2026 Speed Challenge - Telnar1236
- Thread starter telnar1236
- Start date
Houndpup Rc
Legendary member
Nice!!
telnar1236
Master member
Unfortunately, I think the Rapier is pushing up against the limits of the power system - I might get a bit more speed by optimizing my dive and flying with a strong tail wind, but realistically, 133 mph is close to the max. And even though it won't win, I'm happy with that speed out of a 64mm EDF even if this is my final number. And of course, I'm trying to get the Super Duper Sabre up and running for this competition which should be substantially faster
telnar1236
Master member
I've been fighting with my 3D printer for the past week or so which has been limiting progress on the Super Duper Sabre. Part way through a print run, the Y stepper started making an awful noise and it wasn't really reasonable for me to keep running the printer. So of course I replaced the stepper motor, and what do you know, the new one also made a horrible sound. It turned out the Y axis stepper driver was in the process of failing and the company that makes the printer doesn't seem to sell replacement main boards for this model. I was able to tune the settings so that the printer was able to run a lot quieter again, but it ruined the tolerances on my Y-axis and led to some unusable parts, so I finally gave up and replaced the 3D printer and have been tuning it in for the past day or two - and it's finally ready to start making airplane parts again
telnar1236
Master member
And we're back in business - got the canopy for the Super Duper Sabre printed - only things remaining are the flaps, nose gear, rudder, latch, and some control linkages
Houndpup Rc
Legendary member
Nice!! I need to get some LW PLa or LW ABS sometime!
telnar1236
Master member
Just normal ABS is probably the best bet - I haven't tried foaming ABS, but LW-ASA is awful in terms of strength
Houndpup Rc
Legendary member
edit: I need to get some ABS sometime!😂😂
telnar1236
Master member
Continuing to do anything to procrastinate building the Super Duper Sabre, I've been thinking about what I would do for a foam board speed plane. The layout is determined by the limitations of foam board and my limitations as a pilot. For a foam board design, an EDF will not cut it - the combination of the poor efficiency of an EDF and higher drag of foam board won't work well together so a prop is necessary. However, I tend to really struggle with the torque from the powerful single prop needed to drive a plane very fast, so a twin motor design will make life much simpler. Adding nacelles either side of a central fuselage also adds drag, and just doubling up the fuselage is sleeker so I ended up with a design something like an F-82 Twin Mustang. The wing is thin but still airfoiled since this is lower drag than just having a single flat plate for larger chord lengths but the tail is a flat plate design since it's a shorter chord.
I didn't try to round the edges of the fuselage since I'm not a particularly good foam board builder so limiting the number of folds and complexity of the build is very much in my interest. The wings are designed to use carbon fiber spars and the entire airframe is meant to be wrapped in packing tape to add strength. Flutter is also a concern with foam board so I'm thinking that adding 3D printed mass balances to the control surfaces may be a good idea. In general, I plan to 3D parts that would typically be made of plywood since that's a lower effort option for me.
Not sure if I'll try to build this and it would definitely come after the Super Duper Sabre if I do but it's a fun thought experiment at a minimum.
I didn't try to round the edges of the fuselage since I'm not a particularly good foam board builder so limiting the number of folds and complexity of the build is very much in my interest. The wings are designed to use carbon fiber spars and the entire airframe is meant to be wrapped in packing tape to add strength. Flutter is also a concern with foam board so I'm thinking that adding 3D printed mass balances to the control surfaces may be a good idea. In general, I plan to 3D parts that would typically be made of plywood since that's a lower effort option for me.
Not sure if I'll try to build this and it would definitely come after the Super Duper Sabre if I do but it's a fun thought experiment at a minimum.
RickHunter
Elite member
Nice design. I did something similar(ish) with a modified FT Bronco design. With two 3536 1780kv on 6s with 8x6 propellers I got to the high 120s mph. This is a much more sleek design and wonder what it could with a similar setup.
Mr Man
Mr SPEED!
Cool! Looks like what I imagine Ken would look like in the reno races 👍
telnar1236
Master member
Predicted top speed is ballpark 180 mph, but I have so little data on props and no data on foam board planes, so that could be very far off in either direction. The intent would be to run 5x8 props on twin 2306 1900 kv motors, but I've struggled to find to find such high pitch small diameter props in the past and have gotten stuck with 6x6 props. Should draw around 120A on 6s with only a 30" wingspan.
Houndpup Rc
Legendary member
Looks kinda like the F-82!😁👍
telnar1236
Master member
One of my main sources of inspiration. My design was mostly inspired by wanting to minimize the impact of the motor's torque, but I also remember seeing somewhere that WW2 twin fuselage designs were something like 20 mph faster than their single fuselage counterparts - as you see with the Twin Mustang (F-82G) having a top speed of 461 mph vs. 440 mph for the P-51D.
The other one was the Pond Racer which isn't really a twin fuselage design but still has a similar look to it. There's a pretty neat 3D printed version of it that I saw a video of a while back and I've been itching to try my hand at something similar.
Pond racer 1200mm
This replica of the Pond racer is designed for quick and easy construction and printed using regular PLA. Designed to suit the 3548 900kv motor this model has a significant amount of power and is happy to cruise around at 50% power on 3s. Utilizing 6 channels; Ailerons, Elevator, Flaps...
RickHunter
Elite member
That pond racer is pretty cool. I have a foamy f-82 in my hanger. It was never built for speed, but it is a lot of fun and looks cool in the air. Plus it does flat spins like crazy. There is no torque roll whatsoever with the duel props in opposite rotation.
L Edge
Legendary member
Suggest you get in contact with APC props on the west coast.
Ask to talk with the teck person and explain your situation and this guy should give you a handle on what to do.
Years ago, I was interested in 4D flying and asked him about reversible props. They designed one and he stated that it was about 80% efficient in both directions. Never even expected that. So give them a call. Also they have quite a data bank on their props and what they can do. May have to hunt their site to find info. Pylon racers are always trying different engines and need different props.
With dual engines, agree like others, that you will need cw/ccw props. On my 2 motor VTOL, ran just CW props, then CCW props and then CW/CCW and best result was CW/CCW with the FC. Also flew a big flat piece of blue foam doing cw/ccw and would not with 2 cw motors with a FC..
Frontal drag is the biggest culprit, if you are looking for speed, if the tail feathers can be V-tail, it will add big gains. Pylon racers proved that.
Gadeirus
Active member
Can't say that I've read EVERY word in this thread, but it certainly is interesting. I also think it kind of highlights that having 3DP aircraft and DTFB aircraft competing against each other is bit....skewed?
I would like to ask, what CAD software are you using, and what are you using for CFD? Simscale perhaps?
I would like to ask, what CAD software are you using, and what are you using for CFD? Simscale perhaps?
Houndpup Rc
Legendary member
Meaning that its easier or harder?
Gadeirus
Active member
Both methods have their own difficulties for sure, not saying one is easier than the other. Rather, the DTFB will never be able to compete with the aerodynamics possible with 3D printing.
Houndpup Rc
Legendary member
Fair point! But I think the skill level it takes to get there involves so much more IMO, (Takes more CAD knowledge ect) that they deserve to win if they can get it that fast!😂
I think the current record for a 3D printed plane is only 181mph....only 6mph faster than the currently foam board record of 175mph. Though it will probably get to the point where there is a bigger gap and should be separated, at this point I think its still where they are pretty close and I hope we can set new records with both materials!😁👍
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