B-58 Hustler - Quad 70mm EDF Foamboard Beast

[L Edge]

You do great work Ben. I wish I had the time to delve into some of your builds. I've used the Spektrum AR636, AR7350, Hobby Eagle A3 Super II and 3 different Lemon-Rx stabs. I rarely pay attention to where they are placed with respect to the CG. They don't have to be placed on the CG in order to get good stabilization. By far the AR636 has been the best ANGLE stab for self-leveling. The Lemons are just as good at RATE stab and much cheaper than the Spektrums. And you can put a Lemon 10Ch Rx (non-stab Rx) in there and program the AR636 for higher channels to take advantage of a higher channel count, but they are no longer being made. I'm currently working on trying to get my 8.5lb SR-71 (empty weight) w/twin Freewing 12-Blade 70mm EDFs airborne with 6lbs thrust. It's going on a diet. I think maybe my airfoil isn't quite right? I should've left the balsa covering off.

Are you planning on launching it soon?

 

[hifinsword]

Are you planning on launching it soon?

It's flown twice but the wheels on grass create a lot of drag. On both flights the CG was too far aft, hence the pitch up on the landing. Here's a video of the last flight. I'll try it again soon when the grass has died down.

 

[L Edge]

It's flown twice but the wheels on grass create a lot of drag. On both flights the CG was too far aft, hence the pitch up on the landing. Here's a video of the last flight. I'll try it again soon when the grass has died down.

Congrats!!!! that was nice to see you accomplished that flight.
Did you incorporate differential thrust into your system?
Like your inlet design. Could you explain what you did and some pics please?

 

[hifinsword]

Congrats!!!! that was nice to see you accomplished that flight.
Did you incorporate differential thrust into your system?
Like your inlet design. Could you explain what you did and some pics please?

I did set it up for DT but took the mixes out when I realized the thrust to weight ratio was very low. After a few failed attempts I added the cheater vents and the thrust went from 4.4lbs to 5lbs. So I thought I might need all the thrust available. My DT mixes would reduce the one motor in a turn so some thrust would be lost. The nacelle spikes will go back in if I can fly it successfully a few times.

The inlet design was based around the 70mm EDF's diameter, which dictated the scale, 1:17.47. The nacelles are rather rough. I did the inlet edges at the front from the rounded tops of cream cheese container edges but I may ask a flying club member with a 3D printer, to print me some nacelle inlets. To make the nacelles, I took Dollar Tree foam, removed the inner paper and got it rounded. Then I heated some wet 1/16th balsa soaked in ammonia water, and used Gorilla Glue to form it to the foam. I wrapped it around some bottles and rubber banded it overnight. The ducts are actually halves glued together. They are centered around, and hide a flat triangular plywood spar that extends along the leading edge, and then through the nacelles to support the outer wing tips. Actually the halves are not split equally. Based on the Dryden Research 3 View I worked from, the top is larger than the bottom half. Initially most of the fuselage and chines were covered in balsa, but I've since cut major sections out and put in Dollar Tree foam to reduce weight. The one attached picture shows the initial layout in plywood. I used too much. The fuselage was two 3 inch mailing cardboard tubes. They are heavy and I ended up cutting most of it off the top, reinforcing the foam removeable access sections with the rounded cardboard strips, and reattaching them with magnets. Almost the entire top of the fuselage can be removed for access to the ESCs, battery tray, blue box multiconnector and the Rx.

I also moved the 2 inner elevon servos (HiTec D-85MGs) forward 10 inches (23g each) to move some weight forward. If I were to rebuild, I would leave most of the balsa out and strengthen the foam with only WBPU and see how that goes. If it went well, then I'd cover it better with something like Polyspan or that laminating film at Alofthobbies 1.5mil thick. New Stuff / Laminating Films (alofthobbies.com)

Twice I've aborted takeoffs due to low speed and found the plastic hub was melted around the axle on one wheel. Either wheel alignment problems or too much speed on the roll was the problem. I tried initially with dual 45mm tires on the mains, but one was always still in the airstream when retracted. So I've put one 2.5" tires on each main, duals on the nose LG, with a bushing in the hubs for the next attempt. I would like to try bearings in the hub but the ones I've tried were not good. I'm too cheap to buy good ones. The grass is the main problem with too much drag. Cooler denser air and dead grass will help the most when I try again - soon I hope.
Don

 

[L Edge]

Actually, you almost did it!!!!!

2 Suggestions:
Raise the nose gear so it is a positive angle into the airflow so it helps you liftoff. Your fuse is so long and a lot of weight in rear. You had plenty of speed for takeoff and it would have lifted off a lot shorter.
For landing, on final approach, keep some power on and slight nose down, then as you finally get close to ground(now ground effects come in), you need to start flaring and bring the nose up a tad and kill power and let it settle in. Do not overdue pitch!!

Like the real SR-71 in it's large turning radius, the Rc version requires small changes in pitch thru out the flight.

Got some other suggestions to help you with stability and rudder if you like. Took my SR-71(have thread, do search) apart after 25 flights to use the 64 EDF's.

 

[pdxpeter]

B-58 plan printing. Did you take the plans to a copy shop? What size? I tried to use my 🖨️ and the size fit on one page. Is this plan available at flitetest?