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Which engine to use?

Mark Lund

Jewell, Iowa
I'm building an experimental SuperCub. I've restored a 65 hp and an 85 hp J3 and I understand and appreciate the advantages and disadvantages of certified and experimental aircraft. This experimental is my toy. The fuselage is ready to cover and the wings are ready to assemble. The wings don't have flaps and I'm not excited about adding the flap mechanism to either the fuselage or the wings. It's time to build the boot cowl and as I understand it, how that is built depends on the engine selection. My two options are an O-200 Continental or an o-320 Lycoming.

I want to do some flying in the Western US, but most of the time my Iowa buddies and I fly our J-3's, PA-11 replicas and Supercubs out of airports and farm fields at 1000 ft MSL. Eight hundred feet is a short strip around here. I've flown in Alaska and I know this "ain't nothing". Of course we all like to brag about who has the best STOL aircraft. And my J-3 will often beat most of the above. But it's also slower than some of my neighbor's John Deere combines. Hence the desire for something with better cruise and some type of STOL performance.

I've read all the "manufacturer's specs" on different cubs and I'm skeptical of all their claims. I'm going without an electrical system. I will have two 18 gallon fuel tanks with either engine choice. I know many out there have experience flying light cubs with small engines and no flaps or electrical system. Here's my question. If I go with the 150 hp engine with no flaps or electrical system, what kind of cruise and STOL performance gains (if any) over a small engine could I reasonably expect? I'm willing to pay the higher initial engine costs and on going fuel costs if the difference in cruise is significant. I know STOL performance without flaps will be less than a PA-18-150. I can accept that but I don't want to look like a PA-28 on takeoff either.

I know I'll get a lot of recommendations from you guys. I'm really curious to know if someone is out there flying an experimental O-320 without flaps and electrical system and what they think of it.

I think you need to fly an 18-150 with flaps for 2 to 3 hours. I think you'll know the answer to your question. No electric is just inconvenience. Building a 18 with out flaps would be like building it with tri pacer wings -just doesn't make since. To answer your speed question 118 at 2500 with standard cruise/climb prop,and 9 gal/hour down low. Go fly a 18-150 with flaps and then let us know what your opinion is. Be sure to perform some full flap departures.
I once owned a J-3 that I converted to PA-11 arrangement. Added flaps and dual 18 gal tanks and other PA-18 modifications. I had a 85 hp Continental that I installed the O-200 crank STC for more power. The aircraft performed satisfactory when light on fuel and just the pilot. However, when fully loaded it was a lead sled!

I have just completed building an experimental PA-18 replica with 160 hp Lycoming. After 30 years of flying 65 and 85 hp Cubs, all I can say is, WOW!

So, IMHO there is no substitute for horspower. Go with the Lycoming.

As far as the flaps go, I agree with the previous post, try it you will like it. The advantage of the flaps far outweigh the weight disadvantage. Go with the flaps.

The electrical system is up for grabs here. I hand proped the little Continentals for year with no problem, but I did not want to deal with the big Lycoming. If you have no problem with that, then fine. I went with the electrical system. I used the Hawker Odssey lightweight battery, the B&C assessory case mount alternator and the lightweight starter. The 160 hp Lycoming handles all with no problem!
Ramchaser and others. Thanks for the replies.

I've flown PA-18-150's. I know how well they perform. Max gross wt I'm looking for would be around 1600 lbs. Most of the time I will be much lighter.

I'm estimating empty wt with an O-200 at 800#'s with no electrical. I believe an O-320 runs about 50#'s heavier, so 850# +/- with a 320.

If I'm not hauling a big load, maybe I should be looking at the lighter engine if I don't add flaps.
I fly an L18C with a C-90 and electrical. Weighs a little over 900# with light weight battery and starter, till has the heavy generator. No flaps w/36 gallons of gas and headerless fuel system. OT/OP, AS, Alt, compass electric T&B, Micro-Air Com. I love it. I have flown 150 hp SC and like them too but the L18C is more fun to me to just fly. Lighter on the controls, enough power to get in and out and more comfortable than a J-3. I have a project L18C that I plan to build light without electric and have thought about adding flaps. Don't know what it would weigh to do this but would be really slow to land where now I slip her in.
Gross weight on the L18C is 1500 lbs. 945 lbs. empty with above equipment plus 8.50 tires, Clevland wheels and brakes, Atlee saftey cables, micro VGs, Scott 3200 tailwheel, RT-A600 fire extinguisher, Dan's under seat battery, CC under seat storage, pilot seat inertia reel shoulder harness, B&C starter, El Reno oil filter adapter, M20 air/oil sep and a Rosen sun visor, Stits fabric with Polytone. Using a Sensenich M76AK-2-41 prop and cruise somewhere around 85-90 mph. Lost 7-8 mph when I took the fabric of the gear and had the prop pitched from 44" to 41". Non-scientific just kinda an average noticed cause I fly it a lot.
Mark, Get the big engine. I am tired of flying circles around you on a trip. With the big engine I'll let you follow me to Montana next summer.

Mark mentioned the boot cowl. Is the PA-18-95 boot different than a 150? I had a L-18C for years but I don't remember. I think the 95 might have been narrower, but I am not sure.
Thanks Steve. Mark has an old 150 boot of mine he can use for a pattern and the Northland CD has drawings for the Lyc. boot. Any ideas where one might find drawings for the 95 cowl? The PA-11 might be an option but will the longer and narrower (at the top) PA-11 windshield match up with the 18 upper fues.? Maybe a PA-11 boot with 18 windshield strips?
Some info to back up Steve's figues on the "95". We had the "95" in our 18 since bought in 1964 (a 1959). Upgraded recently to a 135. We were some what heavy like Steve also. We were around 950 empty. Our strip was 1,100' for 20+ yrs with power line a little ways off the west end. As long as you didn't put 36 gals in . . with 2 people on a hot day . . you did fine. But with the Cub . . if you can't go over . . go around. Fun . .cheap flying with the "95". Std. prop at 2350 would 95-97. At 2250 90-92. With climb prop. 2350 would see 90-92. Today on skis (30 degrees & 25 gals & solo) at 2,200' msl (800'), showed 108 at 2300. As for flaps . . don't have them (ran out of money during rebuild. But Husky says they figure they get aprox 3 miles an hr. more out of their flapless wing do to undistrubed airflow. Don't know if it is true .. just what I read. As for take off & climb performance . . . . the 135 makes me smile every time. But a 45% increase in hp. would make anyone smile. Have fun!!
I forgot to add info on the boot cowl for the "95". As I had to replace mine for the 135. . . the "95" boot is narrower. The windshield is longer on the "95". It comes to about where the vent is on the larger boot cowl. A new boot for either will set you back over $800, plus windshield channel & shipping from Univar. I still have mine from the "95". It is not beat up & has the windshield strip & a venturi on it. If interest I can send a picture.
Larry C.