Introduction

I was reintroduced to slope soaring only around Christmas time last year when I flew a couple of times, as a guest on one of the local slopes. When I say reintroduced it is a bit misleading since my previous experience was limited to 2 outings only. I brought myself a Zagi SI for Christmas and flew that between Christmas and the new year. I was flying against another flying wing that looked similar to my Zagi but consistently out climbed, out turned, was faster and flew in lighter lift. I found out that this was a Predator and is not widely available but is produced almost, it seems, to order when Alex has the time. I found out how to get one and talked my kids into buying it for my birthday.

First Impressions:

The kit was delivered by Andy after one of his F3F excursions somewhere down south. The first thing you notice is the lack of fancy coloured pictures on the box. What box? There is no box. Everything is neatly packed in a plastic bag, except there isn't a plastic bag either. Here is a kit where you only pay for the kit and not the package it comes in.

Kit Contents:

One pair of UPP (black foam) wings supplied in wing blanks, one carbon spar, one pair of correx elevons, one pair of correx wing tips and a hardware pack containing clevises, horns etc. And the instruction sheets. The foam cutting is to a high standard and good quality hardware is supplied, with the exception of the screwed rod supplied to connect the clevices to the flexible push rods. These screwed rods appear to have been cropped at each end and hence need some work with a file to get them to screw into the clevice. No locknuts are supplied.
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Also Required to complete:

Please note that this is what I used and not necessarily specified. Radio gear - 2 standard servo's, receiver and nicad (I wasn't using a switch but disconnecting the battery lead). Transmitter with elevon mixing. An on board elevon mixer is another possibility but I didn't need to go that way. Spray adhesive (the type carpet fitters use for sticking down foam backed carpet) £3.50 from Welch Mill Carpets - Leigh. Fibreglass tape and covering tape. Available from model shops but mine came from Superronic Models because it was cheap.

Building:

Building an EPP model is not a satisfying build in the same way as a balsa kit but it goes together quickly and the material is highly suitable for this purpose. In all the kit reviews I have read in the magazines they always say they will not give a "stick part a to part b" report. In this review I will because there are only 7 pieces. As with all kits, the first thing to do is read and re-read the instructions. Or you can look at the kit and start.

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The first instructions are to separate the wing core and pick off the melted foam. Very therapeutic. Sand the leading edge and join the wing. No problems. I used spray adhesive to join the wings, this is the first time I have used this adhesive, it comes out like string and is very sticky. Also test it on a scrap piece of foam first or you could end up with a gooey mess. Fortunately mine was ok. The next job was to install the spar. This did cause me some problems. Firstly the instructions suggest drawing along the spar with a fine marker. I thought an easier way was to pin the spar into the wing and cut along it (a picture explains what I mean). Next you "ease up the foam carefully along this line, your aim is to end up with a 20" long slot in the wing and a corresponding strip of foam". What I ended up with was a 20" long slot in the wing and corresponding strips of foam, none of them longer than about 3". I decided that the wing blanks could be put to good use, suitably cut they would cap the spar adequately. I was surprised how easily and cleanly the EPP foam cut with a scalpel. With the spar epoxied in place the total build time so far is about 1 hour. Left overnight for the epoxy to cure. Spar cap glued in place and trimmed. So far so good.

The next stage was a divergence from the instructions. I decided that it may be a good idea to allow the model to carry extra ballast. A trip to Andy's was called for to produce the lead slugs and ballast tube. Five slugs were cast, each of about 2 oz. The tube was polyester and resin cast over a piece of chromed pipe, but that's another story probably to be told by Andy. I left his house that night with the weights, the tube and a piece of bent piano wire.

Click to Enlarge	I had already checked that the ballast tube would fit within the wing depth at the C of G position. I hadn't thought until now about the position of the C of G in relation to the already installed carbon spar. A quick look at the instructions stated the C of G to be 8-1/8" from the front and the spar should be 9" from the same position. This gives a clear distance of 7/8" (about 22mm). Plenty of room (fortunately).
The next job was the installation of the radio gear. The nicad, receiver and servo's were positioned on the top surface. Holes dug with a sharp scalpel. These holes allowed the radio gear to be a tight fit since only the nicad was being glued in position. The servo's were firmly pushed home and covered with fibre tape. The nicad was fixed in place with silicon and a flap of EPP placed over the top. The receiver was made accessible to allow a crystal change if required.	Click to Enlarge

The ballast tube was the next item to install. The position was marked on the top side of the wing and the bent piano wire, produced on the same night as the ballast tube and the slugs, was heated with a blowtorch and cutting the slot for the tube was an easy job. Care needs to be taken at this point to prevent cutting this slot too deep and coming through the bottom of the wing. I know this is good advice, I just wish it had been given to me! The ballast tube was siliconed in position and when dry an EPP cover was epoxied in place and shaped to fit. The model was now liberally sprayed with adhesive and allowed to dry. The instructions say that this adhesive aids the strength of the model. Fibre tape was used to cover the centre section to the servo's and the wing leading and trailing edge.

The colour scheme was chosen and the tape applied. So far the total time taken on the build, including the ballast tube production, was about 5hours.

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The CofG was checked and 5oz of lead was required to be buried towards the leading edge. Almost there now. The linkages were connected up and the throws set as per the instructions. The wing tips were fixed with double sided tape, later found to be a mistake. The model was weighed and found to be 1lb 12oz ready to fly.

Flying


Off to the hill. The wind blowing a steady 25mph. The model thrown into wind and trimmed. Once done it was time to see what it would do. The climb was impressive. It turned well without loosing too much speed. Inverted flight was great. Anything I could think of doing with the Predator and it would oblige. I couldn't fault it.

Was the ballast tube a worthwhile addition? 4 slugs installed and off again. Penetration was slightly better but overall the model felt sluggish. Maybe too much. 2 slugs were removed and replaced with balsa dowles. Again thrown into the lift, performance was transformed. The predator would climb and turn just the same as un-ballasted, penetration both into wind and crosswind was greatly improved.

The main purpose of this model is combat, how does it fare? Even in my inexperienced hands it performs very well. Even when hit hard enough to bend the screwed rod connecting the pushrod to the clevis, it recovered well and even requiring full down trim to compensate it continued with the battle. One problem I have had is a broken servo arm. This is also a problem I had with the Zagi (it must be me). I will consider covering this area in some way to see if that helps.

As I said earlier, fixing the wingtips with double sided tape was a mistake. On a couple of occasions the wingtip was knocked off. The Predator still flew without problem, with only a bit of waggling noticed on tight turns. I will refit them with Velcro as I had some success with this method on my Zagi or maybe servo tape.

Recommendations

Would I recommend the predator? Without reservation. Would I recommend the ballast tube? Being new to slope soaring I need some more experience in differing wind conditions. Would I recommend slope combat? Definitely. Standing on a windy hillside in the cold with a number of like minded people, having FUN.
When flying, either for fun or combat, the predator is my first choice model and it has now been flown from a number of sites with wind strengths of 5mph to 85mph and it has performed to the extent of my ability.

Steve Evens