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ScramJet

3" Ducted fan power. 42" WS  area=390 sq" AUW projected at 22oz. with  6 or 7 cell nicad from 1100 to 1250 mah. Totally built from blucor except outlet duct. Light weight paperboard tunnel was real easy to make. Hot glue only for assembly.  As soon as the ship flys i will draw a complete set of plans to download.  

 

 

 

 

The very large intake(4x fan area) has just enough room to remove the fan without hassel. Top section of tunnel will be removed when fitting to wing. I built the tunnel with the top section for the event of multiple wings to fit on the plane.

Looking down the pipe. The EDF 75 from a popular marketing company.

Note (I try not to use RC marketing or  manufacturing companies names in my website without compensation{$}, I do have favorites but if you need any specifics email me. )

 

 

Blucor wing getting ready to glue up

 

 

The fuse shape could be what ever you wanted. Box construction so you could use the profile of  military jets or like i did this one just off the cuff. I basically built it just big enough for sub C cell nicads. 

 

Here's the picture of the tunnel to wing installation. You can see the vertical's attached directly to the wing bottom section. I removed the top of the tunnel to stream line airflow and lighten the ship. So now the wing is not detachable. This is really to big of a model for not having removable wing but o well. It will fit in my truck just fine and its intergraded structure will  spread loads out further in the case of a crash(i hope).

 

 

 

 

 

 

Update : First test glide was tricky. CG was way aft. After adding lead {2oz} to the nose She was really starting to show promise. Even at 2oz it was still not rite. It was a cold January day(5 dgF). Wind was gusting approx 15 mph ide say. The temperature  didn't seam to bother any equipment. After a dozen glides into the tall dead weeds. I ran out of lead and was real close to where i wanted the CG to be so motor on flights began. The cg problem was more pronounced with the fan running and flights were kept low and short as possible. I also felt that the plane was not effected allot by the extra weight and knew at that point  it was best head home and modify the fuse for more cells and new CG point. One note also the plane glide crashed into the weeds more than a dozen time with zero damage.

 

So for the cure i lengthened the fuse 4 ". I plan for a room to allow up to 10 cells even though 6 cell 1100 is my biggest pack in good operation. Actually its my only sub c pack and the fan is drawing 13 amps at 15,000 rpm. Thats about 5k to slow in my book but that little fan will surprise you. The next pics are after the mod to the fuse

 

 

The new cg is 1.25" further forward. With alot more room for cells and some to spare.

 

 

Update :  A very cold day again with winds out of the southwest 5 - 10mph. Wind chill was 0'F. But like a hard core I gave her a toss. All i could do was hover in the wind. Ordered  a 9 cell pack so the next test flight should be fast. I hope to get 22,000 rpms with 9 cells. That should bring the eflux speed up 7k and make it a diving rocketship. I dont think the can motor will last long but thats ok. Very happy with the stability of this ship. Even though it couldn't penetrate the fierce wind with 6 cells the result is very good.

 

 

 

Update: I acquired an 7 cell cp1300src pack to test fly. Cold day in January but mild winds 4-6mph from the southeast. Perfect day to fly at Whitys airfield. The ship still didn't have the thrust to establish an controlled flight. I spent most of my time keeping it from sliding in. That evening i decided to do a extreme weight reduction and emphasize on flat plate area. I could just invest in some cobalt or blushless setup's but i rather find a frame for the inexpensive EDF75 from GWS.  The pics below illustrate the end result. The tubes are fiberglass of .325 OD. Very strong and lite. The over all weight reduction was 3oz. Flat plate area reduced by 21% and wet area reduced by 8%. 

 

 

 

 

 

 

Above is my blucor intake ring. 5 layers carved and sanded by hand to make a shape i thought would increase thrust. Testing the new ring increased the fan 1500rpms. I figured i my figures were wrong so i took  the ring off and lost 1500rpm's. I was amazed at the increase of power with the ring and wished i had made this a long time back. But thats how it goes, Sometimes you just wish your foresight was farther.

 

 

 

As you can see the front section has been shortened closer to the length that it was when i started. Obviously the battery could be located more aft than before so the nose could be shorter. With the majority of the  mass closer to the cg i figured this will make a very pitch sensitive ship. But that just means that the best cg will be more difficult to acquire witch will result in more patience needed  to get her balanced. 

 

 

The biggest downfall from all this design change is that the fan is now vulnerable to damage from the slightest nose in. I will have to be more precise during test flights. But due to the proved stability of the wing, I  remain confident that test glide's will prove that this beast is ready for power on flights.

 

Update: A beautiful February day and i headed to the field. Finally this wannabe jet flew and for a whapping 1 min before the fan speed dropped of below stall speed. But it was really cool and as i figured when i landed in the grass the fan cracked. All fixed up now and waiting for another day. Its still to heavy for the fan for a good time so a lighter wing from balsa would be ideal. But to keep it simple i would half cut the sheet and cut the weight to optimum. Considering the very stable characteristics of the wing i will definitely keep on pursuing. But you could still run a finer brushless setup and have a real cheap EDF that is extremely easy to fly.

 

Update:  Fixed the crack in the fan shroud with ca and lightened the ship a little more. Ready for a the next chance to take her up. I ordered a couple more 1300SCR's and plan on expanding my pack to 9 cells. Also the little GWS motor has lost 1500rpm's from its newest day. Thats really bad since ive only put about 30 minutes on the motor with 7 cells.