Help Please on kit-bash mistake
 

I made a mistake while changing the design on a Sig Senior. I cut the dihedral in half and added ailerons. There was the mistake. While cutting the ribs to make the barn door ailerons I cut it at the rear spar. My thinking was keep the wood count low instead of adding another sub spar. I cut it 6 bays wide. Now at covering stage I look at it and see that it is WAY too big!

How will this affect the flying? Servo size? Should I rebuild wing?

Thank You for any help/advice.
Attachment 2223453

Kit bash
 

I would go this this set up as is. Standard servo's will work I would set travel at about 3/8 inch on low rates and try 5/8 inch on high rates. Fly plane and see how she handles and go from there If you need more control move push rod in on control horn one hole to increase travel and go from there. Good luck.

Boy is my club going to have fun with me at the field! LOL

Why would you say that? Just tell them you wanted to make sure the plane had good control so you went large. Just be gentle on your sticks and try Ziggy's settings and see what happens

It will be fine. The inner part of an aileron doesn't contribute much to the aileron's effectiveness. I've built a couple of Ultrasports with full-span strip ailerons and one with the inner six inches or so used for flaps instead of being part of the aileron, and there's no noticeable difference in how they fly.

I'm not sure that I would trust a standard servo on ailerons that large, especially with a big 4 stroke in the nose. I would go with servos with a minimum of 75 oz. You will also notice that you will need more aileron differential. I personally would start with 1/2" up and 3/8" down. If that proves to be not enough ( which I doubt ) then go with 5/8" up and 1/2" down.

Good point on the differential. Hadn't thought about that.

How will I know if the servo is being over-taxed? Currently set up using Futaba S3004 servo at 6 volts. Specs at 57 oz-in with full charge.
S3010 comes in about right and the same physical size but height. Will have to check the room in wing for that.

Thank you all for your input.

f asked at the club what you were thinking tell them it is a 3D trainer.

IMHO std servos will do just fine.

Servo load is significantly controlled by the pilots flying style and air frame involved. Even with large control surfaces, servos will be lightly loaded if you are not flying radical rapid maneuvers especially on a Sig Senior. It will be hard for you to load up aileron servos. I am assuming a two servo arrangement as that is the cleanest, most direct plan. For me, standard servos will be fine.

Good looking job!

Bedford

3D trainer! I love it! I'll just toss it around the sky a few times and freak everyone out! J/K. Good one. lol.
Yes it is a 2 servo setup.
I am more of a controlled slow roll kinda guy. Fast rolls aren't my style. For me I practice my control flying. This plane is for getting back in hobby after 22 year absence. My comfort go to.

Thank you all for your input. I'll try it and see how it goes.

Dual rates and a shed load of exponential would be a good idea for the first flight.

Need help
 

You will find standard servos an small control movements will work well on 60 size trainer and sport planes. I fly a Stinger 120 with a US 41 gas burner on it with standard servos on low and med. rates with on problems. In fact I learned to fly on this very same plan using about 1/4 travel on all surfaces. I make my first solo flight on it, many years ago and still fly it now and then. With low travel rate you will NOT need a ton of expo, in fact just the opposite as high expo causes more control movement as you move sticks toward high end and this would cause over control, I think this is something you want to avoid on first flight. If you want to play safe use servos rated around 60 in/oz and a 6 volt or LiFe battery and you will have all to control you need. Good luck and keep balance point toward front, nose heavy planes fly, not too well but are controllable, tail heavy planes are almost impossible to fly and crash. Play it safe on first flight and go easy until you are comfortable with it, then slowly try more maneuvers and larger control throws slowly and you and plane will do GREAT.

Expo doesn't increase the total amount of throw the surface in question has, it just moves more of the throw from the neutral point to the ends. With expo, stick movements near the neutral point give you less surface movement than if you had no expo; stick movements near the end points give you more. The total surface movement is the same with or without expo.It isn't something a tame airplane like the Kadet Senior needs, though. As for balance points, the recommended balance point on the Kadet Senior gives you a somewhat nose-heavy plane. I wouldn't recommend balancing one any farther forward than what the plans show. In any event, the OP doesn't seem to be a beginner. Beginners don't usually modify their first kits.

Thanks for all the input.
I have put in just a small amount of expo. Just to assure I don't get too twitchy as my thumbs are out of practice. R/c flight sim has helped reacquaint my thumbs but think it's no substitute.
I am no beginner but am treating myself as one after the absence. (Perhaps that in itself qualifies me as "no newbie')
My mods to plane include ailerons, half the dihedral, tail-dragger, and bolt on wing with some structural mods to support said changes.

I just finished monokote and will be painting color scheme starting today. Yes paint as I am too much a perfectionist on certain things and tested then hated the look of mono over mono. Yes I tried the Windex routine but I could still see the small "warts" of leftover bubble. This can be addressed in a separate post. Decision made.

By now the decison is to just fly it and see what happens. Thank you all for your support.

I'd like to add.....
This has been not only a trainer as far as flying is concerned but a trainer for building. It showed me many many things I would/should have done different, (mistakes) and will do in the future. ALL aspects of building! Everyone should have a trainer build to start out. As in, not take too serious.

Just my 2 cents.

Here is some help in calculating the best approximation to the required servo torque for ANY airplane...

First, you will need the theoretical speed:
Pitch Speed Calculator

Then you plug the speed into this calculator:
Calculate Required Servo Torque

Hope this gets you close to what you need.

Rafael

That is a good calculator for servo torque. I've used it with good results. Sometimes even doubling the value will surprise you how little is needed.

With that said....... When you set up the servos use the maximum amount of servo travel. Use the innermost hole on the servo if necessary and the outermost hole on the control surface. It this gets you the maximum required surface movement you are golden. As an example; Servo torque is 50 oz. Servo hole is 1" from the center of the servo arm and control surface hole is 1" from the hinge line you have 50oz available at the control surface. Now if you move the pushrod to the servo hole 1/2" from the center and the control surface hole is 1" from the hinge line you have just doubled the amount of torque at the control surface. Now you're up to 100 oz of torque!!

You can use the calculator to see how reducing the servo movement also impacts how much torque is available. Small servo movements usually mean low torque values.

Don't let the 3D craze influence you on how much surface movement you need. With the large ailerons you built, you just need to move them less. That has the benefit of less drag on the airframe. You did a good thing and didn't even know it!!!!:D

Ken

You guys really rock! Fantastic info! TYVM!
I'm all about data.

Good thing I ran spar webs to the end to strengthen the outermost portion of the wing forward and rear. Some unneeded weight, but piece of mind, especially now.

I would still urge you to select your servos carefully. The more surface area you have the more prone to flutter the surface will be. This has nothing to do with the amount of deflection you are running but does have a tie it to airspeed and harmonics. You have a very light weight airplane with a thumper 4 stroke in the nose and very large ailerons. I see the red flags.

I am going to get the bigger servo's. Not like I'll never have a use for servo's. :) Better safe than sorry. Not afraid to spend the money. I'll use em.

Formula for determining servo in. oz.of torque is, 1(one) oz for each square inch of controlled surface plus add 20% to the total to lower the load on the servo, other words don't max it out and it's easier on the battery drain.

Example; say you have a 30 square inch surface, a 47 in.oz. standard servo will be fine.

Leroy

IMHO, on a well designed plane this formula is very useful. In this case, the ailerons are definitely over-sized and will not be used to their potential. There will be very little deflection for the desired effect.

In this case they are 5 x 19.5 in size. 97.5 square inch. Times 1.2 results in 117 in.oz.
In thinking this control surface will not be used to potential I feel the S3010 will do nicely although by that formula will be under powered. Using a 6 volt NiMh 5 cell battery pack yields 90 oz-in at 6 volts and 72 oz-in at 4.8 battery drain.
This plane is spec'd at 6 pounds with 12oz/sq ft and powered by a OS 62FS. No barn burner.

Just my thoughts. But excellent formula Leroy. I saved it.

If you like to experiment, install some boost tabs on those ailerons. You will then find that even 30 in/oz servos will be more than adequate. Make them 8 to not more than 10% of the aileron surface area. I've flown 1/4 scale Gasoline powered biplanes with boost tabs and 30 in/oz servos with no problems. Even better, add some mass balance to the ailerons as that will take a lot of the stress off the servos, especially on hard landings where the weight of the ailerons put an undue force on the servo gears.

Update. I have 10 flights on this now. Flies well. After the first 5 flights I bumped up all the throws and the Ailerons are now at 7/8 up and 3/4 down to get the roll rate where I liked it. I'm thinking even when cutting the dihedral in half from the plans it is still somewhat effecting the aileron roll rate but I'm happy where it is now. I've found that for more scale like turns, especially in windy conditions, some reverse ailerons in turns keeps it more scale like in turns.
Thank you for all the advice. Did not create half the problems that I thought. Flies nice!
Here is the picture of the plane. Cowl is off as I wanted to be sure that the engine thrust was finalized before fitting it.
The second picture gives a better perspective of aileron sizing.
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