TopZueg

My Feedback: (5)

Wow, great write up. Thanks for all your time. I just purchased a CMP 50 Corsair today from a guy builtr but with no motor. I am defenitly going to do all the mods you suggest. Guys like you who take the time to help people out are rare to find. Thanks for your great written article!!!!!!!

Capt. John

[font="Verdana"][size=2]Have just found this thread and have questions that someone may be able to help me. I have completed the build on the CMP F4U Corsair 50 ARF, with the lousy builders schematic for a manual. I am very surprised that the plane is so tail heavy. It looks like I will need to add 2 to 2 1/2 lbs of lead to the firewall to bring the tail up and get the CG to the recommended 80-85 mm. I have installed retracts, an OS 46 AX engine with a pits muffleer and installed the battery as far forward as possible. How in the world do you get that much lead. I'm considering cutting up some old lead diving weights into pieces and screwing/siliconing them to the front firewall.

But I'm also concerned that the motor size. I figured the 46 AX was adequate, but if I add that much weight, it may not be enough, even tho the manufacturer recommends a 40 to 50 size engine. Perhaps the 55AX would be a better choice now, and I wouldn't have to make any adjustments to the mount.

Capt. John

I have just completed building this plane and the last item before installing the battery was to check the CG. Wow!! What a surprise. It looks like I'll have to add 2 to 2 1/2 lbs of lead to the firewall to bring the tail up and balance to the recommended 80-85mm CG. How in the world could this be so far off and how can I get that much lead installed?

I have installed 90 deg rotating mechanical retracts, that are working fine on the plane. I also installed an OS 46 AX motor. I did install the battery as far forward on the servo panel as I could, which of course, didn't make much difference.

So, my questions are: 1. Is this really the right CG? The magazine build article I used confirmed it, and this thread seems to confirm it. I have inverted the plane on the CG Machine and left retracts in the up position. Should the plane be right side up, and should the retracts be down? I am wondering if the schematic plans, which were showing fixed landing gear, assumed that the CG would be checked with retracts down, as retracts are a option.

2. With that much weight added, is the 46 AX going to fly it very well? I can change to a 55AX without making any changes to mounting or cowl cutting, or throttle rod. So this is easy to do. But it will only add a couple ounces to the nose weight, still requiring lots of lead. If I go to the much greater expense of a larger 4 stroke engine, I will have to make much more changes to the mounting, but can add more weight. Is it worth it?

w1nd6urfa

My Feedback: (4)

Hi Captain,
First, switch to the 55AX.
Before adding any weight, try moving the engine mount 1" forward by adding some hardwood. I had actually done that after doing this build thread, and I also switched to a 55AX and the weight needed was minimal (1 oz)

This setup is used in the photo below.

CG 80-85 is good ALWAYS test with retracts UP and tank EMPTY.

Cheers
Nick

Capt. John

Thanks for your input. Sorry for the double posting, I thought the first one didn't make onto the forum. I just didn't go to the second page.

Can you tell me if the plane should be balanced upright or inverted? My past experience says to do it inverted, but another pilot in our club said to try right side up as well, to compare. What worked for you?

Also, I have a Saito 82 that I could install in place of the 46 AX. It's a little heavier than the 55AX, and I'm told will have about the same power. I checked it out, and it looks like the additional cutting to the cowl would be minimal, and the other openings will work as they already are. And I wouldn't have to buy another motor, since I'm motor heavy in the closet now as it is. Any thoughts on that?

How did you mount the extra length on the firewall. Just epoxy and screw a chunk of ???? in that area for the mount, or did you cover the whole cowl area? And how did this affect the mounting for the cowl? I have some room to move it forward, but not sure if I have a full inch. However, I would think that even 3/4 inch would be an improvement.

Capt. John

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Capt. John

I have more closely examined the Saito 82 on this plane, and the mount would have to be changed, and there actually would be considerably more cutting to the cowl than I originally could see. So I've decided NOT to use the Saito and instead have ordered the OS 55AX. I am also going to take your suggestion and add a piece of hardwood/plywood between the engine mount and the firewall, then check the CG.

I did not get the photo you sent with your last post, and if it shows how you mounted this piece of wood, I've like to see it. Can you resend the photo?

w1nd6urfa

My Feedback: (4)

Right, here's the photos with the 55AX, unfortunately I don't have one of the engine mount. I used 4 pieces of 3/8" square hardwood placed behind the plastic engine mounts (2 vertically and 2 horizontally that join under the screws) and long firewall screws. If you see further up in my build when I had the 91 fs installed the firewall-to-prop plate was 140 mm, I think I got the same with the 55AX.
If I were you I would give it a shot with the Saito 82, I got this engine on a Kyosho FW190 and its the most reliable and sweet sounding engine ever!

As you see in the photos I got a silver marker and made those panel lines stand out, it really adds to the plane's looks

Cheers
Nick

Capt. John

Thanks for the info. Great looking plane, the right photo makes it look real. And yes, the silver marker added some great character.

If I understand your description, you used four blocks, one behind each bolt on the engine mount, as opposed to one large block glued onto the firewall, then drilling four holes for the mount. This would allow access to your fuel lines without having to drill another large hole in the center of the block. Good idea!! And the 3/8" distance helped enough? I was looking for wood an inch thick or 3/4 at least. I expect I'll still have to add some lead, just not as much, which will also help to keep the weight down.

ZERO-322

My Feedback: (2)

As suggested earlier it would cut down a great deal of the lead needed by moving the engine forward, another trick you may consider is build a bracket and foam padded box and hang your battery off the engine mount, the idea is to move as much usable weight as far forward as possible, a weighted prop nut will also help, this will add about two and half Oz in the forward most part of the engine compartment , center CG is checked on a low wing with plane inverted retracts extended and fuel tank empty, hope this helps

Mike

mike early

http://rc-castle.com/shop/product_in...oducts_id=1626

SHEPSTER

My Feedback: (2)

I just got the corsair and had a couple questions 1 push rod for elev and rudder . one says adjustable and not adjustabale. does tell what the different is.2 need cheapest retract that will fit.wil the post above work if so that would be ok and 3 will a evolation 46 nitro pull this plane.and im sure ill have more ?

NCIS

The main retracts look way to samll in diameter and to long for such a small model. Sorry but sometimes the truth hurts. Try to get closer to scale if you can!

JMHO,

Barry

SHEPSTER

My Feedback: (2)

someone posted it here so i assumed they would fit

w1nd6urfa

My Feedback: (4)

SHEPSTER,
I remember both pushrods being adjustable (carbon main rod with alum ends and small piano wire adjustable with grub screw). Glue well after adjusting, and use heatshrink tube over the joint.

I hadn't installed retracts on this plane, I guess a 60-size rotating mechanical set will do but some re-inforcement might be needed. Use 5mm struts if possible

I had initially installed a 46 AX on Corsair #1, it flew but was kind of anaemic (read: full throttle needed for turning) so I would go 55-70 2-stroke or 80-90 4-stroke which helps in getting the CG right

Nick

SHEPSTER

My Feedback: (2)

Thanks for info,guess i gota shop for bigger motor

SHEPSTER

My Feedback: (2)

ok question- on front of each wing it says to put alum. joiner and a block of wood. I FIGURED OUT ABOUT JOINERS WHERETHEY GO INTO FUSE.WONDERING ABOUT BLOCKSOFWOOD IS IT FOR SCREWS TO ANVHOR TO ON THE SKID PLATE THAT COVERS WINGS

w1nd6urfa

My Feedback: (4)

I can't remember any blocks of wood on wing saddle, there were some ply rings though that you glue into recesses in the fuse - that's where the alum dowels attach, did you mean those

Post some pics if possible

Nick

Experten109/40

My Feedback: (-1)

well instead of sarcasm, why not offer some advice?

anyways, nice Corsair Nick!...

SHEPSTER

My Feedback: (2)

trying to upload plans, shows 4 wood blocks and the cover screwa into wood blocks. do you glue wings together.i got rods glued to one side to where i can slide together but do you glue pemently?

SHEPSTER

My Feedback: (2)

when u mount the wing cover your 2 front screw shows blocks of wood the screw mounts too

w1nd6urfa

My Feedback: (4)

OK, I really can't remember such wood blocks, maybe yours is a later version? Anyways, instead of wood blocks I used pieces of plastic pushrod tube where the screws go, I guess wood will do as well.

Glue the wing halves permanently, there is nothing else to hold them together.

SHEPSTER

My Feedback: (2)

thanks, Ill take your advice.i have a eveo 49 2 stroke but affraid its not enough so gona go wit 55 or 61 ,for now im good except what and were to get retacts and kinda cheap but good

SHEPSTER

My Feedback: (2)

on the pushrod does thes black tubes need to be cut.they seem kinda long to fit.the wire rods to elevator are side by side and tight do u bend theses.seem they would rip horns off. when the rod goes into fuse how do you get each metal rods to seperate to go out slots that you cut out for elevator.ican seeon rudder but confused on elevator

TopZueg

My Feedback: (5)

These look like great retracts and are shock absorbing. I think someone else provided this link in this forum but here it is again.
http://rc-castle.com/shop/product_in...oducts_id=1626
I have electric retracts like these in a p-51 but non rotating of coarse.