Konrad

Here I’ve fitted the firewall (nose ring mount) to the fuselage I’m really liking that from the outside we are only seeing about a 2mm ring of fiberglass to allow a smooth transition from the fuselage to the ring and then the spinner. This is also the first time I’ve used West Systems SIX10 epoxy glueing in the nose mount. When setting up the motor mount, not only are we concerned with the thrust line but we are also concerned about hoe the motor is indexed. Here I wanted the wires from the motor to be at the bottom to allow easy access to the batteries by keeping the ESC out of the way. With my particular motor this ment that I placed the mounting screw holes about 10° off the center line With the rather fat, great sport, fuse I couldn't get the CN 11 x 8 blades to lay flat against the fuselage. I’ll need to look for a set of blades that has a rather large pin off set. I recall that Graupneer use to offer such a blade design.

At low wind speeds a nice veneer wing can hold its own against any or most mouldies. The benefit of moulding is in airfoil fidelity (assuming proper manufacturing process) and added strength to allow exaggerated ballasting (weight)!

Mike, this is actually what I want folks to be thinking about, drag reduction even if it means adding weight. I’m happy to see you caught the concept of addressing variables with an exponent associated with it, rather than the linear variable such as weight, counter to lift. I started this thread as I saw guys sacrificing control, stability and reliability in the name of weight saving. This is just wrong! Now I was an engineer but never was an Aerodynamicist so take what follows with a grain of salt. See Martin Hepperle, a real Aerodynamicist, on the subject on the drag of flap and aileron linkages. (Under Other Topics, Aerodynamics) https://www.mh-aerotools.de/airfoils/index.htm You might want to look into tape style gap seal. I find that a well sanded paint surface is superior to film covering. Many full size ships have simple flat plate surfaces. The real benefit of a fleshed out surfaces is that you can get the same stiffness as a flat plate but at a significant weight reduction. (The geometry of the structure adds a lot of strength) A secondary benefit is that the air will separate at a much higher critical angle, meaning that you can get a lot more control and stability with less area or movement (AKA less drag).

I assume you ment the lower Reynolds number of our models. Not just full size aviation but most of my RC soaring ships have provisions for ballast. Weight is importance, so is its placement. In thermal duration ships I try to keep it out of the extreme ends of the model. This is done to help the model signal the conditions of the surrounding air (lift as well as sink). With slope ships I often like to ballast the wings to dampen the effects of turbulence.

WOW, It really is fun to be building a model where the designer is showing some obvious engineering acumen! I’m really liking the sliding block wedge for the vertical fin mounting.

Yes flaps are used. Mainly as a way to change the camber of the airfoil. Like you mentioned speed (reflex to remove camber) Thermal (droop to add camber). The articulated TE uses flaps in conjunction with the ailerons. Again flaps are generally not used alone. Huge flap deflection of around 85° to 90° as is typically used in a crow set up, is again used to change the drag profile dramatically during landing. With high performance gliders this allows for an interesting set of controls. Per the lift equation trust is used to appose drag. Since gliders don’t have thrust (typically) we can use the drag from the flaps (crow) to control the speed, glide slope, just like we do with thrust on normal power fixed wings aircraft. Again this is all about drag not weight. Even in my small 1.5 meter gliders I like to add the weight of 6 servos for the added control and flexibility (efficiency).

No not really. Remember that a little more speed produces a lot more lift. When in ground effect most find that they are dealing with too much lift. Most modern gliders have some kind of lift dump device, such as spoilers, spoilerons or a crow feature. These really increase the drag profile of the glider allowing the glider to land using a reasonably short approach landing profile. Flaps only are a holdout from full size aviation and rarely used in modern RC soaring machines.

Thank you John. I too am impressed with the results. Particularly when one realizes that I’m not in my workshop. Here at the family home in Denver I’m using little more than a pair of scissors, a knife, sanding block and drill motor. I haven’t glued in the motor mount as I have to assemble the motor and ESC and index them to allow the batteries to fit. With the limited space in today’s narrow fuselages one needs to think 3 or 4 steps ahead in the assembly process.

I can just imagine the damage to the wings should one land with partial water ballast in the tanks. Learning how to use ballast is another topic we should cover in detail.

Well, that worked out better than I had hoped. I now have a very solid press fit nose mount. I’m wondering if I actually have stronger nose with all that added glass.

Thank you, Yes profile or parasitic drag is lower at lower speeds. While induced drag increases as the speed drops for the same amount of lift. At some point these drag lines cross. I think we both agree that if in sink, no mater how light your wing loading is you are going down. This is the key observation that is at the core of modern thermal flying. Get out of sink as fast as you can. I don’t think you have seen many modern thermal duration ships if you think a stick and tissue open frame K-8 can out thermal an FAI F3J or F5J class of glass slipper. Yes a scale glider is on another level of graceful and elegance. Please don’t think I was endorsing the idea that a ship be built out of lead. I was just trying to show that weight is not the enemy so many think it is. Yes, build light as weight has its own drag penalty. But the real killer of soaring performance is drag!

Now I should mention that I was very impressed with the tail boom stub. The sides of this stub were laid up with the outer surface having a peal ply (shark Skin) surface finish. This is a much better prep than what we can get by roughening the bonding surface with sandpaper.

I’ve hit my first configuration issue. Per the sales sites it is advertised that the nose can fit 32mm spinners. I don’t know if this unique to my particular NoBody fuselage or is typical. But, I can’t fit a 32mm firewall (motor mount) to the nose of the fuselage. The motor mount just falls through. It is so louse that I cant even pilot on the OD of the retention ring of the CN motor mount. It looks like if the nose was 8mm to 10mm longer the nose tapper night have allowed for 32mm spinners. As a result of the short nose or oversized fuselage diameter, I’ve had to build up the nose with a few layers of 150 gram fiber glass. Here are some in process photos. Key is that I had to roughen the ID of the nose to allow sufficient teeth to allow the epoxy to bond to the fuselage. As this glass sleeve will be taking all the loads from the motor and much of the landing loads I’ve prepped the inside aft for over 90mm. I’ve found that I can’t do a continuous fiber layup on ID features. As a result I pieced the nose extension allowing me to keep the glass layers against the ID of the nose. I’m showing how ugly the layup looks as I wait for the initial set of the epoxy. While the epoxy is green (set but not hard) I trimmed the glass as shown. I have so many layers that I can’t fit the firewall inside the fuse. I’ll have to wait until the epoxy is fully cured to allow me to grind the ID of the nose to a snug fit with the firewall/motor mount.

Yes, weight is a concern. But contrary to intuition weight is NOT the primary concern when it comes to getting the most from your aircraft. In fact it should be a secondary or more accurately a tertiary concern. I say this as per the lift equation lift goes up by a square function of the velocity of the wing. So for a little bit of speed you gain a lot of lift. The primary concern should be structural integrity and controllability. I’ve actually seen low time builder/pilots leave out the shear webs between the spars in an effort to save weight. This is an extreme example but it highlights the need to understand the how and why things are done. Another example is we have all seen planes where the builder left off covers and fairings again thinking this was an advantage as it saves weight. Again we can look at the lift equation and see that parasitic drag goes up by a cubic function of speed. So to get that little bit of speed needed to carry the weight will have a huge cost in energy to overcome the drag. So now that we know the relationship between lift, velocity and drag. It should be clear that when setting up our models and sailplanes in particular we need to focus on the variables with the largest exponential functions to gain the most performance for our efforts. And the largest is the cubic function of DRAG. When building your models keep an eye out for how to reduce drag. Time and time again we see linkages with large holes to allow the push rod to pass. Wings that don’t seal against the fuselage. Features that have high junction drag associated with them. Do what you can to seal up holes (don’t make them in the first place) and smooth any transition and/or protrusions. Linkages are a surprisingly large component to drag. Their placement and improper shrouding often results in added drag equivalent to adding a second stabilizer. Now weight is a component that not only acts against lift but does produce drag. This is known as induced drag. It comes from the wing needing to work harder and comes from the induced angle of attack of the wing to generate lift, hence the term induced drag. Again looking at the lift equation we see that this is more of an issue at lower speeds. So yes, reducing weight is important to reducing drag. Now where induced drag raises its ugly head is in control deflections. Having linkages that are solid will pay huge benefits as the control surface will not wonder. Surfaces that keep their position add to the flight performance as we or the gyro don’t need to constantly be deflecting the surface adding to that cubic function, DRAG! If you hope to get the most from your glider please add weight in the way of solid hinging and control rods, covers, fairing and servo mounts. The weight is well worth it!

I can honor that. That was never my intention. I wish you the best in your endeavors into high performance sailplanes. Be safe. Konrad