Raised Rivets made easy
I had originally intended for our last article and this one to be a single write-up. However, as I continued to write more and more on the construction, I realized that the article really needed to be split into two. Also, since detailing and the application of raised rivets is extensible to more than just speed brakes, I figured a single article on this process would be good since it is a process that can be applied to aircraft as a whole. As with the last article, I’ve also included a how-to video to help illustrate the process which is at the end of the article.
Let’s Get Things Ready
Last time we built our speed brake assemblies to where we had 4 fully functional speed brakes that could be installed into the airframe. However, detailing the internals is quite a bit simpler with the speed brakes outside of the airframe and broken down into their components. The first item of business was to finish the inside speed brake by adding the sheet metal close out surface on the inside. This was cut from 1/64″ ply and glued onto the basswood stiffeners that create our hinge mentioned previously. Continue reading
All I wanted was to install bulkheads…but somehow ended up with 4 speed brakes instead…
We have a pretty sizable article this week which is the first in a two part series discussing how the speed brakes were built, actuated and detailed for our Frankel F4D Skyray. In addition, I’ve put together a couple how-to videos to support (the first being below). So, let’s get to it!
Fuselage ready for surgery.
In our previous article, we completed (mostly) our dorsal assembly. With that completed, we can finally move on to work on the fuselage. Typically I would go to the wings next (I generally like to work on the largest parts last), but in the case of this build, we need to have bulkheads installed in the fuselage first before working on the wings. This is so that the wing mounts and spars can be setup in the foam cores before they are sheeted.
So, this originally was going to be a quick task; cutting hatches, installing bulkheads, that’s quick right?!… Continue reading
Finishing Fiberglass – Let’s finish that dorsal!
Last time we finished up construction of our rudder/dorsal assemblies and built our offset rudder hinge. So, now it’s time to clean these assemblies all up and make them as ready as they can be to be installed onto the fuselage. The installation of the dorsal onto the fuselage will occur once all of the construction of the fuse is finished however. The primary reason for this is so that all work on the fuselage can be done without the dorsal being in the way as the fuselage is rotated around while it’s worked on.
Primer – Sand…repeat, repeat, repeat…
With the dorsal and rudders being glassed (see Part 5 for that discussion), the first item of business is to start the Continue reading
Fiberglassing and Hinges…now we’re getting somewhere!
With the dorsal and rudder shaped, the next step is fiberglassing and hinging each of the parts. I didn’t take many pictures during the glassing process (performed this before starting this blog), but I will talk through it a little bit. When I get to fiberglassing the wings, I plan to make a complete tutorial video. The pic to the left is ultimately what we are striving for…
Some Notes on Fiberglassing
Now, I typically don’t hinge control surfaces until after glassing. I’ve done it both ways (hinging before and after glassing) and have found hinging after glassing is definitely my preference. The reason for this is that when I make the slots in the control surfaces to receive the hinges, I can get much cleaner and crisper corners since the glass hardens the wood. Otherwise, the balsa can crush in around the slot and it doesn’t come out as cleanly. In terms of glassing, I use 3/4 oz fiberglass cloth and Pacer Z-Poxy Finishing Resin finishing epoxy resin to apply the glass. The fiberglass is cut out around the surface allowing significant overlap and laid flat onto the surface dry (important!). From there, I mix up the Z-Poxy Resin as directed (50/50 mix Continue reading
Rudder me This!
Final test fit of the dorsal before fibreglass
With the final shape of the dorsal completed for our RC Jet, it is on to cutting out and shaping the rudder. On the full size Skyray, the rudder was split into an upper and lower half. The upper portion acted as a yaw damper primarily while also acting in unison with the rudder. The lower half acted as the primary rudder surface. Interestingly, in looking at videos of the Skyray in flight, the yaw damper doesn’t seem to act much in unison with the rudder at all. Also, in talking with Mark Frankel, the rudder is quite effective on the model causing it to roll pretty substantially. So, based on those two things, my intention on this model is to make the yaw damper fixed and use the lower half as the rudder. We will be cutting out both the damper and rudder and splitting them, but when final installed into place, the yaw damper will be fixed. This way, it will still appear to be a moveable surface.
Rudder template in place, ready for cutting
Checking my 3-view to the plans, I traced the rudder shape and transferred it to the dorsal. The key here when plotting it out is the allowances for the balsa rudder cap (in this case it’s about ½” of material) as well as the spar in the dorsal itself. In other words, ½” of the rudder leading edge will be removed and thrown away and replaced with a solid balsa cap that gets sanded to shape. Also, I had to take time to ensure I accounted and had a plan for the location of the spar so I had the proper scuffer setup on the dorsal as well once everything is hinged. The idea is to have a nice scale looking flange on the dorsal and rounded Continue reading
Final shaped dorsal test fit on fuselage
When you build an RC jet like this one, it’s nice to start off small. Progress comes with small milestones accomplished by small steps at a time. It really only takes a few hours per week to see notable progress and the key is to just get into the shop and make that progress happen. Yes, it takes time and will take a while to get done, but that’s half the fun. So, with that in mind, I started off construction with the dorsal. Note that I started this build before starting this blog, so in some cases, I’m limited on the pictures that I took.
Sub leading edge glued in place
With everything unboxed and setup in my shop, the first item of business was sheeting the dorsal foam core (I plan to make a tutorial video on how to do this when I sheet the wings). Mark’s design incorporates a sub leading edge before sheeting, so that was installed first with some wood glue (I like to use Titebond Premium Wood Glue). The sheeting was made from contest grade 1/16” balsa (as light as possible) glued edge to edge as necessary to get full coverage over the core. The grain of the wood runs parallel to the leading edge (important!) which helps with strength as well as makes it easier for the wood to contour over the foam core. I used Pacer PT-40 Z-Poxy Finishing Resin to adhere the sheeting Continue reading
Let’s talk about resources and documentation for Scale Competition for a minute…
If there is anything debated in scale competition, it sure seems to be scale documentation. 😉 I say this only from the standpoint that there’s really no one right way, or one right answer when it comes to a documentation book. It’s ultimately how well you prove your model matches your documentation. Also, I bring this up at the beginning of this build because, without a good solid documentation book, it’s very difficult to be competitive in a scale competition setting (static score is HALF of the total score). Plus, if you are building your competition bird, it’s necessary to have a clear vision of the project from the start.
First of all, it’s important to know the rules. For this bird, I will be primarily competing in the Scale Masters competitions, and so have gone through those rules numerous times (as well as have competed several times previously). USSMA also has a decent aid on their website for how to put together a quality documentation book. So, before starting, know what is necessary to present to the judges and have sufficient documentation for your aircraft. From the start, a good 3-view resource is necessary so that one can ensure the shapes of the model match the drawing. The paint scheme can evolve as the build progresses as sometimes you may have something in mind initially, and in the research process you may come across something you like more and/or can document color and markings better.
For me, I love the research and will typically buy whatever books I can find (it’s kind of a sickness that my wife gives me a hard time for) and spend numerous hours searching the internet. For the Skyray, there are two definitive books that are absolutely a must for any Skyray fan and are listed below. Also a must is a plastic kit (if available) as it helps to visualize shapes Continue reading
Let the Building BEGIN!!
I’m starting this blog with a series titled, “How to Build an RC Jet.” The subject of the study is a Mark Frankel F4D-1 Skyray kit (I love deltas!) of which I plan to build into a competition ready model for the US Scale Masters (and/or Top Gun if I can ever afford the trip some year). As I build the kit and document it here, I plan to cover not just basic building techniques (including tutorial videos along the way) but also all of the details that go into a competition model and the tools that are used in the process. These techniques are extensible to any model aircraft project and so I hope that I can provide anyone out there reading this some basic tools to do something out of the ordinary.
Regarding some specifics on the kit, the design is an exact 1/7 scale which puts the fuselage length at 77.6″ and the wingspan at 57.4″. This kit was first designed around glow ducted fan back in the mid to late 1980’s and flew excellent with that power. According to Mark, he designed it as large as he could while still getting a great flying airplane given the available glow power systems. The design has flown on glow and turbine power, however this will be the first to fly on Electric Ducted Fan (EDF) power and I expect performance to be excellent! Some of the features I intend to build into the airplane are: Continue reading