Posts: 366
Score: 100 Joined: 6/9/2008 Last Login: 4/28/2013 From: Perth WA, AUSTRALIA Status: offline
I thought it will be good to highlight here few issues I had with the Ripmax WOT 4 XL Mk2 I just completed.
The kit came nicely packed without any damage, and the build went together reasonably quick (putting the main components such as wings, tail surfaces and the landing gear).
However, this is where the fun ended. As I looked at attaching the wing I found that only one hole was drilled for the wing screws. Not a worry, I measured and drilled the second hole. Then, as I was fitting the supplied screws, one side went in perfect, but the other didn't. As I was worried that I will ruin the thread, I had a look and found that the lock-nut thread was damaged from the factory... the lock-nut had to be replaced. Lucky, I had some Du-Bro nylon wing screws and matching lock-nuts in stock. This is the first time I used a hammer on an aeroplane at the build stage, but this was the only way to get the lock-nut out. But this was just the beginning...
Then, came the Pull-Pull setup. This stage starts with installing the threaded horn through the pre-drilled hole in the rudder. Unfortunately, the hole is not wide enough... So the hand drill came out and the hole was enlarged to the correct size.
Then, I was surprised to find that the instructions suggest that the cable will be passed through the brass tube, looped through the adaptor and back though the tube in a loop, only secured by crimping and CA glue (see picture). My experience with Pull-Pull always had a third pass through the brass tube so the edge of the cable cannot come loose. The brass tube supplied was too narrow for and only "two" wires could pass through. The other issue was that the metal cable was bare, and touching the slot edge it would cut into the fuselage. I replaced the whole system with Du-Bro 4-40 Pull Pull (lucky I keep my own stock of miscellaneous items).
Then, you are instructed to push the wires through the slot in the fuselage "ensuring they remain untwisted" shaking the wires into the radio bay. One word of advice here, if you do that, you will not be able to fit the elevator rod...
So, on to the elevator rod, which has Y fork at the end which you suppose pass through the cut-out slots at the sides of the fuselage "using couple of lengths of scrap snake"... Obviously everybody have some at their disposal. I actually did found some that will fit the 4-40 thread at the end of the Y fork, and after much struggle got the fork out. There is no way, to my opinion, to insert this rod if the rudder wires are already in place.
Now, if you wondered how easy it is to bring flexible pull-pull wires from the tail to the radio bay when obstruction in the shape of control rod with Y fork are in place, I can save you the guess and tell you it is not going to happen. You get the point by now... Very poor design for the whole setup. I had to use long metal rod with "hook" at the end to "fish" out the wires pulling them above the rod. I got both through on the 6th attempt (3.5 hours bending over the aeroplane so I can see into the tail) If Ripmax would have left draw wires in the body for the pull-pull it would be the easiest of jobs...
Control Horns - Obviously Ripmax use the "one size fit all" method. Look at the length of the screws supplied with the control horns in the photos... When you try to apply pressure on a screw that long, to fit into the SQUEAR notch, guess where the screw driver is going to end? If you answered the horizontal stabiliser, you need read no more... The control horns were replaced by a Du-Bro set... I could probably use the supplied set, but I lost my temper by the third hole in the stabiliser.
Balance - The left wing half was much heavier then the right wing half, so the sticker was applied to the right wing with 10g weight glued to the wing tip (inserted and then re-covered on top). With batteries in the proposed location (the bay in front of the receiver in the photo), the aeroplane was extremely tail heavy. Both batteries (one for ignition and one for radio) went into the fuel tank compartment.
OK, now to some modifications / my installation preferences I made to accommodate the Saito FG-20 petrol 4 stroke which I had from previous aeroplane to be fitted to this one: 1. I modified the fuel tank with a set up for petrol operation (petrol compatible gasket, Tygon tubes etc). 2. I installed the engine upright to easy the access to the throttle arm, which on the Saito is at the centre. 3. I used the Saito metal engine mount using my own mounting screws with nylon insert lock nuts. 4. I cut the top of the front of the fuselage and made a hatch. I then installed one 5 cell NiMh Eneloop battery pack under the fuel tank and one on top of it, and also inserted the ignition system. All this weight was required to balance the aeroplane. 5. Rexcel optical kill-switch was installed for safety 6. The cowl will be fitted at a later stage.
For to control system, I used the following: 1. Two JR Heavy Duty switches with charge socket installed 2. All servos are Hitec digital servos (different servos I had laying around), all rated higher the required. 3. Receiver is Spektrum AR7000
If all goes well test flight will be done tomorrow. This aeroplane is intended to be my "throw around" model, with second use for introduction flights to potential new club members (on very reduced rates and dual TX)
Posts: 366
Score: 100 Joined: 6/9/2008 Last Login: 4/28/2013 From: Perth WA, AUSTRALIA Status: offline
I had the maiden flight today. The good news is that it all went well and the aeroplane fly as expected. Smooth, predictable, exactly what you read about when the WOT 4 is discussed. The aeroplane make you feel in control from the second the wheels leave the ground. Balance was spot on as in instructions, my WOT 4 was balanced at the middle of the range
The bad news from today, is that couple of major issues were discovered.
1. Ground handling - Very poor, almost not exist. The tail is too light to provide steering and the main wheels are too far back causing tendency to nose over. I will move the landing gear forward and install bigger wheels and see if this improves.
2. The control horn opened up in flight. See photos below, one aileron disconnected and the other started to open up. The threaded section of the clevis actually opened up. This is outright dangerous, occurring in 3 clevises in a single flight.
Conclusion so far: Get the kit, but treat it as scratch build. Replace everything to do with control supplied with this kit as a safety precaution. Definitely the clevises and the pull-pull system. Re-locate the landing gear forward to improve the ground handling
Posts: 366
Score: 100 Joined: 6/9/2008 Last Login: 4/28/2013 From: Perth WA, AUSTRALIA Status: offline
Now that I started to address some of the issues, I found out how bad the clevises were. The 3 clevises in the photo are from the Elevator setup. All started to open up. Only one out of seven used on this aeroplane didn't open up.
I replaced all clevises with the Great Planes product as in the photos, which I happen to have in stock. Also having the retaining mechanism, I still used the silicon tube just in case.
I replaced the second nylon wing bolt and lock-nut with DuBro parts, and re-located the landing gear a bit forward.
Posts: 1088
Score: 150 Joined: 7/16/2002 Last Login: 5/21/2013 From: La Porte, TX, USA Status: offline
It seems as though the cheap hardware is universal in almost all ARFS. No reason to loose a good model over some junk metal and brittle plastic. I hope yours has a long life!
Posts: 366
Score: 100 Joined: 6/9/2008 Last Login: 4/28/2013 From: Perth WA, AUSTRALIA Status: offline
Texastbird - You are correct. I wonder when the ARF manufacturers will figure out that we are happy to pay the extra for quality hardware up front instead of crashing an expensive aeroplane... It is anyway more expensive for us to buy the items separately, where they will receive quantity discount...
It has been a while since I built an ARF which was not made by Great Planes, and the reason was that I found GP ARF's of very high standard. But even GP, failed me a bit with the latest WACO YMF-5D. It had major quality issues with metal fittings for the "N struts" that snapped under load and fibreglass fairing for the landing gear that cracked. This is on top of a design flow for the Landing Gear bracket which result in very weak landing gear fitting.
This is part of the reason why I am venturing back into the semi-kit world. At least I can choose what hardware to install and this way, I know that it is the best I can afford. My Fliteskin 1/5 scale Messerschmitt ME-109 build thread is here http://www.rcuniverse.com/forum/m_10698905/tm.htm
Posts: 366
Score: 100 Joined: 6/9/2008 Last Login: 4/28/2013 From: Perth WA, AUSTRALIA Status: offline
Finally had an opportunity to complete the modifications. I installed quick fill and re-balanced the aeroplane. With the landing gear now further out forward, one battery had to be moved just behind the former for the fuel tank compartment for perfect balance.
Hopefully the weather will cooperate tomorrow and it will be possible to test fly,
Posts: 1088
Score: 150 Joined: 7/16/2002 Last Login: 5/21/2013 From: La Porte, TX, USA Status: offline
I don't guess this is a bird that we will see over here in the States. I hope the flying went well today, or is that yesterday?? I can't ever figure out that intl. date line, ha, ha.
Posts: 366
Score: 100 Joined: 6/9/2008 Last Login: 4/28/2013 From: Perth WA, AUSTRALIA Status: offline
Texastbird - I didn't see this ARF in shops in the States. I got it from the UK.
I had 3 flights today and am happy to say that the modifications worked as expected. The most significant is the landing gear now allowing taxi. I should have moved it even further as it is still not great, but it is better. The roll rate is very good now (that both ailerons working), and general flying performance are great. The next thing to fix is the limited rudder movement which I will fix when I will have too much time on my hands, and fitting larger wheels to further improve the ground handling.
What I did remember today was to take the camera with me, so finally few photos out in the sun. It was getting too hot to stay out with temperature climbing to 41 Celsius (106 F), so I called it a day early .
Search This Thread
Printable Version
All Forums >> RC Airplanes >> ARF or RTF >> Ripmax WOT 4 XL Mk2 
Ripmax WOT 4 XL Mk2 - 
