The grey hulled Dehler 34 were built with a layer of Kevlar over the whole hull, this can be checked by trying to drill a hole in the hull, the 34’s with a white hull had no Kevlar.
" Incidentally, comparing a summer day at 30C and a winter day at 0C with the same air pressure, the difference in density is about 10%"
In 1973 the difference was measured at 19%. (at the same wind speed) If you want confermation of the effect of density, ask an airline or a glider pilot or...
I had the same problem, I found out it did this when I transmited on the VHF. Try testing it if this is the problem let me know. I may be able to fix it.
Two bladed feathering propeller (Prowell of Germany), 17" X 13" , to fit a 30mm shaft, c/w streamlined Zinc anode nose cone. Little used. £200 + P&P
The reason for sale, I have sold my beautiful Dehler cws and bought a Nimbus.