Battery retention for your electric models

When the Aventura II was introduced by Hobby Lobby, I thought it looked like an interesting plane. However, when the Twin Aventura came out, I really got interested. I knew from my experience with the Multiplex Twin Star that twin speed 400's packed quite a punch, so the idea of a twin 400 seaplane seemed like a natural.

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Specifications

Wingspan:

43 inches

Length:

33.8 inches

Wing Area:

333 sq. in.

Weight RTF:

42 oz.

Wing loading:

18.2 oz./sq. ft.

Airfoil:

Clark Y (modified)

Power:

2 X speed 400 (6 volt)

ESC:

Jeti JES 250

Props:

Gunther 4.9X4.3

Battery Pack:

8 X CP1700 Nicad

R/C Gear:

Hitec 555 Receiver, 4 HS-81 Servos

Available From:

Hobby Lobby

Introduction

When the Aventura II was introduced by Hobby Lobby, I thought it looked like an interesting plane. However, when the Twin Aventura came out, I really got interested. I knew from my experience with the Multiplex Twin Star that twin speed 400's packed quite a punch, so the idea of a twin 400 seaplane seemed like a natural. I liked the look of the fiberglass fuselage/hull, and the design of the motor nacelles built right into the wing looked very attractive. When I got a chance to do a review, I jumped at it.

Kit Contents

The plane arrived from Hobby Lobby in a "box-within-a-box" neatly packed and well-protected. The wing and tail feathers were wrapped in bubble wrap. The gel-coated fiberglass fuse was very impressive, and the covering job on the built up wing and tail feathers was excellent.

I was a bit disappointed at first with the instruction sheet. The drawings were very small. The written instructions were few and far between, and the English translation left a bit to be desired. (Example: "After the find of the right position of the CG fit the battery by Velcro.") Once I got moving on the building job, however, I realized that the instructions were actually quite complete. They include a complete parts list with both a written description and a drawing of each part, and once I got used to their small size, I realized that the drawings that accompanied each step of the construction were actually very thorough and informative. All the essential data was actually there - it was just presented in a very bare-bones format.

Construction

I started with the wing. It comes in three pieces - the two built-up and covered wing halves, and a wing joiner make out of solid balsa that serves to hold the two halves together and mounts to the top of the fuselage with two nylon screws. The aileron servos are mounted in plastic recesses on the bottom of each wing half, and the motors fit in lite ply recesses on the top of each wing half at the leading edge. This means that the wires for the motors and aileron servos have to be threaded through the wing into holes on each side of the wing joiner where they meet and then exit through a hole in the bottom of the joiner. Threading the servo lead through was accomplished pretty easily by pushing the wire through and using tweezers to reach in and pull out the connector at the end of the lead.

The motor leads, however, were a bit trickier to get through the wing. I used a piece of copper wire to do this, first pushing the wire through the opening at the root of each wing and out the openings in the servo and motor compartments, then attaching the leads, and pulling them back through the wing and back out the opening at the root.

This was a bit like the experience I assume most of us have had of trying to unlock your car with a piece of wire coat hanger after locking the keys inside. Because the covering of the wing was transparent, I could see the copper wire as I tried to thread it through the proper openings, making a 90 degree turn. However, like the piece of coat hanger wire that you're trying to get to that door lock release button, being able to see the wire and being able to get it to go where you want it are two different things!

Once the wires were in place, the next step was to glue the wing halves to the wing joiner, making sure that the proper amount of dihedral was locked into the wing. This was a bit difficult because the large bundle of wires protruding from the bottom of the wing joiner meant that I couldn't just tape the wing down to a board or other flat surface. The solution was to take a board and drill a hole in it for the wires to fit through. I then applied 30 minute epoxy to the wing roots (and dowel that fits through the wing joiner and into holes drilled in the main spar on each wing), and taped the wing firmly down onto the board with blocks at the wingtips to ensure the correct amount of dihedral.

After making sure that the epoxy was well-cured, the next step was to set up the ailerons. Here, it was evident that the manufacturer took a bit of a short-cut. The wing of the Twin Aventura is identical to the wing of the Aventura II with the exception of the ailerons. Rather than completely cut out the ailerons on the wing for the "III," the manufacturer simply cut a vee-shaped grove about half-way through the wing at the leading edge of the ailerons. The whole wing was then covered. The result is that you have to (1) cut the ailerons free from the wing (cutting through the covering, of course); (2) sand the leading edge of each aileron to get the proper angle so that the ailerons will be free to move down sufficiently; and (3) then use the piece of supplied covering material to recover the trailing edge of the wing and the leading edge of each aileron. This is a bit time consuming, and requires some experience with covering. I sanded the proper angle onto the leading edge of the ailerons by sticking a strip of sandpaper to my workbench and holding the aileron against the sandpaper at the correct angle.

In addition, slots have to be cut in the trailing edge of the wing at the third rib in from the tip to accommodate the rubber bands which secure the tip floats to the wing. The inside of the slots, in turn, need to be covered with strips of covering material to protect the balsa from the water. This again was a slow job, at least for me, although I was quite happy with the result.

I found that it was fortunate that I was very careful in cutting the covering material from the thin strip provided as it turned out that there was just enough for the required recovering jobs. Also, the dimensions and the location for the slot appear down in the corner of one of the already small drawings in the instructions, and this time I really had to use a magnifying glass to see what they were talking about! The ailerons were attached with transparent hinging tape on the top, and I secured the aileron servos in the servo bays with double-sided foam tape. The provided plastic aileron control horns looked too small to me to stay put in the ailerons, so I made a new set of larger horns out of 1/32 inch lite ply which I epoxied firmly into the ailerons. I used adjustable clevises from Hobby Lobby that I learned about from Jimmy Best's Hellcat review. These units (Stock number RA107) are perfect for speed 400 size planes, and enable you to easily adjust the control linkages with a simple set screw without removing the clevis.

The motors were attached to lite ply plates in the wing with nylon tie wraps. I used a piece of double-sided foam tape under each motor to make sure that they were held firmly in place by the tie wrap. I also took the precaution of putting two coats of polycrylic varnish on the bare wood plates since I assumed that some water was going to get into this area. The vacuum formed plastic servo covers and motor nacelles were then installed with transparent tape. The blind nuts for the wing attachment are then glued to the top of the fuselage, and the wing is then attached with the provided nylon screws. The tail feathers were next. The two elevator halves have to be joined with a piece of music wire which had to be bent to the proper dimensions. As noted above finding this information in the tiny drawings was a bit of challenge, but once I understood what was being depicted, I found them very helpful. The elevators had to be drilled out to accept the wire joiner, and grooves to fit the wire needed to be cut in the leading edge of the elevators so that the wire didn't interfere with the elevator travel.

The horizontal stab was epoxied to the fuse (after cutting away the covering in the area of the glue joint), and then the vertical fin was glued to the horizontal stab the same way. The rudder is attached with the provided nylon hinges, and the elevator is hinged with tape. (A notch needed to be cut in the rudder to avoid hitting the elevator linkage. This, again, required searching for that one remaining scrap of covering material to cover the inside of the notch to protect the balsa from the water.)

The water rudder, cut from a piece of translucent plastic, attaches to the bottom of the rudder with a screw. The control wire system for the rudder and elevator is very straightforward using the supplied "tube-within-a-tube" system and plastic control horns and clevises. This system is a good choice for a seaplane since it's both water tight and avoids the use of any metal parts which could rust and then bind. The rudder and elevator servos mount inside the fuselage in box-type mounts constructed out of the provided pieces of lite ply. This is very straight forward and well illustrated in the instructions.

All that was left at this point was the tip floats. I followed the procedure outlined in Shaun Cronin's E Zone review of the Aventura II for the assembly of the tip floats using a combination of epoxy and silicone to make sure they were water tight. The instructions lacked any explanation of how to attach the vertical supports for the tip floats to the horizontal supports that fit under the wing. I ended up cutting slots in the horizontal supports and gluing in the vertical supports with CA. I then sanded, sealed, and painted the float supports with white Krylon interior/exterior spray paint from the local hardware store. This paint is excellent, gives a very smooth finish, and dries in only 12 minutes. The tip floats are then attached to the wings with the supplied rubber bands which fit through the slots mentioned above that have been cut between the trailing edge of the wing and the leading edge of the ailerons. The only modification I made to the float attachment was to use some tiny screws at each end of the horizontal float support to hold the rubber bands in place.

Radio equipment was then installed. There's plenty of room to attach the receiver and speed control to the sides of the fuselage nice and high up where they will keep dry in the event that some unwanted water finds its way into the fuselage. I used a Dean's antenna that came with a rubber grommet, which I sealed with silicone, so that no water would leak in. I epoxied a piece of lite ply to the bottom of the fuse between the servo mounts as a battery tray, and secured the battery with Velcro. The vacuum formed windshield was then cut out and fitted into place and attached with transparent tape.

Flying

I decided to have the first flight on dry land so that I could make sure the plane was trimmed properly and flying well without having to worry about going for a swim if things didn't work out.

It turned out I had nothing to worry about. The maiden flight, held at a big grass field, was a total success. I had a friend gently toss the plane, and it flew right out of his hand and climbed aggressively at full throttle. Given that the Aventura weighed about half a pound less than a Twin Star (with a sleeker airframe to boot), I assumed it would fly even better than the popular Multiplex twin. However, I wasn't quite prepared for how overpowered the Aventura would be. It continued to climb as I throttled back, and I found that I had to cut back to about one third throttle for level flight. The controls were very positive, the stall was totally straight ahead (both power on and power off), and the glide path was remarkably shallow. The landing was very easy - I just cut power and let the plane glide in on the wet grass. Since I was using so little throttle for most of the flight, I determined that duration would be in the eight to ten minute range using the CP1700 cells. I couldn't wait to get the plane out on the water where it would truly be in its element. A few days later I went to a local lake with a group of friends who I fly float planes with. When I put the Aventura in the water, I was a little concerned with how low in the water it rode at rest. It taxied around well at idle with good control from the water rudder, but the slightest increase in throttle would result in the nose going under.

When I followed the instructions and gave it full power with full up elevator, however, it popped up "on step" within about five feet and picked up speed rapidly as it skimmed over the top of the surface.

I relaxed the elevator as soon as it got up on step, let it gain airspeed, and then gave it another blip of up elevator after a run of about 30 feet. The plane lifted gently off the water in a very scale fashion and was airborne. I quickly determined that this was the best flying and handling float plane I had ever seen. The hull shape makes for superb water handling, and I could find no bad habits in its flying characteristics. As noted above, it has power to spare. Loops from level flight are no problem, it rolls nicely, and does a very impressive hammerhead stall. Although tempted, I declined any further aerobatic tomfoolery, fearing that a snap roll might dislodge the tip floats. The most fun I had was doing touch and goes (or "splash and goes" I should say). At first, the shallow glide path took some getting used to - the plane just wants to keep flying, even when you cut the throttle completely. Once I got accustomed to the sink rate, it was great fun gliding down onto the glassy surface, gunning the throttle just as the plane hit the water, and skimming across for another take off.

The inside of the fuselage was bone dry after the flight. The only somewhat annoying feature of the plane is the fact that the windshield has to be removed to switch the battery and then thoroughly resealed with transparent tape at the beginning of each flight. A supply of paper towels helps to dry off the surfaces to be sure that the tape will stick each time. I have thought about some alternative way of getting access to the battery, but I haven't come up with one.

One Little Problem
At first I thought I would have nothing negative to write about this plane at all. However, one slight problem did develop after several fights. The problem was with the water rudder. As noted above, it was attached to the bottom of the rudder with a single screw so that it could pivot up out of harms way for land-based flying. I found that the shock of a few touch and goes in the water (or maybe even just the airflow from normal flight) was enough to cause the water rudder to fold back during the flight. This wasn't good since it's at the end of a flight that you need the water rudder to enable yourself to taxi back to shore. I tried to tighten the screw to hold the rudder in place, but a wood screw in soft balsa is not a good way to hold something securely. Then, at the end of about my third flight, I tried to taxi back and found that I had no control at all. Fortunately, I was near shore so I was able to maneuver the plane in, only to find that the water rudder had broken off completely. My solution to this problem was to make a sturdier water rudder out of credit card material (actually a hotel "key card" - I always save these as I find the material useful for numerous modeling purposes). I also drilled out the rudder and glued in a length of hardwood dowel to serve as a hard point for the water rudder attachment so I could really tighten the attachment screw. Finally, I glued a piece of wet/dry 600 grade sandpaper to both the rudder and the water rudder at the attachment point to provide some friction to keep the water rudder from folding up when the attachment screw was tightened. This system has worked fine.

Conclusion

I highly recommend this plane! It's well made, attractive, flies beautifully, and most importantly, handles the water superbly. For anyone interested in float flying, the Twin Aventura is a great choice and will provide many hours of enjoyment.

Thread Tools
Apr 25, 2001, 05:52 AM
RIP Azarr - "Old age is not for sissies"
Azarr's Avatar
Check out www.veltye.com. I've been using their stuff for years. I've never had the adhesive let go on their sticky backed stuff and their "One Wrap" is doubled sided, fuzzy on one side, teeth on the other, perfect for belting in packs as Brian suggested.

Azarr
www.azarr.com

Quote:
Originally posted by leccyflyer:
Hi

Just in case anyone has missed this tip for battery retention by velcro seat belts I'm posting it here. You all may already be doing this but I thought it was a good easy solution to a problem and that I'd mention it anyway.
http://hometown.aol.co.uk/leccyflyer...age/hobby.html

Hope someone finds it useful

cheers

Brian
Apr 25, 2001, 11:52 AM
Registered User
Brian,

Nice Job.
I've got a supply of "velcro role" that is double sided so as to stick when you role it up on itself. It is used for tieing cable bunches in computer closets that would otherwise be floating loose or permanently tied down with nylon wraps. The stuff I use comes in 18" lengths at about 1" wide. They can be purchased at better electronic stores (I doubt RS has them). Anyway they are VERY sturdy, and epoxy quite nicely to a fuse or mount due to the roughness of the velcro.
Apr 25, 2001, 01:24 PM
Registered User
Actually, RS does sell them, but in 8" by 1/2" strips. In four colors, no less.
Apr 25, 2001, 02:08 PM
Restful User
Jacques Flambeau's Avatar
And ACE Hardware has the "Veltye"-style strips in stock.

--Bill
Apr 25, 2001, 03:18 PM
Registered User
I now have a roll of the double sided stuff so my Twinstar MkII will have some mods done int the battery department.

BTW I found a "before" picture (Thought I had missed out that vital picture)
http://homepages.paradise.net.nz/net...r/twinstar.jpg

Heather


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