What would YOU do to this !!! (picture)
 

Hello everyone and thanks in advance for your time.

I have this 25cc homlite engine which I wanted to mount to this plane, but the homlite has a rear mount while my plane, as you can see from the picture, has a standard wooden beam mount. The wooden engine mount beam is very sturdy, but the firewall on this is very thin and not strong at all. Secondly the firewall is not straight, it is slanted backwards.

Now since I am not a knowledgeable builder, I was wondering if you kind people could give me YOUR views on how YOU would go about fixing this, so that I will get some ideas.

Finely, when I DO go about fixing a new firewall, should it be EXACLY perpendicular to the stabilizer?

Sincerely yours,

Mohammad Reza

RE: What would YOU do to this !!! (picture)
 

What do you mean "slanted backwards"? Remove the beams. Increase the firewall thickness to 3/8". Use whatever method the engine needs to secure it to the firewall (bolts, screws, blind nuts, etc.). Are you sure that plane will handle such a large engine? How big is the plane and what engine was it designed for? For a 0-0 thrust line, the firewall should be perpendicular in both axes to a line drawn fron the center of the leading edge of the wing through the center of the trailing edge.

Dr.1

RE: What would YOU do to this !!! (picture)
 

Just rip out the beams and Firewall, and add a new firewall (use a good quality 1/4 - 5/16" Ply)

You can just "eyeball" the straightness of the firewall, or put a level on the tail, block up the Fuse so it's level, and use a vertical level on the firewall.

Then, add some Tri-Stock behind the firewall for strength.

RE: What would YOU do to this !!! (picture)
 

Use your monokote heat gun and heat the epoxy holding the rails and the firewall. Chances are pretty high that the heat will release them so you don't have to cut them out. Would be a lot easier.

RE: What would YOU do to this !!! (picture)
 

I bought this plane from a yard sale, and the previous owner recommended a 1.2 glow engine at the minimum as it is kinda heavy and big. so I decided to go with the 25cc homlite.

Anyhow your sugestions are all appreciated and I will do as you fellas have instructed.

Thanks again.

(BTW by slanted, I meant that the firewall was not exactly vertical, but sort of like at an angle)

RE: What would YOU do to this !!! (picture)
 

A 'slanted backward' firewall would indicate upthrust, though I'm not sure of many planes that use upthrust.

RE: What would YOU do to this !!! (picture)
 

probably a goof in construction

RE: What would YOU do to this !!! (picture)
 

I love the monster truck wheels:D

RE: What would YOU do to this !!! (picture)
 

Overall construction looks very poor. I would double glue everything you can get to, use at least 1/4 in ply for the firewall when you put the new one in, and put triangle stock behind it like mike said earler.

RE: What would YOU do to this !!! (picture)
 

It also wouldn't hurt to pin the firewall. This will help take the pull from the motor and make sure you're firewall won't pull out.

Hope this helps

Ken

RE: What would YOU do to this !!! (picture)
 

Speaking of monster truck tires, you might want to de-groundloop that left wheel. :D

RE: What would YOU do to this !!! (picture)
 

Thanks so much guys for all the helpfull ideas, the firewall on this is useless, as the engine is mounted on the horizontal wooden beams and not attached to the firewall.

When I bought it, it had no wheels, and big wheels at my LHS were so expensive, so I just ripped off two tires from my sons toy truck that was broken.

By pinning, do you mean I get some needles and insert them from the fuselage side, penetrating the firewall?

Sincerely yours.

RE: What would YOU do to this !!! (picture)
 

By pinning I think he actually means what you described but with dowels not pins,,But I think I would just go with triangle stock between the fuse and firewall and then slather it up with epoxy front and back.....now just for fun what is the wingspan on that beast?!!...Rog
oh the slanting...most all of my smaller planes require a slight angle of down and to the right to compensate for the thrust of the engine..hence the term downthrust...

RE: What would YOU do to this !!! (picture)
 

Pinning mean using dowels inserted through the fuselage walls into the firewall. This is a very strong method to reinforce the firewall.

Ken

RE: What would YOU do to this !!! (picture)
 

I would think that those wooden beam should be tied into the firewall. You stated earlier they weren't? If not the I'd redesign it so that the beams were epoxied to the firewall then that joint can be enforced with more triangle stock.. Make your new firewall out of good quality 1/4 - 5/16 ply like Minn said, Then add some triangle stock to your firewall joints and pin it.. That thing will be like a tank.

Also I can't tell but be sure to fuel proof your tank comp. and Firewall/ beams using Thinned epoxy.

RE: What would YOU do to this !!! (picture)
 

The poster stated that he is going to use an engine with a rear radial mount. Those beams have got to go, remove them.

Fatboy you have all the best suggestions already by RCKen and others.

1. Get rid of the old beam mounts. Hack, grind, chainsaw or use a machete.

2. Cut out the old firewall and fit a new one and epoxy to the cleaned up fuselage sides. I would highly suggest at least 5/16" not 1/4".

3. Get some large balsa tristock (at least 3/4" on the long side) and epoxy to the sides and firewall just exactly like Kens drawing illustrates

4. Drill 2 or 3 1/16th holes through the sides into the plywood. Does not have be very deep and push in 1/16 dowels and drip all around each dowel with this CA.

Last but not least harden the tristock by dripping thin CA on the exposed part of the tristock inside the compartment.


How about a better picture of the whole airplane. Some of us derive great joy out of fixing up an old clunker and making a good flyer out of it.;)


Almost forgot, do allow for a little downthrust by angling the firewall downward (the top edge a little further forward than the bottom edge). Actually the allows the crankshaft to point slightly downward. On a highwing cabin type like yours doing this will minimise pitch trim changes every time you change the power a little. It only needs to be just a few degrees.

John

Team Geritol

RE: What would YOU do to this !!! (picture)
 

Oh, Sorry I must Have missed that part.. Sorry:eek:

RE: What would YOU do to this !!! (picture)
 

No big deal we all miss stuff once and a while. Hm think I go have another spoonful of Geritol :D

RE: What would YOU do to this !!! (picture)
 

Hello again and excuse me for the long delay.

All your suggestions were absoulutly briliant and I thank all for thier time and drawings.

I also would love to see this baby fly, But I am having serious doubts as to weather the plane can take this engine or not, Here is 2 more pictures of the whole plane.

As mentioned, the engine is a 1.8kg Homelite 25cc converted by www.scottellingson.com
The palne weighs about 12lb without the tank, pushrods or radio, and has a wingspan of 94 inches.

I really hope it will fly well.

Mohammad Reza

RE: What would YOU do to this !!! (picture)
 

Looks like an old Telemaster

RE: What would YOU do to this !!! (picture)
 

ST On the tail? Wasn't there or is there a Senior Telemaster?

RE: What would YOU do to this !!! (picture)
 

With regard to the engine size, I have a friend that is flying a Senior Telemaster with an Irvine .60 glow engine
and it is plenty of power for it. The wing on that airplane is HUGE, thus creating loads of lift. Plus the tail is also airfoiled and lifts as well. It is a great trainer airframe. It flys very gently and does not do anything funny. Why not slap a .60 size glow in it and keep it the way it is?

RE: What would YOU do to this !!! (picture)
 

You mean this one? http://www.hobby-lobby.com/srtele.htm :D

RE: What would YOU do to this !!! (picture)
 

Looks like it!

RE: What would YOU do to this !!! (picture)
 

Looking at the left wing, you can still see the hobby lobby senior sticker. The rest has been, well, "covered."