Author Topic: Ben Feist's Curtiss R3C-2 (Read 29427 times)

bfeist · « **on:** September 30, 2005, 06:28:39 pm »

Finally decided:
I'm going to give a Curtiss R3C-2 a try. It's a beautiful plane and was piloted to victory by James Doolittle in 1925. http://www.geocities.com/CapeCanaveral/Lab/4515/r3c2.htm

[edited Oct 1]
Here are some additional fantastic detail shots:
http://www.airminded.net/r3c/r3c.html

I found a 1/6th scale short-kit with a 48" wing span (top wing) that reportedly has an all up weight (without fuel) of about 7.5 lbs. That would hopefully put it at about 8 - 8.5 lbs with electric equipment.

It'll be my first float plane (my previous was a trainer conversion to floats), my first bi-plane, my first outrunner brushless, my first big lipo purchase, and the first plane i've built myself in years. A tall order.

The seller of the short kit mentioned that A&J carries them, and that Jack is building one too.

As for the electric conversion I could use some help to figure out the motor config, although i'll buy the power system last. I was thinking of an AXI 4120/14 with a 4s3p lipo pack spinning a 14x9 (probably about 7200 rpm) which would produce ~500W (but at 40A). Feedback anyone? think this would do it? The AXI specs say this motor is for 6.5lb planes, but compares the performance to a 4-stroke 90 glow. I'm hesitant to go to 5s with a lower kV motor due to my charger only being able to handle 4s. I suppose I could break down and buy a new charger.

Lots of steps between here and completion. Any input/help/sanity is welcomed.

Benjamin Feist - EMFSO Site Developer

piker · « **Reply #1 on:** September 30, 2005, 08:10:44 pm »

Ben,

Is that a local guy selling the kit? If so, I saw the plane at the Aurora Swap meet last spring. The model on display looked great.

It's bigger than what most others are building, but it'll be an impressive build. Your power thoughts seem reasonable so far, but you MAY want more power. However, with some careful lightening of the structure and the use of Li-po, you may be able to keep the weight down to even lighter than 7.5 lbs.

I would REALLY like to see the kit/plans when you get them. I'll try to help find places to shed some weight.

Robert

Martin Irvine · « **Reply #2 on:** October 01, 2005, 01:00:59 pm »

I'd like to see these plans too Ben. You know, you could do a photo reduction to 400 sq. in.....
I'm sure Robert can show you how to loose half the weight. It sounds heavy.

Martin

piker · « **Reply #3 on:** October 01, 2005, 01:56:32 pm »

My Libtery Sport had a 57" top wing and weighed 7.5 lbs with a geared AF40 on 20 cell. I don't think there was a lot more room for lightening. It didn't have two large floats on it either.

However, at 44" span, I think you may be right, Martin. With Li-po he may be able to get it down to 6.5 lbs..... or even lighter.

Ben, Why not share the link that you sent me?

Robert

bfeist · « **Reply #4 on:** October 01, 2005, 02:45:30 pm »

Well, I bought the short kit at A&J's today. Looks fantastic. I bought a lot of the wood required as well from the parts list in the instructions. It looks like it uses pretty normal stuff:

Wings sheeted with 3/32 balsa
Fuse sheeted with 1/16 balsa
Floats sheeted on top with 1/16 balsa and sheeted on the bottom with 1/32 ply
Rudder servo in one of the floats etc.

There are a few strange items listed like a piece of 5/8" x 4" x 24" balsa used on the wings somewhere--maybe the piece that connects the top and bottom wing. I'll read through the instructions and take a closer look at the plans tonight.

I don't know how I could post the plans for everyone to see, they're huge. Maybe a digital picture of them--i'll give it a shot. The link to the short kit manufacturer that Robert was talking about is here: http://www.gdhconsulting.ca/page9.html

Benjamin Feist - EMFSO Site Developer

bfeist · « **Reply #5 on:** October 01, 2005, 05:45:21 pm »

I took some shots of the plans (not great) and a few pages of the instruction book. You can view them here: https://plus.google.com/u/0/photos/115501856346560787992/albums/5757076170782257457

I read through the instructions--70 pages, 165 steps. My thoughts now are that it is a bit of a meaty construction. Lots of thick balsa and almost completely sheeted wings. One of the shots I took shows an image in the manual of the completed but still uncovered plane. You can see how substantial it is. It has strange things like 1/2" cap strips made from 3/32" balsa. The 5/8 x 4 x 24 piece is for the wingtips (sand to shape).
Does any of this strike anyone as unusual?

I'm looking at 25-28 oz/sq ft. according to the approx. 680 sq.in. the plans list. I calculated 725 sq.in. This puts it closer to 23-25 oz/sq ft.

I need about 600-700W i'm guessing. Anyone?

Benjamin Feist - EMFSO Site Developer

Martin Irvine · « **Reply #6 on:** October 02, 2005, 05:32:37 pm »

With only 5 sq.ft. I'd be looking at 16-18oz./sq.ft.That means 5-5.7lb. To lose 2 lb. will mean a complete redesign. (Sorry!)

Martin

bfeist · « **Reply #7 on:** October 03, 2005, 04:23:06 am »

How can that make sense? This is a plan and kit that has been built before and is sold to come in at 7.5-8lbs. Has one never flown?

Benjamin Feist - EMFSO Website Developer

Martin Irvine · « **Reply #8 on:** October 03, 2005, 09:07:36 am »

Sorry, I didn't mean to imply that it hasn't been done. I'm sure that the prototype flew and probably one or two others before a kit would be even considered. I just meant that for pleasant, everyday flying, it will be a little hot at 7.5-8lb. It will certainly be flyable, but personally I would prefer a lighter wing loading. It would be easier to fly.
At 5.5lb, 400W would be sufficient and that could be obtained with a brushless Astro 05G
and a 3S pack. That would be a power system (IIRC)of just over 1 lb so with the radio, equipment could be 1.5 lb leaving 4 lb for the airframe. I'll bet that the airframe could be done for even less than that.

Just my 2 cents.

Martin

Electroflyer · « **Reply #9 on:** October 03, 2005, 11:30:57 am »

Ben,
I would suggest that you lose the sheeted fuselage and wings. Add stringers to the fuselage and Make a "D" tube wing(s) all covered with monokote or equivilant. When your airplane is complete, purchase your power system knowing what you then truly need.
Glenn

bfeist · « **Reply #10 on:** October 03, 2005, 07:29:28 pm »

Sounds like a plan. I'm not worried about it being a hot plane (it is a racer after all), i was more worried that it might not be flyable.

Maybe I could get you and Rob to take a look at the plans and i'll throw away half of the wood i just bought (i'm an idiot).

Benjamin Feist - EMFSO Website Developer

piker · « **Reply #11 on:** October 03, 2005, 08:14:18 pm »

Let me know which trash can you throw it in !!!

Don't worry, you'll probably be able to use most of the wood. The rest can be used for your next project.

Let's plan a time on the weekend. Maybe Glenn and I can come over for a visit on Saturday, or something. You supply the beer.

Robert

Martin Irvine · « **Reply #12 on:** October 04, 2005, 12:44:44 pm »

Am I detecting a topical trend?

Martin

gordonbw · « **Reply #13 on:** October 04, 2005, 01:43:59 pm »

I saw a completed GDH Consulting R3C-2 at the Heydenshore Pavilion show in Whitby the spring. That's SOME airplane... Ben, you are going to have your hands full this winter.

Gordon Braun-Woodbury
"How on earth do I land this thing?"

piker · « **Reply #14 on:** October 04, 2005, 09:24:39 pm »

The beer topic? I think so.

quote:
Ben, you are going to have your hands full this winter

Ah, common.... you guys are freakin' Ben out!!!!

Don't worry Ben, you'll show 'em

Robert