jrf

My Feedback: (551)

rcairplanenut:

That is perfect description of "too much up-thrust". Try adding washers behind the top of the engine mount.

Jim

rcairplanenut

the prop is half a foot above the CG changeing the angle will not help there is no horizontal conponent

sg

jrf

My Feedback: (551)

Ahhh.. You are saying that the thrust angle of the engine doesn't matter because it is so far from the centerline of the airplane? So you could have 10 degrees upthrust or 10 degrees downthrust and it would fly the same? How about a Sea Master, Mariner or Sea Dancer? The thrust angle doesn't matter? Sorry my friend, you'd better rethink that one.

Jim

rcairplanenut

[>:]


You are comparing apples and oranges the Arrow is totally different then the Sea Master configuration aircraft. In the context of this argument the Arrow’s prop is close to or right on the CG. The Sea Master configuration aircraft have there props at or in front of the Leading Edge far away from the CG.

Sea masters and those other planes have there props several inches in front of the CG the Arrows prop is right on top of the CG, the purpose of Up or Down thrust is to produce a small amount of thrust at a distance from the CG. Force “trust� multiplied times a distance produces a moment “torq� this torq counter acts pitch up or down tendencies. If you multiply a number by 0 YOU WILL ALLWAYS GET 0 (math & algebra 101 “pal) , The horizontal distance from the prop to the CG is extremely small, mine sits right on the CG. For my plane giving up or down thrust times 0 distance will not do anything!!!! The reason it works on the other type of planes is that the prop is not on or near the CG they are on the leading edge several inches in front of the CG.

So what I would recommend for you Jim is get a set of Arrow plans (if you haven’t all ready) so YOU would know what you are talking about.

I do happen to have an Aeronautical / Aerospace Engineering degree so I do know what I’m talking about.

I don’t want to be a Jerk but 0 X anything = 0 all the time every day 365 days a year.

SG BSAE ERAU

retransit

My Feedback: (18)

I love the word "pal".

Bob

jrf

My Feedback: (551)

rcairplanenut:

Since you are an engineer, I can't debate theory with you, but you might want to consider the difference between CG and Center of Drag. The Arrow engine is mounted several inches above the vertical center of drag and thus imparts a rotational force about the center of drag (not the CG) to lower the nose. The effective magnitude of that force is modified by raising or lowering the thrust angle of the engine.

I don't know this because I am an engineer, I know this because I have tried it and it works.

Jim

rcairplanenut

You have tried it on aircraft that are not like the Arrow even the North Star is slightly different then the Arrow, IF the engine was several inches in front or behind the CG your solution would work perfect, But the Arrows prop is right on the CG.

Here is a diagram of what’s going on.

SG

jrf

My Feedback: (551)

rcairplanenut:

You're still ignoring the Center of Drag, but accepting your argument for a moment, I think you had better check your plans. The Arrow's propeller is 6 inches behind the CG.

Anything X 6 is not 0.

Jim

typhoo

Hello all you nice people who have tried to give me useful advice.This has been my very first E-mail to a forum for help and it is gratifying to see modellers trying to help some of us who are not as knowledgeable.I can certainly see SG point regarding thrust and CG position.Jim may have a valid point with the drag situation.Since I have 2 arrows(and a third on the board) I think I will add some down thrust on on to see if the situation is helped.Unfortunately the water flying season in Scotland has finished so I'll have to wait until next year to try them out.The other problem with the arrow is that when you push her you can do a very good impression of a flat spin something I didn't think delta craft could do.Could it be due to the engine mass high up?Anyway thanks to all that responded and I'll keep tuning in and reading all the chat.

rcairplanenut

Forces and Moments act on the Center of Mass (CG) of an aircraft Not the Center of Drag

Static’s
Physics
Dynamics
Aerodynamics
Stability and control

Its all from these subjects / classes I have taken them have you?

SGG

rcairplanenut

Because I have a K&B .65 on a long mount my prop is right over the CG, the plans show it slightly behind. If it works for you great, go celebrate and take a trip to Disney land. Jim just build an Arrow try your idea and tell us if it works. I’m tired of arguing with people on this stupid web site!!!!!!

SG

Razguel

my head hurts [&:]

iflyj3

My Feedback: (7)

Rumors, myth's and old wife's tales out weigh science any day!

Just look at what the electric car people do to NiCd's.

retransit

My Feedback: (18)

So now the web site is stupid! It has to do with input from supposedly educated human beings. Let's see if we can have a civil discussion based on fact without throwing out our credentials. (We can accept actual experience.)

Bob

jrf

My Feedback: (551)

I have the Arrow plans in front of me and a fairly reliable ruler, and the prop is 6" behind the CG. I don't know what you're trying to accomplish here, but it is clear that you don't live in same reality as the rest of us.

Maybe it's best for everyone if you stop arguing on this stupid website and stick to your local "small pond" where people don't challange you.

Jim

typhoo

Hello all again.I must admit to being a little disappionted by the level of '*****yness' which has started to develop on the back of a simple question that I asked.Can't we all get along even if our views differ. I'm certainly no engineer in fact I look after pigs for a living but I hope that if I have something to say that I'm not ridiculed or belittled by people for saying it. After all is this not what the forum is for the movement of ideas and beliefs wether fact or fiction.

rcairplanenut

jim i dont give a flying F__K

jrf

My Feedback: (551)

Typhoo:

You are right. My apologies to all for any discomfort I may have caused.

Jim

N1EDM

My Feedback: (2)

Typhoo,
As a bystander, I subscribed to this thread to get more info on an Arrow. I'll be sending for the plans after the first of the year, by the way. Where you've built 3, I'd be curious about your observations. I've never built a delta or a water craft before, but I know that Laddie has been designing and publishing planes for years, so he's got something going somewhere. I was pleasantly surprised that Laddie himself showed up and commented on some of the ideas proposed for his design. That was a real bonus.

I got a lot out of his comments and suggestions, and from those of others who contributed.

I think that you'll find that most of the posts and threads work out very nicely on this or any other Forum.

Don't be afraid to start a thread or contribute to an existing one. These can be awfully habit-forming.

jrf, there's nothing to apologize for from this bystanders viewpoint.

Just my $.02

Bob

rcairplanenut

I think I will no longer contribute to this thread seeing that what I have added to this thread is not liked or welcomed!!!

SG

retransit

My Feedback: (18)

No one said they didn't welcome your input. I think what you should be looking at is your presentation. You are going to get disagreements. To sway the other's thinking, present your views in a civil and factual manner without going off. I've read your comments on other threads and you don't seem to have a problem over there.

Bob

sderyck

first timer here...

somewhere in this thread I read that someone was possibly making an ARF for this.

any update on that

Regards
Scott

sderyck

an arf for the Arrow or Northstar thatis

regards,
Scott

John Hawkins

My Feedback: (2)

A friend flew his Arrow on it's maiden flight this weekend past. A video is here: [link=http://rcalbum.rchomepage.com/Home.html]Arrow[/link] Follow the video link and it is at the bottom of the page.

Power came from a YS53 turninng a 10x10 at 11,500 RPM. According to Andy Lennon's nomogram this would yield a level flight speed of 130 mph (210 kph)

retransit

My Feedback: (18)

You guys from up north are a hearty bunch. Wow, flying in weather requiring gloves. It's 82 degrees here today. I'll stay with this weather.
How did he find the engine pod? It looked like it snapped off and went flying out in front of the fuse.