We are organizing a group build of our Tony Elliott designed 1:3 scale Slingsby Type 13 Petrel. Bob Morrow had the original idea for the group build project and is collaborating with us on the project. There are several goals we have in mind for organizing the group build. They are:
1. Group Motivation. This is a "paced" build project with a construction schedule designed to have the Petrel's done in time for the May 2014 JR Aerotow. Nothing like a group effort, with scheduled activities and an end goal to get motivated.
2. Designer Support. Tony Elliott, the designer of our 1:3 scale Petrel will be available for ongoing support and advice as we progress through the build. Additionally, one of the advantages of a group build, is that we can share ideas and help support each other as the build progresses.
3. Comprehensive Build Log. We will be running two build threads - one at RCAerotowing.com and at Aerosente.com. Depending upon the groups participation, we hope to have a comprehensive build resource with narrative, photos and videos.
4. Better Pricing and Sourcing. I will be offering both a short kit and a complete kit for the group build. I have to put in place both a minimum and a maximum number of kits in order for this to work for Aerosente. The short kit for the group build is $795. The complete kit which includes essentially everything except electronics and fabric (sheeting, spars, stringers, laser cut parts, fabricated parts, and hardware) is $1,495.
5. Research and Development. I will building a kit myself with the idea of testing out some new ideas. Inspired by Tony Elliott's 1:2 Wein, one of the ideas we're toying with is a "vintaged" UPandGO sustainer for the Petrel. It would be top-mounted in the fuselage and we would design appropriately "vintaged" hatches etc.
For more details on the group build project visit this page http://www.aerosente.com/13-scale-slingsby-type-13-petrel.html for pictures of the kit contents including a detailed list of what comes in each kit.
With this being a group build, I will need at least three short kits and three complete kits sold in order for the group dynamics to work. I also have a maximum number of kits I can produce in this time frame so it will be first come first serve for the production slots.
Here are the details on the group build. Bob Morrow did most of the heavy lifting on the schedule. This is adaptable based upon input from the group.
Project Goal:
The goal of the project is to have a monthly build goal leading to completion by the beginning of the end of 2014.
Projected Timeline:
Because of the scope of this project as well as the size of the Petrel that is being built it is expected to take a full 12 months for completion. This time frame includes not only the building of the airframe, but also the installation of all electronics, complete finishing and detail work.
Order Deadline: September 30, 2013
Shipping Date: October 30, 2013
December 2013 PROJECT ORIENTATION
Begin project.
Initial purchase of kits and all materials for the build. This will include the following:
• Laser cut parts, wood parts, flat sheet as well as strip woods. All composites for structures (carbon fiber, fiberglass, kevlar).
• Control surface linkages, linkage rods, tow release mechanisms, assorted hardware as needed.
• Adhesives including alpha cyanoacrylates, epoxy resins, aliphatic resins, and various fillers. These should be purchased fresh to insure proper bonding of all materials during the project.
• Various finishing materials such as covering and paints may be purchased at this time, or purchased at a later date during the project build. Do note that various flying surfaces will need to be covered during the build for completion of the airframe prior to final finish work. Covering materials are at the discretion of the individual builder, but do remember that the Petrel is a vintage sailplane that was typically finished in wood and fabric covering.
• Various materials for building boards and building jugs as needed, especially for the gull wings. These can be plywood or particle board. The jigs will need to be constructed prior to the build of specific components of the airframe.
• All electronics including receiver, servos, wiring materials, batteries (two packs as primary and secondary for the receiver and servos, which must be the same chemistry and matched).
• A receiver/power board such as a SmartFly or Royal is highly recommended due to the size and complexity of the electronics installation.
Many of these various parts and components are at the discretion of the individual builder, but there would be specific recommendations made for specific materials based on the specifications of the plans and build instructions included with the kit.
Also note that the specifications of the radio and electronics equipment must be carefully considered due to the size of the airframe in which these components will be installed. It is critical to use reliable electronics such as a 2.4GHz receiver, a power board or similar due to the number of servos, and servos that are sufficient in torque for the various control surfaces and mechanisms of the Petrel. I would personally recommend all HV digital metal geared servos, using a minimum of 100 in/oz to 200 in/oz torque or more for the ailerons, elevators, and rudder. The spoilers do not need as high a torque, but they should also be HV digital metal geared and be able to operate the spoilers without fail. The tow release should be a HV digital metal geared servo with a minimum of 200 in/oz to 400 in/oz of torque or more.
Any of the popular brands of electronics currently in use should be excellent for this airframe. These may include Airtronics, Futaba, Graupner, HiTec, Jeti, and JR just to name a few.
It would be suggested that the choice of transmitter be one that has at least 9 or more channels for functions and would be a computer controlled radio to help with mixing of various flying modes and functions. While this is suggested it should be noted that there are transmitters less capable than these specifications that would still be able to fly this airframe adequately.
Most important is the ability to control all functions of the airframe with ease and also your familiarity and comfort with your transmitter for the safe flying of a 6m size airframe.
A personal note regarding electronics:
While my suggested specifications I have given previously may seem beyond the needs for this project it has been my experience that using only the best electronics that are beyond the required specifications will help prevent many issues or failures for various airframes that I have flown over 35 + years now. It is not the normal flights or the routine flying that we should be concerned about, but rather the unexpected events and potential over stressing of the airframe that we hope we may have compensated for by choosing components and building methods carefully for a project of this nature and size.
FUSELAGE Pages 5-8 of instructions
Begin initial construction based on the plans and suggested construction sequence of the included instructions. This would be starting the build with the fuselage halves, general sheeting, bellcrank installation, and final joining of the halves to the finished full fuselage.
Note: there will be needed installations of various electronic components during the building and assembly process to allow adequate access and adjustment. Be sure to create adequate access to these electronics should it be necessary to adjust or replace components throughout the life of the airframe.
STABILIZER/RUDDER pages 8-9 of instructions
Assembly of the stabilizer and rudder as per instructions. Complete fitting of these parts on the completed fuselage, adding fairings and sheeting for final assembly as needed.
Note: as with the initial fuselage assembly there will be a need to add various components during the assembly process prior to final assembly to insure all control surfaces function properly. Use the plans and instructions as a guide for this and do read through the steps prior to any final assembly and glue-up.
WINGS Page 10 of instructions
Initial wing assembly beginning with creating of the wing building jigs as outlined in the instructions and plans. These can be built with a variety of materials, but it is important to make sure they are ones that will not warp or flex during the building process. It is critical to build a straight and true wing and that both wing halves are symmetrical with each other once completed
After completion of the building jigs the spars will then be constructed as per instructions and plans. These must be constructed carefully as per instructions and plans as they are critical to the structure and strength of the completed wing panels.
WINGS Pages 10-13 of instructions
Build both right and left wing panels using the jigs and spars previously completed. The panels should be assembled as per all instructions and plans and should be completed for spoiler assembly.
Note this process is all dry assembly at this point. Glue-up will take place after other structures and component of the wing assembly are in place and all is aligned for final assembly.
Spoiler assembly and installation follows, completing all steps of the instructions and plans. Note the installation of various electronics component and servos for these steps prior to final assembly.
After all components of the wing assembly have been dry fit and completed final assembly and glue-up is completed.
WINGS Pages 13-14 of instructions
Sheeting of the wing should be completed at this stage following instructions and plans.
December 2013: WINGS Pages 15-16 of instructions
At this point the build of the ailerons and bottom of the wings will be completed as per instructions and plans.
ALIGNMENT AND FITTING Pages 16-17 of instructions
Final alignment and assembly of fuselage, wings and tail assemblies. Complete all steps for this process and prepare the airframe for installations of electronics as well as all finishing.
February 2014: FINISHING Page 17 of instructions
Begin finishing and installations. At this point final choices about finish, color schemes, graphics and scale details should be made.
Complete the appropriate installations of all electronics and preliminary adjustments of flying surfaces prior to final finishing.
The fuselage should be properly fiberglassed as per instructions to help with the structural integrity. Care should be taken with this process with thought as to the final finish and color(s) that will be used for the completed Petrel. Fiberglassing can be completed and a natural wood finish can be obtained as long as appropriate weight cloth and resins are used. Of course a painted finish is easily applied to a properly glassed surface as well.
Scale detailing of the cockpit and other components should be completed at this stage, other than details that would need to be completed after painting.
FINISHING
Complete finishing of the airframe, covering of all open surfaces that have not previously been covered during construction and complete painting and application of graphics.
Note: seal all edges of covering material to prevent it from peeling or opening. This can be accomplished in a variety of ways and methods, but is important to the longevity of the airframe.
Complete all detailing and installation of any equipment or parts that have been on hold.
Installation of the pilot and final balancing should be completed as a final step, Use the plans and instructions with care for this, adjusting the balance to be nose heavy for initial flights.
A note on balancing: I prefer to always use lead shot (#8 or #9) in conjunction with diluted resin for the final balancing. I typically use this in the nose of the sailplane and make sure to keep it light by about 4-6 ounces of the recommended balance point.
To achieve the final balance I like to use strips of lead that can be attached via screw in placement panels in the nose sections. This allows me to add or remove strips as desired to reach the final balance point that the sailplanes flies well at. I always start with the sailplane somewhat nose heavy for docile flying characteristics and then adjust as I complete test flights and changes in the radio programming.
ELECTRONICS
Complete any electronics assemblies and installations as well as initial programming of the radio system. Check all surfaces for correct movement and begin making adjustments for various flight modes.
After initial set-up and programming is complete the initial test flights should be made to dial in programming.
Set control throws for standard thro initially, adding throw after the first test flights. It may be of help to use exponential in the setup of the throws for all flight surfaces. Remember to use differential in the ailerons to have effective turning ability and this can often be mixed with the rudder for thermal and landing modes.
I typically have three flight modes for my large sailplanes, the flight mode switch is a three position switch on the top left front of my transmitter:
Launch mode: switch is in the forward position in which I have flaps active with the ailerons for full surface deflection to increase the lift of the wing (the Petrel does not have flaps, and as such there will not be mixing of these functions for this airframe). In this mode the ailerons are independent of the rudder and I do not have them mixed, as the critical issue with launch is to get off the ground and keep the wings level during tow. I also have the tow release active in this mode to enable release at any point during launch and tow. I typically have my tow release switch on the upper back right of my transmitter, as an on/off toggle. I have always kept this position for the release to have consistency between sailplanes.
Thermal mode: switch is in the middle position in which I now have the ailerons and the rudder electronically mixed to help with thermal turns. All functions are active in this mode as well as spoilers.
Landing mode: switch is in the backward position and in this mode I have my spoilers and elevator mixed to adjust for landing approaches. This is designed to help compensate for the effects of the spoilers on the pitch of the sailplane as they are deployed, to keep a slightly nose down attitude.
Final adjustments and mixing is definitely a personal preference to the individual and also an art form specific to the airframe. The Petrel was designed to fly in a comfortable envelope of speed, but not necessarily at high speeds. It should thermal gracefully and be able to detect light lift with the movement of the wingtips or pitch change as tell tales.
TEST FLIGHTS
Continue test flights and adjustments of programming for the airframe. After several flights the lead ballast should be adjusted and fine-tuned to the specific choices of your flying style. Many choose to have the sailplane slightly nose heavy and be a bit more docile, yet others may prefer to start moving the balance point rearward and find a point where the sailplane “talks” as flying conditions and thermals vary. This is really a matter of personal preferences. Do be aware that movement of the balance point rearward should be completed and tested in very small increments, as there may be a point of instability that is reached quickly leading to the loss of the sailplane as well as safety concerns.
Once the sailplane is flying well I always make copies of the programming of my radio as back-up and keep the programming in my computer system. This will allow me to fine tune as desired and also to reprogram the transmitter in the case of the loss of programming by error (which has happened more than once to me !).
Additionally replacements supplies should be assembled that include replacement servos, horns, connectors etc. It is always a good idea to have a “Kit” for each specific model that would include replacements for the sailplane. I will typically have several extra servos that are used for the various control surfaces and functions as well as a range of other materials and replacement parts. Having spares while traveling and flying at various events helps with keeping the sailplane in flying condition. The extent of these spares depends on the individual and also the rigor of the flying season. I will typically attend several events from the months of April through October as well as local flying in the nearby sites where I live. While at events I will use spares as needed, but while in my local area I always bring the sailplane home to do complete inspections and replacements in the shop where I can focus on the work carefully and hopefully catch any other issues or problems that I may have missed at the field.
A very astute pilot once told me that all launches are optional but landings are required !
June 2014: JR AEROTOW
JR Aerotow………finally !
