Dash7ATP

Building my Yellow Aircraft P-47

This will be a new experience for me. While Ihave been building for many years, trying to post the build online is new. I have built a few warbirds, but not for competation. A few photos are below:
The natural aluminum P-47 is a scratch built 1/12 model covered in silver Monocoat. It flys pretty well, but was not finished in a scale scheme.

The OD P-40 is a Giant Scale Models ARFi extensively modified and repainted to replicate a full scale P-40 a friend of mine flies. It's based in VABeach.

I bought the P-47 on EBay several years ago and got an older early Yellow Aircraft kit. It did not come with the fiberglass controll surfaces, one piece fuselege, and tapered nose area for better cooling. All Ireceived for the controls were the skins and stock for the leading edges. I didn't even get a set of plans! An inquiry here had a few fellows send me what they had. If you happen to be one of those and want them back, contact me please.

I had started in full speed ahead on the build and hit a snag that stopped me cold. The way the wing was cut resulted in a very thin aileron leading edge at the inboard end, and the same for the outboard end of the flaps. In other words, the contour of the top of the wing was negative at the hinge line near the center of each wing. I just gave up on it for awhile. I had already made the engine mount /fuel tank box in the nose and had mounted the cowl. The retracts ( Yellow Aircraft ) had also been bought, So, I was bummed out. I worked on other areas of the model until I figured out what to do about the wing. I even designed and built a tailwheel retract system! Photos below.

Dash7ATP

Continuing my first post:

I have now built the ailerons and flaps but I think I have a problem with the gear mounting system. I spent several nights reading several builds on another site, and apparently there have been problems with the YA P-47 folding wings near the aileron servo well just outboard of the gear mountsl If you know anything about this, please let me know. I can fix that problem with Carbon fiber strips let into the wing skins.

The gear mounting pads are what have me really concerned. If you look at the photos, I have stuck a straight pin into the wing skins around the gear mounts. These are only 1/4 inch plywood! Imarked the outer edges of the plywood. As you can see, the area of the mounts are pretty small. Considering how long the gear is, and the weight of this model, I'm almost positive there were problems with the mounts breaking out of the wing in almost any but a perfect landing. Agan, if you have any experience with this older kit, I would like to know of your experience with the gear mounts. Finally, I'm looking for suggestions of what to do about this problem. My thoughts are to cut out the bottom skins and remove the current plywood mounts, and extendheavier ones to the rear about four inches, as well as inboard several inches. The model also has a problem with the mounts setting so high that the gear extends above the wing surface making it impossible to let the gear doors sit flush with the surface of the wing. I could fix that at the same time by lowereing the mounts about 1/8 inch.

Comments please!

Joe

Dash7ATP

I'm not getting much help here fellows. Infact, none. Ihad to stop work on this for a few days while I make a carrying / storage box for some sails for my RCSAilboat, and EC-12. They have been in a storage shed since we moved into a Condo 1 1/2 years ago. It doesn't make sense to pay $55.00 a month just to store them. I'm almost finished with that project and want to get started on the 47 again.

No suggestions on how to beef up the gear mounts? As you can see, they are pretty small for such a large model. Can anyone relate their experience on this kit? I think it was the Bert Baker design that Yellow Aircraft kitted, and then modifed to what they are selling now.

I hope to post some more photos next week after Icut into the wing to remove the old mounts. Stay tuned.

Joe

Dash7ATP

I forgot to show this on post showing my tail wheel. The photos here are of my tailwheel doors. The hinges are 1/2A pinned hinges from which I remover the pins and used a piece of small piano wire the entire length. After mounting them on the wire Iepoxied them to a small strip of 1/16 plywood to hole them together as a unit. This was then mounted to the doors and mounted into the fuselege. They are secured in place with the small flathead screws you can see in the photos.

The other two photos show howI'm mounting the cowl, and my Moki 2.1 .
JL

c550

My Feedback: (16)

Joe,

You might try using 1/8 diameter bamboo skewers to tie the hardwood to the foam. Drill 1/8 holes(one on each end trough the mounts and the top wing skin, use wood glue to secure the bambo to the mount and foam. Also the fiberglass will help strengthen the wing skin which supports the foam which supports the gear mounts.  I had a hard(very hard) landing with my YA P-47 and it tried to send the gear mounts through the top of the wing. I epoxied it all back together, and a little surface touch up and it is back flying. You will enjoy your P-47, as they are all great flyers.

Regards,

Dave

Dash7ATP

Dave,

Thanks for the suggestion. I  had not thought of that. Was your P-47 one of the early kits or a newer one which came with fiberglass control surfaces?  It appears that the newer kits have given more thought to the landing gear mounts.  I have considered several options and I'm trying to avoid anything which transfers a load to the upper surface.

Some years ago (15+) I had a JHH F-86. This came with foam core wings which had to have the gear mounts installed prior to sheeting the wings. The mounts for that plane (it had a 50 inch span) were larger than this P-47! In any case, I sheeted the inside of the gear well. After a pretty hard landing I noticed a crack in the top skin.  I tore into the wing to make the repair and found the foam and gear mounts were still solid. The sheeting in the gear well,  which was glued to the gear mount and both skins,  had cracked the upper skin when the foam  compressed a little on the landing. It was a lot of work for nothing.  All I had to do was smooth and repaint the top skin.

I have been somewhat leary of making that same mistake again. Of course, you have to start with a solid gear mount, which I don't believe this  has right now. Part of what concerns me is a hard landing will try to bend the gear to the rear, and it has a lot of leverage. There is about an inch of plywood on the aft side of the gear mount and I just don't think that is enough.

Thanks for your reply.

Joe

c550

My Feedback: (16)

Joe,

My kit was a newer one. I do remember that the instructions had you extend the heavy glass past the gear mounts, and lighter cloth out towards the wing tips. BTW I use a Moki 1.8, its nice to see someone else use glow in one of these.

Regards,

Dave

Dash7ATP

Hi again,


I'm also glad to hear about you using the Moki 180. How did it fly. I"m not looking for high speed, way above scale speeds, but honest and comfortable power that will allow loops from a slight dive if neccessary.

I'm interested in your ID; c550. It wouldn't have to do with a particular model Cessna jet, would it?

Joe

c550

My Feedback: (16)

Joe,

The moki will give you the type of performance you want. Mine was underpowered with a master airscrew 18x8, when I changed to a Xoar 19x8 the P-47 flew perfectly. You might look into the Xoar 20x8 for the 2.10 Yes, I primarily fly the 550, I'll take a wild guess as to what the dash 7 stands for.

Regards,

Dave

Dash7ATP

You would probably be correct on the Dash 7. Iretired from Piedmont Airlines, a USAirways Express affiliate, in 2001. Iflew the Dash 7 for over ten years. It was a great plane and fun to fly. Ifigured the 550 was a citation , but I'm not real familiar with which one it may be. Igot typed on the DA20 (Falcon 20) but never got to fly one.

Thanks for you input on my P-47. I'll be cuttin ginto the wing to replace the gear mounts this coming week, Ihope. I'll post my precedure here when I get started. I'm not familiar at all with the prop you mentioned. I'll have to check up on it.

Joe

Dash7ATP

Here we go again on my build! '
It's hard to believe it's been over a month since my last post.

As mentioned above in an eariler post, I'm really concerned about the size of the plywood gear mounts. Photo #1 shows the relative difference in size between what is in the wing now (green outline) and my proposed new mounts. I have made a template(photo # 4) and now cut the 3/8" plywood mounts (photo # 6) to replace the ones installed in the wings. I have made a template of the wing surface and the location of the gear pads after they are installed 1/8" lower than the current ones to allow the strut to be below the surface (photo # 2) . This should allow the doors to close flush. As you can see, the new mounts will be much more robust than what came installed.

I'm dreading the next phase of this installiation, as it will be pretty critical to get the new mounts installed at the correct angle and depth. I'll be setting up a jig to allow me to hot wire cut the new surface for the larger mounts. More to follow.

Gremlin Castle

My Feedback: (14)

I just came across your thread so here goes. I am still flying a 17 year old YA P-47. I fly from both grass and hard surface using the YA retracts and the original gear mounts. While I have had no major problems with the mounts I would consider adding carbon fiber on the bottom side of the wing to compensate for the notch caused by the gear and servo wells.

Mine flys on a Brison 2.4 and now weighs a little over 18.5 lbs. It has had the fuselage half torn in two and the firewall torn from the fuselage along with the right wing broken in half at the servo well. This was the resuld of running out of fuel,airspeed, and altitude on a base leg with 25 mph winds. The reason was multiple go arounds waiting for a guy to clear the runway trying to find a wheel collar of all things.

Everything that you are doing looks right.

Dash7ATP

Gremlin,

Many thanks for your reply. It sounds like my concerns may not be as serious as I thought, but the mounts still concern me. I'm going to proceed with the change.

As for the wing failures at the servo well, I'm going to put a layer of light carbon cloth over the wings to about three inches beyond the servo mounts and then the FG fabric. I may also insert a carbon spar vertically in the wing to add some strength there as well.

The old fuselege had a rather tight clearance for cooling between the cowl and fuselage that was opened a lot on the newer kits; Did you stay with that , or have you done something else for additional cooling? It may not be a problem, but I was giving some thought to additional outlets for airflow.

Joe

Gremlin Castle

My Feedback: (14)

The annular clearance between the fuselage and the cowl flap area on mine is just about 1/4" all around.
My engine is baffled and the frontal airflow is restricted by the dummy radial and oil cooler chin under the motor. This bird has lived it's whole life in Texas heat with out problems. I think that the cowl clearance is adequate if the inlet air is restricted to just what will flow over the cylinder.
Also if it is not too late in your build try your best to cram everything possible as far forward as you can get it. I was able to balance mine without adding additional weight but that was with a gas eingine having the ignition pack on a platform over the motor crank case and a Frank Tiano resin dummy radialhung on brackets in front of the motor.
I also turned the 24 Oz fuel tank cross wise behind the firewall and stuffed both flight batteries under it down where the fuselage turns up for the wing dowls. This let me put the rudder, elevator and throttle servo side by side right at the front of the fuselage just behind the tank.
The retract servo and air tank are mounted on the top of the wing using Robart air connectors for the tail wheel.
I finished mine using Sig dope which has made for easy repairs and good results on the weathering and aging work.
Hope that this is not too late to be of use to you.

Ross

Dash7ATP

Gremlin,

Thanks for your input. I was hoping someone who had built the older kit would weigh in. That's what makes these fourns so valuable!  \

I wrote up a long response to your post and then it timed out, so I'm starting over, and  will be briefer.

1. My cowl clearance seems to be about the same as yours. Baffles seem to be the trick . I'll do that to mine as well.
2. Keeping weight forward is good. You went to a lot of extra effort; it seems to have paid off. I'll make an effor to do the same.
3. Currently I have the Top Flight vacuum formed radial. It's going to the next swap shop. No good for this model. I'll look into FTE for one.
4. Took one skin off of the wing and will post some photos later.

Thanks again.

Joe

Asanders

Gremlin, it is good to hear and see that your 47 is back in operation after an unfortunate dead stick. I have the same plane. I bought it from a friend. It weighs 30 pounds and has a 70 cc in it. It flies well but of course landings are a little faster than the average 47. I think it weighs so miuch because he had theplane painted professionally with automotive paint and of course the larger engine.

Dash7ATP

The gear mounting plates have been exposed. It took a little work to get the skin off, but that's behind me. I have made a hot wire tool to cut the surface for the new mounts. Now Ihave to fashion a set of rails for it to position the wire at the proper depth to set the mounting plates. Since it is thicker and the surface will be set 1/8"lower than the ones shown, the new surface will be 1/4" lower than the current mounting plates.

Idid have one surprise. There were four 1/4 " dowels through the mounts into the foam below, shown circled in the first photo. Ihave drilled them out so Ican cut under the plywood. I'll use part of a broken band saw blade to under cut the mount.

Dash7ATP

First pad cut out!
This afternoon I took the big step and removed the old landing gear mounting pad and cut the foam one half inch deeper for the new gear pad on the left wing. I'll try to explain the photos to show the steps Itook. For reference, I'll refer to the photos from left to right, top to bottom 1 thru 12.

1.This is ajig Imade from balsa that is fitted to the wing and can be pinned down in a repeatable position. It will hold theguides for the foam cutter.
2 & 4.These show the hot wire cutting tool Imade. The wire is two inches below the wood holder for easy measuring. I'm trying to show that the guides have to be on the same plane as the gear mount to ensure the gear sets at the propper angle.
7. The jig has been set up and the ends of the hot wire cutter are one half inch above the guides. In use, the toolwill ride on these and will place the hot wire 1/2 inch below the bottom of the current gear mount.
3. Setting up the jig.
8.This photo is out of position. The old gear pad has been removed. It wasn't easy. The dowels were not completely out of the way!
5, 6, & 9.. These show the hot wire cutter set up and how it looked right after Ihad used it to cut the foam down to the new surface for the larger mounts.
10 &11. This was not an oops! Due to the angle the gear is mounted, the 3/8"plywood mounts will extend through the surface of the wing. This is probably why the kit had such a small mounting pad. I'll sand off the hatched area flush with the wing surface and fair it in with filler. Once glassed over, it will not show, but the gluing surface will be over twice what the orginial was.
12.This is a trail fit to ensure the gear fits in the propper location in the gear well. I think it will be much better.

Any suggestions as to what adhesive to use for gluing in the new plywood mounts? Currently I'm planning to use Epoxy, but Gorilla Glue keeps coming up. I know it's tough, but does it maintain it's strength when it has to fill gaps like I'll have around and under the plywood?

Time to go to work on the other side!

Dash7ATP

Right side complete!

Getting set up for the other side was pretty quick. My Dad was a very good carpenter and he always told me " to measure twice and cut once". It has stood me well. After measuring out from the center edge of the wing to set up the jig, everything fell into place. The old pad even came out easier.
1. This was a trial jig set-up prior to cutting out the old mount.
2. The old mount has been removed and the jig is set-up ready to use.
3 & 4. A test fit shows the two gear mounts to be properly set and the gear are parallel.

Next step will be to sand down the aft edge of the gear pads to the level of the wing surface.

Dash7ATP

Resuming my work on the P-47.

It's been a month or two since I have updated my work on the P-47. I stopped for awhile to finish up a TGAF-15 I've had in primer since the spring. I have to paint with the garage door open, so I was waiting for warm weather.

To resume where Ileft off, the new gear pads have been epoxied in place. You can see that the aft edge where it extended through the wing surface has been cut and sanded down to just below the surface. Once the pad was glued in place, Ifilled in the space above the plywood with soft balsa and sanded it flush with the surface. Since thefill-in piece extended up over 1/4 inch to start with at the leading edge, I used the small one-inch-wide Stanley plane for the roughing in. If you don't have one of these, look into it. They are available at most hardware stores with a good tool dept. The work very well on balsa! Once I got close to the final surface, I appleid masking tape on both sides of my work area to prevent my corse sanding bar from cutting into the surrounding wing. When you are getting real close, make marks with a felt tip across the edge of the high area so you can tell when you are close to being flush with your wing surface. Remove the tape only when you are ready to do the finish sanding with 180 to 220 grit paper.

Finally, Ifill the glue joints and any low areas with DAPVinyl Spackle. This is very heavy in the little plastic tubs it comes in, howevera lot of the weight is water. You can smear it on pretty heavy, because this stuff sands to a feather edge better than any other material I have used, and once you are finished, there is not enough left to be concerned with, weight wise.

Dash7ATP

Here we go again!Idon't know what happened to the last photos that posted full size. We'll see what happens here.

As you noted, I have the new gear mounts in place. Now I'll proceed with making and attaching the gear doors. First, Ilined the gear well with 3/32 balsa. Idid use 1/32 plywood as the lining for the inside of the wing skin. This just looks better than the bare balsa as well as offering some protection to the wing skin from the gear itself.

Idecided to make the doors from fiberglass rather than use the 1/16" plywood provided in the kit. By doing this, Ican mold them to fit flush with the surface of the wing, rather than trying to make the plywood conform to the curved surface. Icovered the gear well area with .015" clear acetate like you would use to vacuum form a canopy. Once this was taped down and the area I actually want to layup with the glass cloth, was taped off, Ibrushed on two coats of PVAmold release film. Iused four layers of fiber glass. Three layers were .007" thick with the second layer on the bias (45 degrees) and the final layer of .6 oz finishing cloth. The finished layup is .025" thick.

Iused West System resin for the layup because Ihad some from a boat project Iused it on. Otherwise, I would have used Z-Poxy finishing resin. I applied it to one layer of cloth at a time so Icould keep the resin volumn to a minimum. Iadded the next layer and tried to soak up as much resin from the previous coat before I added more resin. The final layer of .6 oz cloth just wet out from the resin in the last layer of heavier cloth. The end result was a smooth outer layer with minimum resin. It shouldn't take much primer to fill it prior to the final finish.

My next post will cover my method of fitting the doors flush with the surface of the wing, and how I mount them will follow that.

Dash7ATP

Fitting the doors

The door layup went very well and I'm satsified with the results. Now I'll cover getting the door skins to fit into the wing.

First, Iwant to make a place for the edges of the doors to rest on when retracted to keep them flush with the wing surface. I used soft 1/8 "balsa and cut a lot of strips from the end of a three inch sheet. This gave me a 1/8 " square piece of end grain that would bend around the curved areas inside of the gear well. I glued these around the inside edge about 1/32 inch below the surface of the wing. Ifigured by the time Iget this finished, the paint would reduce this to just about the thickness of the edge of the doors. The CAglue really soaks into the end grain and makes for a hard lip for the door to seat on.

Ithen used my always handy Sanford fine tip pin and marked lines even with the inside surface of the door wells. I taped the door molding in place and transfered the lines to the skins. By carefully cutting close to the line and sanding the rest, a very neat fit can be achieved in fitting the doors into the wing.

The next step will be to fit the lower gear door to the strut and line the door with 3/16 sheet balsa. The upper door strut has to hinge on the gear mount cover, and the inboard door is hinged to the inboard end on the wing. Stay tuned........

Dash7ATP

Progress is slow, but it's still progress!Every thing Ido is one less Ihave to do later. As I said previously, the door skin layup went well and the skin in one piece was fitted into the gear well. I bought a small attachment for my Dremal tool several yeas ago that makes pretty quick work of making a recess for a flush mount for servo covers, gear mount covers, etc. More details on this can be posted if Iget a request.
The photos below show the four pieces cut apart and fitted into place. The main door cover, the largest piece, is actually attached directly to the gear strut. Each gear yoke had the two holes already drilled for this. The plywood pieces screwed to each side extended above the gear about 1/64 of an inch. Iput a piece of scotch tape on the gear and covered it with a light layer of vaselene as a release agent. With the gear in place, I put Epoxy on the plywood pieces and placed the doors in place over them with a weight to keep them tight against the plywood. Once the epoxy cured, they popped right off. Epoxy will not stick to grease.
The next step was to fit the door leg cover to the cover of the gear mounting pads, and attach the hinges. Iactually had to remake the strut and mount covers. After Ihad them hinged and mounted, they did not line up propperly with the lower, main door cover. The hinge angle was wrong. If you are going to do this, I'd advise you make a cardboard template and experment with the hinge angle to ensure they look correct when extended.
The inner door is hinged on the wing near the root, and was something of a problem. On the full scale door , the hinge line is almost flat so it just folds down very simply. The lower surface on this model has a pronounced curve , so a smiple hinge would not work. Rather than hinge it on the edge, where it would bind near the center, Ihad to make the hinge line inboard of the edge so the curve would have a place to go as the door opened. Ithink you can see this in the photos. I glued a small plywood pad in the gear well and attached the Robart hinge points as you can see. It took a little time to get it right, but it seems to work fine and doesn't look too bad.
The actuating cylinder will be attached to the top of the wing. The cardboard sketch shows how this will be done.
I haven't mentioned this, but the door liners are made from soft 1/8 sheet balsa. I was first going to use 3/16 sheet, but decided this would look too thick. The edge of the liner is set back from the edge of the door and beveled slightly to help with seating in the opening. Where the upper door comes up (down actually) as the gear extends, it slides down over the wheel cover. I let the lower door liner extend about 1/8 inch cover and sanded a bevel on it. Isanded a matching surface on the strut cover so the the cover had to slide over the lower piece and not jam. It works well.

FlickSpinCrashBurn

Joe,

The mechanism looks a work of art - I wish I had both your skill and patience!

I wish I had seen your post some time ago as I may have attempted to persuade you to go with mechanical retracts. I have recently been developing a PIC microcontroller that will control 3 undercarriage mechanisms and 3 doors independently. Each can use an independent mini/micro servo for full flexibility, or a single normal size servo can be used to control more than one undercarriage leg with appropriate linkages. The reason for going for a potential maximum of 6 micro servos is to allow each door and undercarriage to have its minimum and maximum travels adjustable independently for ease of set-up. However, it also allows the individual undercarriage legs to be lowered at different rates. In this way you can mimic the undercarriage of the old spitfires etc where the gear never came up symmetrically. The doors are of course fully syncronised at all times with the undercarriage legs (not possible with pneumatic systems) so there is never any possibility of the undercarriage fouling. Timing for both doors and gear are fully adjustible ranging from as quick as the servos can manage to several minutes. In the event of an emergency, say deadstick, the slow (default) setting can be overridden and the gear lowers in about a second (again not possible with pneumatic retracts).

Anyway, I realise that it is too late for this model as you will not wish to have to modify such beautiful work, but:

a) I need a test bed for my system if you or someone you know has one in the pipeline
b) If you need some sequencing for your pneumatic undercarriage and doors, then give me a call.

Best wishes for your project and I hope every hurdle you encounter is as artfully overcome,

Dempster

Dash7ATP

hi Dempster,

Thanks for your comments!The controller you made me for my F-15 nose wheel door works great, but Istill haven't made the maiden flight on it.

As for mechanical retracts for this model, I'm not aware of any that are large enough or strong enough or with a mount that will hold up to the weight or loads that might be placed on this gear. The struts are 5/8" dia, and over eight inches long with five inch wheels. They are probably available, but I'm not aware of them. As for the sequencing of the doors, the controller I'm using will handle that nicely (I hope).

I don't know of any projects for you to test your system on, but maybe someone on line here will.

Thanks for the contact.

Joe

ps. Look for an update here soon.