After many months of distractions and projects, I have finally gotten around to finishing off my Sportjet build log. I wanted to make sure that the mods I performed lived up to my expectations before posting anything, but after months of flight experience on the jet, I feel confident in recommending the mods, and feel that it would be worthwhile to post my detailed build log. That being the case, here we go….

Although I love my Hobby King Sportjet 70 (identical to the eRC Rebel and Freewing Cobra), the stock jet has a few idiosyncrasies that have always nagged at me:
1.) It is nearly impossible to balance it where it needs to balance (and, it needs to be balanced differently than what the manufacturer recommends…). Even when balanced at the manufacturer-specified position, it is nose-heavy, making the small elevators even less effective. Most owners end up putting lead weight in the rudder island to help it balance. The problem is exacerbated with a battery larger than 2200 mAH (I use a 2260 50C). The tight fit of the battery cage results in very limited flexibility to position the battery to help the balance problem. There’s simply no way to move the battery back without a major mod to the airframe.
2.) The elevators are way too small and marginally effective. Coupled with the nose-heavy nature of the airplane, inverted flight is hard to maintain, loops are really large, and rolls can look awkward.
3.) The jet seems to wallow in yaw at low power settings....Continue Reading

PREFACE

This build log is extremely long (some might say “ridiculously long"), so I have divided it up into sections. Because of the length, each section is a separate post in this blog. There was so much involved in pasting the different sections from my MS Word file into the post, that I ended up screwing up some of the section numbering. If anyone has any idea of how to edit a post title, I'd appreciate the info!

The Introduction And Overview Section/post provides my bottom-line comments and observations, if you don’t want to wade through the whole thing. If you DO want to wade through the whole thing, but your laptop battery won’t last that long, I have put the whole thing, including pictures, into pdf format. Due to the 3 MB limit of pdf files for RCGroups, I had to break the document into two parts, so be sure to download both file to get the entire build log.

The outline is below. Hope someone finds this useful!

OUTLINE:

1.0 INTRODUCTION AND OVERVIEW
2.0 BACKGROUND
3.0 UNBOXING AND FIRST IMPRESSIONS
4.0 POWER SYSTEM SELECTION
5.0 CENTER OF GRAVITY AND STATIC MARGIN ANALYSIS
6.0 BUILD NOTES: Miscellaneous Notes and Observations
7.0 BUILD NOTES: Battery Mount
8.0 BUILD NOTES: Installing The Retracts
9.0 BUILD NOTES: Nosewheel Steering
10.0 BUILD NOTES: Servicing the Pneumatic System
11.0 BUILD NOTES: Motor Mount
12.0 Canopy Latches
13.0 There is no 13. I screwed up the numbering making the post.
14.0 BUILD NOTES: Cowling Baffle
15.0 BUILD NOTES: Wing Removal
16.0 BUILD NOTES: Decals
17.0 BUILD NOTES: The Tiger Mouth Markings
18.0 FINAL SPECIFICATIONS
19.0 There is no 19. I screwed up the numbering making the post.
8.0 CONTROL SETUP AND MAIDEN FLIGHT (Yeah, another numbering screwup)
20.0 IF PHOENIX EVER ASKED, HERE’S WHAT I WOULD CHANGE

I am happy to say that I have now joined the ranks of the Foam Glider Conversion Club. I’ve always liked the looks of the Air Hogs Titan, and I had a lot of spare electronics sitting in my parts bin, so I thought I would go ahead and invest $9 in an airframe so I could put those old parts to good use.

DESIGN

My goals for the project were:

1. Put all my extra, unused 3S LiPo batteries to use;
2. Have a plane I can fly on the (seemingly frequent) days when there is an acute cross-wind to my runway (translates as: hand-launch, belly-land in tall grass adjacent to the runway);
3. Have a plane I can just throw in the trunk of my car and head to the field at a moment’s notice;
4. And, have a fun flyer that I don’t have a lot of dollars invested in.

In summary, I wanted a flyer that was fun and would not induce stress. I have a lot of expensive (in my universe) tail-draggers in my fleet, and tall, strong, Texas weeds totally enclose the narrow landing strip. Too many times cross winds have resulted in my wingtip grabbing a a weed when landing, and cartwheel off the runway, resulting in a lot of down-time and expense for repairs. I just wanted to throw this one up and not worry about it, and be able to fly on days that the rest of my rolling-takeoff-and-landing fleet would be grounded.

The power system I had available may not be optimum for the Titan, but at least I didn’t have to go buy anything: I had an unused spare 1100KV motor from a Dynam Grand Cruiser,...Continue Reading

It took about three months of off-again/on-again build effort, but I finally maidened my HK P-38. Winds were light, but a little gusty, and sometimes cross to the road I use as a runway. I still have some finishing touches to apply, but since the planets aligned such that I had no family obligations and the weather was good, I headed out to my flying site to get it in the air. I was there by myself, so no pictures of the airplane in flight. I had several notes regarding my build, though, and thought I would go ahead and give the full rundown now. I’m hoping in the next few weeks I can get some formation-flight photos with my Lightening and my buddy’s Banana Hobby F-35 Lightening II.

CONFIGURATION/MODS: It is a version 1 from Hobby King that came with mechanical retracts. All-in-all, I was pleased with what I saw in the box. No damage or major warpage, paint looked pretty good, all parts were there, and it even came with a carbon spar in each wing (though the spars were not connected to each other. My build took about three months because of other projects I had on-going, holiday obligations, a car crisis (ran into a ferrule hog that caused about $4200 in damage!), work conflicts, and of course, weather. There were also the complications of having to fix and modify the model. My mods included installation of E-Flight servoless retracts, 2 1/4-in. foam main wheels, 1 ¾-in foam nose wheel, installation of a nacelle-to-nacelle carbon fiber rod wing spar,...Continue Reading