Fair DR1 thrust angles/mounting
 

I have a Flair DR1 kit,which upfront,will be a 1.20fs,the plan shows no reference to the required engine thrust angles,and i was wondering if i induced 3 degrees in side/down,would be a good starting point.

Another area that i find difficult.is marking out the position of the mounting holes,to allow for offset,i have thought of offsetting the firewall,but if things require changing,would it be better to just offset the mount

If you have ways of doing the above,any help very much welcome

Thanks

Eindecker

Fair DR1 thrust angles/mounting
 

Eindecker:

That plane is so close coupled that three degrees might turn out to be just the starting point.

I'd install the firewall with the three degrees right and down, then offset the engine mount to center the prop in the cowling.

A nice thing about planes like that is being able to have the prop not quite centered, and still not have it show too much.

So if you have it centered with the 3-3 angle, any adjustments wont be terribly apparent.

Have a good time with it.

Bill.

offset calculator
 

Go to www.gsal.org

tools

motor offset calculator


This will tell you how much to move your engine mount to keep the prop hub centered in the opening

randy

Fair DR1 thrust angles/mounting
 

Thanks guys for the information sofar,all very helpful.

I have one more question regarding engine mount.

If i were to install two beech bearers,set at 3 degrees down,and screw a ply plate to these,with a cutout also at 3 degress,what thickness should the ply be,for a 1,20fs, say 1/4"?,would this be ok.
Adjusting side thrust would only mean cutting anew plate,with increase/decrease thrust angle,down thrust would just need alittle shim under plate.
Looking at plan etc,if i were to angle firewall etc,its going to make things alittle difficult,as new firewall will have to made up,to allow for angle,also its going to effect the rest of the front end,and new parts will have to be made up.
Using the bearer method is going to make things alot easier overall.plus it will keep everything else to plan.

Your views, thoughts and suggestions please

Eindecker

Fair DR1 thrust angles/mounting
 

Eindecker:

You have a good idea, I only see one problem.

Engines, when you get that large, have some pretty hard vibrations. Fastened rigidly to the plywood and the beech bearers every bit of that vibration is going straight into the airframe.

If you have the room, you can use a FRP mount with the beams 3/4 to 1 inch wider than the engine needs, and then use your ply plate between the mount and the engine. The fiber reinforced plastic mount is a pretty good vibration isolator. Or you could get a Du-Bro soft mount, the Great Planes "Large Engine Isolation Mount," or any one of several others. The GP mount is just the isolator, you'll have to use a conventional FRP mount with it, unless you get a radial mount adaptor for your engine.

As I said, you had a good idea. And you might not have any vibration problems, anyway.

Bill.

Fair DR1 thrust angles/mounting
 

Bill,

That looks like agood idea,ive had a quick look at the du-pro soft mount,but the one available was for an 80 4 st,but with a price tag of 30 pounds,here in the uk,so going by that a larger version will be alittle more,going by that,it seems to be an expensive bit of kit!!!.then ive still got to mount it 3 degrees
down!!
Maybe,i could isolate the engine,by placing some rubber material,under the engine lugs,or under ply plate,before screwing down ,to absorb some of the vibration,or something like that!!!,im no scientist!!!,maybe some other ideas might spring to mind

Just for the record,what can go wrong,with excess vibration to airframe,joints are one point in question if weak,the radio gear if poorly insulated is another,sure there are other areas?

Thanks Bill for past posts,all very intreasting

Cheers

Eindecker

Fair DR1 thrust angles/mounting
 

Eindecker:

The Great Planes "Large Engine Isolation Mount" is a 5 1/4" by 4 3/4" chunk of 1/4" ply with rubber mounts at the corners. exactly what you had suggested.
he FRP mount is fastened to the ply plate, and the ply plate is then attached to the firewall through its soft mounts. And its price is a small fraction of Du-Bro's.

Vibration, at its worst, will shake the airplane apart, strip servo gears. greatly increase battery drain, flex all the wires and break them, just about any problem that could arise from shaking. It is to be avoided a much as possible.

Bill.

Fair DR1 thrust angles/mounting
 

I built the Flair DR1 about 4 years ago . Mine has an Enya120r in it , is 13lbs ,has 16-6 master airscrew . Flys great , don't forget to correct the cut out in the middle wing , not on plans . I don't have plans anymore , but i have just put incidence meter on it .
It has on the eng , 3degrees right , zero down . Now don't forget the stab; has some 3 degrees pos; on it , so that is the 3 degrees down on eng ; you mentioned . Can't remember 4 years back , but I think the firewall has that built into it ? They stretched the nose , but at least it doesn't nose over too often ,

Fair DR1 thrust angles/mounting
 

Hurri,

Thanks for the info,the firewall is 90 deg to sides,so with a suitable mount,alittle 3 deg right thrust shimming will be all that is required!!.and confirm 3 pos on stab,and as you said,thats why zero down on eng. Atleast it will give some reference for first flights.
Thanks again

Eindecker