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Seagull Boomerang II Tail Dragger

Anyone built one recently as a taildragger?

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Patrick O13/01/2015 10:14:02
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20 forum posts

I need to ask - has anyone built this plane as a tail dragger recently using the included taildragger conversion parts?

The tailwheel steerable rod has a bend on it.. and I need to know if this affects the whole thing as when I'm test fitting mine, it does not look like it will work (mind you, I have not bend the upper part yet that goes into the rudder so maybe I need to do that?)

The problem that I can see is... one I have the tailwheel rod thru the hole of the plane and against the vertical fin, and once it's aligned, if I turn the wheel left, making sure the long rod is aligned still with the vertical fin, the plastic mount on the bottom gets pulled from the bottom of the plane.. because of the bend on the bottom of the rod.

top left of this photo (below the spinner) shows the tail wheel rod with the bend:

Apologies I don't have a photo or video of what I mean. I just decided to post this now before I forget. I'll do a video tonight when I'm home

Rosco13/01/2015 13:29:51
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448 forum posts
386 photos
Sounds like your tailwheel rod is binding because you have the mount too far down the rod. The mount needs to sit with the bottom of it inline with the small bend. Rosco

Edited By Ross Piantedosi on 13/01/2015 13:54:46

Patrick O13/01/2015 13:45:20
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20 forum posts

Thanks Ross... I'll put a better photo/video tonight. The rod is quite long so I don't know if the problem will go away once I bend the top of the rod to go inside the rudder bit... but I don't want to bend the rod yet in case I make a mistake. I should find a cheap thin wire and test my theory out first.

I got this plane on Boxing day and I'm nowhere near finishing it!! Planes are definitely harder to build than helis! I fly helis mainly.

Patrick O13/01/2015 13:48:24
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20 forum posts

Also the modelshop sold me these 1/8" Robart Hinge pins to fix the rudder.. but I don't know if the pins are too big for the width of my rudder? I would have wanted CA hinges again but they're right - I have nowhere to cut slots in as the old slots are filled with ca and the remaining ca hinge.

 

And this is the plane:

 

 

Edited By Patrick O on 13/01/2015 13:50:11

Edited By Patrick O on 13/01/2015 13:50:38

Dave Hopkin13/01/2015 14:38:40
3672 forum posts
294 photos

I think I would be looking at a size smaller hinges, if you used those there wouldn't be a lot of meat left to support them

Patrick O13/01/2015 19:27:07
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20 forum posts

Here is the video

Dave Hopkin13/01/2015 19:32:08
3672 forum posts
294 photos

What happens if you turn the control horn upside down so it angles away from the Fus?

cymaz13/01/2015 19:53:12
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9246 forum posts
1194 photos

Fuzzy hinges wouldn't be a problem, not for a trainer smiley

GrahamWh13/01/2015 19:59:23
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356 forum posts
53 photos

Patrick you will need to straighten out the wire where the odd bend is just above the mount, then make a wedge of balsa to go between the plastic mount and the bottom of the fuselage so the mount can sit with the bit of wire that goes through it exactly in line with the hinge line of the rudder.

The wheel unit is probably a standard item supplied with many different kits. They need modifying to fit sometimes.

Also have the bend in the wire that takes the wire horizontally to the wheel rubbing against the mount - that way the weight of the back of the plane will be on the mount (could put a washer in to help) and not on the rudder hinges.

Like this, though the example is a Black Horse Renegade: (my wedge had to be on the front end of the mount, yours will be on the back)

 

wheel.jpg

Edited By GrahamWh on 13/01/2015 20:02:03

Edited By GrahamWh on 13/01/2015 20:02:55

Edited By GrahamWh on 13/01/2015 20:03:38

Patrick O13/01/2015 20:16:44
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20 forum posts

Posted by Dave Hopkin on 13/01/2015 19:32:08:

What happens if you turn the control horn upside down so it angles away from the Fus?

Hi - I can't.. because it's only the flat bit of the mount (I'm guessing you're talking about the white plastic?) that has the holes for the screw.

Patrick O13/01/2015 20:18:18
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20 forum posts
Posted by GrahamWh on 13/01/2015 19:59:23:

Patrick you will need to straighten out the wire where the odd bend is just above the mount, then make a wedge of balsa to go between the plastic mount and the bottom of the fuselage so the mount can sit with the bit of wire that goes through it exactly in line with the hinge line of the rudder.

The wheel unit is probably a standard item supplied with many different kits. They need modifying to fit sometimes.

Also have the bend in the wire that takes the wire horizontally to the wheel rubbing against the mount - that way the weight of the back of the plane will be on the mount (could put a washer in to help) and not on the rudder hinges.

Like this, though the example is a Black Horse Renegade: (my wedge had to be on the front end of the mount, yours will be on the back)

wheel.jpg

Thanks - I did think about wedging the plastic mount and straightening the rod.. I'll have a think and if I can't do anything, then I'll do as you've suggested.. I need to go back to the model shop to get a few more items before I can work on this.. mainly the drill jig for the pin hinge

Patrick O14/01/2015 11:57:58
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20 forum posts

This is the tailwheel rod held against the tail to show you guys that the rod looks perfect... so I'm thinking I need to follow the manual and do that bend on top for the rudder and it will work as expected?!

Keith Evans 314/01/2015 13:36:08
393 forum posts
148 photos

How will you hinge the rudder to the fin?

Martyn K14/01/2015 13:54:50
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5083 forum posts
3678 photos

Hi Patrick

You need to keep the rod from the spring up to the rudder absolutely straight or it will bind. I would do as Graham suggested - pack the white mount or possibly file it down slightly to fit.

You may actually get away with it being a simple tail dragger with a locked rear wheel. They tend to be light on the tail and many people have used them successfully like this.

If you do go for a steerable rear wheel, my advise would be to bend the rod and attach it to the lower edge of the rudder. You will need to bend it at the right height - make sure that there is no stress on the rudder though when the model is sitting on the tailwheel, run it along the rudder for about 30mm then bend it up so it locates in a little hole in the bottom of the rudder - about 10mm.

Regarding hinges. Those Robarts look like they are far too big for this job. Hairy Mylar will be more than adequate strength wise, you just need to cut the slots (carefully) in the fin and rudder in the gaps between where the other hinges were located. Put a pin through them as well to make sure they cant pull out. Glue the pin and cut off the excess

Good luck

Martyn

Patrick O14/01/2015 13:57:02
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20 forum posts

I was going to cut new slots for ca hinge but I was told there is no room for new slots and the best way is to use pin hinges so model shop gave me Robarts.. but I think they are too big for my rudder?

Engine Doctor14/01/2015 16:23:50
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2506 forum posts
39 photos

The Robart hinges will be fine in that thickness of wood. Oil the actual hinge part before gluing in place . before fitting the hinges in your drilled holes drill a hole in apiece of scrap balsa and test fit a hinge . Make sure you can remove it as once pushed into a hole of the recommended size they are virtually impossible to remove . When happy with fit Glue in place .

Patrick O02/02/2015 09:40:53
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20 forum posts

UPDATE:

Well, I've only just managed to make a wood wedge and straighten the rod and install it over the weekend (yeah I know - the plane should have taken just a couple of hours but it's taking me months! )

I think I'm gonna stick to helis after this!

I still need to bend the top part to go into the rudder.

I also still need to drill holes on the tail fin and rudder for the Robart pin hinges to go in. I'll do that next weekend or something.

NEXT QUESTION: How high should the tail wheel be? Or how low should it be? I think mine is a bit high when in place and I might need to bend the rod back a bit?

 

Edited By Patrick O on 02/02/2015 09:41:48

David Hardaker02/02/2015 14:07:16
118 forum posts

Patrick

Tail wheel arm needs to be shorter, if poss. Although for what fraction of an inch you'll gain, it's barely worth the effort.

A low tailwheel reduces the angle of attack attainable on the ground. This may prolong the takeoff run, especially on soft ground/long grass. The tricycle u/c version will get airborne in less room because it can obtain a larger angle of attack ('cos the mainwheels are further back) and there's no tailwheel to limit the nose-up attitude.

Whatever, the Boomerang leaps off the ground easily.  Excellent model.

D

 

Edited By David Hardaker on 02/02/2015 14:15:26

Patrick O02/02/2015 14:20:37
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20 forum posts

Hi David - thanks. 2 things:

What do you mean by tail wheel arm needs to be shorter? What's an arm?

 

Low tailwheel - did you mean high? Because the way I see it, a low tailwheel should give more angle of attack as the tail will be lower to the ground thus tilting the nose higher for a higher attack angle?

EDIT: Oh hang on - I think I know what you mean now - a tailwheel config will limit the angle of attack attained during take off compared to a tricycle because of the presence of the tailwheel itself.

I should have ignored myself and gone for a tricycle config right from the beginning, I would have finished and flown this plane already! ;o)

But because I made a mistake when I cut the covering underneath for the undercarriage (I accidentally cut the slots for the tail dragger) and I didn't want to recut and make the underside look ugly, I stuck with the taildragger config - even tho I do prefer the look of the taildragger... but this has given me lots of problems which is not good for a first time plane build like myself

Edited By Patrick O on 02/02/2015 14:24:44

David Hardaker02/02/2015 14:28:32
118 forum posts

Patrick.

Tailwheel arm is the straight bit of wire between the coil spring and the wheel..

The vertical distance between the bottom of the fuselage and the tailwheel needs to be as small as poss,

Does this help ?

D

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