Cowls, How do you mount them??

Here is are pics of my cowl and how I mount it.

It works real well for about 1/2 a season. But after many engine changes it just wears out the holes that go through the cowl.

Could some of you please elaborate on how you mount your cowls and make them withstand the abuse.

I use brass inserts to screw into set in balsa and that works for a while but the balsa lets go. This next time around I will set the brass inserts into basswood. That should hold up much better. I use arrow shafts at the back and use a couple of dowels mounted to the cowl at the back. They slide in and then mount it down with the 4/40s in the front.

How do you guys do it?

Ted you have killer cowls. How do you mount them?

That is just too cool!!
So where does the air come out?
Show us the whole plane!!!

Thanks
Paul

Doug,

My Mustang cowl is retained (in front) by a single hardwood peg into a plywood nose ring. The rear uses 2 4-40 screws into threaded brass tubes. The threaded brass tubes have been my problem also. Though I run smaller engines than your PA, my maintenance is considerable as I am always removing the cowl to back-flush the fuel filter or clean the fuel residue out of the engine compartment (Fox 35s just blow oil all over).

A friend of mine uses threaded inserts that he makes himself from #8 (I think) brass or aluminum screws. He drills out the center of the screw and taps it 4-40, then slots one end. His home-made threaded inserts are considerably smaller diameter than the commercial ones. He uses these inserts for engine installations. For a cowl application the threads should be more than adequate. These should hold up when screwed into CA hardened balsa or basswood.

Fred

Doug,

I don't have pictures. Or even a good description of what I do. Try following, fiddle with it, see if it has an application for your models.

Buy 4-40 size Gold-N-Rod. You only want the splined tubes. Drill 13/64" hole in scrap of wood. Pound short length of splined tube into hole. Hit with thin CA. Trim flush.

You have now embedded a tough, light piece of nylon tubing in wood. A 4-40 screw will self-tap into tube. As important, there is a self-locking feature in that screw will not back out unless you want it to.

Gold-N-Rod also available in 2-56 size, which is actually what I use for cowls, tank and access hatches.

Dang! Dan, great tip.

(You are definitely born again hard. I may let you be a rifleman in my beloved Corps..)

Maybe we need a repository of tips on "RC bashed" stuff for Stunt..

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"If you have an important point to make, don't try to be subtle or clever. Use a pile driver. Hit the point once. Then come back and hit it again. Then hit it a third time - a tremendous whack." -Winston Churchill

LAST EDITED ON Jun-09-04 AT 07:12 PM (CDT)
 
Hi Doug,

Mine is both more complicated and easier. I use a couple of machined aluminum hooks. They slide onto a retaining pin and are cut at an angle so that as the cowl slides forward, it is drawn down tight. 1 4/40 socket head screw that goes into a brass insert or boxed blind nut keep the cowl from moving back. I use a piece of carbon fiber tube with a glasses plug as a guide for the screw.

There were pictures of it in Stunt news an issue or two ago. Kinda of a pin to put together, but it holds up really well.

Edit: OK, I got home and will post a picture.

Dang! Dan, great tip.

Larry,

You bet. Wait until you start fiddling with this material, you won't believe the number of applications where it is 100% suitable.

My ARF Flite Streaks and the Skyray 20 have these lengths of tubing embedded almost every place there is a flat surface, serving to retain sheet landing gear strut, tank hooks in multiples as I didn't know which tank I would use or where it would be positioned, tail wheel strut, nose weight, tail weight, tip weight.

For a tank hatch, one of my methods involves simply gluing oversize squares of balsa in each corner of tank compartment, strapping block which will be carved to shape later down with tape, shooting a 3/32" drill through block/hatch and into blocks in compartment.

Now everything fits, drill blocks in compartment to accept 2-56 or 4-40 size Gold-N-rod. With anchors glued in place and trimmed, simple deal to grind away excess balsa (or ply, or maple or bass), leaving neat, light installation.

Do whatever you like to reinforce hatch, giving cap screws a hard point to rest against.

Since beginning to use this material and switching to brass threaded inserts for engine attachment I have not used a single blind nut.

Love shooting, let me know when there is an opening...

Dan,

Do you have any pics?

I think I get what you are saying and it sounds great!

Doug

>Dan,
>
>Do you have any pics?
>
>I think I get what you are saying and it sounds great!
>
>Doug

Doug,

No. Sorry. When I get that plan set mailed back to you--first of next year be okay!?--will include some samples.

>>Dan,
>>
>>Do you have any pics?
>>
>>I think I get what you are saying and it sounds great!
>>
>>Doug
>
>Doug,
>
>No. Sorry. When I get that plan set mailed back to
>you--first of next year be okay!?--will include some
>samples.
>
>Dan
>

Dan,

First of next year??? I really dont care if I ever see those plans again. I thought you guys were all in a rush to get that plane going so I sent them right out. Heck it is a profile it takes 20 hours to build and finish. Maybe less time typing and more time building...??? Just kidding...

LAST EDITED ON Jun-11-04 AT 05:02 AM (CDT)
 
Doug,

Time old method using a single bicycle spoke and accompanying bolt as is used to adjust tension of the spoke. Cowl reinforced with 2mm plywood on the inside so it can't be pulled through the soft balsa and flanges on the inside of the cowl to hold it in position.

You can see the spoke just behind the engine.

The system i use is rather simple if you want to jsut get it on, look neat and professional

All I do Is make up a balsa block jsut below the line of where the cowl sits on the fuzz side, and mount a plywood plate to the top of that.
Then, on the cowl side I use carbon fibre arrow shafts to give me a nice hole to put the tool to do it up with inside so you dont damage the cowl.. At the bottom of the cowl, I use a 2-56 Threded screw than u jsut do up into the ply plate. And to prevert the screw from coming out, i jsut countersink another small ply plate into the cowl so it sits flush.

last one was good for 3 years.

LAST EDITED ON Jun-21-04 AT 10:09 AM (CDT)
 
Doug,

The system I use is largely dependent on the type of cowl I build. Since they are molded of 3/32" balsa, I have to hold them with multiple screws. Here is Snaggletooth's cowl with its 8 2/56 screws. This is very easy to do, and makes for a very secure, tight fitting cowl. It takes about 10 seconds to remove each screw, so I can get the cowl off in less than 2 minutes. I use filtered fuel, so once I get the tank height set, I only remove the cowl every 50 flights to check the tightness of the engine mounting screws.