multiflyer

Yes, my .40s have seen better days. I have 2 Webra Silverline, and K&B, and OS. That's why I gave prop and RPM, so you can compare directly. And those are Zinger 10x6 wood props. My thrust to weight is about 1 to 1. But the thing is, to get good vertical your thrust to weight has to be more like at least 130% or more. 1 to 1 will just hover. If you want to fly straight up and maintain some speed, your thrust needs to be one for the weight of the plane, plus enough to overcome air drag. That takes about 50% more to maintain some speed also. I would definitely go with the .46. You can always throttle back.

Multiflyer[img][/img]

roofus4

Well I decided to go with the TT Pro .36 engines just because of the tremendous weight difference. I can use less wood to build the nascels, smaller fuel tanks, and the difference in the weight of the engines alone will result in a weight reduction of 24oz. 24 oz just from the engines. The 36s weigh 11oz, and the 46s weigh 17oz a piece. My other concern is the structural ability of the wing to support all those engines.

Rob

multiflyer

Those are good reasons for your choice of the .36 engine size. I discovered a similar reality. I wanted more vertical so I started mounting .46 size engines on mine. I found that I got more thrust but I also got a significant weight increase with it. Heavier engines plus a lot more fuel weight that I had to haul along with it. So the net effect was a plane that was less fun to fly with no improvement in vertical. Just more expensive, about $3 per flight in glow fuel as opposed to about $2 with the .40 size. I found that the bushing type motors are the best choice for the same reason. Bushing motors that hardly anyone makes any more are about 3 ounces lighter than a bearing motor of the same size, and they consume about 25% less fuel (and cost much less, and no bearings to worry about rusting). They don't put out quite as much power as the bearing version but you can go up a motor size to compensate and still be lighter. Also because of their more user friendly porting and carburetion, they are less hassle to keep running. I also ran into vibration problems with larger motors. I propped all engines differently so rpms would stay away from each other. No resonance. This helped.

The .36 are 6 oz lighter plus saving about 3 or 4 ounces on the fuel weight. Altogether that's nearly 2.5 lb savings! And you should be able to trim at least another pound or 2 from the airframe to go with the smaller engines. So your (just like my) 15 lb plane could become an 11 pound plane! I haven't gotten around to building my 4 engine plane version 2 yet but it is on my short list. The engines I am looking at using are the Thunder Tiger bushing .42.

How far along is your project?

Multiflyer

roofus4

Multiflyer,

Thanks for the input. I just got my TT .36s from Tower. I am still working on the Fuse. My current focus is the tail right now. I want to get the fuse done before I even start on the wing. My plan is to be able to mount the wing to the finished fuse, then to jury-rig fake mounts to the wing with the engines on them and try to find the correct balance point with 4 engines on the wing.

Does anyone have any simple tips on how to save weight? Also any ideas on how thick and what kind of wood to make the naceles out of. On my previous twin, I feel that I over enginered the naceles and made it a bit heavy.

By the way Multiflyer, I think your Quad Pattern looks awsome!

vlizard

Do I get points for phonetically displaying it here? (hi per bo lee)

multiflyer

Thanks for the compliment on my 4 banger. It was the 32nd airplane I have built. 8 years old now and almost 500 flights.

I have been scratch building my own designs for nearly 30 years now. I see 4 general reasons why weight gets out of control:

1. The obvious one is excessive structure. This is usually the result of using way too much ply or light ply. Balsa is the strongest for the weight, especially if you select the good stuff, “contest� grade. Only use ply where you need high strength in a small part like a firewall.
2. Next is too heavy of a finish. Basically you have to compromise here. Those mirror flat jobs add weight. Just no way around that.
3. The third involves the tail. Each ounce in the tail takes 3 or more in the nose to balance it out. Every extra ounce in the tail is like adding a quarter pound or more to the overall weight. So the tail is where the effect of the first 2 reasons gets amplified greatly. Do what it takes to keep the tail light.
4. The last is the most overlooked. This is control surface weight. Most control surfaces are way way overbuilt. Then because the surfaces are heavy, they tend to flutter. So the structure becomes over done to survive this. Counterbalancing is a way to control flutter, but reducing the weight of the control surface reduces the need for counter balancing, and helps a lot with issue #3.

Fortunately there are many fine examples of very light and strong airframes. Check out the structures of the hovering aerobatic and “3D� type planes. Also the electric movement is producing some fine structures. Design by comparison is the way to go. And don’t be afraid to reduce the structure. Use a scale and weigh everything while you build. See for yourself where the weight is coming from. Knock together a cheep prototype. Go test fly the heck out of it and see how it holds up. It may suffer a structural problem but most likely not. The bottom line is developing a great airframe takes a few tries. This is how you learn. After you get it right, build a pretty one.

Since you ask specifically about the nacelles, find a few very light successful sport designs flying your size of motor. Build your nacelles just like how the forward fuselages of these planes are built. Sorry this advice is so general. Naming a specific size of wood is not very meaningful. There are just too many different ways to create a structure.

Hope that helps

Multiflyer

forestroke

multiflyer - that is a beautiful plane. it's lines are elegant and graceful with a touch of vintage.

William Robison

My Feedback: (3)

multiflyer:

Absolutely a beautiful airplane. Makes me think of a Duellist with four engines.

Being a long-time Duellist fan, I'd be interested in drawings, or at least dimensions and notes on its construction.

Picture is your "Quadist" and the Duellist built by Chuck Auger.

Bill.

multiflyer

Forestroke,

Thanks for the compliments. That's a very nice description you gave.

Bill,

I've flown the Dualist. A very nice plane. Actually the canopy on this one and some of the wood came from a Dualist kit that got trashed by its former owner. I liked the canopy because it was thick gage plastic, very sturdy, no worrying about denting it during ground handling. Nothing else in common though.

I have no plans. I just built this one straight out of my imagination. Just decided on a target weight, wing loading, and general engine size(s). That gives the wing area needed. The rest was simply "form follows function" all the way. I did make a small sketch or 2 just to figure out how things will relate in a few critical areas. Nothing I kept.

I did nothing unconventional aerodynamically. I wanted a sweetie and I got it. Flies great. No mean bones at all. With 2 engines out on the same side it flies better than my other twins with one out. 4 engines really is nice. loosing one is not anywhere near as critical as with a twin. It handles so well due to the generous proportions. Very stable. I say to everyone interested in multiengine flying, build a twin for the learning experience, then go 4 engines for the enjoyment.

One of these days (years) I will make the new and improved version and offer professionally done plans. I can see where the improvements can be made, but this one has been so fun that I'm in no hurry. So many other projects on the to-do list and so little free time these days. I can post the basic dimensions and some constructions notes. Basically everything just like all the old pattern ships, but with a bit more vertical fin area.

Thanks again for the compliments.

Multiflyer

multiflyer

My 4 engine sport plane shown above is designed just like all those good old .60 size pattern ships. Structure is typical built up balsa. Wing is fully sheeted. Engine nacelles are simple box. All wing and tail tips, nacelle tops and bottoms, and nose are carved soft balsa. Horizontal and vertical tail are built up just like a mini wing. Symmetrical airfoils on all surfaces. I used about 15 to 18% thickness on all surfaces. I would have liked a little thinner but staying thicker makes a stronger structure. I kept the engines fairly close to the fuselage. Long fuse length and generous tail area produce very good natural stability and nice predictable flying qualities.

Wing span 81�
Overall fuselage length 69�
Vertical tail overall height 14�
Horizontal tail span 34�

Weight 15 lb, Power 4 tired .40 glow 2 stroke.
Wing area 6.4 sqft, wing loading 2.3 oz/sqft.
Performance would be fantastic if I could get 2 more pounds out of it – my goal for the next one I build.

Multiflyer