo travel so there is plenty more if we want, but even with ďreasonableĒ throws the plane rolls quickly, loops in 10í diameter circles, does some of the quickest race turns youíve ever seen! All in all, itís a blast to fly!

The only thing you need to do is keep it in fairly close as it gets small very quickly. For ďin your faceĒ aerobatics, itís perfect. We plan on taking it out to some smaller slopes when the winds are a bit less, but we had a blast in high winds. Now that we have the fuselage reinforced, weíll let other pilotís have a hand at her in the high winds. Itís a riot!

Is This For a Beginner?

A lot of times, beginners think that small means beginner-friendly. Unfortunately, this isn't always the case. Even though construction and radio installation are documented extremely well in the instruction, due to its speed and aerobatic tendencies, we canít recommend it to beginners as a first or even as a second airplane.

Flight Video/Photo Gallery

http://www.vimeo.com/2046000: The Minus in action. This video was shot by my buddy luger007.

Conclusion

If you are a seasoned pilot wanting something unique that you can fly almost anywhere and do more than simple side to side passes, the Minus fills the bill. Construction is dead easy, and there is no reason the airframe canít be built in about 4 hours. Covering will probably take longer than building. It carries momentum better than expected, fits in the back seat or trunk of even something as small as a Smart Car, so now youíll have no more excuses for not having a slope plane to fly.

Pluses:

well engineered kit

unique looks

easy radio installation

excellent quality components

Minuses:

definitely not for beginners

control hookups require complete builder attention and are non-adjustable when complete

Last edited by Angela H; Jun 27, 2010 at 02:07 PM..
Thread Tools
Jun 28, 2010, 01:03 PM
Registered User
machinate's Avatar
Great review, and what a nice-looking plane!

It sounds like you had a lot of fun with strong winds; how does the Minus handle very light lift? I don't have very much around here by way of hills, but I've been wanting to try my hand at slope soaring, and this looks like it might be the plane for me.
Jun 28, 2010, 05:14 PM
Registered User
gavoss's Avatar
The plane does well in 5-10. However the shape of the slope and the angle of the hill have a lot to do with lift produced. If you can give me an idea of what the surrounding areas you are likely to fly in, I'm sure I (we) can give you some guidence.
Jul 02, 2010, 11:24 AM
Registered User
machinate's Avatar
I've got only one barely tolerable hill, about a hundred vertical feet with about a 1:1 slope. There are unfortunately a few trees at the bottom of the hill, but when it's windy you can feel the wind coming up the slope, so presumably there's at least some lift available. I gave the concept a try with a fanfold flying wing, but it wasn't nearly sleek enough for that hill - the horizontal component of the wind was too much and the plane couldn't make forward progress or even hold ground without losing too much speed. It's been a while since I tried it, but I distinctly remember thinking that something with similar wing loading but a way better L/D ratio would work.
Jul 02, 2010, 02:37 PM
Registered User
gavoss's Avatar
The hill sound at least try-able. 1-1 is very good but the trees, depending on their height and density will make a huge difference in how clean the wind comes up the hill. If you have a Gentle Lady or something similar, I'd try that first. If that works, then the Minus just might do the trick! I hope that helps. George
Jul 04, 2010, 02:10 AM
Registered User
I can't seem to get the links to the MFR or retailers to work. Seems they might like to sell me a kit.

Thanks for the help.

Walter
Jul 04, 2010, 10:34 AM
Registered User
gavoss's Avatar
http://www.icare-rc.com/

Tell them George and the gang at RC Groups sent you.
Aug 14, 2010, 03:43 PM
Registered User
Thanks for the excellent review, George!
I'm just thinking about battery for this plane. Please can you tell me weight of your battery pack? I'm really thinking about using 1s LiPoly with voltage booster to 5V and I'm not sure what capacity to choose.

Thanks for help.

Jakub
Aug 14, 2010, 03:49 PM
Registered User
gavoss's Avatar
The adverts say 4-5.5 grams each. Add a few grams for wire and plug.

I thought about going with a lipo, but the NiMh seemed like a much easier solution given the space alloted. George
Aug 14, 2010, 04:05 PM
Registered User
Try this:
400mah 1S Lipol
http://www.hobbyking.com/hobbyking/s...idProduct=7570
with Booster:
http://www.hobbyking.com/hobbyking/s...idProduct=7884
Weight of the LiPol should be 10g, Booster could be around 5g max I guess.
Sep 25, 2010, 01:54 PM
Registered User
I finished the Minus Acro finally. Plan to paint the canopy with silver spray later.
Final (ready to fly) weight with 2 leads in the fuselage: 100g
Electronics:
- 3x BMS 303 JST Servos (replaced connectors with standard conn. since I didn't notice the wrong connector while buying).
- DSM2 Compatible Parkflyer 2.4Ghz Receiver from HobbyKing
- 1S 400mAh Li-Pol
- Voltage Booster for BEC

Don't buy any bigger battery since this is maximum width that fits! It's pretty tight there in the fuselage as you can see on the second image.

I wanted to do a maiden flight today but since it was terrible weather here - raining for the whole day, I'll need to postpone it (very difficult to adore ).
Oct 08, 2010, 07:28 AM
Registered User
Tested last weekend on a slope in wind between 4-8m/s. Great flying performance in wind gusting at 8m/s, I couldn't believe how easily it flies. Turbulences are not a big issue for this pretty agile model.
I let the recommended maximum throws as it is (12mm ailerons and and 8mm rudder and elevator) without any expo (100% expo). Haven't flown more agile model ever.
Definitely not for beginners but on the other side the model flies nice and there are no tip stall issues or other deadly stalls etc.
It can fly both slow and fast without any problem.
I can strongly recommend this model to anybody who ballances between buy or not to buy dilemma .
Sep 08, 2011, 07:04 AM
Registered User
warriorswede's Avatar
I recently got a hold of this kit, it looks like a fun plane

It's my first pure glider and a question pops up...

topmodel writes on their site: "For the slope or in towing behind a park-flyer."

But I can't find any info on where or how I should mount a hook for towing, can anyone help me here?
Sep 08, 2011, 09:32 PM
Brett
bjaffee's Avatar
Quote:
Originally Posted by warriorswede
But I can't find any info on where or how I should mount a hook for towing, can anyone help me here?
As for location, as close to the nose as possible (or in the nose) is usually best for aero-towing. You'll need some sort of tow release, of course.

A long time ago I did a review of the Scorpio Habicht, which has a tow release in the nose, that's driven off the elevator servo (meaning you have to give a quick jab of full elevator for it to release)....


Basically you've got a little pushrod that engages into the metal loop at the front. The push rod pulls back from the loop and allows the tow hook to disengage.

There's a few more pics in the article...
https://www.rcgroups.com/forums/showthread.php?t=129168
Sep 09, 2011, 12:15 AM
Registered User
warriorswede's Avatar
Nice! Thank you.
Nov 01, 2011, 02:49 AM
Registered User

Done


She is finally done!

I added some reinforecments to the tail, one standing and one flat CF strip, her tail is very stiff so she should be able to handle some rough landings

I havent put her on the scales complete yet but she's on the heavy side I'm guessing 115g lol

There havent been weather or time to allow for a maiden yet so I don't know how she performs, hopefully I'll get her in the air some day soon.

This is how she looks:


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Anyone flown a Topmodel Minus or Minus Acro? slippy_fish Slope 62 May 17, 2011 04:18 AM
Sold New, never flown Wilco/Tiger F5B Topmodel/CZ complete minus rx AndrewsJr Aircraft - Sailplanes (FS/W) 8 Nov 06, 2009 12:31 PM
Discussion Topmodel Minus toyheli Slope 2 Jun 22, 2009 12:11 PM
Video Topmodel Minus Acro LnsPilot Sailplane Talk 7 Mar 30, 2009 05:09 PM
Sold Awesome MINI SR7 slope soaring AIRPLANE ready to fly minus RX camperfan Aircraft - Sailplanes (FS/W) 2 Mar 03, 2008 02:01 PM