Sams Race engine help
 

All,

I havent had much time to build some race planes but I was helping out the woodland quickie and Q40 stuff. Richard talked me into at least going and watching the next SAMS race in couple of weeks. well I couldnt have anything built in time but I do have a Eflight P-51B electric kit sitting around. Now before some of you jump in here and say its an electric arf and all, let me say I have been modding arfs for a long time and making them go fast. I think the airframe will hold up. Full sheeted wing and Fus. spar has full length sheer webs. So anyway It has 460 sq of wing and I so happen to have a New 91 AC in the box.

Ok now for the questions.

1. what is the max nitro for the stock engine?
2. What is the max ground RPM?
3. Is there anything I need to pay attention to on the 91?

I am planning on running a 12x14 on 50% or more but I have no experience with this engine. Will this be to much of a load? I have some 11x14 props also. If I stay with stock airframe the 14" pitch might be to much as the plane has a thick14% wing and has the belly scoop. the only class I would want to run in would be the Gold class. I can shorten the wing to 440 Sq for the 91 and remove the belly scoop. The weight looks like it will come out to around 6 lbs.

Ok valid thoughts welcome.

Jeff, the only experience I have with a 91 AC was in a pattern airplane and I ran Powermaster 20/20 through it with a 15X8. I think guys are propping all the YS engines to spin between 10K and 11K. I can't see where the RPM numbers would be different with the 91.

As far as the airplane goes, if you think it will stay together then I say go for it. Unless you are going to mod it to closely resemble a Reno P-51 that did not have a belly pan then I'm pretty sure you are going to have to keep it. I would also keep the wing area. There comes a point where less wing area is slower in the straits because of the added AOA needed to support the weight of the airplane. IMO 6 lbs with less then 475 sq in is in that zone. The added wing area will actually get the airplane through the turns faster and there are 20 turns per race. Loosing 1/2 second per turn puts you down 10 seconds or 1.5 laps. It would be great to have you out there but having an airplane that runs with these guys right out the gate is a very tall order. Of course I will be the first one to shake your hand should you pull it off.

I will run some times here first to see. I really dont want to run silver as there is a million people in that one. I have some planes and kits that i could compete with but I don't have the time to build them. I had same thoughts on the wing. I will look on line to see if and B model ones had a scoop removed. the plane is way over built. i think stronger than the WM mustangs by far. I know I wont win with it but I will try lol

I will do more racing next year for sure. I think i would like to beat the record with a two stroke again since it now stands with a 115

If you intend to race you need to get registered. JR is putting a cap of 60 entrants. It's filling up fast.

yes I heard that

YS91 on 30 to 40% nitro with an apc 12x12 narrow will be a good place to start.

I ran my 91's back in the day with either the 12x13n on high nitro, and also the 13x12n. RPM for the .91 should be around 11K. I wouldn't push it much past that.
Skids

ok Thanks Guys I am thinking it will be a Silver plane but i know everyone flys that class. I signed online tonight in the gold. If RC country doesnt have any fuel where locally can I get it or will there be some at the race?

I have some experience with the B model. I have been racing them with e-power for a couple years. I also built one for a 115. It currently has a 110 in it. The only real structural upgrade I had to do was the front end of the fuse to take the jarring from the 4 stroke. An electric doesn't do that. Biggest challenge with that plane is landing it. With the weight you'll be carrying it has to land with some speed and the runway starts getting short. Other than that, I love the way they fly. On the electric I run an 11x12 but that is at 13.8K rpm. I'm running a 13x13n on the 110. Have fun with it.

Blessings, Terry

The Bill model doesn't have enough wing for the 110 or 115 for the SAMS racing or am I wrong. it only has 460 SQ

The wing area for 1.10-1.19 4 stroke would need to be 515 square inches or greater for the S.A.M. Series rules. You are correct, if using a YS the .91 four stroke would be 440 square inches or greater for wing area.

Jimmy Skids

ok Just checking. I havent read the rules in a couple of months. I might even race in the bronze with my T-34 since they are allowed now. I just dont need any Mid air's and I will be fine.

How are are most of the racers, are they all over the course or can they hold a line?

That is a loaded question. I have witnessed many mid-airs where at least one pilot would say that the other didn't hold their line. Bronze class seems to have the least amount of mid-airs. Might be based upon registration, speed, etc. Not really sure. Silver and Gold have their fair share of them. A couple guys have lost multiple planes this year. When I fly I try to find open space. This isn't always easy.
Jimmy Skids

Yes I know. i will just have to stay in front of the guys that are not so inclined to stay on a line. have you guy cut off registration yet? I sent an online form for the Gold name is Jeff Robinson but will send one in for the Bronze. Did you receive the one for the gold?

It currenlty looks as if registration is still open. I have sent a text to JR who can confirm. If you have registered in one class you should of received an email from JR already. Any questions about additional registrations and/or the original can be sent to him. I know he has posted his email address elsewhere on RCU so I'll post it here so that you can contact him with addtional quesitons if needed: [email protected]

Jimmy Skids

Thanks Jimmy. I sent an email to him.