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Model Forum / Radio Controlled / Air Models / July 2004Drilled F/W holes too close together.
I'm building my first R/C plane (a SIG Four-Star 40). When I drilled the 4 holes in the firewall to mount the engine mounts I screwed up. The holes are about 1/8" too close together. The engine will not fit between the mounts. I measured and checked and measured again. I don't know what I did wrong, but I know have a firewall with the wrong holes. Can anyone offer me suggestions on how to fix this? The wrong holes are too close to where the right holes belong to redrill. I'd just end up with elongated holes. Also, I don't have a drill press so I couldn't easily do that in any case. Thanks for any help you might offer. Bill Baker Fill the holes with epoxy and do it again, this time in the right place. Regards Tom Watson Sydney Australia > I'm building my first R/C plane (a SIG Four-Star 40). > When I drilled the 4 holes in the firewall to mount the [quoted text clipped - 15 lines] > > Bill Baker > Fill the holes with epoxy and do it again, this time in the right place. > > Regards > > Tom Watson > Sydney Australia Thank's Tom. I will probably try that this weekend. Epoxy hardwood dowels into holes and redrill. Red S. > I'm building my first R/C plane (a SIG Four-Star 40). > When I drilled the 4 holes in the firewall to mount the [quoted text clipped - 15 lines] > > Bill Baker > Epoxy hardwood dowels into holes and redrill. > > Red S. Thanks Red. I don't have any hardwood dowels handy. Tom Watson suggested just filling the holes in with epoxy. I can see that the hardwood dowels would work better for larger holes but these are only 3/16" dia. What problems would I have if I just used epoxy to fill the holes? Bill >> Epoxy hardwood dowels into holes and redrill. >> [quoted text clipped - 8 lines] > > Bill Epoxy is heavier than wood, but the small amount you need for the small holes is negligigble. OTOH, dowels are not that expensive at the local hardware store. And you will have leftover dowel for another project. Epoxy would either be too soft and allow the drill to wander, or too hard and shatter. A fine balance would be needed. Hardwood dowels are usually the same type wood as the ply so the density is closer. -- Paul McIntosh http://www.rc-bearings.com > > Epoxy hardwood dowels into holes and redrill. > > [quoted text clipped - 7 lines] > > Bill Bill, I tend to agree with the fellows that suggested you use dowels to fill the holes. If the new holes are too close to the original then the drill will probably wander. I am not sure about drilling a big hole. just fill the first holes and redrill. Also make a template and use it to mark the firewall. Regards Tom Watson Sydney Australia > > Epoxy hardwood dowels into holes and redrill. > > [quoted text clipped - 7 lines] > > Bill A suggestion: 1. Epoxy pieces of wooden dowl, of the same diameter as the original holes in the firewall, ensuring the dowls are flush with the surface to preclude left/right or up/down thrust. Let the epoxy dry thoroughly. Sand smooth and refuel-proof. 2. Make a template, if one was not provided with the mount, of the mounting hole pattern. Paper works well here. Temporarily adhere the template to the firewall and, with either a small drill, pin, or similar sharp object, pierce the paper template at the designated holes to transfer the pattern to the wood. 3. Remove the template and drill the correct size hole in the new pattern. Install the blind nuts on the reverse side of the firewall and happy landings! Steve Barnett Annapolis, MD > 2. Make a template, if one was not provided with the mount, of the mounting > hole pattern. Paper works well here. Temporarily adhere the template to the [quoted text clipped - 3 lines] > Steve Barnett > Annapolis, MD The mount came with the kit. The engine (obviously) was bought seperately. How would I go about making a template? What I did (wrongly as it turns out) was to measure the width of the engine and the width of each of the mounts. I then drew lines on the firewall to mark the outside of each mount based on those measurements. From the plans I marked the thrust line and figured out where the mount needed to be to put the prop shaft on the thrust line. In otherwords, I thought I was drawing a template on the firewall itself. Since I obviously got it wrong I guess I could use some suggestions on how to do it right. Thanks, Bill If these are those atrocious two piece separate mounts, I would get rid of them and start with a DuBro, Sullivan or Great Planes mount made for the engine. This will make mounting and adjustments a lot easier. -- Paul McIntosh http://www.rc-bearings.com > > 2. Make a template, if one was not provided with the mount, of the mounting > > hole pattern. Paper works well here. Temporarily adhere the template to the [quoted text clipped - 20 lines] > Thanks, > Bill > > 2. Make a template, if one was not provided with the mount, of the mounting > > hole pattern. Paper works well here. Temporarily adhere the template to the [quoted text clipped - 20 lines] > Thanks, > Bill Bill, a good way I found to make sure the holes are lined up is to use a small amount of CA to glue the mount to the firewall, than drill through the holes in the mount. If you're sparing with the CA, you can then pop off the mount. Morris > In otherwords, I thought I was drawing a template on the firewall > itself. Since I obviously got it wrong I guess I could use some > suggestions on how to do it right. The easiest thing to do is mount the engine on the engine mount so as to hold the beams in proper alignment. Then you can measure the distance between the holes, and mark them on the firewall. One way I fixed this was to drill out the holes so that the correct ones would be iside the open area (know what I mean?). In your case, holes about 1/2". Then I epoxied in pieces of hardwood dowel flush with the front of the firewall. Now, you can position the mount and redrill the holes. I have never tried to measure the holes. I always tack-glued the mount to the firewall and drilled pilot holes. -- Paul McIntosh http://www.rc-bearings.com > I'm building my first R/C plane (a SIG Four-Star 40). > When I drilled the 4 holes in the firewall to mount the [quoted text clipped - 15 lines] > > Bill Baker Bill -- epoxy some dowels to fill the old holes then carefully redrill. Remember the old carpenters' motto -- "Measure Twice; Cut Once". If perchance the holes get elongated, add a small (1") 1/8" ply circle behind the firewall for the blind nuts. Cheers -- \__________Lyman Slack_________/ \______AMA6430 IMAA1564___/ \____Flying Gators R/C______/ \__Gainesville FL _________/ Visit my Web Site at: http://www.LymanSlack.com "Bill Baker" The holes are about 1/8" too > close together. The engine will not fit between the > mounts. >I'm building my first R/C plane (a SIG Four-Star 40). >When I drilled the 4 holes in the firewall to mount the [quoted text clipped - 13 lines] > >Thanks for any help you might offer. 1. So what if the holes are elongated so ovalize 'em and take care to fuelproof. 2. Make a new firewall. 3. Use a Great Planes adjustable engine mount, one of the few accessories that GP got right. It allows you to adust the beam width no sweat. 4. (What I would do lacking a GP mount if I didn't give a crap about [1] ). Using wood glue, glue appropriate sized dowels into the existing holes and redrill. Texas Pete On 7/23/2004 3:52 PM Ted shuffled out of his cave and grunted these great (and sometimes not so great) words of knowledge: > I'm building my first R/C plane (a SIG Four-Star 40). > When I drilled the 4 holes in the firewall to mount the [quoted text clipped - 15 lines] > > Bill Baker Epoxy dowels into the current holes (make sure they are flush with the INSIDE of the firewall - if they protrude they will be hard to get flush and may interfere with blind nut installation), lets dry, then sand flush and re fuel proof. Tack glue the motor mounts to the firewall (one or 2 SMALL drops of CA are all you need), mark the holes and redrill the holes and install the blind nuts. I would not suggest epoxying the holes in for the following reasons: If the epoxy is too soft, the drill bit will wander, if it is too hard the epoxy may shatter. If the epoxy is too soft the blind nuts may not hold properly and if the epoxy is too hard the prongs on the blind nuts may shatter the epoxy. I would not elongate the holes because: If you elongate the holes, the blind nuts will not be able to adhear/grab properly, in addition to which they may also shift position. Hope this helps. Not sure if this will work for you, but most of the 2 part engine mounts have slots which allow you to adjust the spacing - I think these are fairly heap so might be an option if you do not want to fill the holes and drill again, plus they allow you some latitude in that even if your mount to firewall holes are off a bit the slot makes this a no problem error David - who also has problems getting holes in the right place a times > I'm building my first R/C plane (a SIG Four-Star 40). > When I drilled the 4 holes in the firewall to mount the [quoted text clipped - 15 lines] > > Bill Baker  SignatureIf we're not supposed to eat animals, why are they made out of meat? Best tool for this problem is the hole center by Great Planes. Very "must have" > Not sure if this will work for you, but most of the 2 part engine mounts > have slots which allow you to adjust the spacing - I think these are [quoted text clipped - 3 lines] > > David - who also has problems getting holes in the right place a times Take a piece of good 1/8 inch ply and epoxy it to the firewall. Make sure the piece is large enough to accomodate the engine mount with the proper spacing. John VB > I'm building my first R/C plane (a SIG Four-Star 40). > When I drilled the 4 holes in the firewall to mount the [quoted text clipped - 15 lines] > > Bill Baker > Can anyone offer me suggestions on how to fix this? The > wrong holes are too close to where the right holes belong > to redrill. You can enlarge the wrong holes to whatever size dowel you have handy, tap them in, cut flush then use thin CA. The firewall won't mind at all. You can redrill right next to it. m. |
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