My First Crutch!!

[MrSteve09]

Hi All,...

After building profiles for three years, I'm finally building my first full fuselage stunt plane.  The plane I've chosen is Windy Urtnowski's Cardinal Evolution.  Here are some photos of the fuselage build so far.  I've built my first motor crutch!! 

Any thoughts comments or suggestions are most welcome.  A motor crutch might not seem all that exciting but when its your first one I can't help but get a little gitty, ha!!

Sincerely,
Steve T.
Monson, MA

[TDM]

It looks great.
Screw the pads in place before drilling the holes for the motor. You need to measure the hole size in the motor with a nice pair of calipers. When you drill the motor holes see if you can buy a longer drill (McMaster Carr has them). Use this tighter drill just to spot the holes then drill with the appropriate size for the blind nuts. This way you will have nicely centered holes.

[john e. holliday]

Crutch is looking good.  I seen something at the KCRC Fun Fly at the Lee Machine Shop booth.  He is now making drill guides for engines.  As Jim stated, "He could never get all four holes right".  Might check with him on what is available.

[Tim Wescott]

It looks great.
When you drill the motor holes see if you can buy a longer drill (McMaster Carr has them). Use this tighter drill just to spot the holes then drill with the appropriate size for the blind nuts.

Longer?

Usually you want shorter -- you want what's called a "spotting drill", which is very short, to increase the overall rigidity of your machine/drill/part system, and enforce where you're trying to put the hole.

Note that if you're doing this without a drill press or with a really flimsy drill press you're probably better off using a scriber or some other tool borrowed from Og, your local caveman, to dig out a starter dimple in the wood right where you want the hole to be -- then use a regular length drill bit, which will want to locate itself in your dimple.

I'm lucky enough to have access to a machine shop, so I do this job with a spotting drill and a precision table.

[proparc]

Thats the stuff!!
Anything you want to know, I am sure just about everybody on this forum will be more than happy to hook you.

[john e. holliday]

A thousand people and a thousand ways of messing it up.  No really the guys on this forum are great and willing to help.   

[Matt Colan]

Good stuff Steve!  You making it to Lee this weekend?

[minnesotamodeler]

Funny, I interpreted the "longer drill bit" as a means to enable marking through the actual flange while the engine is sitting on the crutch.  Longer so as to get the drill above the engine.   

[Rob Killick]

What minnestamodeler said...

[Paul Smith]

After decade of using hand drills, last year a bought a cheap, tabe top drill press from Harbor, about $70.  I wish I done it sooner.  It make a world of difference, and it didnt; cost a more than a hand held cordless.  In additiuon to the straightness,  Ican get the RPM up here it needs to be to drill a clean, small hole.

Drilling the through the engine is always BAD bidness.

Mark ONE hole with a transfer punch (the same size as the engine's holes).  Drill that hole.  Install one bolt and mark the diagonal hole with the transfer punch.  Install two bolts and mark the two remaining hole.  Drill them and you're done.

Harbor has a transfer punch index with all sizes of punches, either English or French gauge.  The right way to get the hole on center.

[john e. holliday]

Tower Hobbies sells a neat tool for marking holes to be drilled.  It is a long tube with a cone on the end.  A long drill bit goes thru the tube.  Push the tool onto/into the mount lug hole.   A couple of twists and the mounts are ready to be drilled.  I use mine quite a bit.  But, as Paul says, " Drill one hole and then bolt the engine in place".  Double check to she how close it is and then mark the other holes.  Takes time to do it this way, but is so much more accurate. 

[Allan Perret]

You did a nice job with the tapered mounts and curve for the nose..

Get the long drill bits especially if you are using a hand drill.  It gives you more of a reference to help you drill perpendicular holes.  The long bit also gets you drill motor elevated so you can use the motor as a drilling template.  Drill holes with bit that gives you a snug fit to you mounting screws.  Drill 1st hole, put screw in 1st hole, drill 2nd hole and put screw in it, so on so forth.  Your holes will be perfectly aligned.  

If you are interesed in building in 1° downthrust,  I have a good trick for that.  I use phenolic for mounting pads instead of aluminum.  I epoxy the phenolic to the maple mounts, no need for screws.  After pads are epoxied on, glue a piece of ~100 grit sandpaper to a flat surface.  Surface needs to be a little wider than your crutch and about twice as long as the crutch.  Sandpaper only needs to be about 6" long.   You want paper only where the pads are,  so as not to sand anything off of the aft end of you crutch.   Put crutch top down on sanding surface and sand the taper into the pads.  By keeping only 2 contact points, the pads and the aft end of the crutch on the sanding surface the taper will be automatic.  Before start sanding, with felt tip pen put mark down the middle of each pad.  This will be a reference to let you know when done.  The sanding line will progress from rear of pad to the front.  When you have just sanded off the full length of the mark you have created a flat surface on the pads that will have slightly less than 1°.  If you want to try it I can send you a couple of the pads in an envelope.  Let me know what size you want.    This method can also be done with the aluminum, but the phenolic sands easier and is plenty tought enough for the purpose.  If you do it with aluminum, do it without the screws in them.   If you switch to 150 paper right at the end you will have a nicer finish to pad surface.  

[TDM]

Usually you want shorter -- you want what's called a "spotting drill", which is very short, to increase the overall rigidity of your machine/drill/part system, and enforce where you're trying to put the hole.

The idea here is to place the motor in position and clamp it and then use it as a template to spot the hoes.
The longer drill is necessary so you can clear the motor and not hit it with the drill. If you have a drill close to the size of the hole in the motor mount hole size then it will locate just fine.

Plan B if you have a milling machine use the spotter drill you mentioned and go to coordinates of the hole position.

[Steve Scott]

Usually you want shorter -- you want what's called a "spotting drill", which is very short, to increase the overall rigidity of your machine/drill/part system, and enforce where you're trying to put the hole.

Ditto on the shorter drill bit.  I have a 12" long 1/8" bit which is handy for clearing an engine but it will wander off.  The Great Planes Dead Center Locator mentioned previously is also an invaluable help.

This brings me to the question of drill bit/bolt size.  I've been using a 1/8" hole with a 4-40 bolt in mid-size engines but the result is a pretty sloppy fit, allowing the motor to shift around quite a bit.  On profiles, this results in unintended up/down thrust.  Not a pleasant flying experience.  Besides, I'm sure the engine lugs are drilled for a metric hole so perhaps a 3mm bolt might work better than our standard 4-40 hardware.

Anyone converted to metric mounting hardware yet?

[Allan Perret]

Get a set of number bits.  #33 is a nice slip fit for a 4-40..

[Bill Little]

Hi Steve,

Your work looks great!  Nice workmanship, and you will really enjoy the new plane, I am sure.

Drilling mounting holes is done differently by everyone it seems, so just make sure you do it a way that will be accurate for you.  I started with a hand held drill a long, long time ago.  Later I got a drill press, and that is something I cannot live without!

One thing I will add is that I drill the holes through the aluminum pads slightly larger (usually 9/64ths for 4-40 bolts).  Doesn't hurt a thing and can make things a little simpler.  No binding ever for the bolts.

Big Bear

[MrSteve09]

Hey Guys,...

Thanks for all the advice and suggestions!!  I finally got back to working on my Cardinal Evolution engine crutch.  As was suggested, I decided to screw the aluminum motor pads to the motor crutch using #5 X 1/2" wood screws.  I located and marked where the screws would go, drilled a through hole.  Using a 17/64" dia. drill bit (same dia. as the screw head) as a counter sink tool, drill just deep enough so that the screw head would be flush on the top surface of the motor pad.

[MrSteve09]

Continuing on with the installation of the Super Tigre 51 on my motor crutch.

I used a hole center locater to mark the hole centers.  I have no idea where I got this tool, (it could be a Harry Higley tool?) after being in the hobby for over thirty years you just accumulate stuff that you can't remember its origin, and this is one of those things.  Again,... as was suggested I only marked, and drilled two holes at a time.  Bolted the engine to the crutch and then marked the next two holes.  This kinda guarantees  that all the holes will line up.

Using the marks from the hole center locating tool, I first I drilled a 5/64" dia pilot hole.  Then I flipped the crutch over to drill a recess hole for the blind nut using a 3/8" dia. brad point bit.  Then while the crutch is still flipped over I drilled a 5/32" dia recess to accommodate the shank of the blind nut.  After all that I finally opened up the remained of the hole to 1/8" dia. for the 4-40 cap screw to pass through.

Hope all that makes sense.  It seems like a nice, neat, and tidy installation.

Thanks for everyone's help and input.  I certainly appreciate it.

Sincerely
Steve T.
Monson, Massachusetts

[Paul Taylor]

Looking good Steve!!!

[Allan Perret]

That's a Dubro tool you have there..
I dont countersink the blind nuts into the motor mounts,  instead I cut spots in the topblock. 
Either way is good, what ever is easier for you.

[W.D. Roland]

I cheat

On profiles I rubber band the engine on to set the up/down thrust to "0" and then super glue it in place!

If I have a piece of music wire that fits snug in the lug, hammer the end of wire flat then grind a V shape on that and narrow the flanks down to match original wire od. Sometimes just make a center punch from wire or welding rod( what ever fits) and bump it with the mato.

Then with a hand drill make the centers(dimples)
Then if I have a 36inch long drill bit the right size for bolt shank I drill right then.
Long drill bits from Harbor Freight.

If not I pop the engine loose and use a regular bit. sometimes I can do it in drill press sometimes hand drill.

When worst comes to worst I use a pin vice and do it by hand, Does not take long.

Almost always drill a counter bore for the blind nut. Use a drill stop or get out some good luck.

I do this after Wing is glued in the fuselage so the Robart meter can be put to use for zero zero.



So Dats da way dis hill billy do it!

David

[Michael Massey]

Hate to seem backward but I have yet to build my first built up fuselage.  I think I gathered the idea of the crutch but I would like anyone with a full explanation of the crutch to explain it in more detail as to why, how etc etc.

Tx.

Mike

[john e. holliday]

David,  looking thru this thread again, it dawned on me when I was getting into this madness.  Dad had the tools to start with bare ground and build a house from the basement up to moving in.  The inspectors would ask him about licenses for being able to do the work.  10 times out of 10 his work was much more than local city, county or even state requirements.  But, he had nothing as far as drills for my models.  Out comes the nail box and he finds one that fits the mounting lugs of the engine.  A hammer and file was used to make a drill bit.  Had to go slow to keep from splitting the motor mounts, but it worked.  Lost count of how many planes had the motor mounts drilled with that nail.   

[Bill Little]

Hate to seem backward but I have yet to build my first built up fuselage.  I think I gathered the idea of the crutch but I would like anyone with a full explanation of the crutch to explain it in more detail as to why, how etc etc.

Tx.

Mike

Hi Mike,

The *crutch* is simply a different way to build the front end of a full body model.  We used to glue the motor mounts onto the sides of the fuselage, and then join them with the front formers.  The crutch makes a stronger system (balsa added cross grained between the MMs) and more accurate.  The MMs are set to the width of the engine before assembly, then everything is built up as a unit.  This makes adding the fuselage sides to the assembled *crutch* more accurate, IMHO. 

Big Bear

[Michael Massey]

Looked and sounded like that but you know about ASSUMING. 

Thanks,

Mike

[MrSteve09]

Michael,...

This is how I added the fuselage sides to the motor crutch. 

After pinning the Motor Crutch to a "flat" work surface, the fuselage side were glued to the motor crutch.  And the fuselage bulkhead was glued in place.  I clamped everything together with parallel clamps.  Because the front of the motor mounts begin to tapper I had to add clamps to the front of the fuselage sides as well.

Because the motor crutch has been predrilled and the blind nuts already set in place the motor is a drop in fit at this point!!

Hope this explains things in more detail.

Sincerely,
Steve T.

[MrSteve09]

Now I am ready to add a few fuselage formers.  There are no dimensions or patterns for the fuselage formers on the plans so I guess I have to just make them up as I go?

Steve T.

[Michael Massey]

Thanks for your help.

Mike

[Bill Little]

Now I am ready to add a few fuselage formers.  There are no dimensions or patterns for the fuselage formers on the plans so I guess I have to just make them up as I go?

Steve T.

Hi Steve,

When there are no patterns of the formers, measure the top and side views of the plans..

Mongo

[MrSteve09]

Haven't posted here in a while, but I've been working on the Cardinal fuselage.  Since last time I added fuselage formers.  Laminated five pieces of 1/2 inch balsa to form a 2 1/2 inch thick block for the top block.  Tack glued the top block in place and began carving to shape.  Also laminated pieces of 1/2 balsa to form the chin block and got that carved to shape.

Next I'll pop the chin block off and begin hollowing it out to fit the engine in.

I'm really excited about how this is coming out and am anxious to finish it!!

Since this is the first full fuselage stunt ship I've ever built, I'm anxious to hear any comments or suggestion that anyone has.  Thanks for reading and following my progress! 

Sincerely,
Steve Teerlinck
AMA 382673
Monson, Massachusetts

[Airacobra]

That's looking great Steve, Keep up the work, this should be a great flyer for you.

[john e. holliday]

That is looking great.  I see you used the top view for the width.   

[Bill Little]

Great progress, Steve!  Really looking good!

Big Bear

[Bill Sawyer]

I know it is too late for you to try this method of making a crutch but you might consider it for some other plane. In woodworking the strongest joint is the mortise and tenon. A good example of a mortise and tenon joint is where chair leg braces are inserted in the legs. I adapted this to my crutches and have provided an assembled crutch in some of my kits. Basically I use a router table to remove a 1/4 inch wide by 3/16 inch deep grove in the maple mounts. I then epoxy a sheet of cross grain balsa from mount to mount with the ends inserted in the maple. The slot is 1/16 inch from the surface where the tank mounts and I fill in between the mounts with 1/16 inch plywood. Pictures below.

[Bruce Perry]

What Bill said!!  Once I saw his method I abandoned all others.  His is the last word in crutch construction, Others work great, this is the strongest to be sure.

B

[MrSteve09]

Bill,...

That is amazing!!  I'll definitely have to try that on my next plane!!  That looks so cool to build.

Do you do anything with the gap or space on the "top" of the crutch?  Do you use anything to fill the space between the crutch and the top balsa block?

Thanks for sharing

Sincerely,
Steve T.
Monson, Massachusetts

[Michael Massey]

Another question.  What is the purpose of the aluminum spacers under the motor mounts?

Tx.

Mike

[Bill Sawyer]

Steve,
    I have only filled the space between where the tank sits so the space is flat and easy to seal and clean. The inserted balsa gives enough strength that filling the other side ( or top ) is not needed. If you like to see it filled you can but I have never done it.

   When you cut the slots in the mounts, you will have to stop before you get to the end on one mount and the other one will be dropped at the starting point. With the fence at the rear of the cutter, both mounts are started at the right and they move left as the cut is made. If you go the other way the cutter will have a tendency to push the mount toward you and spoil the cut. I use a piece of tape on the fence as a guide as to where to start and end the cuts. The end of the cuts will be round and instead of rounding over the balsa where it goes in the mount I use a 1/4 inch chisel to square up the end of the cut. When you first start you need to allow extra length on the mounts to trim off once the crutch is done,

   The metal plates are used to prevent the engine from sinking into the mounts but it also allows the adjustment upward for the tank if needed.

[MrSteve09]

Hi Guys,...

Its been a long time since I last worked on my Cardinal Evolution.  Since then I've put together an SV-11 and a Vector 40.  Now that I'm "between" projects, I thought I'd plink away at the Cardinal Evolution.  I built a wing using a rib set from the Brodak Profile kit.  Made elevator and stab pieces using patterns and shapes from the Brodak profile Cardinal.

I've got the wing in the fuselage and it took some shimming to get the wing incidence to line up with the engine thrust line.

All for now.

Steve T.

[MrSteve09]

When building the flaps,... I wanted a hard anchor point for the control horn wire in the flaps, therefore I drilled out a piece of 3/16 inch 5-layer plywood to accept the control horn.  Created a "pocket" in the flap to accept the plywood, and sandwiched all that together between two pieces of 1/64" plywood.  Notice the edges of the plywood were tapered in advance of epoxying they to the surface of the flap.  I will also feather the plywood in with some Sig Epoxolite filler material.

Steve T.

[Tim Wescott]

It's looking good so far!

[MrSteve09]

The latest Cardinal Evolution update,... The wing has been glued in place the flap to elevator pushrod was measured and cut to length.  With the flaps temporarily clamped in place at neutral, I used the elevator control horn with the swivel ball link and threaded rod to measure mark and cut the pushrod to length.  Then everything was dry fit together to verify the elevator was indeed at neutral.  Once satisfied, the elevator was epoxied in place.

Next I have to work on the other end of the plane and get the fuel tank installed and cowl hollowed out!

Steve T.

[Damian_Sheehy]

Looks terrific, Steve!
Will it be ready for Lee?

[MrSteve09]

No,... Damian, I don't think so!

Steve T.

[john e. holliday]

That is looking good and I like your setup.