Homebuilt F5J Soarer (Kevin Beale & Colin Paddon)
After a long gestation period, we are pleased to announce the birth of a rare beast … a competition homebuilt 3.8m F5J soarer!
When the F5J class came into being, it shone out as a great opportunity to once again be able to produce a homebuilt model which would be able to compete well against the superb moulded manufacturers offerings. With no F3J launch stress to consider, Kevin Beale & I (Colin Paddon) decided this was a totally feasible option albeit one that to date had not been taken up by many other F5J competition pilots, at least here in the UK. So we decided that together we would design and build our own “Medium Tech Composite” 3.8m F5J Soarer. To be able to do this would however require that we master some new building skills and techniques and that turned out to be more involved than we originally thought! We weren’t however starting from scratch as Kevin had a lot of experience in producing moulded fuselages and ditto myself in producing foam wings. It did require though a lot of time and effort in pulling together the requisite moulds, building the automated foam wing cutter, many jigs/templates, vacuum pump rig etc. On top of that many tests were undertaken to understand/achieve the best utilization of materials and hone the required composite skills/techniques of which there were many.
It was decided from the outset that if cost effective commercially made components were readily available then we would use them. In our case this meant that we bought the carbon fuselage pod boom and the protruded 10x1mm carbon wing spars and wing joiners. Everything else is self-built.
The first thing we needed to do was to hone down a general design brief. After some discussion we ended up with the following:
- 3.8m wingspan
- Medium Tech composite construction
- Vacuum Bagged wings, tailplane elevator/Fin Rudder coupled to a composite fuz pod and boom.
- Total AU finished flying weight of between 1.4 -1.7kg
- Proper ballasting capability
- Good working space within the fuz pod
- Wide performance envelope to cope with different weather conditions
- Light enough to be able to use a direct drive motor if required
Kevin was tasked to come up with the wing plan-form/ spar layout and I think the finished wing shape is very nice. The fuz pod design/implementation works well and his moulding technique improves incrementally with each one he produces. Again many different lay-ups have been tried out to see what works best. An airfoil section was chosen that would provide good all round performance. We decided to try out various alternatives of tail end layouts including all flying tailplanes through to separate tailplanes/elevators both on the fin, in front of the fin and under the fin/rudder. It came down to personal preference in the end but a fixed tailplane with a separate elevator regardless of layout proved to be our preferred type.
The fin/rudder on the version shown here is completely removable from the boom itself to aid transport (i.e. to get it to fit in the transport box) and also to provide access to the tailplane/rudder servo’s. Whilst the finish on the wing is acceptable, with the further testing on surface finish we have now done, we are reasonably confident that we will be able to obtain an excellent paint/surface finish.
For his first full prototype, Kevin has gone for the under the wing Elevator/Rudder servo set-up and increased the tip dihedral slightly as we felt Prototype No1 may have been slightly less than optimal although the initial flight tests have proven this may well not to be the case. (see photo of Kevin’s plane in garage)
The first completed full prototype is the version you see here and despite several mishaps/mistakes during construction with the worst being when the vacuum pump decided to go open circuit over-night and pulled massive vacuum pressure rather than the 15-18Hg it was set to, it still turned out to be relatively OK though. (I can now vouch for the compressive strength of pink/peach foam although it did mean that the spars on the centre panel were a little proud! Another mistake occurred in the painting of the mylers in as much as we didn’t extend the black far enough along to cover the servo well reinforcements on the tips. As it was only a prototype though, it didn’t really matter.
We tested four different types of paint on different weights of glass to see which provided the best release/finish. Halfords spray gloss black turned out to be the best for the black with fluorescent tree marking spray being best for the fluro Orange as it did not require a backing coat of white to achieve the bright fluro result required, i.e. lighter. The wing control surfaces are all hinged with silicon as is the tailplane/ elevator. You wouldn’t think there is much to do to get silicon hinging right but again the right silicon coupled with using the right application technique & custom spreader tool took a while to nail down along with yet mini samples to get it 100% right.
This first completed PROGLIDE prototype seen here weighs 1460g ready to fly which for a first prototype isn’t too shabby. It uses a direct drive 28mm diameter outrunner motor turning a 11x7” Aeronaut folding Prop, 40 Amp ESC and a 3S 1300Mah Lipo. The gadget with the two green LED’s is a home built Ubec/ESC BEC change over unit. (If one of the BEC’s fails the other takes over automatically).
How does it fly? Well we only managed to fly it twice before it poured down but so far we think it fulfils the design brief nicely. We are extremely pleased with its handling/flying performance but the true test of how good a plane is, comes when its flown in competition against other planes.
The feeling of achievement derived from designing and building our own competition models once again is amazing. Yes, the journey involved a steep learning curve with many ups and downs along the way, but if we can do it so can others. Knowing what we now know, we are confident we can get the overall AU flying weight down to around 1250-1300g if required. For UK flying this is really not required but with mainland Europe in mind, an ultra-lightweight model at 3.8m will be worth having in the quiver. The next PROGLIDE versions will be laid up to achieve an AUW of around 1700-1750g ready to fly.
We now plan to continue to refine and further develop the PROGLIDE series along with our composite building skills.
Hopefully this article might provide the inspiration for others to try similar projects.
Kevin Beale/Colin Paddon