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  1. #1

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    Repairing my Alpha .40

    Hi All,
    Before I ask for your advice on a repair to my Hangar 9 Alpha .40 you need to know this will be my first repair attempt on an RC plane.
    The other day I had my first crash with my Alpha .40, as I took off a crosswind came up and the plane veared to the right, and hit the wind sock pole dead center. The glue holding the wing joint came unglued, the spinner disentigrated, the prop blades could not be found, but those are a no brainer to fix. However the firewall came loose on one side (the left side), and it has a small crack in it. My instructor told me to take the engine, and engine mount off the plane, and epoxy a wood brace to the firewall, and the fuesalodge in order to hold the fire wall in place.
    But another fellow told me it would be better if I just pulled the firewall out, and made an exact template of the firewall, and just make a new firewall, and epoxy the new firewall in the plane. I feel both methods will work, but I would greatly appriciate some other opinions on which fix would be the best way to go. I do have a scroll saw so makeing a new firewall will not be hard, I just don't know what to expect to find or whats all is involved if I pull out the old firewall and replace it. Any help with this will be greatly appriciated.
    Paul

  2. #2
    flyinwalenda's Avatar
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    RE: Repairing my Alpha .40

    Hi,
    Good for you wanting to make the repairs yourself. Depending on you skill level this could take a little while or a few hours but it sounds like something you should be able to handle.
    If you could take a few pictures of the damage that would help everyone.
    If the firewall cracked or separated from the side of the fuselage then you would take some glue(yellow carpenters glue or 15-30min epoxy) and brush the glue between the joint and move it back in place and clamp it till it dries. Then go behind (backside of the firewall)and reinforce the edges where the firewall meets the fuselage with some 3/8 or 1/2 inch triangle stock balsa and glue those in place on each side for additional support.
    If the firewall is cracked through the main part ,it really depends how bad and where the crack is.
    If the crack is on the rear of the firewall,it could be reinforced from the rear by cutting a piece of thin plywood the size of the firewall and gluing it directly to the back and then re-drill the holes through for the engine mount.
    If it's cracked on the front it could be repaired in a similar fashion but it depends where the crack is located. It may be better to carefully cut out the firewall from the fuselage sides and bottom using a thin saw blade(a hacksaw blade works good for this)and make a new firewall. You can take a piece of heavy paper and make a template of the firewall before removing to mark the mounting holes or depending how well you cut out the existing one you could use it. Then glue the replacement back in and reinforce from the rear with triangle stock.
    Depending how you make the repairs,when you have finished, take some epoxy glue and thin it down to the consistency of paint and brush it onto all of the new/bare wood you replaced or added on the rear and/or front . This will help keep the fuel or any other liquid from soaking into the wood.

    Brian Ray

  3. #3
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    RE: Repairing my Alpha .40

    Firewalls are a pain as they are not made to come apart . Whichever you choose.. keep in mind the little tihngs like making holes for fuel lines... maybe needing longer bolts if your doubling up the firewall.. geting the blind nuts out ofthe original, etc. For thinning epoxy... I just pass my covering gun over it.. turns to a runny syrup and flows in all the nooks and crannies... i often brush it in as well.. but will also kick off faster due to the heat. But this way there's no thinning or add'l mixing needed.

    Good to see you fixing.. once you get in there... it's not really that big a deal... the next one goes faster.. and the one after that even faster

    In our club... one guy tore his landing gear out and was goingto buy a whole new fuselage... craszy.... so i fixed it for him.
    Mike -
    I was born a pilot... 100 years to late.

  4. #4

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    RE: Repairing my Alpha .40

    here is a good rule of thumb to remember when glueing pieces back together. Do not try to glue something that has dried epoxy at the glue joint. the old epoxy will not bind with new epoxy very well and it will create a point that will tend to shear away easily. best solution is to sand the epoxy down to wood so the new mixed epoxy has some exposed wood to seep into and bind with

  5. #5

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    RE: Repairing my Alpha .40

    My sons Alpha 40 needed 3/4 oz weight in the nose to ballance.  If yours needs weight in the nose I would just remove the blind nuts, double up the plywood with some good epoxy, add tri stock as mentioned and install new blind nuts.  If it is not tail heavy I would remove the old wood and install new.  The firewall on that plane is notched into the fuselage for strength so you will have to epoxy tri stock in with the new wood to strengthen it.  Here is a thread of the repairs on my son's Alpha 40. http://www.rcuniverse.com/forum/m_11...m.htm#11237977


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