motor box top plate - ok to use screws or is epoxy a must
- Thread starter skunkwurk
- Start date
Terryscustom
640cc Uber Pimp
Holy crap, I was focused on the engine box, those are too long for a 120! 1" max on that beast.
Jedijody
50cc
Uh yeah, that ain't gonna work! You've already cracked the firewall where the bolts go through the pieces of Al angle. You should make the pieces fit better before tightening them down. You also need more bolts/screws, fasteners are your friend. Lastly, never put a screw into the edge of any kind of plywood if its going to see any kind of stress. That box won't last through the maiden if it makes it through ground runs.
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Flatspinjim
50cc
Like Dimes said, laminated ply mount for sure. Is there room for the ignition and battery to go on the outside of the motor box?
jaybird
70cc twin V2
On that plane I would tri-stock the top and bottom of the firewall, tri-stock and epoxy the top plate, and definitely toss the standoffs and use a laminated ply mount.
If it's possible I let the motor box extend 1/2" or so past the firewall and tri-stock all 4 sides.
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If it's possible I let the motor box extend 1/2" or so past the firewall and tri-stock all 4 sides.
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stangflyer
I like 'em "BIG"!
Yikes, Was so concerned about the firewall I didn't even look at the standoffs..... Laminated Mount fo' sho'!
skunkwurk
50cc
Hi guys,
First of all, Happy Thanksgiving. Thank you for all of the feedback, I sincerely appreciate the assistance. The amount of knowledge amassed when we converge on these forums is amazing. Love GSN so far.
Some feedback, keep in mind that this is an ARF, the aluminum angles were installed at the factory. I was pretty pissed when I saw the fractured plywood myself. I'll try to correct that a bit by removing them and adjusting the fit, and it should relieve some of the stress on the front plate. I think I may also add more fasteners, as JediJody has suggested. Perhaps two more to each side with washers, and I'll upgrade the hardware.
I knew that hand drilling and using screws into edge of plywood wasn't a good idea, but it didn't sink-in until I was done and stood back. Then I decided to consult you guys., to confirm or defuse my concern.
I'll tri stock around the top plate back, sides and front. I can add some on to the bottom plate as well, if you believe its necessary. I can add it to the sides and some on the back and front.
Regarding the standoffs, they are 2" and designed by SWB. They are one piece each which measure 1" in diameter at the base to improve load bearing on the wood, and necks down to 5/8" in diameter at the motor and has a 1/4" hole. They are designed for this range of displacement motor. I don't want to instigate a religious battle, but I would like to solicit feedback, both pro and con on their use. I've used standoffs before on smaller displacement gas motors, always positive, so I'm interested in your thoughts. My personal preference would be not to toss them.
Would you guys consider laminating the sides with lite ply past the firewall and tri-stock around the front? I am obviously going to cut a new top plate, I can easily make that longer. Would you guys consider 3/32 lite ply?
Lastly, a lot of guys flew this plane with the DA-100, BME and others in the range w/out much mods. I bring that up because I don't want to go overboard either. I would rather build it so it's right, but avoid overbuilding. A tradeoff based sweet spot.
Thanks again guys.
Regards,
sc
First of all, Happy Thanksgiving. Thank you for all of the feedback, I sincerely appreciate the assistance. The amount of knowledge amassed when we converge on these forums is amazing. Love GSN so far.
Some feedback, keep in mind that this is an ARF, the aluminum angles were installed at the factory. I was pretty pissed when I saw the fractured plywood myself. I'll try to correct that a bit by removing them and adjusting the fit, and it should relieve some of the stress on the front plate. I think I may also add more fasteners, as JediJody has suggested. Perhaps two more to each side with washers, and I'll upgrade the hardware.
I knew that hand drilling and using screws into edge of plywood wasn't a good idea, but it didn't sink-in until I was done and stood back. Then I decided to consult you guys., to confirm or defuse my concern.
I'll tri stock around the top plate back, sides and front. I can add some on to the bottom plate as well, if you believe its necessary. I can add it to the sides and some on the back and front.
Regarding the standoffs, they are 2" and designed by SWB. They are one piece each which measure 1" in diameter at the base to improve load bearing on the wood, and necks down to 5/8" in diameter at the motor and has a 1/4" hole. They are designed for this range of displacement motor. I don't want to instigate a religious battle, but I would like to solicit feedback, both pro and con on their use. I've used standoffs before on smaller displacement gas motors, always positive, so I'm interested in your thoughts. My personal preference would be not to toss them.
Would you guys consider laminating the sides with lite ply past the firewall and tri-stock around the front? I am obviously going to cut a new top plate, I can easily make that longer. Would you guys consider 3/32 lite ply?
Lastly, a lot of guys flew this plane with the DA-100, BME and others in the range w/out much mods. I bring that up because I don't want to go overboard either. I would rather build it so it's right, but avoid overbuilding. A tradeoff based sweet spot.
Thanks again guys.
Regards,
sc
Terryscustom
640cc Uber Pimp
Long standoffs are OK on smaller engines but the DA120 is a brute, plain and simply not even in the same ballpark as the BME100. What you will find with longer standoffs is over time the vibes and forces exerted on them will eventually vibrate them loose. HOWEVER, I see that you have used a long 1/4" bolt, large washers and nylock nuts on the inside so you may be OK, but keep a watchful eye on them over time. What I typically do if I need more space is install a maple block on the firewall and use as short of an aluminum standoff as I can get away with.
Jumping ahead to your question and reference to lite ply......lite ply should never be used on the engine box except of maybe the top if it is permanently affixed.
What I would do is remove those aluminum brackets, scuff the backsides of them with 60-80 grit paper and re-install them with epoxy evenly coating the back of them. And the original bolts obviously.
Then, Modify the engine box top like I showed above if you absolutely must have an opening in the top. Best option is no hole in it though.
Then install tri-stock around the upper inside of the engine box and epoxy the box top onto the engine box and install the screws.
Lastly drill and pin the firewall from the sides and top with 1/8" wood dowels, epoxy those in and sand flush after epoxy is dried.
Then you can also put some tri stock where the engine box meets the F-1 former.
Keep an eye on those standoffs and the mounting bolts, you can always upgrade that if they show signs of wear on the firewall.
Just what I would do......minimum, to support the DA120
Jumping ahead to your question and reference to lite ply......lite ply should never be used on the engine box except of maybe the top if it is permanently affixed.
What I would do is remove those aluminum brackets, scuff the backsides of them with 60-80 grit paper and re-install them with epoxy evenly coating the back of them. And the original bolts obviously.
Then, Modify the engine box top like I showed above if you absolutely must have an opening in the top. Best option is no hole in it though.
Then install tri-stock around the upper inside of the engine box and epoxy the box top onto the engine box and install the screws.
Lastly drill and pin the firewall from the sides and top with 1/8" wood dowels, epoxy those in and sand flush after epoxy is dried.
Then you can also put some tri stock where the engine box meets the F-1 former.
Keep an eye on those standoffs and the mounting bolts, you can always upgrade that if they show signs of wear on the firewall.
Just what I would do......minimum, to support the DA120
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