How much to shorten the nose?

[Warren Leadbeatter]

Hi all,

I have a Brodak Cardinal kit here that I am going to start building soon and I am thinking about putting a OS FS52 Surpass on.  I know this engine is a little big for this plane and I will need to shorten the nose a bit so it's not too nose heavy. The question is: How do I work out how much I need to shorten the nose by?  Any ideas or suggestions?

Regards, Warren.

[Ray]

At different times, I have left the stab location undertermined in case I needed a longer tail to balance things just with leverage, and left the nose area partly incomplete for the same reason. 

A simple option would be to check around for someone with the same plane, and prevail on them to allow you to take your engine, wrapped in foam or other scratch-defying protection, over and with his own engine choice removed, attach yours (in some non-damaging manner) to the top of the plane's nose a couple of inches rearward of the normal spot, to try to use this procedure to help determine what to do. 

[Rudy Taube]

Hi Warren,

Here is an accurate method you may want to try.

All you need is the weight of the engine that was used on the plans that made the CG come out as shown on the plans (or where you want it, and or where others have found it to be correct). Or at least the weight of the average engine used in this very popular plane. My guess is that a Brodak .40 or the OS .46 would do fine for your sample purposes. Here is the link with the weight you need for the OS .46:

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXPUE3&P=7

Now measure the distance from the CG on the plans and the center of the above engine as shown on the plans, (or where you or others have put it in the past to balance the model on the CG). Multiply this measurement times the weight of the above engine. You will now have the moment arm.

Now, divide the above moment arm # by the weight of your 4stroke engine. The answer is the distance between the CG and where your new 4 stroke engine (center line) will be mounted.

This will get you very close to where you need to be. The smaller fuel tank that will be used by your 4 stroke will make a small difference, and if you want you can compute it's impact using the above procedure.

This is the method I used to locate all my ECL equipment when it replaced a 2 stroke wet engine. It worked perfectly. I am a little AR so I made a SS for several planes, very easy to do. 

Remember to use the weight of your mufflers, if any. If you want better accuracy you may want to weigh the props, the 4 stroke prop will be larger, and maybe the spinner if it will be different. Just include these weights as part of their respective engines, but use the actual (weight CG) center line of these combined items when measuring.

I think you will really like this 4 stroke in your plane. I love mine! They are almost as good, and almost as quiet as my ECL planes. :-)

Regards, 

[Vincent Corwell]

Hi Warren

A good friend of mine has this setup
we shortened the nose until the 4 oz sullivan clunk
tank barely fit between wing LE and motor
the plane flies really well and will do the pattern
Last time we flew it I felt it was still too nose heavy
and want to put 1 oz of lead under the tail but have
not had the opportunity to do so yet as my friend
only comes flying once or twice a year?
Once the needle is dialled in though there is plenty of power
and tension overhead was good on 68' x 018 lines
12 x 6 Zinger wood and 11 x 7 APC much the same
good luck with your own efforts
Vincent

[Warren Leadbeatter]

Hi guys

Thanks for the feedback so far...  According to Rudy's formula I will need to move the engine back about 4 inches, which matches what Vincent has said.

If I move the engine back further I guess I will have to mount the tank inboard as there will only be 3.4 inches between the wing LE and the back of the engine.  All the plastic 4 oz tanks seem to be about 4.5 inches long.

Perhaps I should do a built up a full fuselage version of the Cardinal.  Anyone know where I can get a plan?

Cheers

[David Shad]

Windy Urtnowski designed the profile and full fuse version and has plans I believe. Give him a call.

[Willis Swindell]

I put a Saito 50 in a Cardinal years ago. I cut about an inch of the nose I don’t  remember  adding any  tail weight but I might have. The Saito weighs about 16 oz.
Willis

[Bill Little]

Windy Urtnowski designed the profile and full fuse version and has plans I believe. Give him a call.

Hi David,

Warren *might* have a problem calling Windy since Warren lives in Australia.  

But Windy DOES have 40 size full fuselage Cardinal plans. As well as several others.

[SteveMoon]

Warren: I have done a lot of flying with the OS 52 FS, as well as the
Saito 40, 56, & 72, and in my experience I found it unnecessary
to shorten the nose on any of the planes that I used the 4S motors with.
When I first started using 4S motors almost 10 years ago I did shorten
the nose on a couple of planes, including a profile with a Saito 56. I then
tried some planes without the nose shortened. I found out that it made
no difference, and actually, in my mind the planes that I left stock
flew better than the ones with shortened noses.

Why? I don't have some long winded scientific explanation, this is just
the way it has worked out. It must be something to do with the torque
generated by the 4S motor, but that's all I can come up with.

Steve

[Jim Oliver]

Warren,

I would suggest that you adjust the engine position so that the prop is in the same place as it would be with a two stroke installed.  That will probably require a slight adjustment of the engine bay length, but not length of the nose, ifg that makes any sense.........

Cheers,
Jim

[Warren Leadbeatter]

Ok now I am confused... so you guys that have _not_ shortened the nose you must have added so tail weight to make the CG right or did the CG move forward too?   The Brodak 40 with muffler weighs ~9 oz, the FS52 weighs ~15 oz, that a difference of 6 oz!!!  I recon this would put the CG infront of the LE if I dont add weight.

I'm going to fly this morning with our local Cardinal expert... (Ian Smith, who owns a full fuse Cardinal 60)  I will seek his opinion also....

[Jim Oliver]

Warren,
To, maybe, help clearify my comment a bit, I have never used a 4 stroke on a CL plane so can't address the "unexplained" flight characteristics which are sometimes attributed to 4 strokes.

My intention was to encourage you to move the engine back far enough to cause the prop to be in it's "normal" location.  Doing this will very slightly reduce the forward CG condition, but will most likely not get the CG to the point specified on the plans.  If it were my model, I would shorten the nose as much as necessary (if possible) to get the CG in the right spot without needing much (if any) tail weight.

I fail to understand how is is possible for a 4 stroke powered model, with a CG well forward of the normal position, to turn as well as a 2 stroke model with the CG placed at the "right" spot.  Not saying that it doesn't happen, just that I don't understand the process.

If someone can explain how it works, it would be much appreciated.

Cheers,

Jim

[Warren Leadbeatter]

I have a Sig Twister with a Saito 30 on it and a Ringmaster with a Saito 30 as well. On both of these planes I didnt shorten the nose and on both of these planes I had to add significant tail wait to get them to turn properly. 

So hence I decided if I am to put the FS52 on the Cardinal profile I will need to shorten the nose to maintain the correct CG without adding more weight. (at the tail). 

Another option I have is moving the wing forward. ie lengthening the tail moment.  But while this will mainain the correct CG it will obviously change the flying characteristics somewhat.

I think I might do what Vincent did and move the engine back but only enough to allow for a 4 oz tank to still fit.  If I have to still add tail weight then so be it. 

How does that sound?

Cheers

[john e. holliday]

If you haven't started yet, why not move the wing forward in the fuselage.  I know it will change moments, but, most 4S setups I've seen from over seas has a short nose and long tail for their 4S setups.  DOC Holliday

[Leo Mehl]

I would move the engine back 1" and balance it with the tail. I think you will find that the 52 is not as heavy as you think. I put a 52 in one of my stunters that had a Magnam 53 in it and I had to change nothing.

[Bryan Higgins]

Hello Warren

Today we are seeing four strokes as a normal standard for control line planes.  Mostly in the .50 to .60
stunt plane size. This has been going on for the last ten years or so.  Some build new ships designed
for these engines and some use existing C/L kits.
From what i am seeing most that use an existing kit are building the plane true to the plans and forget
about wieght issues.  Adding longer ply doublers and leaving more material on the fuselage top and
bottom blocks.  In your case a bigger profile cheek cowl making in more vibration proof.

Most like this advantage , they can build a sturdy plane without worrying about wieght and put a show
stopping paint job on the plane.

Some are not buying this right now , but it is going on and will be more popular down the road.....
Look at Pat Johnstons P-51D Mustang stunt ship. 56" WS - 39"Length  and the Saito .56
And he WON.
You are going to be fine. Just take the advice of the people on this site that are interrested.  And look
at the other fine models with four strokes. Ultra hobby Products i think it is has been doing this for
years.  They have a club but i cant think of it right now.     

                                                                                     Bryan

[Bob Reeves]

I don't understand why either but all except one of my FS powered airplanes has the CG ahead of what the plans show and the one that didn't has an ounce of nose weight added to make it grove. The most strange is the TwistMaster, a Twister with a Saito 40 swinging an 11-7 that balances right on the leading edge of the wing but boy will it turn.

Guess what I'm trying to say is go ahead and shorten the nose but don't be too worried if the CG turns out ahead of the plans location, it will proably fly great.

[Warren Leadbeatter]

Hi Bob

Yes I think Steve Moon has has had the same experience [see his earlier post]  I asked Windy and he suggested to chop off 1.5 inches minimum and to make a custom tank if neccessary, so I chopped off 2".

Construction is underway and I expect will be complete sometime over Easter. (Wet weather is predicted here for easter) 

I checked and my Saito 30 powered Twister has the CG forward too and it turns pretty well too.

Thank you for you input.

Regards
Warren