The Ohmen

[Former Member]

[This posting has been removed]

[Martin McIntosh]

Tried it today and it will spin without any other changes. Still pushes to the u/c in KE, more so left than right so increased the rud/el mix. I tend to fly with the least possible throws so it would stand much more elevator on high rate. I am probably being a bit picky here since this really is a pleasant model to fly.

[Former Member]

[This posting has been removed]

[Peter Miller]

I am intrigued at the reference to rudder elevator mixing.

I just use the sticks separately.

[Martin McIntosh]

Percy, I would yes, it is worth doing. Maybe even 1" rake back.

Peter, it makes use of your computer gear and life easier. No more hit and miss.

[Peter Miller]

Ah!! Do you think that the pilots of Extras etc.rely on computers and mixers to perform properly? Do they stop after each flight and think "I want a little more rudder or elevator or ailerons mixed in to get that perfect"

[Martin McIntosh]

No, but they do not have to wait and observe an error as we do.

As a former twice British F3A team member and British champion I would almost have given my right arm for the radios we have today. We had to keep tweaking various bits of the design to get things as near perfect as possible. Corrections became automatic reactions after many hours of practice. I can still do it but prefer to take the easy way out.

[Trevor Crook]

Every time I fly my Sebart Angel knife edge, I promise myself I'll mix in a little up elevator with rudder, then promptly forget! Haven't played with KE much with the Ohmen yet.

Martin makes a valid point in that we are not sitting in our aircraft, so it takes us longer than a full-size pilot to perceive that a correction is needed, and how much to apply. Mixing is a great help in this respect. My most frequently used mix is CAR, engaged on high wingers and biplanes because I haven't got a turn and slip indicator to look at.

Nothing wrong with doing it all with your eyes, brain, fingers and thumbs if you prefer though Peter.

[Peter Miller]

Interesting that mixing two controls to correct errors in one manoeuver has no effect on the accuracy of another

[Martin McIntosh]

You are correct of course Peter, but if the model in question is near enough anyway then this does not become too much of an issue.

I have only built one design, the Dalotel, which rarely needs electronic or manual correction. I am now on about my eighth one, between 48 and 78" spans. Still have three. Amazing since only one full size prototype was ever made.

The only other model I have which comes near to this is a Curare.

[Peter Miller]

Ah Well, ASfar as I am concerned my sports models are just designed to be thrown around in a long sequence of aerobatics. As I always say, the only time they fly straight and level is when they are inverted.

A Currare it is NOT and is not intended to be.

[Dean Sarelius]

Hi All,

Here are some pics of the Ohmen so far.

Parts have been cut with my Chinese 40W laser cutter and the bulkheads and wing halves glued with epoxy. Will make a start on the undercarriage next and will take Martins lead and mount it to the outside.

Cheers,

Dean

[Dean Sarelius]

OK not sure what happened with the pictures so have provided the links here below.

Laser cut bulkheads

**LINK**

Wing halves epoxied together

https://www.dropbox.com/s/zd9m9qkwhu9m6bd/IMG_20190329_190435.jpg?dl=0

Fuselage

https://www.dropbox.com/s/qnmxc3zqs2jo1rl/IMG_20190516_072558.jpg?dl=0

Wing

https://www.dropbox.com/s/pwssr3r57n874e7/IMG_20190516_072625.jpg?dl=0

Wing and fuselage 1

https://www.dropbox.com/s/0i5qdsbchfe0v4l/IMG_20190516_072658.jpg?dl=0

Wing and fuselage 2

https://www.dropbox.com/s/xruyixoiichwr5s/IMG_20190516_072706.jpg?dl=0

[Former Member]

[This posting has been removed]

[Dean Sarelius]

Thanks Percy,

Here are the pics from my album.

Cheers

Dean

[Peter Miller]

That is looking very nice indeed.

Just one thought. You do sandpaper all the charred black off the edges befofre gluing don't you?

[Dean Sarelius]

Hi Peter

I sand off the burnt edges with 220 and on account of the laser I also square off the edges before gluing.

The balsa cuts much quicker so tends not to get as burnt as the ply.

Cheers

Dean

[Peter Miller]

I only mention it as we had someone whose engine came out because they had not sanded the char off

[Dean Sarelius]

Hi All,

I am just setting up to build the cowl for the Ohmen.

After fitting I find there is very little space between the cowl ring and the motor. If I was to provide a 1mm gap between the spinner and the cowl ring the cowl ring will be rubbing up against the motor.

Just wondering if anyone else has run into the same problem and if there could be any easy fix..?

Cheers,

Dean

[Peter Miller]

It looks as if you are using a different motor and prop driver to my original.

If using a different set up it is just a case of cutting and adjusting to suit.

It looks as if you could open up the hole in the ply ring to clear the motor. The cowl ring might end up about 1/8" wide but it isn't load bearing so that is no problem.

Your prop driver looks thinner thanthe one on my 4-Max motor. possibly you could pack the prop forward a little The other possible option would be to cut the ring from 1/16" ply.

I hope this helps.

[Dean Sarelius]

Hi Peter,

Thanks for the quick reply.

I am unable to pack the prop forward for fear of running out of thread.

I think I will take up your advice and open up the cowl ring.

I might just change the shape of the cowl to allow more air to flow around the motor what are your thoughts on this as I think there will be very little air flow around the motor if the cowl is to restrictive..?

Cheers,

Dean

[Peter Miller]

By all means change the cowl shape. Cooling air is pretty important. A small scoop on top of the cowl and of coure the chin intake help.

You should be able to fit a slightly bigger spinneras well.

Modifying and customising a design to suit ones own needs and/or ideas is part of the fun of modelling

[kc]

Sometimes with ic engines the area around the engine was restricted to get more airflw where it was needed. So as long as you have sufficient exit space for the air it should be OK with electric. If in doubt you could always try the plane without the cowl. It's more essential to cool the ESC than the motor.

So you either buid a cowl to suit the motor or perhaps buy a different motor that fits more easily ( that might be one where the shaft projects out front and takes a prop adaptor which has a collet fiting )

I cannot quite see from your photos but did you use triangular stock to reinforce the bulkhead to fuselage sides - an item omitted from the published plans as noted previously.

[Peter Miller]

The ESC should be cooled OK as the chin intake makes sure that there is a flow straight onto it

[Dean Sarelius]

Hi KC,

Thanks for the heads up.

I use slow curing epoxy for all the bulkheads and since the engine bulkhead is mounted directly to the inside plywood laminate sheets there is plenty of strength provided by the epoxy joint so no need to add any stock. By the way the epoxy I use is called Bote-Cote and its the same as that which I have been using for building plywood boats.

You can see some of the boats I have built on my webpage, www.boatandhobbies.com.

One of the advantages with Bote Cote is the long curing times which can vary depending on the ambient temperature anything between 2 hours and 10 hours on a cold night. The longer curing times allow for longer setup and when mixed with a filler provides an extremely strong joint.

I think I will take Peters advice and laser cut a slightly larger cowl ring.

Regarding the air flow do you think it would be advised to add an exit behind the wing perhaps..?

Thanks again for all your good advice.