Question: Can I use glow engines to power my VMAR Twin Offer? If so what sizes are recommended? Any tips you can suggest on what I need to plan for?
Answer: Yes the VMAR Twin Otter can be powered with glow engines. We suggest glow engines be at least .09 cu. in. each as a minimum. Maximum engine size should be limited to .15 cu. in. each. Please note that setting up and operating multiple glow engines is not for novices. It requires considerable expertise with modeling, glow engines and RC flying to be able to successfully equip and fly the Twin Otter with glow engines.
Tips on use of glow power:
1) We recommend two stroke engines for this model. Four stroke engines tend to be bigger and heavier and they may cause structural failure of the standard wood engine mounting pylons.
2) You will need to plan your fuel tanks and engine mounting system with careful consideration for physical space particularly if you wish to try to install the engines so that you can utilize the scale like engine shrouds and nacelles.
3) Do NOT glue the engine mounting pylons (factory assembled of wood) to the wing until you have test fitted the engine mounting pylons, engine mounts, engines, mufflers, fuel tanks, fuel tubing, throttle linkages, engine shrouds and nacelles.
4) Once you have test fitted all of the components related to the glow engines, use 30 Minute Epoxy to attach the engine pylons to the wing. Ensure they are aligned and fitted properly. Let the adhesive cure thoroughly before proceeding.
5) Use Pacer Finishing Resin and a brush to throughly seal any exposed wood, particularly that of the engine mounting pylons and the attachment area on the wing. Also the wing saddle area. The exhaust from glow engines contains lots of hot vapourized and liquid oil residue. Although most of this oil will be channeled out in the exhaust, some oil will inevitably get on the model itself and will be absorbed by any unsealed wood. Oil can weaken glue joints and the wood itself.
6) Glow engines tend to produce considerable vibration particularly in a twin configuration when the engines are not quite at the same RPM. Take particular care to balance your props and to run the engines at the same RPM when compared to each other throughout the range of throttle positions. Vibration can cause fuel feed problems, lean runs and engine cut off as well as structural failure, control surface flutter and/or separation and is very damaging to servos. It is very important to keep vibration to a minimum.